Vegetation Management for Road and Rail Corridors flora and fauna which is documented from the...

Construction, Operations and Maintenance Session

Vegetation Management for Road and Rail Corridors 301 ICOET 2011 Proceedings

Vegetation Management for Road and Rail Corridors

RAILWAY ENVIRONMENTS PRODUCE ECOSYSTEM SERVICES IF MANAGED PROPERLY

Magnus Stenmark (+46709758967, [email protected]), Conservation Biologist,

Faunistica, Dalviksringen 35, SE-55445 Jönköping, Sweden

ABSTRACT

Railway environments, like sand and gravel pits, roadsides and other anthropogenic grassland habitats, are now

recognized for their high species richness. In particular, vascular plants, butterflies, aculeate wasps, beetles and

homopterans are abundant in this environment. Over the last three years, the Swedish Transport Administration

conducted species surveys of railway station environments, listing over 2,400 species from more than 340 spots in

Sweden. Railway areas with their adjacent loading zones were shown to host a particular flora and fauna, thus

constituting a specific ecosystem. In these areas a number of species live without ever leaving the railway environment

and in some cases they are only sporadically distributed in the surrounding non-railway landscape. In this work, the

survey focused on the grassland areas available along the non-urban railway lines. Along the railway lines the area of

herb and shrub flora is often limited to a narrow board and only managed by herbicide spraying. But there are also a

number of items along the lines that are regularly managed by mowing and cutting. In this study, 40 sites were studied

and these were distributed along two separate 80 km lines in central Sweden. Ca. 22,000 insect specimens were

collected and determined to species. The sites were grassland areas near bridges, road crossings, substations and

maintenance roads. The results indicate that the flora and fauna on the railway line sites are different from the typical

railway flora and fauna which is documented from the station areas. The sites along the lines house a surprisingly

diverse and rich herb and shrub flora, but are often small in area and the sites are often isolated from other grasslands.

Unlike railway stations, the sites along the lines include a great variety of biotopes. For example, thin boards of

herbaceous vegetation along railway lines are often important for longhorn beetles and syrphid flies that live in the

forest edges. Similarly, the herbaceous vegetation along lines near water are important for species that habitat

wetlands. Therefore, railway sites are related to the surrounding landscape in a more complex way when compared to

railway station areas. This study shows that the natural values of grasslands along railway lines are highly variable and

rather a product of the surrounding landscape than of the maintenance regularly conducted. Therefore, the grassland

maintenance on sites along railway lines needs to be adjusted to the specific environment in the area.

INTRODUCTION

Railway environments, like sand and gravel pits, roadsides and other anthropogenic grassland habitats, are now

recognized for their high species richness (Saure 1996, Allem 1997, Angold et al. 2006). Most of the species in these

habitats derive from semi-natural grasslands such as pastures and meadows, which represent highly valuable

elements of the European cultural landscape (Norderhaug et al. 2000). The general theory states that biodiversity rich

agricultural ecosystems interact with these areas, creating a buffer zone or being an important resource area delivering

ecosystem services to surrounding grassland ecosystems (Noordijk et al. 2009).

In particular, vascular plants, butterflies, aculeate wasps, beetles and homopterans are abundant in this environment

(Larsson & Knöppel 2009, Lennartsson & Gylje 2009). Over the last three years, the Swedish Transport Administration

conducted species inventories of railway station environments, listing over 2,400 species from more than 340 spots in

Sweden. If including only the spots with a full species inventory (≥1,000 observed individuals, N=75), 62% contained

one or more red-listed species. During these surveys, railway areas with their adjacent loading zones were shown to

host a particular flora and fauna, thus constituting a specific ecosystem.

Today, a number of highly valuable grassland structures are recognized within transport infrastructure biotopes. Such

structures are sand patches, dead wood, paths, slopes and mounds. These important structures that increase the

biodiversity were previously constricted to the cultural landscape. In Sweden, the most threatened species are

associated with farmland and particularly to the hay meadows and natural pastures. Since the 1930s, however, the

mowed areas decreased by over 95% and the area of grazed semi-natural grasslands decreased by 85% (Ekstam et al.

1988). The area of grass- and scrublands in infrastructure biotopes increased during the same time as new roads,

railways and airports were constructed. In Sweden, the surface of mowed grasslands is estimated to 160,000 ha only

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ICOET 2011 Proceedings 302 Session COM-4

along roads, railways and on airports (Faunistica 2010). For comparison,

Sweden has currently about 9,300 ha meadow and 445,000 ha of

pastures (Board of Agriculture 2010).

Management, e.g. mowing, Roundup spraying and cutting for safety

reasons, of railway embankments and railway station grasslands has the

potential to maintain and develop grassland ecosystems (Spooner et al.

2004, Auestad et al. 2010).

In this work the focus is on these grassland areas that are managed and

which are found along railway lines. Along the railway lines the area of herb

and shrub flora is often limited to a narrow board and only managed by

herbicide spraying. But there are also a number of items along the lines

that are regularly managed by cutting and clearing. In this study, 40 sites

were studied and these were distributed along two separate 80 km lines in

central Sweden. The sites were grassland areas near bridges, road

crossings, substations and maintenance roads.

In particular, the following questions were addressed:

Which nature conservation values are there among vascular

plants, butterflies, aculeate wasps, beetles and homopterans on

grassland areas along railway tracks?

Which organism group represents the most biological diverse

group in this environment?

Are the species richness influenced by the presence of sand?

MATERIAL AND METHODS

The field included 40 sites along two railway lines (Figure 1). Each site was visited 4 times during the field season of

2010 and investigated by botanical transects, zoological transects and by insect traps. The nature values in the

selected regions are well documented (Larsson 2010). Both railway lines are stretched through sandy areas (Figure 2a-

c), a documented fact increasing the biological diversity (Karlsson 2008).

Figure 2a-c. An earth map covering the study area. Both railway lines (a – left figure), the

northern part in detail (b – middle figure) and southern (c – right figure). Black dots

indicate study sites. The buffer zones of 1,000 and 5,000 m are indicated. For earth legend

see Stenmark and Larsson (2011).

Figure 2. De två studiesträckorna

med jordartskartan som bakgrund.

Det är tydligt med dominansen av

morän i landskapet men stråken av

sandavlagringar i form av

Figure 1. Study area indicated with

red. The northern railway line

connects the cities Ljusdal with

Bollnäs (74 km) and the southern

Ludvika with Falun (68 km).


Four types of structures with present grass biotopes were

used to categorize the investigated sites: railway bridges over

water, railway bridges over roads or other dry areas, level

crossings and other structures (Table 1). The other structures

include a variety of sites such as substations, bicycle level

crossings, service roads and other structures that have

grassland vegetation that is managed on a regular basis.

Botanical and Zoological Surveys

The botanical transect was performed by walking slowly over

the relevant grassland area at each site. The purpose was to

1, identify red-listed species and 2, perform a quantitate

measure of the so called substrate plant species - those that produce pollen, nectar or being particularly important as a

substrate for other organisms. The zoological transect also included a slow walk through the area and focused on a

quality and quantitate measure of the fauna. The botanical and zoological walks were usually performed within 2 h in

the field. The coloured pant traps (15x20x10 cm) (Figure 3) were filled with propylene glycol. The traps worked

continuously throughout the season by mid-May till early August and were emptied every 4th week. A full description of

each study site is presented on Stenmark & Larsson (2011).

Abiotic Structures

Presence of sand was measured both in the field and by the earth maps delivered by the Geological Survey of Sweden.

A description of how the sand was measured is included in Stenmark & Larsson (2011). During earlier surveys (Larsson

& Knöppel 2009, Larsson 2010) a number of important abiotic and biotic factors have been identified and included in

the field protocols. An abiotic factor quantifies certain structures on the site, e.g. number of sandy slopes, and biotic

factors measure the substrate, e.g. flower density. This list of factors was used in this field survey. In Stenmark &

Larsson (2011) this list is presented with definitions of each factor.

Statistical Analyses

ANOVA, regressions and correlations were used to find evidence of how abiotic and biotic structures influence the

biological diversity.

Ecological Presentation of the Study Groups

Vascular Plants (Tracheophyta)

In Sweden there are 2,200 species of vascular plants (Gärdenfors 2010). Of these, 346 species are red-listed

(Gärdenfors 2010) and 212 of the red-listed species associated with urban habitats or agricultural landscapes. The

vascular plants are the backbone of the ecosystems that include anthropogenic environments. A majority of the

vascular plants require pollination for seeds to germinate and thus form new plants. Some plants, including conifers

and grasses are pollinated by wind. The largest group of vascular

plants have, instead of relying on the wind allied with animals to

transfer pollen from one flower to another. The most common

type of animal pollination is with insects and in particular bees,

butterflies, beetles and flies. Sometimes the pollination system

specializes so that the flowers must be visited by a particular

group of species or by a specific species of an insect. In such

cases, the plant's survival totally depends on the particular

insect's presence. However, most plants are generalists and are

thus dependent on a rich and diverse insect fauna and can easily

handle the loss of one or a few pollinator species. The vascular

plants constitute an important substrate for plant-eating

caterpillars of butterflies and beetles. Different species of insects

eat different parts: roots, stems, leaves, buds or seeds. The

homopterans, have taken the habit of sucking sap from stems

and leaves.

Table 1. In total 40 structures were investigated.

Number of structures per category.

Railway line structure Ljusdal-

Bollnäs

Ludvika-

Falun

Bridge over water 5 5

Bridge over road 5 5

Level crossing 5 5

Other structures 5 5

Figure 3. Insect trap with windows. On

each site 3 colour traps (white, blue and

yellow) were used throughout the season.


Lepidopterans (Lepidoptera)

In Sweden there are 2,792 species of butterflies (Faunistica 2010). Of these, 487 species are red-listed (Gärdenfors

2010) and 298 of these are associated with urban habitats or agricultural landscapes. The wide variety of species is

among the nocturnal groups of butterflies. Butterfly caterpillars feed on leaves or live in the trunk of herbs or woody

plants. Many butterfly species are completely dependent on one or a few plant species during the larval stage. Adult

butterflies are generally not linked to any particular plant, but can suck nectar from a variety of species.

Aculeate Wasps (Hymenoptera: Aculeata)

In Sweden there are 830 species of aculeate wasps (Faunistica 2010). Of these, 126 species are red-listed

(Gärdenfors 2010) and 98 of these are associated with urban habitats or agricultural landscapes. Among aculeate

wasps the most species are predators (62 %) and hunt prey like spiders, flies, beetles, or bees as food for their larvae.

The other species (wild bees) collect pollen and nectar for their larvae. Wild bees are important pollinators because

they regularly visit flowers for pollen. Many species are also linked to a particular host species which they must have in

its flight range to feed their larvae. Aculeate wasps form large communities of workers or live solitary as most other

insect taxa.

Beetles (Coleoptera)

In Sweden there are 4,400 species of beetles (Gärdenfors 2010). Of these, 862 species are red-listed (Gärdenfors

2010) and 330 of these are associated with urban habitats or agricultural landscapes. There is a range of feeding

strategies among beetles. E.g. leaf beetles, longhorn beetles and weevils are often specialized and feed only on plant

parts from a particular plant species. Some of these host plants are linked to the cultivated landscape, while a large

proportion belongs to the forest landscape. Other beetle families feed their larvae with insects or a mixture of plant

parts and insects.

Homopterans (Homoptera: Auchenorrhyncha)

In Sweden there are 448 species of auchenorrhynchaen homopterans (Faunistica 2010). Of these, 20 species are red-

listed (Gärdenfors 2010) and 14 of these are associated with urban habitats or agricultural landscapes. Homopterans

suck sap from plants and remarkably often the species are specialized to a particular host plants. The strong host plant

association makes homopterans a good indicator group on nature values. Homopterans are also an important

substrate for a couple of predator aculeate wasps that are specialized on foraging on these taxa.

RESULTS

In total, 21,600 insect specimens were collected and determined to species. Ca. 1,000 observations of vascular plants

were made. Abiotic and biotic structures were measured in 40 sites and summarized in tables (Stenmark & Larsson

2011).

Sand along the lines

The presence of sand was registered both in the field by visual survey, but also by using the earth map (1:50 000). The

visual survey did not take into account whether the sand was transported to the site during construction work or was

naturally deposited. The study showed that the sites along the route Ljusdal-Bollnäs was more sandy than those along

the route Ludvika-Falun. The presence of sand measured in the field and registered by the soil map did not coincide

(Stenmark & Larsson 2011).

Red-listed species

During the survey eight red-listed species were recorded (Table 2). Each of these species ecology and relevance for

railway ecosystems are discussed in Stenmark & Larsson (2011).


Table 2. The red-listed species (Gärdenfors 2010) that were found during the surveys along the rail

lines in 2010. The IUCN red-list categories Near threatened (NT) and Vulnerable (VU) were relevant.

Coordinates are given according to RT90.

Species IUCN Family Structure Type RN1 RN2

Andrena argentata NT Andrenidae Other Structure 1468209 6682902

Ceutorhynchus pleurostigma VU Curculionidae Level Crossing 1532402 6812195

Chrysolina graminis VU Chrysomelidae Bridge over Road 1531022 6815751

Dasypoda hirtipes NT Melittidae Bridge over Road 1480492 6703862

Dufourea dentiventris NT Halictidae Level Crossing 1532402 6812195

Lordithon pulchellus NT Staphylinidae Bridge over Water 1531076 6808586

Lordithon pulchellus NT Staphylinidae Bridge over Water 1531076 6808586

Margarinotus purpurascens NT Histeridae Other Structure 1468209 6682902

Margarinotus purpurascens NT Histeridae Bridge over Road 1480492 6703862

Margarinotus purpurascens NT Histeridae Bridge over Road 1480492 6703862



Tiphia minuta NT Tiphidae Level Crossing 1532402 6812195

Botany

During the survey we recorded 85 species of vascular plants. The most abundant nectar and pollen plants were

Lathyrus pratensis (registered on 32 railway sites), Galium alba (30 sites), Vicia spp. (30 sites), Trifolium spp. (29 sites)

and Leucanthemum vulgare (28 sites). There were clear differences in the amount of nectar and pollen plants from

structure types. For example, the average number of flower nectar and pollen plants of railway sites in the category of

bridge over water was far lower than level crossings (335 vs. 632) (Tables 3). The number of vascular plant species (the

number of nectar and pollen plant species and rare species pooled) was not different either between different types of

structures between the two sections (Ljusdal-Bollnäs vs. Ludvika-Falun).

Table 3. The number of investigated sites in each category, the average number of species of the

five focus groups, and number of flowering individuals of substrate plants (Sub. Individ.) and the

area of these (Sub. Area) in quadratic meters.

Structure Type Number Plants Leps Wasps Beetles Homopt Sub. Individ. Sub. Area

Other Structures 10 12 0 17 69 3 543 30

Ljusdal-Bollnäs 5 13 0 20 75 2 204 19

Ludvika-Falun 5 10 0 15 63 3 881 41

Bridge over Water 10 13 0 14 61 2 335 17

Ljusdal-Bollnäs 5 12 1 17 65 1 315 15

Ludvika-Falun 5 13 0 10 56 2 355 18

Bridge over Road 10 13 0 18 70 3 771 15

Ljusdal-Bollnäs 5 14 0 13 77 5 308 20

Ludvika-Falun 5 12 0 19 63 2 988 12

Level Crossing 10 16 0 19 69 2 632 30

Ljusdal-Bollnäs 5 17 1 20 68 2 527 25

Ludvika-Falun 5 16 0 18 71 1 737 34

All 40 13 0 17 67 2 539 23

Ljusdal-Bollnäs 20 14 0 17 71 3 339 19

Ludvika-Falun 20 13 0 16 63 2 740 26


Zoology

The material from the insect traps, and by additional field observations, were found to contain six species of butterflies,

151 species of aculeate wasps, 524 species of beetles and 22 species of homopterans (Table 4). On average there

were 0.3 species of butterflies, 17 species of aculeate wasps, 67 species of beetles and 2.4 species of homopterans

on a railway structure (N = 40).

Table 4. The number of red-listed species and the total number of species in the focus groups that

were found on the 40 railway sites. For explanation of the IUCN red-list categories NT, DD, VU, EN

and CR please visit www.artdata.slu.se.

Focus Groups NT DD VU EN CR Non-listed Total

Vascular Plants 85 85

Lepidoptera 6 6

Aculeate Wasps 3 148 151

Beetles 2 2 520 524

Homopterans 22 22

Total Species 5 0 2 0 0 781 788

The number of species between various railway sites varied moderately and the maximum recorded number of species

per structure reached 2, 36, 106 and 8 for the four focus groups. For all the focus groups we found a high proportion of

the species on only one or two railway sites (Table 5). Only vascular plants tended to have a high proportion of species

with a distribution on the majority of the sites (Table 5).

Table 5. The total number of species within each focus group from all 40 railway sites. Species

occurring on only one or two railway sites (1-2 items) and those occurring on more than 20 sites

are presented separately.

Focus Groups No. species <3 sites (%) >20 sites (%)

Vascular Plants 85 42 (49 %) 8 (9 %)

Lepidoptera 6 4 (67 %) 0 (0 %)

Aculeate Wasps 158 90 (57 %) 3 (2 %)

Beetles 345 206 (60 %) 17 (5 %)

Homopterans 22 13 (59 %) 0 (0 %)

Ecological Groups Important to the Railway Sites

More species of specialists in an ecosystem indicates frequent ecological networks and high nature conservation

values. In this work we recorded 92 species with a distinct ecological specialization. These species are clearly linked to

dry habitats and the majority tend to be favoured by sand. These specialized species are generally uncommon, in some

cases endangered and occurs with low population density. These species were distributed among the focus groups as

follows: aculeate wasps 56 species, 21 species of beetles and homopterans 15 species. In the total material the

specialized species accounted for 14 % of the observations made. These specialists were found on each railway site

but in different amount and species composition. We found that there are certain trends among the specialized species

– and to illustrate that we categorized the specialized species into ecological groups. For example, the species of

aculeate wasps that collect pollen only from bluebells are specialists. Likewise, the species of beetles that eat plant

parts or lay eggs only in bluebell flowers are similarly specialized and included in the same ecological group –

Campanulaceae (bluebells). The 14 most important ecological groups were introduced (Stenmark & Larsson 2011).

Generalists are, unlike specialists, will find their food among organisms that do not constitute a special group.


Ecological Groups Controlled by the Sand Supply

The number of specialist species increases with the availability of

sand. The lower category of sand presence measured in the field

(low: <10% cover of sand on the site) yielded a lower number of

specialized species compared to the other categories (intermediate

and high) (ANOVA, F = 6.21, P = 0.005).

The Area of the Railway Sites

The area of the railway sites were on average 1,684 m2, it varied

between 410 and 9,020 m2. The area of the railway sites did not

differ between the different structure types (ANOVA, F = 0.49, P =

0.78), but the category of other structures tended to be larger and

even more varied. The area of the railway sites did not explain

species richness of butterflies, aculeate wasps, beetles or

homopterans, but an increasing area could be linked to an increased

quantity of substrate plants (correlations).

Abiotic Factors

The four different structure types tended to be statistically different with respect to the abiotic factors (ANOVA, F = 2.0,

P = 0.132). The categories of level crossings and bridges over roads included worse abiotic conditions compared to

other structures or bridges over water. The aculeate wasp fauna tended to be richer where the vegetation height was

lower on a railway site (regression, P <0.01). The beetle fauna tended to be represented by more species on the railway

site had more dense shrubbery (regression, P <0.01). The homopterans tended to be positively affected by the

availability of willows (regression, P <0.01).

DISCUSSION

The results indicate that the flora and fauna on the railway line sites are different from the typical railway flora and

fauna which is documented from the station areas. The sites along the lines house a surprisingly diverse and rich herb

and shrub flora, but are often small in area and the sites are often isolated from other grasslands. Unlike railway

stations, the sites along the lines include a great variety of biotopes.

The main conclusion from this work on grassland conservation along railway lines is that the natural value of an

individual grassland patch depends on both the near zone and landscape. The importance of the near zone a grassland

patch along a railway line occupies a small area (from 50 m2 to 1.5 ha). Therefore, these patches, if they are isolated

from other grasslands, have little opportunity to develop a habitat occupied by a wide range of grassland species. The

reason for this is that for most species do not reach the threshold of the substrate. As documented in this study, these

small sites have a higher tendency to develop a generalist fauna that is not dependent on any particular substrate. The

presence of specialized species and their respective ecological groups seem to be favoured by larger area of the patch

itself but also by a high grassland density in the surroundings.

The railway lines are visited by a great variety of insect species. During the survey we found more species of beetles,

compared with previous studies using the same method in railway stations (Larsson & Knöppel 2009). Studies on

roadside flora have shown that sites located in open areas (farmland, urban areas) have higher species numbers

compared with sites surrounded by forest (Tikka et al. 2000). But, contrary this, Runesson (2009) found that shady

areas along roadsides near forests generate more species of vascular plants. Probably species richness must be

broken down into smaller groups to be analysed as an effect of the surrounding neighbourhood. As an example, during

the survey in the present study, wood-nesting aculeate wasps tended to have higher species numbers at sites with

more shrubs. However, when analysing aculeate wasps that whole group there were no differences at all, because the

many species of ground nesting species wiped out the relationship.

Figure 4. A number of insects are

specialized on collecting pollen from

willows (Salix). These specialists are rarer

and are affected to a greater extent by

drastic changes in the landscape if

compared to generalist species.


Table 6. The four types of railway line structures and their history, present and potential value.

Structure History Present Value Future Value

Bridge over

water

Usually on sites where

herb- and shrublands

have long been

established.

Water creates an additional vale.

Slopes that increase diversity are

common. Managed by sporadic

cutting.

High. The water access is important. A

well planned management regime has

the capacity to increase the diversity in

all groups.

Bridge over

road

Limited number. Usually with large slopes. Creates a

base for dry meadow flora and

fauna. Managed by sporadic

cutting, often allows low shrubs.

High. The structure type increases in

number. Combination of road verge and

railway flora and fauna give

opportunities for co-planning.

Level

crossing

High diversity when

unpaved roads

dominated

Often lack slopes. Flower rich

thanks to road verge vegetation.

Managed by mowing and Roundup.

Low. Decreasing importance. Often

small areas. Difficult to come up with a

permanent vegetation management

plan due to small patches and

fluctuating needs.

Other

Structures

Often on sites

previously not

managed.

Small areas. Managed by mowing

or cutting.

Low. Small areas are difficult to use for

nature conservation purposes as

number of grassland species is low and

fluctuating.

Are railway sites objects of grassland species metapopulations or do they constitute an ecological trap? All grasslands

depend on the landscape at a regional level. The larger the grassland, the more self-sustaining, it can be. This means

that a broad and varied flora and fauna can be maintained despite little exchange with other populations. There are

many examples of large grasslands, which although they are separated from similar environments with hundreds of

kilometres still maintain a high biodiversity because there are a large variety of structures and substrates within the

grassland. However, this becomes increasingly difficult the less a grassland patch is. The grassland patches along

railway lines are in this context to be regarded as small or very small. It is therefore natural that most grassland is largely

a product of the surrounding landscape and we can talk about the following processes influencing the railway sites:

The exchange of individuals with surrounding grasslands (metapopulation)

One-way import of organisms from other grasslands (ecological trap)

The first process describes how small grassland patches can be part of a network of grasslands. Thanks to the network

of grasslands can be a number of species established in the area, even if individual grassland is not large enough to

house any species. This network of small populations is called a metapopulation (Fahrig 2003). The second process is

based on the existence of one or more major grassland area in the region that repeatedly colonizes the smaller site. In

the latter case one can consider the railway site a dead end: the site gets colonized by new plants and animals but

those vanish after one or two seasons because the conditions are missing. In this latter case is the railway grassland

patch diversity entirely dependent on the constant flow of individuals from surrounding habitats. This phenomenon is

called ecological traps (Battin 2004). In transport grasslands a possible additional ecological trap might be the

conditions created by the traffic. Trains and other vehicles constantly reduce insect populations by hitting individuals.

However, this effect is probably of minor importance – only a small proportion of species have a tendency to frequently

use the dangerous air space above the rails, over the asphalt or above the runway. When making decisions about

conservation efforts in these environments, it is necessary to sort out the degree to which the area is included in

metapopulations and in ecological traps.

The maintenance of grasslands along railway lines is complex due to the variety of ecological conditions. The four

structure types (bridge over water, bridge over roads, level crossings and other structures) differed significantly in terms

of conservation value (Table 6). In addition, two similar grassland patches can play completely different roles in the

landscape. One patch may not have exchange with other grasslands and, therefore, contain few grassland species, but

may instead be positive for biodiversity in other terms than grassland nature value, such as wetlands and forest. From

a nature conservation point of view, the work has to be done on both a local and a regional scale, both with the overall

goal to increase the biological grassland diversity. The local method of management of the railway line grasslands

should have the goal to develop standard vegetation management methods. The regional approach should take into

account the landscape surrounding the railway grassland sites. One way to work on a regional scale is to prioritize

different nature values and thereby focus on regions with high potential for nature values of dry grassland habitats.


ACKNOWLEDGEMENTS

The Swedish Transport Administration supported this study and gave helpful advices through field work and on earlier

versions of the manuscript.

BIOGRAPHICAL SKETCH

Magnus Stenmark defended his doctoral thesis in 2006 at Uppsala University. The thesis theme was on native bees

and on nature conservation methods using bees as indicators of valuable ecosystems. Since 2006 Magnus has been

working with practical conservation measures at a Swedish County Administration. Nature conservation information

and educational questions to farmers were the main tasks at a position in the Swedish Agriculture Board. Today,

Magnus has developed an own company providing expert issues in the field of nature conservation. The main

customers are national and regional governmental structures and companies in the area of wind power, power lines

and quarries.

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ASSEMBLAGE STRUCTURE OF PLANT COMMUNITIES ALONG THE ROAD CORRIDOR:

ROCK AND SCREE SLOPES – PLANTING VERSUS NATURAL RECOLONIZATION

Rosalyn Thompson (+353 (0) 21 421 1944, [email protected])1,2

Lisa Dolan (+353 21 421 1944, [email protected])1,2

Prof. Mark Emmerson (+44 (0)28 9097 2912, [email protected])1,2,4*

Dr. Jens Dauber (+49 (0)531 596 2586, [email protected])3,5*

Dr. Jane Stout (+353 (0)1 896 3761, [email protected])3

Dr. David Bourke (Tel +353 (0)1 896 3746, [email protected])3

Dr. Pádraig Whelan (Tel: + 353 (0)21 490 4560, [email protected])1,2

1Environmental Research Institute, University College Cork, Cork, Ireland 2 School of Biological, Earth and Environmental Sciences, University College Cork, Cork, Ireland 3 School of Natural Sciences, Trinity College, Dublin 2, Ireland 4*Current address: School of Biological Sciences, Queen’s University, Belfast 5 *Current address: Institute of Biodiversity, Johann Heinrich von Thünen-Institute (vTI), 38116

Braunschweig, Germany

ABSTRACT

Road verges may perform an important function in the preservation of native floral diversity. This function may be

enhanced or diminished according to the landscape treatment which is chosen. Since 2006 a new guideline document

published by the National Roads Authority in Ireland has incorporated an ecological landscape design approach to such

landscaping. This includes a move away from horticultural practices to one which advocates a more sustainable

method. To test whether these guidelines were fulfilling their remit, sites were examined along a 300km primary route

in the south of Ireland. By comparing pre- and post-guideline sites an assessment was made whether stable plant

communities were developing and the nature of their species richness. There appeared to be little overall difference in

the outcome of the developing plant communities, whichever treatment was used. This has important implications in

terms of financial cost and the ultimate environmental sustainability of the landscape treatment used.

INTRODUCTION

The ecological impacts of road construction are well documented and include those visited upon the plant communities

which existed prior to the construction of the route corridor, along the ecotone or interface between the road corridor

and in the adjacent landscape (e.g. Spellerberg, 1998). Apart from the direct impacts on plant communities - i.e.

habitat loss and disturbance of soil systems through the construction of the road corridor - there are also indirect

impacts relating to the transportation and introduction of non-native invasive species. These may arrive through their

deliberate establishment through planting schemes or be accidentally introduced on construction-related and daily

traffic e.g. on tyres (Wace, 1977) and through wind dispersal (Wilcox, 1989). Native species may also have the

opportunity to flourish outside of their normal range e.g. halophytes growing inland, facilitated by the use of de-icing

agents (Scott and Davidson, 1982). Air-borne pollution from exhaust emissions can also alter growth or otherwise put

stress on plants (Angold, 1997).Maintenance activities of both the carriageway itself and of the vegetation immediately

adjacent to the carriageway can have significant impacts on adjacent plant communities (Lugo and Gucinski, 2000).

Ireland has recently undergone an extensive road building programme. Between 2002 and 2007 the national road

network increased substantially: under the Transport 21 programme, 1200km of roads are being developed to dual

carriageway or motorway standard (NRA, 2007; NDP, 2007). Much of this construction has crossed agricultural

landscapes which varied in intensity of management (NDP 2007, 2010). In Ireland, as elsewhere, agriculture is set to

continue along a path of intensification (Boyle, 2009). The potential exists for roads in more intensive agricultural

landscapes to provide not only a refuge for native flora (Perring, 1969), but also a means for the dispersal of certain

species (Tikka et al., 2001).

For the most part roads cut through soil slopes creating soil cuttings, and in undulating landscapes, soil embankments

are also constructed, which generally provide a basis for the establishment of grassland and woodland through planting

or natural recolonization. However, on occasions, roads also cut through gravels, scree and parent bedrock creating

rock-face cuttings or scree slopes. Published research concerning rocks and plant communities in Ireland tends to

centre around either designated conservation areas dominated by exposed bedrock with a high species-diversity i.e.

the Burren in the west of Ireland (e.g. Jeffrey, 2003) or rocky coastal habitats such as sea cliff faces (e.g. Cooper,









1997). Research elsewhere which examines such communities, post-human activity, concentrates on disused quarries

(e.g. Jefferson and Usher, 1989) or spoil from mining (e.g. Fitter and Bradshaw, 1974).

In 2006, Ireland’s National Roads Authority (NRA) published a guideline document on the landscaping of new national

road schemes (NRA, 2006). This ecological landscape design (ELD) approach (Dolan, 2004) provided a strategy to

redress some of the negative impacts of roads on flora and fauna and potentially improve connectivity in certain

intensively managed landscapes. It also advocated a move away from a high input regime stemming from an

agricultural/ horticultural approach (e.g. the creation of fertile conditions suitable for urban parkland style planting

schemes which can require a certain degree of management), to a regime that develops into self-sustaining habitats

which require minimum management. Previous planting schemes were not only costly to implement but have, in the

past, incorporated a significant proportion of non-native species (Dolan et al., 2009). The new guideline document

directed that the design incorporate and enhance existing native plant communities and also addresses arising issues

of fragmentation (Dolan, 2004). The opportunity now presents itself to examine the species richness of the establishing

plant communities which were established in line with the 2006 landscaping guidelines in comparison with roadside

landscapes which were landscaped prior to the introduction of the2006 landscaping guidelines.

For the purposes of this paper all sites created following these 2006 guidelines shall be deemed as being ‘post 2006-

guidelines’ and referred to as natural recolonization (NR) sites. Those sites landscaped in the pre-guidelines manner

are henceforth referred to as ‘planted’ (PL) sites. It should be borne in mind that PL sites, although planted do not

remain exclusively so and are also open to colonization by arriving propagules. In studying these sites an assessment

may be made as to whether the NR sites are creating the desired results.

METHODOLOGY

A 306 km east to west transect of the island of Ireland along the national road network - i.e. on the N25 and the N22

National Primary Route - was surveyed between the extremities of Rosslare, Co. Wexford (51º14’58.35 N, 6º20’36.92

W - in the east) and Tralee, Co. Kerry (52º15’51.46 N, 9º40’28.40 W - in the west). The sites were of a rock or scree

base and had a slope 1:2. Furthermore, sites with a southerly aspect were selected to eliminate the effects of aspect

on species richness.

16 paired sites were surveyed (Table 1). Each pair consisted of 1 x NR and 1 x PL site which were similar both in age

and geographical location so as to avoid temporal or spatial confounding effects (Figure 1).

The above-ground plant community was surveyed in May and June of 2009. At each site two 2m x 2m quadrats were

sampled 10m apart on the rock/scree faces within the centre of the face to avoid edge effects from the adjacent

habitat and away from the immediate road verge (located 1-3m from the pavement). A total of 64 quadrats were

surveyed, recording species on a visually estimated percentage cover basis. Slope, aspect and the presence of all

canopies were also recorded.

In 2010, the below-ground plant community was studied by gathering soil samples and undertaking a seed bank

analysis. This was done the following year in order to incorporate the seeds generated by the plants surveyed in 2009.

Soil was collected between April and June using a corer 6cm wide and to a depth of approximately 10cm. 12 cores

were taken at 1m intervals along a transect placed in the centre of the rock/scree face and parallel to the road

pavement. The transect centred on, and bisected, the original above-ground plant quadrats. For each site, the collected

soil was bulked together and brought back to the laboratory. The soil was then spread thinly (3 to 5mm deep) on beds

of vermiculite in half standard-size seed trays (154 x 205 x 52mm). These were placed outdoors and covered in

horticultural fleece to simulate natural environmental conditions. The fleece covering was employed to prevent seed

establishment in the trays from the surrounding environs. To prevent desiccation, the trays were kept watered and, as

seedlings emerged, they were identified, recorded and removed, or potted on until their identity could be established.

Species nomenclature follows Stace (2010); in addition, references to plant species in the Irish context use Webb et al.,

(1996) and Reynolds (2002).

Data analysis was undertaken using the R 2.8.1 (2008) statistical package. The Kolmogorov-Smirnov test was used to

establish the distribution of the data. Analysis was then undertaken with a paired t-test or Wilcoxon rank sum

distribution test. Sorensen’s Index (β-diversity) was used to calculate, firstly, the similarity of the two quadrats at each

site; and secondly, the similarity between PL and NR in site pairs 1 to 8. The species richness at NR sites as a function

of PL sites was also calculated to assess the relative performance within each pair. The rate of alien invasive species

richness was calculated as the number of alien invasive species recorded in the above-ground communities per

treatment divided by the number of sites in that treatment.


Table 1: Rock/Scree Site Details.

Pair County Lat/Long. Treatment

1 Wexford 52.38046 / 6.86523 PL

52.34809 / 6.61736 NR

2 Wexford 52.38061 / 6.86596 PL

52.3871 / 6.90742 NR

3 Kilkenny 52.3731 / 6.99737 PL

52.30503 / 7.05117 NR

4 Waterford 53.132865 / 7.074819 PL

52.24014 / 7.16460 NR

5 Waterford 52.06021 / 7.66716 PL

52.022869 / 7.393333 NR

6 Cork/Kerry 51.98078 / 9.26069 PL

51.90556 / 8.99386 NR

7 Kerry 51.98103 / 9.26275 PL

51.98774 / 9.2947 NR

8 Kerry 52.26798 / 9.42314 PL

52.12544 / 9.53441 NR

N.B. Some of these roadside landscapes were actually landscaped prior to the publication of the 2006 guidelines,

but following the ecological principles of the post 2006 guidelines. These have been included as NR.

Figure 1: Geographical location of the 8 pairs of sites along the N25 – N22 primary route.

RESULTS

Percentage Cover

The variation in mean percentage cover ranged from 42.5 to 131% in PL and 7.5% to 133% in NR sites (Figure 2).

Where the total exceeded 100%, this reflects complexity in the vegetation structure. The overall mean percentage cover

per treatment was: PL, 88%; NR, 85.5%. The overall median was: PL, 90.25%; NR, 105.75%. In five of the pairs, the

NR site had the higher mean per cent cover. In the three cases where PL had the greater mean cover, the difference


between the PL and NR was noteworthy in that it was greater than 35%. The greatest difference (pair 4) had an 82%

difference; pairs 1 and 7 had a 50% and 37.5% difference, respectively. Pair 3 had the largest difference where a NR

site had the highest per cent cover (67% greater).

Figure 2: the mean % cover of plants found at pre-2006 (PL) and post-2006 (NR) sites.

Species Data

Above-ground Plant Communities

93 species of higher plants and ferns were found in 64 plant quadrats on the rock/scree slopes in the roadside habitat:

34 present only in PL sites; 21 present only in NR sites; 35 common to both PL and NR sites. Of these: 87 were native,

4 were non-native, and 2 were undetermined beyond genus level. The non-native species were: Acer pseudoplatanus

(Sycamore), Aegopodium podagraria (Ground Elder), Cotoneaster sp., and Crocosmia x crocosmiiflora (Montbretia). A.

podagraria has been apparent in the Irish landscape since the mid-19th century and is widespread and frequent

(Reynolds, 2002). It is not currently seen as a threat in terms of displacement or degradation. The other three species

are classified as potential threats by Invasive Species Ireland - a joint British-Irish governmental initiative for the island

of Ireland (Invasive Species Ireland, 2011). The rate of non-native invasive species richness was 0.125 per m2 for PL

sites and 0.5 per m2 for NR.

Below-ground Plant Communities

When the seed bank data were added, an additional 17 species which did not appear in the above-ground plant

community were recorded. Of these: 4 were present only in PL sites; 11 species only in NR; 2 occurring in both. Four of

the additional species were non-native: Epilobium brunnescens, E. ciliatum, E. roseum, and Veronica persica. None of

the aforementioned appear on lists of species which are considered problematic, or potentially so.

Comparison of Above- and Below-ground Plant Communities

The commonest occurring species for both above and below-ground plant communities are listed in Table 2. Of these,

three grass species overlapped (Agrostis capillaris, Agrostis stolonifera and Holcus lanatus), and three forbs

overlapped (Geranium robertianum, Rubus fruticosus agg. and Ulex europaeus) by appearing in both above- and below-

ground communities. The Epilobium spp. were not identifiable at the time of the field surveys as the plants were

immature; however, two species (E. ciliatum and E. obscurum) germinated in many of the seed trays. All species listed

were common to both PL and NR sites with the exception of Holcus lanatus which only germinated in trays from PL

treatments. Full species list: Appendix A.

0

20

40

60

80

100

120

140

160

180

pair 1 pair 2 pair 3 pair 4 pair 5 pair 6 pair 7 pair 8

Sites

Mean

% C

over

Planted

NR


Table 2: Species Most Commonly Occurring in (a) Above-ground Communities or (b) Below-ground Communities.

(a) Above-ground plant species - recorded in at least 25% Quadrats (8)

Monocotyledons Qs PL NR Dicotyledons Qs PL NR

Agrostis capillaris 8 X X Epilobium sp* 8 X X

Agrostis stolonifera 8 X X Geranium robertianum 14 X X

Arrhenatherum elatius 12 X X Rubus fruticosus agg. 20 X X

Festuca rubra 9 X X Hedera sp. 9 X X

Holcus lanatus 10 X X Hypochaeris radicata 8 X X

Ulex europaeus 10 X X

(b) Below-ground plant species recorded in the seed banks of at least 25% Sites

Monocotyledons Sites PL NR Dicotyledons Sites PL NR

Agrostis capillaris 7 X X Cardamine flexuosa 6 X X

Agrostis stolonifera 5 X X Cerastium fontanum 4 X X

Anthoxanthum odoratum 4 X X Epilobium ciliatum 6 X X

Holcus lanatus 4 X Epilobium obscurum 5 X X

Juncus effusus 8 X X Geranium robertianum 7 X X

Leucanthemum vulgare 4 X X

Rubus fruticosus agg. 6 X X

Senecio jacobaea 4 X X

Ulex europaeus 5 X X

Plant Community Stability

A paired t-test was carried out for species richness of the quadrats at each site which revealed no significant difference at

any site (p-values ranged from 0.23 to 0.99). Sorensen’s Index for β-diversity was then applied and used as an indicator of

plant community stability: the greater the homogeneity, the greater the stability – where 0 is completely dissimilar and 1 is

identical. The most heterogeneous site was a PL site with a score of 0.29; the most homogenous one was an NR site with

a similarity index of 0.77. There was an overall pattern in terms of paired sites obtaining scores which ranked them

adjacently (i.e. pairs: 8, 6, 4, 2, 1.) Otherwise, a greater number of NR treatments (3) than PL (2) attained a score less

than 0.5 indicating a lower level of similarity between the quadrats at those sites. At the other end of the scale, nine of the

16 sites were more homogenous than heterogeneous (Sorenson β index > 5.) Five of these sites were NR sites (Table 3).

Table 3: Sorensen β-Diversity score for each site.

Pair Treatment Score

7 PL 0.286

3 NR 0.333

8 NR 0.375

8 PL 0.385

6 NR 0.4

6 PL 0.5

4 PL 0.5

4 NR 0.546

5 PL 0.571

7 NR 0.571

3 PL 0.593

5 NR 0.625

2 PL 0.632

2 NR 0.667

1 PL 0.696

1 NR 0.769


Species Richness

Mean Species Richness

Using the mean number of species per site, a higher species richness was found in PL sites than in NR sites. Not only was

the mean number of species per site lower in the NR sites, the range of species richness was much narrower. The mean

species richness for PL sites was 10.1875 (n=8) and 7.0 (n=8) for NR sites. The median values were 10.75 for PL and

6.75 for NR (Figure 3). Three quarters of the PL sites had a species richness mean greater than nine (mean 1st quartile

9.125); whereas three quarters of the NR sites had a mean species richness of nine or under (mean 3rd quartile 9.0).

Figure 3: the mean variance in species richness by treatment using the mean species richness per

site. Min. per treatment: NR = 4.5, PL = 5.5; Mean: NR = 7.0, PL = 10.1875; Median: NR = 6.75, PL =

10.75; Max: NR = 9, PL = 13.5 (where PL = pre-2006 guidelines and NR = post-2006 guidelines).

The median is denoted by a horizontal bar in the respective boxes.

When the sites within each pair are considered, the mean species richness was greater in the PL site than at the NR

site in seven of the eight pairs of sites. The differences range from one (pair 4) to seven7 (pair 3). In pair 6, where NR

has the higher mean species richness, the difference is 3.5 (Figure 4).

Figure 4: the differences in mean species richness by pairs of sites.

a.Planted b.NR

68

10

12

Treatment

Sp

ecie

s r

ich

ne

ss

0

2

4

6

8

10

12

14

16

18

pair 1 pair 2 pair 3 pair 4 pair 5 pair 6 pair 7 pair 8

Sites

Mean

Sp

ecie

s R

ich

ness

Planted

NR


Total Species Richness

When the total species richness at each site was calculated there was an overall increase in species richness of 26%

(for PL sites) and 38% (for NR sites) over the mean species richness values. However, there was considerable variation

between sites (Table 4). In some cases, the difference between the two treatments increased (such as in pairs 1 and

8); however, in pair 3 the difference between mean and total species richness was less marked.

Table 4: The Comparison of Mean and Total Species Richness by Site.

Pair Treatment Mean Total % increase

1 PL 11.5 15 30

NR 7 8 14

2 PL 10 13 30

NR 6.5 8 23

3 PL 13.5 19 41

NR 6.5 15 130

4 PL 6.5 9 39

NR 5.5 8 46

5 PL 10.5 15 43

NR 8.0 11 38

6 PL 5.5 9 64

NR 9 12 33

7 PL 10.5 18 71

NR 8 15 88

8 PL 13 21 62

NR 9 13 44

Comparison of Quadrat Data versus Quadrat and Seed Bank (S.B.) Data

The data for the seed bank analysis was included to assess the species richness of the below-ground plant community and

also analyse the overall change in species richness totals. Due to a storage problem with one soil sample, data from seven

pairs of sites were used and not eight. As the omitted pair’s sites (PL and NR) both had a below average mean species

richness (6.5 and 5.5 respectively), this resulted in a higher species richness for the seven remaining pairs (Table 5).

Table 5: The Differences in the Species Richness by Mean Treatment

using Quadrat (Q) only or Quadrat + S.B. Data.

PL NR

8 pairs Q data 14.63 11.25

7 pairs Q data 15.43 11.71

7 pairs Q data + S.B. 21.43 17.29

NR was also expressed as a function of PL within paired sites in terms of species richness (Table 6). In some pairs (for

example Pairs 1 and 7) there was relatively little change when the species richness of the below ground plant

community is included, whether mean species richness or total species richness is employed. In other cases, there was

a much greater change within each pair, so NR becomes more similar to PL, or alternatively more dissimilar. However,

the overriding feature of these results is that in all but two cases, the NR treatments result in lower species richness

than the PL treatments (whether mean species richness, total species richness or total species richness and below

ground seed bank species are included). The pairs where NR had greater species richness, this was not seen

consistently through all methods of calculation.


Table 6: The variation in species richness at each pair of sites using NR as a function of PL.

Data Used NR as a function of PL

Pair 1

Mean S.R. – Quadrats 0.61

Count S.R.– Quadrats 0.53

Count S.R .- Quadrats + seed bank 0.52

Pair 2



Count S.R.- Quadrats + seed bank 0.73

Pair 3



Count S.R.- Quadrats + seed bank 0.96

Pair 5



Count S.R. - Quadrats + seed bank 1.06

Pair 6



Count S.R .- Quadrats + seed bank 0.79

Pair 7




Pair 8




DISCUSSION

Percentage Cover

It might have been expected that the PL sites would have a greater percentage cover than the NR sites, due to the

planting of trees and shrubs post-construction of the scheme. Furthermore, PL sites are not isolated entities and, as

such, will be open to the same anemochory, zoochory (and even hydrochory) as NR sites. So it follows that, if the overall

mean percentage cover figures are used the planted sites have a marginally greater cover (88%), than the naturally

recolonized sites (85%). However, if the treatments are considered in pairs, then the picture is quite different as NR

sites have the highest mean cover in 5 of the 8 pairs. This would suggest that in terms of percentage cover, plants

which have naturally colonized the rock/scree faces have out-performed their PL counterparts (which are a combination

of planted species plus naturally colonized species). The two locations where this did not occur (pairs 4 and 7) may

have been the result of extreme environmental factors being exerted at the two NR sites: both were located in exposed

situations favouring colonization by stress-tolerant species, and neither had any complex vegetation adjacent. Stress-

tolerant species are frequently slow growers, which could account for the low percentage cover. The former (in pair 4),

had an ecotone boundary with intensively managed agricultural grassland. This was dominated by Lolium perenne

(Perennial Rye-grass) with Agrostis stolonifera (Creeping Bent) at the margin. L. perenne is typical of highly managed

grassland. Part of this high management is the necessity to reseed the species as it does not persist in grasslands –

having a short-lived seed bank and being poor at spreading vegetatively; furthermore it is most associated with level

ground or gentle slopes and water retentive (but not waterlogged) soils (Grime et al., 1988) A. stolonifera, on the other

hand successfully regenerates by seed or vegetatively and is a successful colonizer; however, it is better associated

with fertile habitats and is not stress tolerant (Grime et al., 1988). The two stress-tolerant species which were recorded

here, in the NR site of pair 4, were Hypochaeris radicata and Ulex europaeus (although young plants of the latter

species are not as stress tolerant) (Grime et al., 1988). Therefore, in addition to exposure, the adjacent highly

managed grassland may have had few species capable of withstanding the conditions. The latter NR site (in pair 7)

had an ecotone boundary with a semi-natural habitat which appeared to fall in to Fossitt’s (2000) Irish habitat category


HH3- wet heath. Molinia caerulea (Purple Moor-grass) and the species with which it is associated (Vaccinium myrtillus,

Calluna vulgaris, Erica tetralix and Erica cinerea which were all present in this habitat) lack ruderality as a trait (Grime

et al., 1988). Furthermore, the average soil depth generally found with this community is 15 to 50cm (Fossitt). On an

exposed slope over 45º in inclination (both PL and NR slopes had similar inclinations (≈ 45º) and orientation (PL =

170º, NR = 190º) soil may take some time to build up, hence slowing overall growth. Species that were found at the

NR site of pair 7which are tolerant of stress (usually infertile) conditions included: Agrostis canina, Calluna vulgaris,

Erica tetralix, Hypochaeris radicata, Hypericum pulchrum, Luzula multiflora and Ulex europaeus (Grime et al., 1988).

Plant Community Stability

A greater number of NR sites (five as opposed to four PL sites) were found to be homogenous (Sorenson similarity index

>0.5). This may be the result of the development of a more homogenous plant communities associated with arrival

and colonization of seed through anemochory (as opposed to zoochory); however the differences between the two sites

within each pair are relatively small – given the number of PL and NR sites from any one pair which are adjacent to

each other in Table 3. From a stability of plant community point of view, it could be argued that there is little overall

difference between the two treatments. Therefore in terms of sustainability, NR is preferred to PL in terms of: costs

incurred with PL (creating the soil base on a rock foundation, herbicides, fertilizers and the plants themselves); genetics

(of native and local species reproducing or otherwise hybridizing with imported plants), and biosecurity (inadvertent

importation of alien species which have arrived with foreign plant material or movements of soil).

Species

Overall, 14 more species were recorded in the PL quadrats (69 species) than in the NR ones (56 species). When the

seed bank data were added the difference narrowed to six species (PL = 75, NR = 69). None of those recorded have

protected status or are considered rare or threatened or listed as being less than ‘locally frequent’ according to Webb

et al., (1996) and Seawright (2010). Although 96% of the species found are ‘native’, many grass species are planted as

cultivars within the grass mixes planted on roadside landscapes; furthermore, such mixes are of non-local provenance.

The tree and shrub species, while they are not generally planted as cultivars, are of non-local provenance also; much of

the plant material originating from mainland Europe.

When the below-ground plant community data are added to the above-ground plant data, three interesting species

appear: all of them from the seed banks of NR sites. Firstly, Hypericum humifusum is described as an ‘occasional’

species (by Webb et al., 1996), appearing in peaty or sandy habitats. However, it may be more frequently found than

previously apparent as it has been listed as common on acidic heaths (Seawright, 2010). Secondly, Centaurium

erythraea was recorded in the soil seed bank from Macroom, Co. Cork (NR site, pair 6). Although not uncommon, it is

relatively rare inland (Webb et al., 1996): Macroom is some 35km from the coast. A similar case concerns Daucus

carota, which was recorded in the seed bank from a rock face in Co. Kilkenny: approximately 17km from the coast –

although less than 4km from a tidal river. This last-mentioned is found inland on limestone rock (Webb et al., 1996)

and the site had a pH of 7.17. However, it has also been commonly incorporated in to grass seed mixes utilized on road

schemes (Paul Green, County Recorder for the Botanical Society of the British Isles, pers. comm.). Although this was an

NR site, there were wide verges in the vicinity which had been sown with a standard grass seed mix.

In contrast, the following undesirable agricultural weeds (Teagasc, undated), which are relatively common species, were

recorded in either the above-ground communities or seed banks – Cirsium arvense (Creeping Thistle), Cirsium vulgare

(Spear Thistle), and Senecio jacobaea (Ragwort). These are notifiable weeds under the Noxious Weeds Act 1936

(Teagasc, undated). S. jacobaea was the only species to be recorded in all situations (i.e. in the above-ground plant

communities and seed banks of both PL and NR sites). Overall, there was no pattern to the presence of these species

in either below- or above-ground plant communities. It should be noted that while deemed undesirable to agriculture,

such species may fill a key ecological role in another species’ life-history. For example, S. jacobaea is the main

caterpillar foodplant for the Cinnabar moth Tyria jacobaeae (Butterfly Conservation).

Four non-native species were recorded: Acer pseudoplatanus (Sycamore), Aegopodium podagraria (Ground Elder),

Cotoneaster sp., and Crocosmia x crocosmiiflora (Montbretia). Three of the species recorded in the above-ground plant

communities occurred in the NR sites only: A. podagraria, Cotoneaster sp., and Crocosmia x crocosmiiflora. The latter

two species are of growing concern in Ireland and the U.K. and they have been included in an action plan under a joint

initiative between the National Parks and Wildlife Service (NPWS) in the Irish Republic and Northern Ireland

Environment Agency in the UK. (Invasive Species Ireland, 2011). In Ireland and in the U.K., Crocosmia x crocosmiiflora

spreads mostly vegetatively and only rarely by seed (NNSS, 2011). Therefore, measures which aim to avoid the

importation of soil and/or plant material and which monitor the movement of soil where Crocosmia x crocosmiiflora is

present within a route corridor should reduce opportunities for the invasion of roadsides by this species. Its presence is


therefore unexpected: did it exceptionally arrive by seed, or was there some other unaccounted for (human) activity

such as dumping of garden waste? Although both records were in rural settings, each had gardens within a few

hundred metres.

Cotoneaster, on the other hand, spreads through zoochory as the seeds are contained within red berries eaten by

garden birds. Its many garden ‘virtues’ and its apparent bonus to wildlife meant that it is extolled by professionals

connected with various sectors of the horticulture industry partly for its ability to colonise rocky surfaces with thin soil

covering. Ultimately, its spread may be more difficult to control as the species is capable of establishing in many

habitats including rough ground, banks and walls: particularly in areas where birds are able to perch (Stace, 2010).

The most recorded non-native species from the below ground plant community was Epilobium ciliatum (American Willow-

herb). Whilst not appearing on any known list for undesirable species, its seeds are dispersed by wind, it has naturalized

well in Europe, is the commonest willow-herb in much of lowland Britain, and, in Ireland, is spreading from urban areas,

particularly in the south of the country (Grime et al., 1988; Reynolds, 2002). It also hybridizes with native species such

as E. montanum and E. obscurum, both of which are amongst the commonest of all willow-herb hybrids (Stace, 2010).

Furthermore it occurs in sites with bare soil and high disturbance, and its seed can survive in the seed bank after the

above ground plants have been displaced by other species (Grime et al., 1988). The findings of this research will be

utilized to provide information on its current status in Ireland and may in turn inform treatment or management

strategies in general. From this research, it is apparent that this species has spread across southern Ireland – it having

germinated from seed banks in the road corridor along the entire 300km of road surveyed as part of this study.

Species Richness

With reference to treatment, PL had a higher species richness (mean: 31% higher, median: 37% higher) than NR. The

higher species richness in PL sites may be attributed to the fact that trees, shrubs and grasses were planted, together

with ground preparation (such as the introduction of soil or hydroseeding), use of herbicides and fertilizers involved with

the landscaping, This introduced a higher amount of plant material which was then in turn able to exploit the higher

availability of resources than would otherwise be available on bare rock or scree. However, the greater species richness

at PL sites also means an introduction of cultivars, as opposed to Irish provenance material; this may be to the

detriment of the local gene pool. The further development of these rock face communities will make an interesting

study in the future to determine any reduction in the difference in species richness between the treatments.

Furthermore, is the higher species richness at PL sites at the cost of being appropriate to its location? A sense of place

needs to be considered with landscape schemes. Just because a species is native to Ireland would not automatically

result in there being a source for its propagules in the vicinity of a newly-landscaped rock face or slope. By using

standard seed mixes or planting schemes, species may establish which are untypical of the wider countryside thus

creating a feature which does not blend with its surroundings. Slower to develop NR sites may need time to close the

gap, yet ultimately appear more in character with the wider landscape. Moreover, the presence of fewer competitive

grasses might leave room for a greater number of forbs and less competitive monocotyledons.

Amongst the lowest recorded species richness at sites in either treatment were those belonging to pair 4. In this pair,

both sites (PL and NR) were located on the ring road that circles Waterford city with landscape treatments dating from

2006. They are both almost equal in terms of species richness. This may be due to both the PL and NR sites being

adjacent to highly managed grassland – so that there are fewer species in the adjacent field to act as a potential

source of propagules.

There was only one pair of sites where the NR species richness exceeded that of the PL site, namely in pair 6. Here,

both sites were among the older pairs in terms of length of time since their creation. However, the key difference may

have been the proximity of mature and complex vegetation.

Total Species Richness and Seed Bank

The overall trend in species richness is similar whether mean, total or total + seed bank is used. That is, the PL sites

have a higher species richness than NR sites. However, certain differences do occur within the results depending on

the data included. Taking NR as a function of PL, Pairs 1 and 6 have a declining trend when mean (pair 1 = 0.62; pair

6 = 1.64), total (pair 1 = 0.53; pair 6 = 1.33), and above and below ground plant communities (pair 1 = 0.52; pair 6 =

0.79) are considered in that order. Pair 3, on the other hand indicates that NR is approaching PL, particularly when the

total species or total + seed bank values are used. The increase in pairs 5 and 8 is most noticeable between total

species counts and the addition of the seed bank data. In pair 5 this is particularly noteworthy as the NR site

‘outperforms’ the PL site.


The method employed for data collection can have a bearing on the results. The inclusion of the seed bank meant that

the overall species numbers increased and included the less common species. The numbers of recorded species in this

study might have been even higher had greenhouse or laboratory conditions been employed. However, one of the aims

of the investigation was to reproduce near natural conditions, to see what might have germinated under natural

conditions. Analysis is still ongoing, including that which includes a second visit to each site carried out in the second

half of the summer of 2009. Although such an approach means a significant investment in time and money, it will be

interesting to examine this fuller picture and assess what is lost if one or more of these elements is not undertaken.

It is not clear why the species in the below ground community were not present in the above ground community. It is

possible that they have been there since road construction and never had the stimulus to germinate. It is also possible

that they may never have germinated unless the soil in which they were located experienced disturbance – such as the

act of removing the soil cores for the seed bank trial. Many seeds can survive underground for years. In the case of PL

sites, it is clear that there are several possibilities for non-planted species to establish – e.g. by “piggybacking” on those

species which are to be planted; arriving by anemochory or zoochory and their subsequently becoming buried. However,

it is harder to account for the seed bank at the NR sites. Build-up of litter and soil may be one possibility with trapped

seeds waiting for the appropriate stimulus to germinate.

Preliminary Conclusions

1) Overall, the stability of the plant community at a site seems to be either no different, or slightly greater, in NR

sites than in the case of PL sites. If this is the case, then this suggests that the costs involved in P treatments

may be avoided without compromising the outcome. Of course, the desirability of the species which colonize

the habitats needs to be examined and further study is ongoing as to the relationship of non-desirable species,

such as (alien) invasive species and varying treatments.

2) In terms of percentage cover of species, the picture was quite mixed and may be dependent on a number of

environmental factors as well as the availability of propagules and the vicinity of complex vegetation structure.

3) Species richness overall was higher in PL sites. However, this is to be expected given that the PL treatment

involves importing plant material to the site, in addition to those species which would colonize naturally from

the surrounding area.

4) If NR and PL are producing almost the same results, then NR should be the treatment adopted as it is more

sustainable than PL.

5) Method of data collection may have a bearing on results: the soil seed bank added important data to the

quadrat data.

ACKNOWLEDGEMENTS

This research is funded by the project SIMBIOSYS (2007-B-CD-1-S1) as part of the Science, Technology, Research and

Innovation for the Environment (STRIVE) Programme, financed by the Irish Government under the National

Development Plan 2007–2013, administered on behalf of the Department of the Environment, Heritage and Local

Government by the Irish Environmental Protection Agency (EPA).

I am also grateful for the advice, direction and support of my supervisors Dr Pádraig Whelan (University College Cork)

and Professor Mark Emmerson (Queen’s University Belfast) and researcher Lisa Dolan. Thanks are also extended to

Paul Green (county recorder for Botanical Society of the British Isles) and Máiread Kiely (senior technical officer,

University College Cork).

BIOGRAPHICAL SKETCHES

Rosalyn Thompson is currently a PhD student at University College Cork (UCC). Part of the national EPA-sponsored

SIMBIOSYS project which is investigating sectoral impacts on biodiversity and ecosystem services, including quantifying

impacts of energy crops, road landscaping and aquaculture on Irish ecosystems – set up in 2008 - her focus is on

invasive plant species and invasion resistance. Originally from Caerleon, South Wales (UK), she graduated from Bath

Spa University with an honours degree in Environmental Science in 2008.

Lisa Dolan is a landscape ecologist whose work to date has focussed on road ecosystems and their impacts on

biodiversity and ecosystem services in the agri-environment. Lisa is currently a research assistant in University College

Cork (UCC). She is a member of the national EPA-sponsored SIMBIOSYS project, set up in 2008, which is investigating

sectoral impacts on biodiversity and ecosystem services, including quantifying impacts of energy crops, road

landscaping and aquaculture on Irish ecosystems


Prof. Mark Emmerson graduated from Queen Mary University of London, UK in 1995 with a BSc (Hons) in Marine and

Freshwater Biology. He then moved to the University of Aberdeen in Scotland where he undertook both an MSc in

Marine and Fisheries Science (1996-1997) and a PhD in Zoology (1997-2001). His PhD was focussed on combining

empirical and theoretical approaches to the study of Biodiversity and Ecosystem Functioning. He then moved to the

University of York where he undertook a Post doc focussed on the role of body size in food webs (2001-2003). He was

appointed as a College Lecturer at University College Cork in the Republic of Ireland in 2003. In 2010, he joined the

School of Biological Sciences at Queens as Chair of Biodiversity. Professor Emmerson's research combines theoretical

and empirical approaches in the study of ecological systems. He is the leader of the SIMBIOSYS workpackage

investigating the impacts of energy crops on biodiversity and ecosystem functioning.

Dr Jens Dauber is a landscape ecologist, working at the Federal Research Institute for Rural Areas, Forestry and

Fisheries, Germany (vTI). His main research interest is on the impact of land-use change and climate change on

biodiversity in agricultural landscapes. He studied Biology at the University of Mainz, Germany, and finished with a

Diploma in Biology in 1995. In 1996, he went to the University of Giessen, Germany, to do a PhD on the effects of land-

use change on ant communities within the framework of the project "Land-use Options for Peripheral Regions" (SFB

299). He continued working in Giessen as post-doctoral research fellow in the project "BIOPLEX – Biodiversity and

Landscape Complexity in Agricultural Areas under Global Change", acting as leader of the Landscape Ecology group

within the Department of Animal Ecology. In 2003, he visited the SLU Uppsala, Sweden, for three month to study ant

communities in fragmented semi-natural grasslands. End of 2006 he moved to the University of Leeds, UK, to work as

research fellow in the EU FP6 project ALARM. In May 2008 he took up the position of project manager of SIMBIOSYS at

Trinity College Dublin, Ireland. He is on the editorial board of BioRisk – Biodiversity and Ecosystem Risk Assessment

and handling editor of Biodiversity and Conservation.

Dr Jane Stout is a Senior Lecturer in the School of Natural Sciences. Jane did her BSc in Environmental Sciences

(1995) and PhD in Ecology (1999) both at the University of Southampton, UK. Her PhD investigated the foraging

ecology of bumblebees, focusing on intrinsic and extrinsic influences on behaviour, and how behaviour influenced plant

reproductive success.

Dr Stout went to Trinity College Dublin as an Enterprise Ireland Post-doctoral Fellow in 2001 to research the role of

native pollinators in the spread of invasive plants, and was appointed a Broad Curriculum Lecturer in 2003 and

Lecturer in Botany in 2007 at TCD. Dr Stout continues to use plant-pollinator interactions as a model system, and her

research focuses on investigating anthropogenic impacts on biodiversity and the delivery of ecosystem services. She is

the co-ordinator of the national EPA-sponsored SIMBIOSYS project which is investigating sectoral impacts on

biodiversity and ecosystem services, including quantifying impacts of energy crops, road landscaping and aquaculture

on Irish ecosystems.

Dr David Bourke is currently a Research Fellow in the School of Natural Sciences, Trinity College Dublin, Ireland.

Previously he held a position of postdoctoral researcher jointly hosted by the Applied Ecology Unit in the Centre for

Environmental Science and the Department of Botany at the National University of Ireland – Galway. His current

research interests are focused on the indirect impacts of climate change mitigation measures such as bioenergy crops

and wind farm developments on biodiversity and ecosystem services. He is also working on the direct impacts of

climate change on biodiversity, specifically on current and future distributions of species and habitats of conservation

value. Dr Bourke gained his PhD from the Department of Botany, Trinity College Dublin working on phosphorus

dynamics in grazed grassland ecosystems. Previously, as a research officer with Teagasc (Agriculture and Food

Development Authority in Ireland), he worked on evaluating the environmental effectiveness of agri-environmental

schemes across Europe. He is the current project manager of SIMBIOSYS.

Dr Pádraig Whelan is a lecturer in the School of Biological, Earth and Environmental Sciences in University College

Cork, Ireland, since 1995. He is the leader of a workpackage on the impacts of roads on biodiversity within the national

EPA-sponsored SIMBIOSYS project, set up in 2008, which is investigating sectoral impacts on biodiversity and

ecosystem services, including quantifying impacts of energy crops, road landscaping and aquaculture on Irish

ecosystems. His BSc (1976) and PhD (1986) are from University College Cork. His interests lie in applied biodiversity

conservation in protected areas and in the wider landscape, as well as the biology and management of invasive alien

species. He has carried out research in South America and Europe.


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Appendix A: Plant Species Recorded

Acer campestre Cotoneaster sp. Holcus lanatus Sagina procumbens

Acer pseudoplatanus Crataegus monogyna Hypochaeris radicata Salix aurita

Achillea millefolium Crepis capillaris Hypericum humifusum Salix cinerea

Aegopodium podagraria Crocosmia x crocosmiiflora Hypericum pulchrum Salix cinerea ssp. oleifolia

Agrostis canina Dactylis glomerata Juncus bufonius Salix cinerea x Salix aurita

(= S. multinervis)

Agrostis capillaris Daucus carota Juncus conglomeratus Scirpus setaceus

Agrostis stolonifera Digitalis purpurea Juncus effusus Scrophularia nodosa

Alopecurus pratensis Dryopteris filix-mas Juncus inflexus Senecio jacobaea

Anagallis arvensis Elytrigia repens Lepidium heterophyllum Senecio vulgaris

Angelica sylvestris Epilobium brunnescens Leucanthemum vulgare Sonchus arvensis

Anthoxanthum odoratum Epilobium ciliatum Lolium perenne Sonchus asper

Arrhenatherum elatius Epilobium hirsutum Lonicera periclymenum Sonchus oleraceus

Arum maculatum Epilobium montanum Lotus pedunculatus Spergula arvensis

Asplenium scolopendrium Epilobium obscurum Luzula multiflora Stachys palustris

Athyrium filix-femina Epilobium parviflorum Lythrum salicaria Stellaria holostea

Bellis perennis Epilobium roseum Matteuccia struthiopteris Stellaria media

Betula pubescens Erica cinerea Montia fontana Taraxacum agg.

Brassica rapa Erica tetralix Plantago lanceolata Teucrium scorodonia

Calluna vulgaris Fallopia convolvulus Plantago major Trifolium repens

Cardamine sp. Festuca rubra Poa annua Ulex europaeus

Cardamine flexuosa Festuca vivipara Poa pratensis Urtica dioica

Carex flacca Fraxinus excelsior Poa trivialis Veronica chamaedrys

Carex pendula Galium aparine Polygonum aviculare Veronica persica

Carex rostrata Galium palustre Polystichum setiferum Veronica sepyllifolia

Centaurium erythraea Geranium molle Potentilla erecta Vicia sepium

Cerastium fontanum Geranium robertianum Pteropsida sp. Viola riviniana

Cerastium glomeratum Geum urbanum Ranunculus repens

Circaea lutetiana Glyceria fluitans Rosa rugosa

Cirsium arvense Hedera hibernica Rubus fruticosus agg.

Cirsium palustre Hedera sp. Rubus idaeus

Cirsium vulgare Heracleum sphondylium Rumex acetosa

Convolvulus arvensis Hieracium pilosella Rumex obtusifolius


ECOLOGICAL RESTORATION OF TRANSPORTATION PROJECTS AS A

SUCCESSFUL MITIGATION MEASURE

Sergio López Noriega (52 (55) 55 56 87 27 00, [email protected]), Biologist, CEO, Grupo

Selome S.A. de C.V., Louisiana 104 Col. Nápoles 03810 Mexico

Norma Fernández Buces, PhD Science (52 (55) 55 56 87 27 00, [email protected]), Scientific

Director, Grupo Selome S.A. de C.V., Louisiana 104 Col. Nápoles 03810 Mexico

ABSTRACT

One of the most important environmental impacts caused by roads is the loss of vegetation cover within the right of way

and hillsides. This impact can be successfully restored as long as appropriate timely actions are considered. The area

to be affected should be carefully studied, previous to the construction of the road, in order to identify types of nearby

vegetation and their characteristics. An ecologically based restoration program should be developed, in which all

actions required are pointed out and adequately planned.

Species composition, community structure, tolerances and endangered or protected species should be identified. This

information will be used to build a plant nursery where native species are to be reproduced and grown before their use

in restoring the landscape, jointly with the organic soil removed during construction. These actions need to be

performed under a specific scheme of planting that will allow the reconstruction of a landscape, similar to the affected

one in its original stages.

A successful example of such actions could be the Ecological Restoration held on to mitigate environmental impact of

the Mexico-Tuxpan highway, in the Tejocotal-Nuevo Necaxa section. In this road, built about 6 years ago, an Ecological

Restoration of the original community of cloud forest was done in 2006, following an innovative plantation design and

using native species integrated by endangered rescued plants, as well as seed produced and cuttings from nearby

plants, grown in a nursery specifically build for this project. This type of forest is scarce in our country; therefore, its

restoration and conservation are very important issues.

Another example of a successful ecological restoration program concerning transportation is the construction of the

Cuyutlan lagoon railroad in Manzanillo, where a full study of vegetation preceded seed and plant recovery, a nursery to

keep rescued plants and produce new ones up to about 120,000 plants needed to fulfill the restoration program

requirements. Soil conservation played an important role in this program as piles of rescued organic soil (from railroad

construction) were mixed with crushed residues from vegetation clearing and organic garbage from the workers lunch

room. Soil was preserved for several months under humid conditions to enable composting and was eventually turned

over for better compost formation.

Ecological restoration of a transportation project as a mitigation measure has great advantages, not only in the

environmental matters, but also in construction costs. It reduces expenses on conservation and maintenance of

vegetation as plants are appropriate for local climate-soil conditions. For these measures to be efficient and effective,

they need to be developed under a planned scheme, an opportune Ecological Restoration Program.

INTRODUCTION

All infrastructure projects in Mexico are required to apply for and obtain an environmental impact authorization. This is

obtained through an Environmental Impact Statement (EIS); which deals with environment fragility, project impacts

during construction and operation, and the proposal of several mitigation measures. Among this mitigation measures,

ecological restoration programs are required by the environmental authorities to be applied at specific sites affected by

transportation projects.

Compliance with mitigation measures and regulation policies is crucial for a project to be successful within a framework

of environmental conservation and social benefit. The adequate execution of restoration programs is important for the

recovery of landscape connectivity and habitat fragmentation, ecosystem properties lost by the construction of a

transportation project.

In this work we present the results of two ecological restoration programs, applied for the mitigation of environmental

impact caused on natural vegetation during the construction of two transportation projects: a highway and a railway in

Mexico. Both case studies were successful restoration experiences related to infrastructure projects. They represent

two different approaches as the first case, Nuevo Necaxa, was done within a government environmental protection




area (ANP), and therefore it required a detailed long term restoration program; whereas the Cuyutlán restoration

program had to be done in a fast and efficient way to cope with time requirements.

STUDY SITES AND BACKGROUND

a) Mexico-Tuxpan highway. A 18 km zone in the Tejocotal-Nuevo Necaxa section (Figure 2a)

An 17.5 km long section of the Mexico-Tuxpan highway, from Tejocotal dam to Nuevo Necaxa (state of Puebla) was built

in 2006 within mountain landscape on a temperate weather, where a cloud forest grows at such high altitude (2,070

and 2,138 masl).

Cloud forest (Figure 1) is scarce in Mexico and it includes several plant species protected by law. This vegetation is

sparsely distributed in the area, as it has been removed by locals for wood and cattle introduction. Habitat loss in the

Tejocotal-Nuevo Necaxa region has been a very serious problem for the last decade, and the construction of this

highway implied removing some patches of remaining cloud forest vegetation along a 6 km section, crossing through

the buffer zone of an environmentally protected area; therefore, as part of the EIA resolution, environmental authorities

required the development of an Ecological Restoration Program of cloud forest vegetation within the right of way and

surrounding area of the highway along those 17.5 km. This program had to consider the rescue of endangered and

ecologically important species and the restoration of cloud forest vegetation in all sites affected by the construction and

inside the highway right of way and its immediate surroundings. An Ecological Restoration program was defined in

2004 and by 2006, when construction ended, restoration actions were applied along the right of way of this highway

and proximities.

Figure 1. Cloud Forest at the Tejocotal-Nuevo Necaxa region in Puebla, Mexico.

b) Cuyutlan lagoon railroad in Manzanillo (Figure 2b).

This railroad runs along the northern coast of the Cuyutlan coastal lagoon, at the southeastern portion of Manzanillo,

state of Colima. It implies a new route and modernization of actual railroad, which needs to be removed in order to

widen the lagoon channel into the ocean, allowing the entrance of tanker ships that will deliver natural gas into a gas

terminal destined to supply the Manzanillo power plant. With this change in fuel supply, the power plant will operate

under more ecological conditions, but the new railroad needs to be operant before the lagoon channel can be widen.

This railroad is very important for the import and export of products on the western coast of Mexico, through the port of

Manzanillo. It is being built on overpasses along the northern margin of the Cuyutlan lagoon, involving both terrestrial

and aquatic ecosystems. It crosses through 2.82 ha of well-preserved tropical deciduous forest on the east margin of

the lagoon, as well as 0.47 ha of mangrove. All of the four mangrove species reported for Mexico and several cactuses

within the tropical deciduous forest are protected by law; therefore, all mitigation measures, especially those regarding

mangrove and tropical deciduous forest protection, conservation and restoration were very important and should be

included in an Ecological Restoration Program.


a b

Figure 2. a) Nuevo Necaxa – Tihuatlan highway, section where ecological restoration of cloud

forest vegetation was done. b) Cuyutlan lagoon railroad and the 4 km section where ecological

restoration program for tropical deciduous forest vegetation was applied.

OBJECTIVE

With these two case studies we want to present the results of well-planned and efficient ecological restoration actions

on damaged sites, based on an Ecological Restoration Program. Both programs were developed in coordination with

the environmental authorities and the construction company, and considered the ecological properties of nearby

vegetation communities in search of reducing fragmentation, habitat loss and increasing connectivity among remaining

vegetation patches.

METHOD

a) Mexico-Tuxpan highway. Tejocotal-Nuevo Necaxa section

Complementary to the EIA study, vegetation communities along the highway right of way were analyzed and species

composition, community structure and degree of human disturbance defined in 20 sampled sites. Herbs, bushes and

trees were sampled using concentric circle method (Merino–Pérez et. al. 2001; Ruiz–Jiménez et. al. 2001). The 17.5

km long section was divided in a GIS in 12 restoration zones, according to the condition of the damaged area, where

topography, remaining top soil horizon, nutrients and nearby vegetation were important variants. Also an edapho-

ecological study was done (Siebe et al.1999) to identify soil properties as well as infiltration, texture and erosion. The

community species composition, structure and successional stage at different reference sites of nearby vegetation

helped established the quantities of each species that needed to be considered within each restoration zone. A buffer

zone of border tolerant native plants (initial succession stages) was selected to be placed along highway proximities.

After vegetation and soil studies were done, restoration priority zones were defined within two sections: Section 1:

included 7 zones within a highway length of 9 km; section 2: included 5 zones within 9 km length. In these zones,

restoration polygons were established considering land use, vegetation, soil, slope and orientation; for each polygon, a

specific restoration strategy was defined.

With a multidisciplinary team, information was systematized and functional and structural role of each species within

the ecosystem was discussed, as well as successional stage of cloud forest in which they are dominant. Guilds of plant

species were established considering their ecological roles, like allowing the colonization of other species, a fast growth

response to disturbance (pioneer species) or usefulness as refuge or food supply to local fauna and landscape

importance. Ecological Restoration strategy scheme charts (scale 1:400) for highway sections of 300 meters were

produced as an integrative result of this Ecological Restoration Program, to be followed by the construction and

gardening companies.

Our main four action lines in defining the Ecological Restoration Program were:

1) Rescue and reproduction (sexual and asexual) of cloud forest species for their reintroduction in the

environment.

2) Ecological Restoration strategy: specific restoration treatment for each one of the 12 zones.

3) Application of soil conservation techniques where needed.

4) Species plantation under specific scheme within each zone.

H u a u c h in a n g o

P re s a

T e jo c o ta l

P re s a

T e n a n g o

5 9 0 0 0 0

5 9 0 0 0 0

5 9 5 0 0 0

5 9 5 0 0 0

6 0 0 0 0 0

6 0 0 0 0 0

2225

000

2225

000

2230

000

2230

000

2235

000

2235

000

590000

2235000

2225000

605000

Tejocotal

Nuevo

Necaxa

13 DE SEPTIEMBRE DE 2010

Railroad tunnel

(2ª phase)

600

150 150325 325

840


b) Cuyutlan lagoon railroad in Manzanillo.

An Ecological Restoration Program (ERP) was defined for this project in which vegetation communities along the

railroad were sampled. As this site is very uniform, vegetation along the railroad area was homogenous, consisting of

tropical deciduous forest and mangrove. Seedlings were rescued as well as all types of germplasm, and taken to a

temporary nursery, specially built for this project, in a site adjacent to the lagoon. Species abundances for each

community were calculated, and tolerance to removal and transplant for each species was analyzed. Restoration

species list was established and plants are being grown in the nursery for a period of 1 year. The construction of the

railroad will end by august 2011, and by then, restoration actions on affected sites defined by the ERP will begin.

Nowadays, trial plots for mangrove restoration within the lagoon are being analyzed to establish the best conditions and

sites for mangrove seedlings transplant.

RESULTS

For both case studies, a Plant rescue, conservation and ecological restoration programs were elaborated. Plantation

design was defined for each one of the surfaces affected by the construction of both transportation projects. Obtained

results are as follows.

a) Mexico-Tuxpan highway. Tejocotal-Nuevo Necaxa section

a.1) Rescue and Reproduction (Sexual and Asexual) of Cloud Forest Species for their Reintroduction in the Environment.

When applying a restoration program, the use of native species is very important. Exotic species like Eucalyptus spp.

and Casuarina spp., were frequently used in the past, as they are easier to obtain, grow fast and have high tolerance to

poor soils; but they compete with the natives, and as they generally lack of specific predators to control their survival;

therefore, displace the original vegetation with a reduction in diversity as a consequence.

Before a restoration program can be done, a native species nursery needs to be installed so that plants can grow to a

good survival opportunity size (figure 3) and cloud forest vegetation species numbers increased thought seed

germination and propagation.

For this particular project, a 1 hectare nursery was installed in the nearby town of Huauchinango, Puebla, on a low

slope surface to allow drainage and sufficient water supply. Seeds and cuttings from 22 native species were collected

according to their fruit maturity period (see appendix 1).

Figure 3.- Nursery installed in Huauchinango, Puebla for the conservation of protected

species and the reproduction of cloud forest species needed for the ecological

restoration of Tejocotal - Nuevo Necaxa highway.

Before vegetation clearance, four species protected by law (Cyathea fulva, Carpinus caroliniana, Acer negundo and

Podocarpus reichei) as well as other ecological or local important species, were rescued from the direct project

occupation zone and taken to the nursery until restoration actions were to be done.

As slopes in the area were considerably steep, plant rescue had to be done by hand, which made this part of the job very

complicated and expensive (figure 4). For the identification of law protected and ecological or local important species

during the rescue actions, an illustrated field guide was made available to all workers. This field guide also showed the

way each species should be extracted from the ground and cared for in the way to the nursery (Grupo Selome, 2003).


Figure 4. Law protected and ecologically important plants from the zone to be affected by highway

construction were rescued by hand (source: ICA-FAPGC, 2008).

An approximate total of 50,000 small plants (10 – 150 cm high) were rescued and taken to the nursery, where they

remained for a period of two years before they were transplanted to the rehabilitation sites (ICA-FAPGC, 2008). Species to

be rescued and reproduced were defined after the evaluation of different vegetation and soil characteristics. Additional to

the 50,000 rescued plants, 120,000 were produced in the nursery for restoration purposes (see appendix 2).

a.2) Ecological Restoration strategy: specific restoration treatment for each one of the 12 zones.

Restoration of ecosystems has been successful in several countries (Berger, 1990; Anderson, 1995). From our

experience, knowing community composition is not enough, as a multidisciplinary approach is needed for the

rehabilitation and restoration of an ecosystem (Tyson, 1990; Hill, 1990 Cruz, 1994). Studies like this are not frequent

in Mexico and the information and restoration proposals in this work are considered to be pioneer exercises that may

establish an important precedent in our country. In this work, our company made the Ecological Restoration Program

(including the ER strategy), the installation and operation of the nursery (which up to now is still producing cloud forest

vegetation species for reintroduction within the area), and the plantation specifications for the restoration.

In table 1 we present the characteristics for each restoration zone. For each one, species reintroduction criteria were

established (see appendix 3).

a.3) Application of soil conservation techniques where needed

Considering other restoration projects and specialized literature, as well as our floristic and soil analyses, three low cost

soil conservation techniques were selected to restore highway construction affected sites: 50x50x50 pits, furrows

following topographic lines and terraces.

3.1 Pits. These were made where remaining soil was still similar to the original and therefore, only an

increase in plant density was needed. Pit size was according to plant root dimensions, with a

maximum size of 0.125 m3. This technique reduces erosion by increasing plant coverture. Soil within

the pit was enriched and a small dike was made to contain water and soil.

3.2 Furrows. This technique was aimed to protect soil from water erosion in places where slopes were

from 4 to 19°; as furrows work like small ditches that reduce runoff along the slope. They were

sketched perpendicular to terrain slope along topographic lines. For more inclined terrains, soil was

grooved to 15-30 cm deep, along 50cm wide and 10 m long stripes. Along the furrows, native

seedlings were planted in pits to increase soil stability.

3.3 Terraces. They were built to reduce slope at sites where it was larger than 20°, and a slope length

of 90 to 120m. They slowed water erosion of existing soil, as they were constructed perpendicularly to

slope. Also they reduce water runoff to allow infiltration. Plants were introduced at 50 cm away from

terrace edge and stakes and logs (from project clearing) along terraces were used to increase stability.


Table 1. Ecological characteristics and recommended species for each zone along the highway.

ZONE SITE CHARACTERISTICS AND SPECIES TO BE CONSIDERED FOR RESTORATION

I

Soft topography, medium slope, high human perturbation (agriculture), scarce and isolated patches of

secondary CF vegetation; mainly along streams and glens.

Species: Crataegus pubescens, Budleia cordata, Quercus spp, Alnus sp. and Archibacaris sp (bush)

II

Steep slopes with high heterogeneity in soils and vegetation.

Species: Quercus spp, Liquidambar styraciflua, Prunus serotina, Clethra sp., Carpinus caroliniana,

Ocotea sp. and Podocarpus reichei

III Open spaces with high human disturbance.

Species: Clethra spp., Podocarpus reichei, Alnus spp. and Quercus spp.

IV High topographic complexity and large patches of cloud forest vegetation.

Species: Podocarpus reichei, Quercus spp and Pinus spp.

V Small hills with deep glens. Vegetation remnants show different degrees of human disturbance.

Species Quercus spp., Pinus patula, Podocarpus reichei and Liquidambar stiraciflua.

VI Deep and large glens with large remnants of cloud forest vegetation, mainly along streams and rivers.

Species: Liquidambar styraciflua, Quercus spp., Alnus spp, Cyathea fulva.

VII

Low forest vegetation, predominance of agriculture and animal husbandry. Remnants of cloud forest

fragmented by human activities, which in turns favors the presence of pioneer and ruderal species.

Species: Rapanea spp., Quercus spp and Pinus spp.

VIII

Canyon and glen dominated landscape with large patches of cloud forest and low human disturbance.

Sites with different humidity and soil properties.

Species: Liquidambar styraciflua , Quercus spp., Pinus spp., Alnus spp., Prunus serotina , Rhamnus

longistila, Tourneifortia acutiflora, Carpinus caroliniana, Beilshmiedia Mexicana and Acer negundo

IX

Similar to zone VIII but with a highest degree of human disturbance by agriculture, animal husbandry

and isolated ranches. Abundance of pioneer species.

Species: Liquidambar styraciflua, Quercus spp., Pinus spp Alnus spp., Prunus serotina, Rhamnus

longistila and Tourneifortia acutiflora

X

There is a large canyon in this zone which determines a highly heterogenic landscape. There are flat

surfaces, which are being used for agriculture, and steep slopes with remnant cloud forest vegetation.

A rise in temperature favors more tropical species.

Species: Carpinus caroliniana, Liquidambar spp., Quercus spp, Podocarpus reichei, Ocotea spp. and

Croton draco.

XI

Large canyon slopes with cloud forest vegetation and secondary vegetation. High density of Carpinus

caroliniana, a species protected by law in slopes and along rivers and streams.

Species: Carpinus caroliniana, Liquidambar styraciflus and Quercus spp.

XII

Highly fragmented landscape, with scarce cloud forest remnants due to land use for ornamental

species.

Species: Croton draco, Liquidambar stiraciflua, Quercus spp., Pinus spp., Platanus mexicana and

Acer negundo.

a.4) Species plantation under specific scheme within each zone (for reforestation).

This work was intended to restore a damaged ecosystem due to highway construction, but also to increase cloud forest

covered surfaces in the region by increasing plant density in the nearby communities. Bare and cultivated sites in the

surrounding area of the highway (within the government environmental protection area) were also re-forested based on

the remaining native plant density. One of the main innovative results of this program was the design of a plantation

template, modularly reproduced at all forested sites. This template, unlike others (in ex. trefoil pattern), represented a

non-systematic pattern, which gave the forested area a more natural aspect when plantation was finished (figure 5).


Figure 5. Plantation template for low (a) and high (b) diversity sites. Measures in meters.

Plantation density was defined in relation to species abundance by surface unit (trunks/ha). Model considered basic

distances between planted trees, which changed accordingly to the required density at each polygon. High density

plantation scheme implied that there was a low density of original vegetation (as in bare or cultivated sites) and

therefore, a larger amount of trees needed to be introduced within the smallest possible available space (5.56x4.23

meters) with smaller plantation distances as observed in the template. Low density plantation was done in sites where

cloud forest vegetation remnants were present as well as other types of introduced vegetation and larger distances

between trees could be considered within an 11.13x8.45 meters templates.

Proposed model observed ecological properties of trees avoiding space competence, compatible with remnant trees,

formation of cloud forest corridors to unite isolated remnant patches, an adequate display of tree canopy allowing

sunlight to penetrate, pivoting roots for support and use soil nutrients, and promote the formation of a seed bank to

increase forest natural recovery.

Main issues in the reforestation were the following:

a) Identification of site characteristics and degree of human disturbance.

b) Defining ecological importance of tree species in the highway surrounding area.

c) Recovery of most of the endangered, ecological or social important species seedlings.

d) Reproduce (sexually and asexually) native plant species to increase diversity.

e) Use plantation schemes and spatial arrangements considering plant guilds in nature and species tolerance to

transplant and border effect.

f) Use as many as possible early successional stages species, to favor a facilitated successional process in

restored sites.

g) In the medium-term, to recover ecological services within the area by reforestation of bare sites, previously

occupied by cloud forest, with the recovery of fauna corridors.

Ecological Restoration Program was carried out in 2006 and initial transplant of seedlings was done accordingly (figure

6a). General monitoring of tree development in 2008 showed a good plant survival (not quantified) and growth of

transplanted individuals (figure 6b). Nowadays, forest recovery en several polygons has been successful and you can

hardly distinguish remnants from transplanted individuals at some sites (figure 6c).

Restored plants were cared for during the first two years by the construction company and the company in charge of

the operation of the highway; they were watered and substituted whenever needed. After those two years, region

humidity and general climate conditions provided an adequate environment for the ecosystem to recover from

construction (high resilience properties).


a

b

c

Figure 6. Transplanted seedlings development in a 5 year period (a: 2006; b: 2008; c: 2011).

b) Cuyutlan lagoon railroad in Manzanillo.

b.1) Compliance with the Plant rescue, conservation and vegetation restoration program

Before plant rescue, conservation and restoration program could be applied, a plant nursery had to be constructed in

the nearby area as presented in former case. A 2 hectare site was chosen close to the construction company’s

temporary. In this case, our company was hired to do the environmental supervision, and therefore, we made sure that

the nursery was accurately built and ready before plant rescue started (Figure 7).


Figure 7. Monitoring the set-up of the nursery required for the plant rescue, conservation and

ecological restoration programs, as part of the mitigation measures derived from the EIM and the

environmental resolution by the authority.

For the second part of the plant rescue program, native plants fruits and seeds were collected from the surrounding

area (figure 8) and were taken to germinate inside the nursery. The project crossed along its first 3 km through a

tropical deciduous forest with some plant species under law protection, therefore, we had to monitor the recovery of all

kinds of plant producing structures like seeds and stakes of different native plants, as well as small plants.

Figure 8. Wild plant seeds, seedlings and stakes from tropical deciduous forest vegetation were

recovered before construction began.

Seeds were cleaned and classified according to the species and a seed bank was established as stated in the program

(Figure 9). Construction worker’s women were hired for such purposes, helping to increase family income and doing an

excellent job in separating seeds from fruits and sheaths, and classifying all seeds according to the species.


Figure 9. Seeds are separated from fruits and classified according to the species. Women related

to the construction workers were hired for this job. Mangrove replanting plots are being tested

before restoration begins.

Also, as the railroad crosses through a coastal lagoon, 0.47 ha of mangrove vegetation had to be removed, and two

species of mangrove (Rizophora mangle and Laguncularia racemosa) are being reproduced in the nursery to restore

damaged sites in the nearby future.

Trial plots of mangrove plantations within the lagoon are already being studied to identify the best conditions for

reforestation and in search for the best places to reintroduce mangrove, as not only project affected surfaces will be

restored, but also previously affected areas within the lagoon.

As railroad construction is to be finished by the end of the summer 2011, plants are being cared for and grown in order

to obtain healthy individuals to use in the Plant Restoration Program, which will restore all surfaces that have been

damaged by the construction.

A total of 120,000 plants will be used for the restoration of damaged sites, including both species of mangroves. By

June 2011, the construction company reported to the environmental supervision, a total of 108,549 plants being kept

in the nursery, as shown in table 2.

Table 2. Total rescued and produced plants by June 2011. Source: Tradeco Construction Company.

June 2011; Report of compliance with mitigation measures for SEMARNAT.

There are 79,034 additional plants being germinated nowadays. Successful ones will be added to the former for a

maximum total of 187,583 available plants for restoration purposes. This mitigation will reduce residual impact on

vegetation caused by deforestation for the railroad construction and help site recovery in a shorter time, as an

approximate proportion of 1:4 is being considered between removed and reforested plants.

b.2) Soil conservation and restoration program.

Soil is a very important natural resource that needs to be recovered and preserved to be used in restoration actions, as

its formation may take thousands of years. During railroad construction, piles or rescued organic soil horizon were kept

aside the construction front. They were covered with grass or plastic to conserve their humidity and protect them from

wind and water erosion for as long as construction will be finished.

TYPE OF PLANTS TOTAL PLANTS

Rescued plants 12,423

Cactus and Bromelias 3,882

Plants produced from seeds (including mangroves) 92,244

TOTAL 108,549


Crushed residues of plant removal and workers meals were used to make a compost (soil conservation will last for at

least 14 months) and increase soil nutrients (Figure 10). These will also reduce costs of disposal and transportation of

soil material to a disposal site, as it will be reused for restoration purposes.

A total of 656 m3 of soil and 253 m3 of litter from the tropical deciduous forest were rescued, as this type of vegetation

produces a good quantity of leaves which include a rich seed bank that will eventually be, jointly with the top soil, used

in the restoration of all sites that were affected by the railway construction as the final part of the mitigation measures.

Figure 10. Piles of rescued soil and composting actions with crushed residues from clearing to

increase its nutrient contents. Courtesy of Tradeco Construction Company: Report of compliance

with mitigation measures. October 2010.

CONCLUSIONS

Best compliance results are being obtained in the execution of all the required programs, as authorities, consulting

companies, constructors and local people are working together to obtain good environmental results.

Planning and good Ecological Restoration Programs applied to construction sites can adequately mitigate negative

impacts of clearing during construction. After 5 years, plant community is starting to look similar to the cleared one.

Adequate management of plants and the increase in native plant numbers within nursery following communities

studies is very useful in the ecological restoration of affected sites.

Mangrove species being reproduced within the nursery are already being tested in plantation plots in order to optimize

plant survival during restoration.

Soil is being conserved and its nutrients and texture improved for future use during ecological restoration activities.

AKNOWLEDGMENTS

SEMARNAT

ICA Contractor

TRADECO Contractor

BIOGRAPHICAL SKETCHES

Norma Fernández Buces has a Masters in Ecology and Applied Sciences and a PhD in Science from the UNAM. She

has been working on Environmental Impact Assessment issues since 1988, mainly related to infrastructure projects.

She has worked at the Mexican Ministry of Ecology (SEMARNAT) and at different environmental consulting companies.

In 1993 she co-founded Grupo Selome, an environmental consulting firm in Mexico City and is currently the Science

Director of the firm.

Sergio López Noriega is the Executive Director of Grupo SELOME, an environmental consulting firm that operates in

Mexico City since 1990. He has a large amount of experience with Environmental Impact Assessment related to

infrastructure projects, as well as in urban impact, remote sensing, GIS, environmental diagnosis and ecological

restoration projects.


APPENDICES

Appendix 1: Native tree species that were produced and conserved in Huauchinango nursery for its

use in the ecological restoration of Tejocotal - Nuevo Necaxa highway.

SPECIES LOCAL NAMEFRUIT MADURATION

PERIOD

TYPE OF

PROPAGATION

NUMBER OF

PRODUCED PLANTS

Acer negundo maple,negundoJune-December cuttings rescued 6,300

1941

Alnus jorullensis July-December seeds 14,000

Alnus acuminata rescued 946

Beilshmeida mexicana Manzanillo June-December seeds 1,500

Buddleia cordata TepozánJune-December seeds rescued 6300

236

Carpinus caroliniana IxticuitlJune-December seeds rescued 5500

2,510

Clethra macropyhlla pahuilla, June-December seeds 500

Clethra aloceri cucharilla 1,594

Crataegus pubescens

tejocote,

texcotl

November-December seeds 900

6,300

149

Croton draco sangre degrado June-September cuttings rescued 5,200

Cupressus benthamiicedro blanco,

tlaxca

September-December seeds rescued 2,600

33

Cyathea fulva rescued 101

Cyathea mexicana

Erythrina sp. ColorínJune-December seeds cuttings 550

6,300

Heliocarpus sp. June-July seeds 2000

Liquidambar styracifluaJune-November seeds rescued 10,600

1,580

Ocotea spp. AguacatilloJune-oct seeds rescued 3,800

1,554

Persea americana AguacateJune-December seeds rescate 250

575

Pinus patula pinos,ocoteSeptember-December seeds rescued 6,000

426

Platanus mexicana álamo, plátano, xilcacuitl June-Novemberrescued 1,399

Podocarpus reicheipalmillo,

compipes

June-November seeds rescued 5,000

3,171

Prunus serotina capulín, capaloitlMay-August seeds rescued 3,500

541

Quercus spp. encino, aoucixtlSeptember-December seeds rescued 16,000

6,656

Rapanea myricoides CoachalalaJune-September seeds rescued 1,000

334

Sambucus mexicana sauco, xometlJune-September cuttings rescued 6,300

65

Ternstroemia sylvatica Trompillo June-September seeds 700

Vaccinium leucanthum CahuitzoJune-September seeds rescued 600

85

Tournefortia acutiflora Capulincillo June-September rescued 6,299

Rhamnus longistyla Cuatatama June-September rescued 5,218

Zanthoxilum sp. Uña de gavilán June-September rescued 2,083

Meliosma alba FresnoJune-September seeds rescued 4,000

260

ailite, aile

Pesma

Jonote, liquidambar,

ocoxote


Appendix 2: Low and high density plantations assigned for species to be introduced in Zone I.

Local name Species

% Ind./Ha

High density

plantations

% Ind./Ha

Low density

plantations

Plantation position

(Within Patch or border)

Ailite, Aile Alnus spp. 10.4 7.0 Border (tolerant)

Maple Acer negundo 6 .0 6.0 Within patch (low tolerance)

y riparian

Manzanillo Beilshmiedia mexicana 0.0 4.0 Within patch (low tolerance)

Tepozán Buddleia cordata 3.0 3.0 Border (tolerant)

Carpinus Carpinus caroliniana 5.0 5.0 Within patch (low tolerance)

Pahuilla Clethra spp. 8.2 8.1 Border (tolerant)

Tejocote Crataegus pubescens 3.6 3.6 Border (tolerant)

Cedro blanco* Cupressus benthamii 1.5 1.5 Border (tolerant)

Colorin* Erythrina coralloides 6.3 6.3 Border (tolerant)

Ocoxote Liquidambar styraciflua 5.5 5.5 Border (tolerant)

Ocote Pinus patula 7.5 7.5 Border (tolerant)*

Capulín Prunus sp. 6.4 6.3 Within patch (low tolerance)

Encino Quercus sp. 19.0 19.0 Border (tolerant)

Sauco Sambucus mexicana 2.5 0.0 Border (tolerant)

Trompillo Ternstroemia sylvatica 0.0 2.0 Within patch (low tolerance)

Cuatatama Rhamnus longistyla 7.3 7.4 Border (tolerant)

Capulincillo Tournefortia acutifolia 7.8 7.8 Border (tolerant)


Appendix 3: Species reintroduction criteria.

1. Species density at each zone should be those defined after field studies and established in low and high

densities species assignment tables for each zone (see example in appendix 2). Low density of plantation

should be made at sites where cloud forest vegetation already exists and this program will only increase tree

density to approximately the original community density. High density plantations are to be done in sites where

cloud forest vegetation is nowadays absent, but originally was the dominant community. Plant density outcome

will be similar to those shown in nearby well preserved communities.

2. Species assignment at each zone should be as follows:

2.1. Specific conformation and soil treatment should be done in each polygon within defined zones,

considering topography, surrounding vegetation or land use and project specifications for the right of way

concerning security and visibility.

2.2. Species availability (and number of individuals) within nursery.

2.3. Re introduction of species of ecological importance which are no longer present in the study area

because of human disturbance, but historical records report them to be present in this type of vegetation.

2.4. Patch preference species should not be planted within the first 5 m of the highway or any other land use

different than cloud forest as they are susceptible to border effect. Species under this restriction are: Acer

negundo, Beilshmiedia mexicana, Carpinus caroliniana, Cyathea fulva, Ocotea sp. Persea americana,

Platanus mexicana, Podocarpus reichei, Prunus serotina, Ternstroemia sylvatica, Vaccinium lecanthum

and Zanthoxilum sp.

2.5. Tolerant species could be planted anywhere as they are pioneer and generalistic species with fast growth

and high tolerances to adverse conditions. Among such species we refer to: Alnus sp. Budleia cordata,

Clethra sp. Crataegus pubescens, Cupressus benthamii, Eritrina coralloides, Fraxinus sp. Liquidambar

styraciflua, Quercus spp. Rapanea myricoides, Rhamnus longistila, Sambucus Mexicana and Tournefortia

acutiflora.

2.6. For Platanus mexicana and Cyathea fulva (occasionally Acer negundo as well), their reintroduction will be

subjected to riparian vegetation, canyons and glens, as they need high humidity levels.

2.7. Pinus patula could be reintroduced anywhere, except for sites at the proximities of streams and rivers,

due to its low tolerance to low drainage soils.

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