The University of Bristol

School of Life Sciences

MSci Practical Project Report

Veteran Trees in PAWS: A Comparison of the Use ofDifferent Ages and Species of Tree by Woodland

Fauna

Author:

Thom Erritt

te0047@my.bris.ac.uk

1019047

Supervisor:

Dr. Jane Memmott

Word Count: 5,998

Veteran Trees in PAWS: A Comparison of the Use of Different Ages and Speciesof Tree by Woodland Fauna

Thom Erritt

School of Life Sciences

The University of Bristol

Abstract

Two distinct yet complementary investigations were carried out to examine the ecological roles of veteran trees in

Plantations on Ancient Woodland Sites (PAWS). The aim of the first investigation was to compare the abundances and

diversities of birds and invertebrates present on the two main categories of tree found in a PAWS; veteran broadleaf

trees and non-native conifers. It was found that the veteran trees were host to significantly higher abundances and

diversities of our survey species, providing evidence that they play an important part in maintaining the biodiversity

of these PAWS. The aim of the second investigation was to examine the relationship between the age of a veteran tree

and the number of invertebrates and microhabitats on its trunk. There was found to be a positive correlation between

the age of a veteran tree and both of these variables. This indicates that the biodiversity of veteran trees may increase

with age and therefore so does their ecological value.

Keywords: veteran tree, PAWS, ecology, birds, invertebrates, microhabitats

1. Introduction1

The diverse range of ecological roles performed by veteran trees make them of huge value to the biodiversity2

of woodland ecosystems across Great Britain (1). Other than their superb ecological value, veteran trees are also3

genetically, aesthetically, culturally and historically valuable. In combination, these values make veteran trees an4

important part of the natural heritage of Great Britain. This project aims to quantify the ecological value of veteran5

trees specifically in Plantations on Ancient Woodland Sites (PAWS). This should provide evidence that they support6

a wide range of woodland species and help to increase the biodiversity of the ecosystems they belong to.7

The term veteran tree can be fairly ambiguous. There are a number of slightly different definitions of the term;8

however one of the most concise and accurate ones comes from Croft (2), who defines a veteran tree as one that9

possesses all or a number of the following characteristics:10

1. Biological, aesthetic or cultural interest because of its great age.11

2. A growth stage that is defined as ancient or post-mature.12

3. A chronological age that is old relative to others of the same species.13

1

One of the reasons that veteran trees have captured numerous imaginations through the ages is due to their aesthetic14

appeal. Their unique visual charm stems from the morphological characteristics that a tree begins to develop as it ages.15

Some of the most important and recognisable of these veteran characteristics are as follows:16

1. Large trunk circumference (compared to other trees of same species) after many years of accumulation of annual17

growth rings.18

2. Progressive diminution in width of successive annual growth rings.19

3. Decay, leading to branch failure and trunk hollowing.20

4. A progressive or episodic reduction in post mature crown size, often known as retrenchment.21

These characteristics, amongst many others, make veteran trees excellent habitats for a wide range of other wood-22

land species; which is why these trees are so ecologically valuable. These species include a multitude of fungi, lichens23

and bryophytes, with up to 2,500 species of fungi and 50 species of moss known to associate with veteran trees in the24

forests of Sweden (3). Other species that are reliant on veteran trees include a wide array of arthropods; these species25

inhabit niches all over the tree, from pollinators in the foliage, to predatory spiders on the bark and fungivorous26

collembola around the base (4). Finally, birds and mammals rely on veteran trees for foraging and nesting, with the27

great spotted woodpecker (Dendrocopus major) relying on insects found in fallen wood for 97% of its diet throughout28

winter (5) while Barbastelle (Barbastella barbastellus) and Daubentons (Myotis daubentonii) bats are known to roost29

and give birth in tree holes during summer months (6) .30

The majority of this project will conducted by surveying the trees found in Plantations on Ancient Woodland Sites.31

Most of the PAWS in the United Kingdom were created between the years of 1941 and 1970 when as much as 44% of32

the UKs surviving ancient woodland was converted to coniferous plantation in order to avoid timber shortages during33

future instances of war, resulting in the formation of around 220,000 hectares of PAWS (7) (8). One interesting feature34

of these PAWS is that they often contain extant features of the ancient woodland that preceded them, which are now35

some of the most rare, yet biodiverse and ecologically valuable ecosystems in the UK (9). These extant features are36

more often than not the veteran trees which were excluded from the initial clear felling and are now surrounded by37

conifer plantation. These are the two categories of tree that this project aims to compare, the dominant non-native38

conifers and the broadleaf veterans that occasionally intersperse them.39

The restoration of PAWS has become a top priority for many woodland managers after the Habitat Action Plans40

for Native Woodland set in motion ideas about enhancing the remaining features of ancient woodland through the41

conversion of PAWS to Restored Native Woodland on Ancient Sites or RNWAS (10). This restoration involves the42

gradual replacement of non-native conifer species with broadleaf species in order to encourage growth of a forest that43

is more valuable for both recreation and biodiversity (11) (12).44

We aim to study the trees within two separate PAWS located in Leigh Woods, North Somerset and Savernake45

Forest, Wiltshire. We will do this by surveying the abundances and diversities of the birds, arthropods and micro-46

habitats that are present on different species and ages of tree. We decided to survey these criteria as they are all47

2

known to be good indicators of the general ecological health of an area. For example, birds are known to be excellent48

ecological indicators because of their widespread presence, high detectability and sensitivity to natural and human49

alteration of environments (13) (14). In addition to this, we chose to include collembola and arachnids in our arthropod50

surveys as collembola are known to be excellent indicators of soil fauna diversity whilst arachnids have been reliably51

used numerous times to determine the ecological value of many different habitats including woodlands, marshlands52

and grasslands (15) (16). The final criteria that we decided to survey was the abundance of microhabitats on the trees,53

this is because microhabitats are known to be an excellent proxy for representing the biodiversity of species that are54

generally difficult to observe such as fungi, lichens, bats and invertebrates (17) (18) (19) (20).55

The knowledge of whether these ecological indicator species are present in higher abundances on different trees56

in PAWS will provide numerous valuable insights with wide-ranging benefits. For example, the ascertainment of the57

fact that the veteran trees in PAWS are host to higher abundances and diversities of woodland fauna than the conifers58

that surround them will provide valuable evidence that veteran trees are helping to increase the levels of biodiversity59

found in PAWS. It should also provide evidence for the importance of future conversion of PAWS to RNWAS by60

replacements of the incumbent conifers with the potentially more ecologically valuable broadleaf trees. Furthermore,61

the ascertainment of whether different species and ages of broadleaf veteran are host to different assemblages of62

species will also be invaluable for the management of currently mature trees, ensuring the most ecologically valuable63

populations of veteran trees in the future.64

2. Methods65

This project was conducted through two distinct yet complementary investigations. The first investigation was an66

intensive study on a small sample of trees found around Bristol, with the aim of directly comparing the differences67

in abundances of birds and arthropods on veteran and conifer trees; this part of the project will be described under68

Objectives 1 and 2. The second investigation was a more extensive study on a much larger sample of veteran trees69

found in Savernake Forest, with the aim of observing how the abundances of invertebrates and microhabitats on70

a veteran tree vary with age and species; this part of the project will be described under Objectives 3 and 4. All71

statistical analyses throughout this project were completed on IBM SPSS 21.72

2.1. Objective 1: Comparing the abundance and diversity of birds found on veterans and conifers in PAWS73

Bird counts were recorded from nine veteran and fourteen conifer trees. Seven of the veteran trees were Sweet74

Chestnuts (Castanea sativa) and two were Oaks (Quercus robur), four of the conifers were Norway spruce (Picea75

abies) and ten of them were Scots Pine (Pinus sylvestris). The veterans were selected as they were the only ones76

located either in PAWS, or in close association with conifer trees in the area surrounding the city of Bristol, UK.77

Three of the nine veteran trees were located in a PAWS at Paradise Bottom, Leigh Woods (51.458269, -2.635398).78

The other six were located in Ashton Court, an area of parkland to the west of Bristol (51.445481, -2.642838). The79

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conifer trees in our survey were randomly selected from all of the conifer trees that surrounded our chosen veteran80

trees. Four conifers were chosen at the Paradise Bottom site as they were estimated to occupy a similar amount of81

space as the veterans there whilst nine conifers were chosen at the Ashton Court site for the same reason.82

Count censuses were used to deduce the abundance and diversity of birds visiting our sample of veteran and83

conifer trees. Birds were counted if they landed in one of our survey trees, birds flying above or landing in trees84

other than our survey trees were ignored. A total of 8 hours of bird watching was carried out at Paradise Bottom as85

it was possible to watch the veterans and conifers simultaneously, while a total of 16 hours was spent bird watching86

at Ashton Court as the veteran trees and the conifers had to be surveyed separately due to the short distance between87

them. Bird species were identified using binoculars and a bird identification guide before being classified as either88

small, medium or large.89

A One-Way ANOVA was used to test for differences between the conifers and the veterans after checking visually90

for assumptions of independence, normality and equal variance. Shannon-Wiener Biodiversity Indices were calculated91

to compare the biodiversity of each group of trees.92

2.2. Objective 2: Comparing the abundance and biodiversity of invertebrates found in veterans and conifers in PAWS93

Bark brushing was used to sample the invertebrates present on the same population of veteran and conifer trees94

that were used in Objective 1. Our methodology was to place string transects around the veteran trees at heights of95

20, 120 and 220cms from the trees base. A large paintbrush was then used to gently brush the bark 10cm above and96

below the full length of the transect whilst catching any invertebrates that fell off in a plastic container. Each transect97

was sampled for five minutes. As the diameter of the conifer trees in our sample were much smaller, the whole basal98

two metres of their trunks was sampled for five minutes. The invertebrates were then euthanized and stored at -20C99

until processing.100

The abundances and diversities of invertebrate morphotypes (collembola, arachnids, mites, flies, grubs, beetles,101

woodlice, other) that were present in each of our samples was determined in the laboratory using a Leica LED3000102

SLI on a Stereo Microscope. The number of invertebrates found per m2 of bark was then calculated using the circum-103

ference of the survey trees; this allowed us to compare the conifers and the veterans accurately. A One-Way ANOVA104

was used to compare the two data sets in the same way as in Objective 1.105

2.3. Objective 3: Comparing the abundance and biodiversity of invertebrates across different ages and species of106

veteran tree in PAWS107

Data was obtained by sampling every veteran tree located in a PAWS in the northern part of Savernake Forest,108

Wiltshire (51.406147, -1.667596). Samples of invertebrates were obtained using the same methodology of bark109

sampling used in Objective 2, the only difference being that only one transect was sampled per tree at a height of110

120cm in order to save time. Our sample initially included a total of 200 veterans comprised of Oaks, Beeches, Sweet111

Chestnuts, Horse Chestnuts, Silver Birches and Sycamores. However statistical analyses were only conducted on a112

4

total of 179 trees comprised of Oaks, Beeches and Sweet Chestnuts as these were the only species of tree whose ages113

could be reliably estimated using the exact methodology suggested by White (21).114

The relationship between tree age and invertebrate population was tested using a linear regression in the same way115

as in Objective 3. A One-Way ANOVA was used to test for differences between invertebrate abundances of different116

species of veteran tree.117

2.4. Objective 4: Comparing the abundance and diversity of microhabitats in different ages and species of veteran118

trees found in PAWS119

Microhabitat abundances were obtained using a point count census of the entire basal two metres of the same sam-120

ple of veteran trees used in Objective 3. Microhabitats were classified into six easily identifiable and distinguishable121

categories: basal hole, trunk hole, flaking bark, crevice in trunk, gall/canker, sap run.122

A linear regression was used to test the relationship between tree age and number and diversity of microhabitats in123

the same way as in Objective 3. A One-Way ANOVA was used to test for differences between microhabitat abundances124

of different species of veteran tree.125

3. Results126

3.1. Objective 1: Comparing the abundance and diversity of birds found on veterans and conifers in PAWS127

A significantly higher number of birds were observed on the veteran trees than on the conifers (P

Figure 1: Mean abundances (+/-SE) of small, medium and large

birds observed on veteran and conifer trees.

Figure 2: Mean abundances (+/-SE) of each morphotype of inver-

tebrate per m2 of bark of veteran and conifer trees.

3.3. Objective 3: Comparing the abundance and biodiversity of invertebrates across different ages and species of142

veteran tree in PAWS143

A weak yet positive correlation was found between the age of a veteran tree and the number of invertebrates found144

on its bark (Ra=0.292, R2=0.085, F177,1=16.459, P

Figure 3: Relationship between the age of all species of tree and

the number of invertebrates per m2 of bark.

Figure 4: Relationship between the age of each species of tree and

the number of microhabitats on its trunk.

Finally, It was also found that the veteran trees at the Bristol survey sites had significantly more microhabitats than162

the conifers present there (veteran mean=19.9, conifer mean=2.0, P

was still possible to obtain significant and conclusive results. I do not believe a larger sample size would have altered182

our major findings however it may have allowed us to gain more insightful conclusions in terms of comparing conifers183

with different species of veteran tree rather than just the population as a whole.184

A second limitation to our study was the time of year that our data was collected. All experimental work was185

carried out over a ten week period from the middle of January to the end of March in order to comply with the term186

schedule of our university. The consequence of this is that many arthropod species would have still been overwintering187

and would not have been active on the bark (22). Ideally, our surveys would have been completed during late spring and188

summer when arthropod activity would be at its peak. However, I do not believe this limitation will have significantly189

affected our findings as it was still possible to collect large numbers of arthropods from both the veterans and the190

conifers that should be proportional to the number of insects that would be active at the height of summer, and thus191

the differences between them would still be present.192

4.2. Objective 1 - Birds193

We can obtain a better understanding of why larger abundances and diversities of birds were sighted in veteran194

trees rather than conifers by considering why avifauna are using these trees in the first place. Birds are known to use195

trees for a diverse range of ecological functions including roosting, breeding, overwintering, perching and foraging (23).196

I would hypothesise that the reason we saw more birds in the veteran trees was because the higher abundances of prey,197

microhabitats and epiphytes on the veterans allowed the birds to perform these functions more efficiently and safely198

than they could in the conifers.199

For example, it is highly likely that birds would have better foraging opportunities on veterans because, as our200

results have shown, they are host to higher abundances of invertebrates than conifers. It has also been proven that201

birds regularly feed on the morphotypes of invertebrate that we found on our survey trees; experiments by Gunnarson202

have shown that collembola and arachnid abundances were significantly higher in sites where bird predation was203

artificially removed (24). Therefore, we can hypothesize that one of the reasons that we encountered more birds in the204

veteran trees than the conifers was that foraging opportunities were better on the veteran trees due to their significantly205

higher abundances of arthropod prey.206

The second reason that birds may find veteran trees more appealing than the surrounding conifers is because of the207

superior nesting and roosting sites on offer. We know that finding a suitable nest site is essential to the life histories208

of many species of bird, who generally rely on trees to provide them. For example, ten of the eleven species of209

European woodpecker and at least ten species of European owl are known to make their nests in tree holes (25) (26).210

Furthermore, Laiolo states that the availability of tree holes is fundamental for woodland birds, and can result in211

severe competition between hole-nesters (23). When considering these facts in combination with our findings from212

Objective 4, that veteran trees have more microhabitats compared to conifers, we can see that birds may have been213

choosing to land in veteran trees as they offer a higher probability of having a microhabitat that would be suitable for214

nesting.215

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It is also possible that we may have seen more birds in the veterans compared to the conifers because of the216

higher number of epiphytes present on veteran trees. Nadkarni found that in forest ecosystems, a higher abundance217

of epiphytes led to a higher abundance of birds (27). Possible reasons for this include that epiphytes increase the218

total amount of resources available, provide opportunities for resource specialisation and temporally spread resources219

throughout the year (28). Although our surveys did not directly compare the number of epiphytes on each category of220

tree, I would consider it likely that there would be higher abundances of epiphytes on the veterans. This is because the221

presence of epiphytes is included as a specifically veteran characteristic in Crofts unifying description of veteran222

trees (2).223

4.3. Objectives 2 and 3 - Invertebrates224

The second major finding of our surveys was that there were higher abundances and diversities of all morphotypes225

of invertebrates in older veteran trees than there were in conifers and younger veteran trees. In this part of the226

discussion I will consider numerous reasons for why we may have seen these differences. However, I feel that it will227

be easiest to explain these differences whilst focusing on only two of the morphotypes that appeared in our surveys:228

arachnids and collembola. This is because these two taxa are known to be excellent ecological indicators as they229

make significant contributions to arboreal food webs. Collembola contribute to food-webs as they are preyed upon230

by a variety of other species, notably arachnids (29); arachnids contribute to food-webs as they are intermediate level231

predators and also act as a food source for birds (30).232

I hypothesise that one of the most probable reasons for why we recorded the highest abundances of arthropods233

on the bark of older veteran trees was because of their increased structural complexity and therefore increased habitat234

heterogeneity.235

The effect of arboreal structural complexity on arthropod populations has been thoroughly studied by Halaj (31).236

This work involved devising a method for comparing the structural complexities of different species of tree in order to237

ascertain which physical characteristics were the best predictors of arachnid abundance and diversity. Halaj deemed238

that a tree was more structurally complex if it had a larger diameter at breast height, larger maximum vertical and239

horizontal branch spread, larger range of branching angles and higher biomass. He then carried out a pair of ex-240

periments whilst using this definition. The first experiment surveyed the natural arachnid abundances of trees with241

differing structural complexities and the second experiment manipulated the complexity of tree branches in a lab and242

viewed its effect on populations of arachnids and collembola.243

The results of the first experiment showed that higher abundances of arachnids were present on more complex244

trees (32). The results of the second experiment showed that reducing the complexity of a habitat reduced the abun-245

dances of arachnids and collembola whilst increasing the complexity of a habitat significantly increased arachnid246

abundances and caused an eight-fold increase in abundances of collembola (31).247

These conclusions allow us to put the results of our own experiments in perspective. We saw almost exactly248

the same pattern as Halaj, our results showed that in more complex environments, i.e. veteran trees with increased249

9

diameter, branch spread, branch angle variability and biomass there were higher abundances of arthropods than in250

less complex conifers. As we can see, the structural complexity of a habitat has a significant influence on the resident251

arthropod community.252

Arthropods use trees for a number of different ecological functions. They are used for shelter, foraging, oviposi-253

tion, sun-basking, sexual display, and for herbivores such as collembola, they provide nutritional value (31). I would254

hypothesise that in a structurally more complex tree, arthropods are able to perform these essential parts of their255

life-histories more efficiently and safely. For example, increased branch biomass correlates positively with increased256

surface area, meaning larger populations and higher densities of arthropods can be supported with less intense com-257

petition. Furthermore, increased branching angles give spiders more options in terms of sites for web attachment as258

well as for finding suitable retreat sites that can be used for egg-laying and predator avoidance. Overall, what we are259

seeing is that increased complexity of veteran trees leads to increased habitat heterogeneity and therefore increased260

capacity to support larger and more diverse populations of invertebrates.261

These ideas can be taken one step further when we consider the complexity of the arboreal environment at an262

even finer scale. Many studies have shown that certain biological surfaces have a fractal, or at least semi-fractal263

structure (33) (34) (35). A surface is fractal if its area increases when a progressively finer unit of measurement is used;264

this is because the finer units of measurement will detect certain irregularities that larger units of measurement would265

not, thus increasing the surface area (36). Experiments by Florin have shown that bark has a fractal structure, meaning266

the surface area of bark becomes greater when the unit of measurement becomes smaller (35).267

The degree of fractality of a certain surface can be worked out by measuring the surface and using a specific268

equation which produces a number between 1 and 2, this number is called the fractal dimension of the surface, or D.269

A surface with a D value nearer to 2 will be more fractal than a surface with a D value nearer to 1 (37). Florin used270

this equation to work out the fractal dimension of the barks of varying ages of plum tree and showed that older, more271

complex, fissured and exfoliated bark tended to have a higher fractal dimension than younger, less complex bark.272

They also found that the age of a plum tree could be accurately predicted from the D value of its bark (35).273

As we now know that different complexities of bark have different fractal dimensions, we can now consider274

what this means for the arthropods living upon it. Gunnarson has hypothesised that if the way an animal perceives275

its environment is related to its body size then an animal with a body length of 3mm will perceive the area of a276

surface with a D value of 1.5 as up to one order of magnitude larger than an animal with a body length of 30mm;277

this increased perceived surface area should be able to support higher population densities of animals with a body278

length of 3mm than 30mm. Gunnarson tested this hypothesis by allowing spiders to invade artificial plant habitats279

with different D values before comparing their population densities and abundances. He found higher densities of280

spiders in environments with high fractal dimensions and lower densities of spiders on environments with lower fractal281

dimensions (38).282

If we now consider the findings of the Florin and Gunnarson experiments together we can obtain an interesting hy-283

pothesis for why we recorded more arthropods on veteran trees than on conifers as well as on older veteran trees than284

10

on younger ones. The Florin paper concluded that the more complex bark from older trees had a higher fractal dimen-285

sion. The Gunnarson paper concluded that structures with higher fractal dimensions supported higher abundances286

of arachnids than structures with lower fractal dimensions. Therefore we could hypothesise that the differences in287

fractal dimensions of bark between our comparison groups, which was deep and fissured in our veteran Oaks and288

Sweet chestnuts (high D value) while smooth and flaky in our conifers (low D value), could have contributed to289

differences in invertebrate abundances in our samples. This is because the high D value bark of older veterans had a290

larger perceived surface area that could support larger populations of arthropods.291

Overall, I believe our findings that invertebrate abundances and diversities are higher in veteran trees than conifers292

as well as in older veteran trees than younger veteran trees are well founded. There is strong evidence that higher293

structural complexity at both a habitat and fractal level can lead to higher abundances of both spiders and collembola,294

reflecting exactly what we discovered in our experiments. These explanations also allows us to hypothesise why we295

saw differences between the invertebrate communities of different species of tree. In theory, the smooth, almost sterile296

looking bark of Beech trees would have a had much lower structural and fractal complexity than the deep, fissured297

bark of Sweet Chestnuts; leading to much lower abundances of invertebrates. This is exactly what we saw in our298

experiments, Sweet Chestnuts were host to the highest abundances of invertebrates whilst Beeches were host to the299

lowest.300

4.4. Objective 4 - Microhabitats301

Our third and final major finding was that as the age of veteran trees increased, so did the number of microhabitats302

on their trunks. These findings support the hypothesis that veteran trees become more ecologically valuable as they303

get older. This is because the abundance of microhabitats in an ecosystem is known to correlate with the abundance304

of many arboreal species such as many passerines, bats and invertebrates (17) (18).305

I believe this correlation exists because the number of microhabitats that a tree has will be likely to represent of306

the number of niches that the tree may have available. Having higher abundances of niches means that a tree has a307

higher capacity to support a larger abundances of certain species with minimal amounts of competition.308

4.5. Tree Size309

One final possible reason for why we observed different abundances and diversities of species in different cate-310

gories of tree is simply to do with their size. The veteran trees in our sample tended to be much larger than the conifer311

trees (mean veteran diameter=99.7cm, mean conifer diameter=46.2cm) as did the older veteran trees compared to the312

younger ones because tree diameter is directly related to age. When considering these differences in size in combina-313

tion with island biogeography theory we can gain some insight into why abundances of certain species differ between314

veterans and conifers.315

It has been proposed that island theory could be useful in explaining the differences in arthropod abundances316

between different species of plant (39). This is because larger islands, in this case larger veteran trees, are more likely317

11

to support higher abundances and diversities of species simply because they offer more available space and are more318

likely to be discovered in the first place (40). Therefore, one possible reason for why we recorded more species in the319

veterans than the conifers was simply because the veterans were larger and were therefore more likely to be discovered320

and populated by arthropods and birds.321

4.6. Conclusions - What Does This Mean for PAWS and Veteran Trees?322

This project has two major implications for PAWS and veteran trees. The first of these is that the current population323

of veteran trees located in PAWS are extremely beneficial to the ecological health and biodiversity of the ecosystems324

that they belong to. Our surveys show that the veterans are acting as islands of high species abundance and richness325

in a sea of less diverse conifers; this has the effect of bringing up the average biodiversity of the PAWS as a whole.326

This is clear evidence that the current population of veteran trees should be conserved and managed to maximise the327

biodiversity they support. For example, we saw that birds were choosing to land in veteran trees rather than conifers328

and that this was most likely due to the better nesting and foraging sites provided by the veteran trees. As competition329

between birds for nest sites is fierce, any loss of veteran trees and their abundance of nest sites from a PAWS would330

almost definitely lead to a drop in bird populations of the area. In contrast, an increase in the number of nest sites331

produced by correct management of veteran trees would likely lead to an increase in the bird population of the area,332

leading to an increase in the overall biodiversity of the PAWS.333

The second implication that can be gleaned from our findings is that gradual replacement of the conifers with334

broadleaf species would have a positive effect on the biodiversity and ecological health of the PAWS ecosystem. This335

is because larger populations of broadleaf species would have the capacity to support higher abundances and more336

diverse assemblages of species than the current population of conifers. In addition to this, the broadleaf trees would337

eventually mature into veteran trees and would hopefully begin to develop characteristics and species assemblages338

similar to those of the ancient woodland that once covered large quantities of the Great Britain. This idea of the339

conversion of PAWS to RNWAS is currently being explored by woodland managers around Great Britain and the340

results of our surveys provide evidence that it would be beneficial to the ecology of these woodlands and the country341

as a whole.342

Another interesting observation was that different species of veteran tree may have been carrying out slightly343

different ecological functions in the PAWS. It was clear that the deep, complex bark of Sweet Chestnuts was an344

excellent habitat for a wide range of invertebrate species. Whilst the complex branching and exposed roots of the345

beech trees we surveyed were home to the greatest number of microhabitats, creating excellent perching, foraging and346

nesting sites for birds. So, we can see that the conservation of a diverse range of veteran trees in PAWS would allow347

the conservation of the greatest range and diversity of ecological roles.348

Overall, we have observed clear differences in the use of different ages and species of trees in PAWS by woodland349

fauna. This has allowed us to conclude that the presence of veteran broadleaf trees and the superior assemblages350

of species that they support are clearly ecologically beneficial to the PAWS that they belong to. Therefore, the351

12

conservation of the veterans and the potential conversion of PAWS to RNWAS will ensure the enhancement and even352

restoration of the remnant assemblages of species and interactions that would have filled the ancient woodland of353

pre-1900s Great Britain.354

5. Competing Interests355

This project has no competing interests.356

6. Acknowledgements357

Firstly, I would like to thank Ellie Lewis for being such an excellent and enthusiastic project partner. I would also358

like to thank Professor Jane Memmott at the University of Bristol for her continued guidance and advice. Finally,359

I would also like to thank Paul Rutter and Tom Blythe at PlantLife and the Forestry Commission for their ongoing360

support and recommendations throughout this project and Millie and Nick Carmichael for their hospitality during our361

stay in Savernake Forest.362

7. Funding363

This project was funded by the University of Bristol.364

8. References365

[1] N. Fay, Environmental arboriculture, tree ecology and veteran tree management, Arboricultural Journal 26 (3) (2002) 213238.366

doi:10.1080/03071375.2002.9747336.367

[2] A. Croft, Ancient and other veteran trees: further guidance on management, Arboricultural Journal 35 (2) (2013) 110111.368

doi:10.1080/03071375.2013.823318.369

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