DEPARTMENT OF BIOLOGICAL AND

ENVIRONMENTAL SCIENCES

Degree project for Bachelor of Science with a major in Environmental Science ES1504, Examination Course in Environmental Science with Emphasis on Earth Sciences, 15 hec

First cycle

Semester/year: Spring 2018

Supervisor: Janina Konarska, Department of Earth Sciences

Examiner: Sofia Thorsson, Department of Earth Sciences

THE PHENOLOGY OF TILIA EUROPAEA

AT CONTRASTING URBAN LOCATIONS

Frida Nilsson

Abstract

The phenology of plants is an important indicator for how the nature is affected by the rapidly

changing climate on Earth today. Changes in the timing of bud- and leaf burst, development of

flowers and fruit, and defoliation is only a few of the factors that can be investigated.

Time and potential difference in leaf burst of the common lime (Tilia europaea) between four

nearby sites with different growing conditions were investigated during the spring of 2018 in

the city of Gothenburg, Sweden. The sites’ environments range from nature-like to more urban.

Since air temperature usually is one of the biggest contributing factors to leaf burst and other

phenological events, this was also recorded at each site to try to explain the possible intra-urban

variations in phenology between the sites. The aim of the study was thus to investigate if any

difference in leaf burst would occur and if the different growing conditions might have an

influence. The data collected showed that the earliest leaf development could be found at the

sites with the biggest growing space and least impervious surfaces, and the latest at the site with

the least growing space and most impervious surfaces. This result did however not follow the

air temperature pattern of the four sites. A literature study was therefore made to investigate

what the different leaf burst results may depend on, if it was not air temperature. The studied

reports suggested that leaf burst and phenology among trees also can depend on water and

nutrient availability, soil composition, growth environment and age of the tree – amongst other

things. In this study the degree of impervious material around the tree seemed to be the biggest

contributing factor to the difference in leaf burst between the sites.

Sammanfattning

Växters fenologi är en viktig indikator på hur naturen påverkas av det klimat som är i ständig

förändring på jorden idag. Förändringar i tidpunkt för knopp- och lövsprickning, utvecklandet

av blommor och frukt, samt lövfällning är bara några av de faktorer som kan undersökas.

Tid och potentiell skillnad i lövsprickning hos parklind (Tilia europaea) mellan fyra olika

närliggande platser med olika växtmiljö undersöktes under våren 2018 i Göteborg, Sverige.

Platsernas omgivning går från naturlik till mer stadslik. Eftersom lufttemperatur vanligtvis är

en av de största bidragande faktorerna till lövsprickning och andra fenologiska händelser så var

även detta dokumenterat vid varje plats för att försöka förklara de potentiella skillnaderna i

fenologi mellan platserna. Syftet med denna studie var därför att undersöka om det skulle uppstå

någon skillnad i lövsprickning och om de olika växtförhållandena kunde ha en påverkan. Data

som samlades in visade att den tidigaste lövutvecklingen kunde hittas på platserna med störst

yta att växa på och med minst andel ogenomträngliga ytor, och sist på platsen med minst yta att

växa på och med störst andel ogenomträngliga ytor. Detta resultat följde dock inte

lufttemperaturmönstret för de fyra platserna. En litteraturstudie gjordes därför för att undersöka

vad skillnaden i lövsprickning kan ha berott på om inte lufttemperaturen. De studerade

rapporterna föreslog att lövsprickning och fenologi hos träd även bland annat kan bero på

vatten- och näringstillgång, jordsammansättning, växtmiljö och ålder på träden. I denna studie

visade sig andelen ogenomträngligt material runt träden vara den största bidragande faktorn till

skillnad i lövsprickning mellan platserna.

Acknowledgements

I would like to give a big thank you to my supervisor, Janina Konarska, from the Department

of Earth Sciences, Gothenburg University for all the help and feedback. Additionally, thank

you to Alexander Walther from the Department of Earth Sciences, Gothenburg University for

helping me with GIS.

I am also very grateful for the help from Katarina Bergman Lyck, student on the bachelor’s

program in geosciences. She has done a similar project to mine and we have been helping each

other out a lot with field work. Without her this project would have been so much more difficult.

Last but not least - the biggest thank you goes to my father for his endless support and always

believing in me no matter what.

TABLE OF CONTENTS

1. INTRODUCTION......................................................................................................................................... 1 1.1 AIM AND PROBLEM STATEMENTS.................................................................................................................... 2

1.1.1 Aim ......................................................................................................................................................... 2 1.1.2 Problem statements ................................................................................................................................ 2

1.2 BACKGROUND ................................................................................................................................................ 2 1.2.1 Phenology .............................................................................................................................................. 2 1.2.2 Tilia europaea ........................................................................................................................................ 2 1.2.3 Earlier research ..................................................................................................................................... 3

2. STUDY AREA AND METHODS................................................................................................................ 4 2.1 SITE DESCRIPTION ........................................................................................................................................... 4

2.1.1 Site 1....................................................................................................................................................... 5 2.1.2 Site 2....................................................................................................................................................... 5 2.1.3 Site 3....................................................................................................................................................... 6 2.1.4 Site 4....................................................................................................................................................... 6

2.2 AIR TEMPERATURE MEASUREMENTS .............................................................................................................. 7 2.3 OBSERVATION ................................................................................................................................................ 8

3. RESULTS ...................................................................................................................................................... 9 3.1 TEMPERATURE ................................................................................................................................................ 9 3.2 LEAF BURST ................................................................................................................................................. 11

4. DISCUSSION .................................................................................................................................................... 12

5. CONCLUSION ................................................................................................................................................. 14

REFERENCES ..................................................................................................................................................... 15

APPENDICES....................................................................................................................................................... 17 APPENDIX A ....................................................................................................................................................... 17 APPENDIX B ....................................................................................................................................................... 20

1

1. Introduction

It is well known that a changing climate is leading to a longer growing season and an earlier

onset of flowering and leaf burst among trees and plants in general (Linkosalo et al. 2008;

Primack et al. 2004; Menzel et al. 2006). However, climate is not only in constant change on a

global scale – within a city or even a district circumstances can be different too. Urban climate

is special in that way that it is usually warmer than its surroundings, this is due to an effect

called ‘The Urban Heat Island’. The materials such as concrete and asphalt, the density and

height of buildings and all the activity in the city is contributing to it being warmer than

adjacent areas, both by creating more heat and keeping it from radiating out of the city. This

is as most prominent at night-time when winds are low and there is weaker mixing of the air.

This allows bigger differences in air temperature between sites with different surface

properties (Oke et al. 2017). Trees and greenery are on the other hand cooling its surroundings

because of shading and transpiration (Oke et al. 1989). When the stomata of the plant are

opening to take in carbon dioxide and let oxygen out it can evaporate water which cools the

plant and its environment. This cooling effect can lead to a lower air temperature in parks and

other green areas, as well as their surroundings. In a review study from 2010 it was found that

urban parks were around 1°C cooler than a non-green urban site (Bowler et al. 2010).

According to Kong et al. (2014) and their study from a city in eastern China, a 10 % increase

in forestry will cool the surface with about 0.83°C. In a similar study from London, Doick et

al. (2014) found that one of London’s largest greenspaces, Kensington Gardens, was on

average 1.1°C cooler than adjacent streets.

Additionally, several studies also show that different growing conditions can affect the trees in

multiple ways. For example, their phenology (Wielgolaski, 2001), growth (Rahman et al. 2013),

transpiration and therefore also cooling of its surroundings can be altered (Konarska et al.

2016).

This study will investigate if there are any differences in leaf burst between different sites

within a local area in the city of Gothenburg and how the different growing conditions between

the sites may affect it. Since air temperature usually is one of the main factors controlling

growth and phenology of trees this was of course recorded on each site. As the sites are located

fairly close temperature might not be the deciding factor for leaf burst in this case. A literature

study was therefore also made to investigate other possible factors that could affect the

phenology and leaf burst of urban trees.

2

1.1 Aim and problem statements

1.1.1 Aim

The aim of the project is to examine how tree growing conditions influence leaf burst timing

of Tilia europaea in Gothenburg

1.1.2 Problem statements

- Does the phenology, mainly leaf burst, of T. europaea differ between trees growing at

contrasting close by urban sites?

- If yes, discuss potential reasons for those differences, e.g. degree of paving, air temperature.

1.2 Background

1.2.1 Phenology

Phenology is the science of reoccurring life cycle events among plants and animals such as

leaf burst, flowering, occurrence of fruit and defoliation. Following the life cycle of plants and

trees has always been important for people in order to know when to sow and harvest their

food. The word in itself though is relatively new – it is thought that its first use was in 1849 in

an article by Charles Morren (Demarée & Rutishauser, 2011). Nowadays phenology is more

commonly used when examining how the nature is affected by climate change. This can be

done by for example examining the length of the growing season over years or the arrival of

leaves, flowers or fruit in response to changing climate (most often rising air temperatures).

There are other reasons to why it is interesting to examine phenology on urban trees, apart

from climate research. One is that it can be used to predict the start and timing of the pollen

season which is important for especially allergic people as well as pharmaceutical companies.

Another is that phenology, or the length of the growing season, affects a lot of important

ecosystem services provided by trees. These can for example be filtering of air pollutants in

cities (Nowak et al. 2006), cooling of the trees’ surroundings by transpiration and shading

(Konarska et al. 2016) and interception of precipitation that can prevent excess run off (Xiao

& McPherson, 2002). Studying phenology is also rather easy and with clear guidelines

practically anyone can do it – this is therefore a good way to make the general public more

interested in nature and science.

1.2.2 Tilia europaea

T. europaea, or common lime, is a hybrid of Tilia cordata (small-leaved lime) and Tilia

platyphyllos (large-leaved lime) (Encyclopædia Britannica, 2008). It is usually 20-30 meters

3

high and is as its name suggests, frequently found in Europe (NE, n.d). It serves as a very

common street tree and in Gothenburg it is the most common one (Sjöman et al. 2012). Its big

abundance in cities is partly due to its resistance against air pollution (Tenche-Constantinescu

et al. 2015).

1.2.3 Earlier research

As mentioned in the introduction climate change and rising temperatures are most likely leading

to an earlier onset of spring phenological events (Linkosalo et al. 2008; Primack et al. 2004;

Menzel et al. 2006). This can be positive since it might lead to a longer growing season which

results in more food and income for a lot of farmers, but it might also be negative. Murray et

al. (1989) mention in their study that a lot of trees require cold temperatures to activate their

winter dormancy and bud development. If the temperatures keep rising and the winters get too

mild there is a possibility that the buds are not developed sufficiently. This can be harmful for

the tree and inhibit the development of buds, leaves and fruits later on in the year. Furthermore,

warm and early spring weather can trick the trees to develop their buds and get rid of their

winter protection too early. If the cold weather then reappears the buds might not survive

(Mustain, 2012, February 7).

In a report from Florence, Italy, Massetti et al. (2014) investigated the flowering of T. europaea

and if distance from the city center affected the time of flowering. The study did not find any

significant relations between start of flowering and distance to the city center. In a similar study

conducted by Gazal et al. (2008) different results were reported. In three out of four temperate

cities and one out of three tropical cities leaf burst occurred significantly earlier in the urban

area compared to the rural surroundings. However, on a bigger, countrywide scale, a report

from Finland (Linkosalo et al. 2008) shows that during the last 160 years leaf bud burst date on

Betula pendula and Prunus padus has occurred earlier and earlier due to higher temperatures.

Similar results were reported by Menzel et al. (2006) who have done a big evaluation and

collected data from the years 1971-2000, from all over Europe from 542 plant species in 21

countries. They found that the earlier spring phenological event that has occurred recently

undoubtedly correlated to the warmer temperatures.

While the impact of climate change on phenology over time is well researched and understood,

contrasting observations of the effect of urban areas on tree phenology are reported. Since there

4

are few studies of leaf burst on T. europaea and considering it is such a common tree in

Gothenburg it is interesting to observe how the urban climate is affecting it.

2. Study area and methods

2.1 Site description

The project was carried out in the city of Gothenburg, Sweden. It is a city on the Swedish west-

coast located 57°71'N and 11°97'E. It has a maritime west coast climate with cool summers and

mild winters. The yearly precipitation is around 760 mm with a wetter autumn and winter and

a drier spring (SMHI, 2014). Regarding the urban vegetation in the city, Tilia is the most

common genus and T. europaea the most common species of tree – standing for 46.3 %

respectively 27.1 % of the total recorded tree population in the city. Interesting is that

recommendations suggests that no species should stand for more than 10 % of the total tree

population in order to have a big enough resistance against for example pests and extreme

weather (Sjöman et al. 2012).

The area examined was concentrated around Ullevigatan – a busy road in the central parts of

Gothenburg with around 14 000 cars passing each day (Göteborgs Stad, 2017), see figure 1.

The selected T. europaea trees on the southern side of Ullevigatan, between Skånegatan and

Fabriksgatan were planted in 1995 and their height ranges from about 5 meters to 10 meters.

The trees’ growth environment differs between small pits filled with gravel surrounded by

pavement (western section), narrow grass lane (eastern section) and a small grass field by a

canal (middle section). In this study these three sites along with one site in an adjacent park

were selected. In each site six T. europaea trees were observed – in total 24 trees. The selected

trees were of approximately the same size and within a close distance from the air temperature

sensor. All the sites and trees were additionally marked in a map in the GIS-program QGIS to

keep track of which trees that were part of the study and to gain a more precise location of

them. Why the chosen sites are particularly interesting is because there are different growing

conditions within a rather small area. Since they grow relatively close to one another it is

interesting to investigate if there still is a difference in phenology between them, especially

since not a lot of previous studies that has been conducted has regarded trees over such a small

distance.

5

Figure 1: Map over the chosen area and the four sites marked out (Source of base map: Google Maps)

2.1.1 Site 1

Site 1 was located at the western section of Ullevigatan. The trees grow in individual pits with

a size of approximately 1.75x1.75 meters that are filled with gravel, surrounded by pavement

(Fig. 2).

Figure 2: Site 1

2.1.2 Site 2

On site 2, located at the eastern section of Ullevigatan the trees grow in a small grass lane,

approximately 2 meters wide and with around 5 meters between each tree (Fig. 3).

6

Figure 3: Site 2

2.1.3 Site 3

The trees in the middle section of Ullevigatan, site 3, grow in a small grass field on either side

of a canal (Fig. 4).

Figure 4: Site 3

2.1.4 Site 4

Site 4 was located in a graveyard and the trees are growing in a grass field with a lot of growing

space (Fig. 5). The site is located 260 meters north of Ullevigatan. The trees here are bigger

and older than the street trees. They are around 15 meters high and were planted around 1960-

1961. This site was added later than sites 1-3 since the previously chosen site 4 did not meet

the criteria, thus both the observations and air temperature measurements were started later here

than on the other sites. However, since the leaves still had not unfolded yet this had no impact

on the final result.

7

Figure 5: Site 4

2.2 Air temperature measurements

After the sites were chosen an air temperature sensor (TinyTag Plus2) was put up at each site

in a tree circa 2-2.5 meters from the ground. The air temperature sensor was located on the

northern side of the tree in a tube coated with reflective plastic to protect it from direct sunlight.

The sensors recorded the air temperature every ten minutes and the data was downloaded

approximately every two weeks to prevent it from being lost. It was then summarized in tables

and graphs and average air temperatures can be seen both for day-(06:00-21:00) and night-time

(21:00-06:00) and the whole day (00:00-23:59).

The reason to have three types of graphs/tables, one for day-time, one for night-time and a third

for the whole 24-hour period is that the urban heat island effect mainly occurs during night time

when winds are weak, and the air is not mixed around. To be able to see if the urban heat island

effect occurs within the four sites it therefore needs to be different tables/graphs showing air

temperatures for these three time periods.

The recording of air temperature and observation of trees started at the end of March but since

site 4 was moved around the middle of April all the results are presented from that date. Since

none of the trees had entered stage 1 before the moving of site 4 this will not affect the outcome

of the observation data nor the air temperature data.

8

2.3 Observation

The trees and its buds were examined three times a week – Monday, Wednesday and Friday at

approximately the same time, between 10:00-14:00. When observing the buds an observation

scale based on a protocol described by Wesołowski & Rowiński (2006) was being used, see

figure 6 and 7. At each observation ten buds were randomly selected from each tree and were

assigned a value between 0-2 based on how far in the leaf bursting process it had come. Each

tree therefore could have a value between 0-20 – where 0 indicates that none of the buds on the

tree has broken yet and 20 means that the whole tree is filled with leaves. Since each site

contained six trees the total value of each site could be between 0-120. These values were later

summed up in tables and graphs to visually get an easy view of which site that got their leaves

first.

Figure 6: Stages of leaf burst in T. cordata (Wesołowski & Rowiński 2006).

Figure 7: Observation scale used during the examinations of the trees (Wesołowski & Rowiński 2006)

9

3. Results

3.1 Temperature

In table 1 average daily, day-time and night-time air temperatures can be seen. The highest

average air temperature was found at site 1, followed by site 2, site 4 and then site 3. As

expected the highest average air temperature could be found at the street sites apart from site

3, which, on the contrary, had the lowest air temperature. However, there is not much

difference, the mean difference between the sites with the lowest and highest values was only

around 0.4°C.

Average day-time air temperatures follow the same pattern as the daily average air temperatures

with site 1 having the highest mean temperature, followed by site 2, 4 and lastly 3. Average

difference between the warmest and coldest site is 0.4°C.

For average night-time air temperature, the result is a bit different compared to the two previous

rows. Site 1 is the warmest, followed by site 2, then site 3 and lastly site 4. It is possible to see

that an urban heat island effect actually is present since site 4 becomes the coldest site during

night time compared to second coldest during day time. Notice that the air temperature

difference between the warmest and coldest site here, 0.4°C, is the same during the day-time.

More detailed day to day air temperatures for all sites time can be seen in appendix A.

Table 1: Average air temperatures, daily, day-time and night-time

Time period/Site Site 1 Site 2 Site 3 Site 4

Daily mean temp (°C) 9.8 9.7 9.4 9.6

Day-time mean temp (°C) 10.6 10.5 10.2 10.5

Night-time mean temp (°C) 8.5 8.4 8.2 8.1

10

Figure 8 shows an hourly summary of all days in the observation period and is visualizing

what can be read in table 1. Most of the time site 1 and 2 are the warmest ones while site 3,

especially during day-time is the coldest one. During the night-hours site 4 is slightly colder,

just as in table 1.

Figure 8: Hourly average air temperatures for all sites

7

8

9

10

11

12

13

00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Air

te

mp

era

ture

(C°)

Hourly average air temperature for the whole observation period

Site 1 Site 2 Site 3 Site 4

11

3.2 Leaf Burst

Figure 9 shows a graph over leaf burst index for all sites. As explained earlier in the methods

section; at each observation ten buds were randomly chosen at each tree. They then got a value

ranging from 0-2 based on how far it had come in the leaf bursting process. Thus, in total every

tree could have a maximum score of 20 and every site 120. As can be seen in figure 9 and table

2; the site where the buds broke first was site 4. This was followed by site 3, site 2 and then site

1. The leaves thus appeared in order first from the site with most growing space to the last site

with the least growing space. It also appears to be a big difference between the sites regarding

the leaf burst of individual trees – at site 4 all trees had entered stage 1 and a few ones even

stage 2 while at site 1 none of the buds had broken yet. To see more detailed leaf burst-index

diagrams for each site, see appendix B.

Figure 9: Leaf burst index of all four sites

Date Site 1 Site 2 Site 3 Site 4

2018-04-13 0 0 0 0

2018-04-16 0 0 0 0

2018-04-18 0 0 0 0 2018-04-20 0 0 0 0

2018-04-23 0 0 0 0

2018-04-25 0 0 0 8

2018-04-27 0 0 0 13

2018-04-30 0 2 6 35

2018-05-02 0 3 10 53

2018-05-04 0 7 19 64

Table 2: Leaf burst index of all

four sites

0

10

20

30

40

50

60

70

2018-

04-13

2018-

04-15

2018-

04-17

2018-

04-19

2018-

04-21

2018-

04-23

2018-

04-25

2018-

04-27

2018-

04-29

2018-

05-01

2018-

05-03

Leaf

bu

rst-

ind

ex

Leaf burst-index for all sites over time

Site 1 Site 2 Site 3 Site 4

12

4. Discussion

To answer the first problem statement of this thesis, does the phenology differ between T.

europaea growing at contrasting close by locations? According to the results it does, site 4 was

clearly the site that reached leaf burst first, then followed by 3, 2 and 1.

As can be seen in the results the air temperature differs as well but does not follow the pattern

of leaf burst - the site with the highest air temperature was 1, followed by 2, 4 and 3 both during

the day and over the whole 24-hour period. During the night site 3 and 4 switched place which

is a proof that the urban heat island actually exists within this area. The difference in air

temperature during day- and night-time was both around 0.4 degrees, this is slightly unusual

since the winds and the strong mixing of the air during the day should prevent that. A potential

reason for the similar differences is that the air temperatures at site 1-3, even though the sensors

are placed on the north side of the tree, could be overestimated due to high sun exposure on

those sites. Simultaneously as the sensor in site 4 is placed in a more shadowed location.

With the very small differences in air temperature between the sites and the fact that the leaf

burst pattern did not follow the pattern of the air temperature there must be other explanations

for the differences in leaf burst. This leads up to the second problem statement of this thesis;

what are other potential reasons for these differences? According to Ununger et al. (1988) and

their study on Picea abies the growth and phenology of a younger tree might differ to that of

an older, possibly due to an increased complexity of the tree as it ages. This can be a reason for

the difference between the trees at the park site and street sites since they are of different age.

However, it does not explain the fact that the trees at the three sites in the street environment

differ in phenology too although they were planted simultaneously and are of the same age.

Wielgolaski (2001) has done a study on different species of trees such as Betula pubescens,

Prunus padus and Sorbus aucuparia and it is stated that different soil compositions and amount

of soil moisture affects the phenology. It is possible that the amount of soil moisture differs

between the sites regarding that the growth environments are very different. For example,

precipitation would have a much easier way down to the soil at site 3 which is situated on a

grass lawn compared to site 1 which is surrounded by highly impervious asphalt where the

water just can run off. Also resources available to the tree, such as nutrients, might affect growth

which in turn might affect phenology (Schiestl-Aalto et al. 2013; Wielgolaski, 2001). For

instance, Wielgolaski (2001) found a negative correlation between phenological development

during 1 February-1 April and available phosphorus, magnesium, calcium and to some extent

13

potassium in the ground. All of these are possible explanations for the differentiating results

between the sites, but without further investigations it is hard to tell if they really are the definite

reasons.

An interesting result that occurred is that the leaves appeared in the order from the site with

most growing space and pervious surface first to the site with the least growing space and the

most impervious surface last. In this study degree of impervious surface seems like the biggest

factor for controlling when leaves arrive. There are actually few studies on the influence of

impervious surfaces on specifically leaf burst but there is all the more on its influence on tree

physiology. For example, it is found that trees growing on pervious surfaces grew faster and

were bigger than the ones growing in an impervious environment, both regarding height, stem

diameter and canopy size (Rahman et al. 2013; Grabosky & Gilman, 2004; Sanders &

Grabosky, 2013). A smaller area of impervious surfaces will also lead to higher stomatal

conductance and therefore higher transpiration and a cooling of the trees’ surroundings

(Rahman et al. 2013; Celestian & Martin, 2005; Konarska et al. 2016). This is possibly due to

the bad water infiltration of impermeable surfaces which makes the soils dry and water deficient

which constrains the transpiration of trees growing in such environments (Konarska et al. 2016;

Close et al. 1996). Based on the results from these studies the overall physiological fitness of

trees is lowered by a higher amount of impervious surface surrounding the tree. Conjoined with

the result of this study it can be concluded that a higher amount of impervious surface will

lower the physical fitness of the tree and delay the leaf burst but only if air temperature

differences are small enough. It would however be interesting to take this further in future

investigations and see if this is a general pattern among trees growing within a close distance

where air temperature differences are small.

Contrary to this result Massetti et. al (2014) got a highly significant result where a 10% increase

in impervious surface resulted in a 1.4 days advance of both start and end of flowering of T.

europaea. Their result hence is completely opposite to that of this study. Worth noting though

is that their study is regarding trees over a bigger distance over the whole city of Florence where

air temperature gradients are more prominent while this study concentrates on trees in a local

area with little air temperature differences. A higher degree of paving was probably found

closer to the city centre where air temperatures also were higher which could be a reason to the

contrasting results between the two studies. However, it would still be of interest to conduct

14

more studies which investigates intra-urban variations between trees on a smaller distance

rather than ones that span over the whole city since that is not equally well explored.

5. Conclusion

To conclude – there was a difference in leaf burst between the sites and even though air

temperature usually is the main factor controlling phenology and thus leaf burst it is not the

definite reason for controlling the phenology here. There are several other explanations for the

differences between the sites as discussed in this study. These can be soil composition, age of

the tree, growth environment, water availability or nutrient availability. However, the main

factor for controlling the leaf burst in this study seems to be the degree of impervious surfaces.

A higher degree of impervious surfaces was in this study found to give a later leaf burst.

15

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17

Appendices

Appendix A

Month/Day

Average

Site 1 (C°)

Average

Site 2 (C°)

Average

Site 3 (C°)

Average

Site 4 (C°)

4 9,90 9,81 9,53 9,68

14 12,94 12,97 12,60 12,60

15 9,24 9,11 8,89 8,93

16 9,46 9,21 9,07 9,18

17 8,43 8,37 8,03 8,25

18 11,11 11,01 10,67 10,89

19 11,81 11,87 11,49 11,67

20 15,26 15,30 14,82 14,74

21 10,55 10,34 10,11 10,27

22 8,76 8,76 8,29 8,61

23 9,75 9,55 9,27 9,48

24 7,87 7,71 7,65 7,80

25 8,16 7,99 7,73 7,99

26 7,70 7,63 7,44 7,67

27 8,86 8,70 8,41 8,71

28 8,82 8,74 8,41 8,65

29 10,20 10,25 9,91 10,01

30 9,29 9,28 9,12 9,12

5 9,44 9,28 9,09 9,19

1 8,77 8,69 8,40 8,49

2 10,49 10,33 10,32 10,14

3 8,90 8,73 8,52 8,74

4 9,63 9,36 9,12 9,39

Total 9,81 9,71 9,44 9,59

A1: Average air temperature

18

Month/Day Average Site 1 (C°)

Average Site 2 (C°)

Average Site 3 (C°)

Average Site 4 (C°)

4 10,65 10,55 10,26 10,53

14 14,21 14,27 13,84 13,95

15 9,30 9,14 8,98 9,17

16 10,05 9,76 9,63 9,79

17 8,42 8,39 8,07 8,42

18 12,06 11,95 11,63 11,92

19 12,69 12,78 12,42 12,78

20 17,57 17,60 17,11 17,03

21 11,29 10,97 10,68 11,12

22 9,54 9,52 9,01 9,61

23 10,33 10,12 9,88 10,16

24 8,05 7,88 7,88 8,05

25 8,84 8,64 8,33 8,73

26 8,09 8,04 7,85 8,12

27 9,63 9,40 9,09 9,60

28 9,83 9,70 9,41 9,78

29 11,19 11,22 10,86 11,01

30 9,93 9,93 9,80 9,80

5 10,44 10,25 10,02 10,24

1 9,68 9,63 9,31 9,45

2 11,68 11,49 11,55 11,31

3 9,67 9,50 9,22 9,63

4 10,74 10,37 10,01 10,56

Total 10,61 10,49 10,22 10,48 A2: Average day time air temperature

19

Month/Day Average Site 1 (C°)

Average Site 2 (C°)

Average Site 3 (C°)

Average Site 4 (C°)

4 8,64 8,59 8,30 8,26

14 10,84 10,82 10,55 10,36

15 9,15 9,05 8,74 8,52

16 8,49 8,29 8,14 8,18

17 8,44 8,33 7,96 7,96

18 9,51 9,45 9,07 9,17

19 10,36 10,37 9,94 9,83

20 11,41 11,47 11,00 10,93

21 9,33 9,28 9,16 8,86

22 7,47 7,49 7,10 6,94

23 8,77 8,62 8,26 8,34

24 7,56 7,45 7,27 7,39

25 7,01 6,91 6,73 6,77

26 7,06 6,96 6,76 6,91

27 7,58 7,53 7,29 7,21

28 7,15 7,14 6,75 6,77

29 8,56 8,64 8,33 8,36

30 8,21 8,19 7,98 7,98

5 7,78 7,65 7,54 7,44

1 7,25 7,11 6,89 6,87

2 8,51 8,39 8,27 8,18

3 7,60 7,44 7,37 7,25

4 7,78 7,68 7,63 7,45

Total 8,48 8,41 8,15 8,11 A3: Average night time air temperature

20

Appendix B

Notes: Leaf burst index for all trees on each site. Note that the y-scale is different in each diagram.

02468

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T2-1 T2-2 T2-3 T2-4 T2-5 T2-6

0

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Site 3

T3-1 T3-2 T3-3 T3-4 T3-5 T3-6

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4-07

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4-09

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4-11

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4-13

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4-15

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4-17

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4-19

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4-21

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4-23

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4-25

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201

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Leaf

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Site 4

T5-1 T5-2 T5-3 T5-4 T5-5 T5-6

B1: Leaf burst index for each tree in site 1 B2: Leaf burst index for each tree in site 2

B3: Leaf burst index for each tree in site 3

B4: Leaf burst index for each tree in site 4