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
References Bowler, D.E., Buyung-Ali, L., Knight, T.M., & Pullin, A.S. (2010). Urban greening to cool towns and cities: A
systematic review of the empirical evidence. Landscape and Urban Planning, 97(3), 147-155.
doi:10.1016/j.landurbplan.2010.05.006
Celestian, S., & Martin, C. (2005). EFFECTS OF PARKING LOT LOCATION ON SIZE AND PHYSIOLOGY
OF FOUR SOUTHWESTERN U.S. LANDSCAPE TREES. Journal of Arboriculture, 31(4), 191-197.
Close, R. E., Nguyen, P. V., & Kielbaso, J. J. (1996). Urban vs. natural sugar maple growth: I. Stress symptoms
and phenology in relation to site characteristics. Journal of Arboriculture, 22(3), 144-150.
Demarée, G., & Rutishauser, R. (2011). From “Periodical Observations” to “Anthochronology” and “Phenology”
– the scientific debate between Adolphe Quetelet and Charles Morren on the origin of the word “Phenology”.
International Journal of Biometeorology, 55(6), 753-761. doi: 10.1007/s00484-011-0442-5
Doick, K.J., Peace, A., & Hutchings, T.R. (2014). The role of one large greenspace in mitigating London's
nocturnal urban heat island. Science of the Total Environment, 493, 662-671. doi:
https://doi.org/10.1016/j.scitotenv.2014.06.048
Encyclopædia Britannica. (2008). Linden. Avalible: https://www.britannica.com/plant/linden-plant#ref270040
Gazal, R., White, M., Gillies, R., Rodemaker, E., Sparrow, E., & Gordon, L. (2008). GLOBE students, teachers,
and scientists demonstrate variable differences between urban and rural leaf phenology. Global Change
Biology, 14(7), 1568-1580. doi: 10.1111/j.1365-2486.2008.01602.x
Grabosky, J., & Gilman, E. (2004). MEASUREMENT AND PREDICTION OF TREE GROWTH REDUCTION
FROM TREE PLANTING SPACE DESIGN IN ESTABLISHED PARKING LOTS. Journal of
Arboriculture, 30(3), 154-164.
Göteborgs Stad. (2017). Trafik på Ullevigatan. Retreived 2018-03-24, from:
http://www.statistik.tkgbg.se/U/Ullevigatan.html
Konarska, J., Uddling, J., Holmer, B., Lutz, M., Lindberg, F., Pleijel, H., & Thorsson, S. (2016). Transpiration of
urban trees and its cooling effect in a high latitude city. International Journal of Biometeorology, 60(1), 159-172.
doi: 10.1007/s00484-015-1014-x
Kong, F., Yin, H., James, P., Hutyra, L.R., & He, H.S. (2014). Effects of spatial pattern of greenspace on urban
cooling in a large metropolitan area of eastern China. Landscape and Urban Planning, 128(2014), 35-47. doi:
https://doi.org/10.1016/j.landurbplan.2014.04.018
Linkosalo, T., Häkkinen, R., Terhivuo, J., Tuomenvirta, H., & Hari, P. (2008). The time series of flowering and
leaf bud burst of boreal trees (1846–2005) support the direct temperature observations of climatic warming.
Agricultural and Forest Meteorology, 149(2009), 453-461. doi: 10.1016/j.agrformet.2008.09.006
Massetti, L., Petralli, M., & Orlandini, S. (2014). The effect of urban morphology on Tilia x europaea flowering.
Urban Forestry & Urban Greening, 14(2015), 187-193. doi: http://dx.doi.org/10.1016/j.ufug.2014.10.005
Menzel, A., Sparks, T., Estrella, N., Koch, E., Aasa, A., Ahas, R., . . . Zust, A. (2006). European phenological
response to climate change matches the warming pattern. Global Change Biology, 12(10), 1969-1976. doi:
10.1111/j.1365-2486.2006.01193.x
Murray, M.B., Cannell, M.G.R., & Smith, R.I. (1989). Date of budburst of fifteen tree species in Britain following
climatic warming. Journal of Applied Ecology, 1989(26), 693-700.
16
Mustain, A. (2012, February 7). A Mild Winter’s Surprising Downsides. Live Science. Retrieved 2018-03-29,
from https://www.livescience.com/18351-mild-winter-surprising-downsides-warm-weather.html
Nationalencyklopedin. (n.d.). Parklind. Avalible: https://www-ne-
se.ezproxy.ub.gu.se/uppslagsverk/encyklopedi/l%C3%A5ng/parklind
Nowak, D.J., Crane, D.E., & Stevens, J.C. (2006). Air pollution removal by urban trees and shrubs in the United
States. Urban Forestry & Urban Greening, 4(3 4), 115-123. doi: 10.1016/j.ufug.2006.01.007
Oke, T.R., Crowther, J.M., McNaughton, K.G., Monteith, J.L., & Gardiner, B. (1989). The Micrometeorology of
the Urban Forest [and discussion]. Biological Sciences, 324(1223), 335-349.
Oke, T.R., Mills, G., Christen, A., & Voogt, J.A. (2017). Urban Climates. Cambridge: Cambridge University
Press.
Primack, D., Imbres, C., Primack, R.B., Miller-Rushing, A.J., & Del Tredici, P. (2004). Herbarium Specimens
Demonstrate Earlier Flowering Times in Response to Warming in Boston. American Journal of Botany, 91(8),
1260-1264.
Rahman, M., Stringer, P., & Ennos, A. (2013). Effect of pit design and soil composition on performance of pyrus
calleryana street trees in the establishment period. Arboriculture and Urban Forestry, 39(6), 256-266.
Sanders, J.R. & Grabosky, J.C. (2013). 20 years later: Does reduced soil area change overall tree growth? Urban
Forestry & Urban Greening, 13(2014), 295-303. doi: http://dx.doi.org/10.1016/j.ufug.2013.12.006
Schiestl-Aalto, P., Nikinmaa, E., & Mäkelä, A. (2013). Duration of shoot elongation in Scots pine varies within
the crown and between years. Annals of Botany, 112(6), 1181-1191. doi: 10.1093/aob/mct180
Sjöman, H., Östberg, J., & Bühler, O. (2011). Diversity and distribution of the urban tree population in ten major
Nordic cities. Urban Forestry & Urban Greening, 11(2012), 31-39. doi: 10.1016/j.ufug.2011.09.004
SMHI. (2014). Dataserier med normalvärden för perioden 1961-1990 – Normalvärden för nederbörd. Retrieved
2018-04-03, from http://www.smhi.se/klimatdata/meteorologi/temperatur/dataserier-med-normalvarden-1.7354
Tenche-Constantinescu, A.M., Madoşa, E., Chira, D., Hernea, C., Ţenche-Constantinescu, R.V., Lalescu, D., &
Borlea, G.F. (2015). Tilia spp. - Urban trees for future. Notulae Botanicae Horti Agrobotanici Cluj-Napoca, 43(1),
259-264. doi: 10.15835/nbha4319794
Ununger, J., Ekberg, I., & Kang, H. (1988). Genetic control and age‐related changes of juvenile growth characters
in Picea abies. Scandinavian Journal of Forest Research, 3(1-4), 55-66. doi: 10.1080/02827588809382495
Wesołowski, T., & Rowiński, P. (2006). Timing of bud burst and tree-leaf development in a multispecies temperate
forest. Forest Ecology and Management, 237(1), 387-393. doi: 10.1016/j.foreco.2006.09.061
Wielgolaski, F. E. (2001). Phenological modifications in plants by various edaphic factors. International Journal
of Biometeorology, 45(4), 196-202. doi: 10.1007/s004840100100
Xiao, Q. & McPherson, E. (2002). Rainfall interception by Santa Monica's municipal urban forest. Urban
Ecosystems, 6(4), 291-302.
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
101214161820
201
8-0
3-28
201
8-0
3-30
201
8-0
4-01
201
8-0
4-03
201
8-0
4-05
201
8-0
4-07
201
8-0
4-09
201
8-0
4-11
201
8-0
4-13
201
8-0
4-15
201
8-0
4-17
201
8-0
4-19
201
8-0
4-21
201
8-0
4-23
201
8-0
4-25
201
8-0
4-27
201
8-0
4-29
201
8-0
5-01
201
8-0
5-03
Leaf
bu
rst
ind
ex
Site 1
T1-1 T1-2 T1-3 T1-4 T1-5 T1-6
0
1
2
201
8-0
3-28
201
8-0
3-30
201
8-0
4-01
201
8-0
4-03
201
8-0
4-05
201
8-0
4-07
201
8-0
4-09
201
8-0
4-11
201
8-0
4-13
201
8-0
4-15
201
8-0
4-17
201
8-0
4-19
201
8-0
4-21
201
8-0
4-23
201
8-0
4-25
201
8-0
4-27
201
8-0
4-29
201
8-0
5-01
201
8-0
5-03
Leaf
bu
rst-
ind
ex
Site 2
T2-1 T2-2 T2-3 T2-4 T2-5 T2-6
0
1
2
3
4
5
201
8-0
3-28
201
8-0
3-30
201
8-0
4-01
201
8-0
4-03
201
8-0
4-05
201
8-0
4-07
201
8-0
4-09
201
8-0
4-11
201
8-0
4-13
201
8-0
4-15
201
8-0
4-17
201
8-0
4-19
201
8-0
4-21
201
8-0
4-23
201
8-0
4-25
201
8-0
4-27
201
8-0
4-29
201
8-0
5-01
201
8-0
5-03
Leaf
bu
rst
ind
ex
Site 3
T3-1 T3-2 T3-3 T3-4 T3-5 T3-6
02468
101214161820
201
8-0
3-28
201
8-0
3-30
201
8-0
4-01
201
8-0
4-03
201
8-0
4-05
201
8-0
4-07
201
8-0
4-09
201
8-0
4-11
201
8-0
4-13
201
8-0
4-15
201
8-0
4-17
201
8-0
4-19
201
8-0
4-21
201
8-0
4-23
201
8-0
4-25
201
8-0
4-27
201
8-0
4-29
201
8-0
5-01
201
8-0
5-03
Leaf
bu
rst-
ind
ex
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