Restoration of Lapsed Beech Pollards: Evaluation of Techniques and Guidance for Future Work Helen J

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Arboricultural Journal: The International Journal of Urban Forestry Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/tarb20 Restoration of lapsed beech pollards: Evaluation of techniques and guidance for future work Helen J. Read a , Jeremy Dagley b , Jose Miguel Elosegui c , Alvaro Sicilia d & C. P. Wheater e a Burnham Beeches Office (City of London), Farnham Common, UK b Epping Forest Office, Loughton, UK c Obispo Huarte 1, Leitza, Spain d C/ Los Herrán 1, Alava, Spain e School of Science and the Environment, Manchester Metropolitan University, Manchester, UK Version of record first published: 02 Jan 2013.

To cite this article: Helen J. Read , Jeremy Dagley , Jose Miguel Elosegui , Alvaro Sicilia & C. P. Wheater (2013): Restoration of lapsed beech pollards: Evaluation of techniques and guidance for future work, Arboricultural Journal: The International Journal of Urban Forestry, DOI:10.1080/03071375.2013.747720 To link to this article: http://dx.doi.org/10.1080/03071375.2013.747720

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Restoration of lapsed beech pollards: Evaluation of techniques and guidance for future work Helen J. Reada*, Jeremy Dagleyb, Jose Miguel Eloseguic, Alvaro Siciliad and C.P. Wheatere

aBurnham Beeches Office (City of London), Farnham Common, UK; bEpping Forest Office Loughton, UK; cObispo Huarte 1, Leitza, Spain; dC/ Los Herrań 1, Alava, Spain; eSchool of Science and the Environment, Manchester Metropolitan University, Manchester, UK

We examined the impact of two pollard restoration techniques on 38 ancient, lapsed beech pollards in the Basque Country (northern Spain) in four locations from 2007 to 2009. In 2007, prior to the trials, the trees were generally in good condition. Trials involved recutting the branches of trees with axes and/or chainsaws, and compared traditional Basque-style cuts, immediately above the bolling (main stem) close to the site of previous pollarding cuts, with gradual restoration techniques involving significantly smaller reductions of the canopy branches. Although one tree died following cutting, the responses of 36 pollards in 2009 (the third full season of regrowth), were generally good across the sites. Responses measured included the production of new shoots from dormant buds below the cuts and increases in the annual extension growth of retained branches. Stub length of cut branches was important with stubs longer than 500 mm producing significantly more new shoots from dormant buds. This finding supports results from recutting ancient beech pollards in England. The Basque-style cuts promoted more and longer epicormic growth. In addition, axe cuts encouraged more new shoots on cut branches, although the sample size and the possible confounding factor of stub length requires that this result be investigated further. Keywords: pollard; pollarding; beech; axe

Introduction Pollarded trees are found across Europe and result from the once commonly-practised technique of lopping branches on a regular cycle at a height above the ground so a product could be obtained from the tree while surrounding land was used for crops or grazing. Today in Britain there are remnants of this tradition, but in places large numbers of

Downloaded by [Guildhall Library], [Helen Read] at 09:00 02 January 2013 neglected trees remain. Aside from willow, pollards of other deciduous trees were generally cut for the leaves as fodder or for firewood (Read, 2007a). Pollards were common in some agricultural systems but became particularly abundant as the need for fuel-wood rose to an industrial scale, for example, in Epping Forest, England (Dagley & Burman, 1996) and Gipuzkoa in the Basque Country (where wood was needed to fuel iron foundries). Beech (Fagus sylvatica L.) trees were pollarded for firewood in many countries in their native range. Today, beech pollards are most abundant in northern Spain, the Basque Country (both France and Spain), and with a significant population in southern

*Corresponding author. Email: helen.read@cityoﬂondon.gov.uk

q 2013 Taylor & Francis and Aboricultural Association 2 H.J. Read et al.

England. It is likely that they are widespread and locally common in Romania and some sites or individual trees are known from Hungary, Italy, Germany and southern Sweden (Read, 2007a). A side effect of regular pollarding is that trees generally live longer than uncut or maiden trees (Lonsdale, 1993a). Repeated cutting creates a bolling (trunk) of uneven shape with hollows where rainwater collects and that, with age, develops a core of decaying wood. These age and growth characteristics frequently promote high wildlife importance and, although the cultural landscapes with which pollards are associated are often undervalued for nature conservation, concentrations of pollards often form biodiversity-rich cores of high-quality nature reserves. A wide range of saprophytic fungi and saproxylic invertebrates (reliant on decaying wood) areas associated with older beech trees, particularly Diptera such as crane-flies and hoverflies (e.g. for Epping Forest: Ismay, 2001). Thus, there are sound nature conservation reasons to ensure that old beech pollards stay alive as long as possible providing continuity of habitat (Read, 2000). Pollards are important culturally and aesthetically; inspiring artists, poets and musicians and are remnants of land-use systems of historical interest (Watkins, 1998). Pollarded beech are normally cut on a 10–25 year cycle (Dagley & Burman, 1996; Read, 2000). Many pollarded trees alive today are “lapsed”, with some in England having been last cut over 120 years ago (8–10 cycles), and are thus “out of cycle”. In the Basque Country the last cuts may have been over 50–60 years ago which, even with possible longer cutting cycles, means these too can be considered as lapsed. This, together with the tendency of beech to be less responsive to cutting than other tree species, presents problems for pollard restoration. Lessons learnt on beech, are likely to be transferable to other tree species. Restoration techniques for lapsed pollards have developed in the last 20 years from an early perception that no such work was worthwhile (Edlin, 1971) to the development of pollard restoration guidelines. Mitchell (1989) presented preliminary suggestions which have since been expanded upon (T. Green, 1996; Read, 2000; Read, Wheater, Forbes, & Young, 2010). Restoration of lapsed pollards has been carried out at Burnham Beeches and Epping Forest since the early 1990s (Frater, 1995; Dagley & Burman, 1996; Read, Frater, & Turney, 1991; Read, Frater, & Noble, 1996, Read et al., 2010; Dagley, 2007), but at Burnham Beeches the relatively small number of old pollards to work on has made comparative analysis difficult. Beech pollards are found across the Basque Country of France and particularly Spain where they can be especially numerous. Although many are in areas of high nature conservation value, their saproxylic fauna had not been appreciated until the beginning of the twenty-first century. Aragon Ruano’s (2001) review raised awareness of the historical Downloaded by [Guildhall Library], [Helen Read] at 09:00 02 January 2013 and cultural value of such trees and recent exchange visits between arboriculturists and nature conservationists in the Basque Country and England have highlighted their biological value. The current study was part of a co-operative project between English and Basque arboriculturists working on lapsed beech pollards in Spain. The aim was to compare two cutting techniques and different cutting tools to inform pollard restoration work in both the UK and Spain.

The sites and trees Trees studied were from four locations in northern Spain, three close to Leitza in the province of Navarra (at Pastain Borda, Urkizu and Areso) and at Oianleku, 25 km to the north-east, within Aiako Harria Natural Park in the province of Gipuzkoa. In Gipuzkoa the Arboricultural Journal: The International Journal of Urban Forestry 3

history of pollarding has been well documented and was a signiﬁcant economic activity (Read, 2007b). At Aiako Harria, the pollards formed part of the thousands of beech pollards that once provided timbers for ship-building in San Sebastian and later wood-fuel for the nineteenth-century iron foundries along the Basque coast (Aragon Ruano, 2001). At Leitza, pollarding has been for more local use, especially charcoal, and pollards were less regularly spaced and less uniform in character (Read, 2007b). For more details of the sites and trees chosen see Table 1.

Methods A total of 38 lapsed beech pollards, chosen in Leitza by the local people and in Aiako Harria by the park authorities, were cut in January and February 2007 in four locations. Of these trees, 27 (238 branches) were cut in the traditional Basque style, with large branches removed close to the bolling (i.e. “classic” pollarding), whilst 11 trees (107 branches) were cut using a gradual pollard restoration method pioneered in England (similar to heavy crown reduction and considered to be the first stage in a programme of staged tree reduction intended to restore the lapsed pollards into a regular cutting cycle again). Using gradual pollard restoration, branches were reduced in length rather than removed and smaller branches bearing leaves always retained below the point of cutting. Thus, the tree crown was reduced in height by 20–40% (Dagley, 2007). Figure 1 shows examples of the pollard restoration methods employed during this study. Six trees were cut entirely by axe, 29 with a chainsaw, and three trees had some branches cut by axe and some by chainsaw. Overall, 57 branches were cut with an axe and 288 with a chainsaw. For each tree, the cutting technique was recorded together with data based on ancient tree recording forms (Fay & De Berker, 1996). Due to time constraints some trees had more pre-cutting details recorded than others. The responses of trees and individual branches were evaluated after three growing seasons (in October 2009). Aspects relating to whole trees were recorded from the ground and photographs were taken of the tree at each cardinal compass point. Factors recorded included girth at 1.5 m, amount of dead bark, epicormic growth and shade for each quadrant of the tree (i.e. north, south, east and west), together with a visual score of tree response. The impact of technique on the amount of epicormic growth and its length was estimated for the bolling, the top of trunk, mid trunk, and base of trunk. Each tree was climbed by an arboriculturist who examined cut branches and measured the numbers of new shoots, stub length and branch diameter for up to 10 cut branches for each tree depending on how many branches had been cut. The number of new shoots emanating from each stub was counted, with clusters of shoots (two or more) arising from Downloaded by [Guildhall Library], [Helen Read] at 09:00 02 January 2013 the same point being counted as one shoot. The number of clusters was also recorded. The length of stub was measured as the distance from the cut surface to the first retained branch. Where there was no retained branch, the distance to the bolling was recorded. Stub diameter was measured as the maximum diameter. Dieback length was measured from the cut to the boundary between green live- and brown dead-wood identified by exposing a small area under the bark using a knife. In addition, branches retained in 2007 were examined from three trees at Leitza and one tree at Aiako Harria. The lengths between terminal bud scars (one year’s growth) were measured and measurements were extended back along each branch to obtain data for three years’ growth prior to cutting in 2007 and three years’ extension growth after cutting. Increment core samples were extracted from seven trees at two sites (Aiako Harria and Leitza), to examine annual, whole-tree growth patterns over a longer period. Downloaded by [Guildhall Library], [Helen Read] at 09:00 02 January 2013 4

Table 1. Site and tree characteristics in 2007. Read H.J.

Areso Pastain Borda Aiako Harria Urkizu

Province Navarra Navarra Gipuzkoa Navarra al. et Location Inland Inland Coastal mountains Inland Lithography Limestone Sandstone Granite Sandstone Landscape history Local use as Local use as “Industrial” Local use as common land common land wood production common land Historical cutting cycle (years) Up to 50 Up to 50 15–20 Up to 50 Years since last pollarded ,50 ,50 ,50 ,50 Girth of trees (cm) mean ^ standard error (n) 284.5 ^ 27.58 (4) 376.9 ^ 25.73 (7) 299.6 ^ 22.36 (8) 300.4 ^ 13.07 (18) Number of trees cut with axe 2 1 0 3 Number of trees cut with chainsaw 3 5 8 13 Number of trees cut half with chain saw half with axe 0 1 0 2 Number of branches recorded 45 66 69 165 Number of trees cut in Basque-style 2 5 4 16 Number of trees cut using gradual pollard restoration 3 2 4 2 Mean tree vitality before cutting* (n) 1.4 (5) Not assessed 1.6 (7) 1.2 (5) Live growth in crown* (n)1(5) Not assessed 1.1 (7) 1.0 (5) Crown architecture* (n) 1.2 (5) Not assessed 1.4 (7) 0.3 (5) Twig structure* (n) 1.6 (5) Not assessed 2.0 (7) 0.2 (5) Crown loss* (n) 1.4 (5) Not assessed 1.3 (7) 1.1 (5) Shade (whole tree)* (n) 1.4 (5) Not assessed 0.9 (8) 0.6 (5) Ground compaction* (n) 0.2 (5) Not assessed 0.6 (8) 1.4 (5) Decline score* (n) 1.2 (5) Not assessed 1.4 (7) 1.0 (5) Presence of branches , 50 mm* (n) 1.0 (5) Not assessed 0.4 (8) 0.7 (3) Total live poles . 50 mm (n) 8.2 (5) Not assessed 6.8 (8) 9.0 (3) Total dead poles (n)0(5) Not assessed 0.1 (8) 0.5 (4) Potential for collapse* (n) 1.6 (5) Not assessed 1.4 (7) 1.6 (4)

Note: *Scoring was on a scale of 0 (good) to 4 (poor). Arboricultural Journal: The International Journal of Urban Forestry 5

Downloaded by [Guildhall Library], [Helen Read] at 09:00 02 January 2013 Figure 1. Two recently cut beech pollards at Leitza in Navarra (February 2007). In the foreground is a gradual restoration of a pollard cut by chainsaw whilst in the background is a Basque-style axe- cut pollard, cut a year earlier in 2006.

Due to the relatively small sample sizes and unbalanced experimental design, not all data were normally distributed for all factors measured. Where a large amount of data were gathered and testing demonstrated normality and homoscedasticity, parametric ANOVA was employed using SPSS (V8). For most analyses this was not the case, so for potential differences between factors, non-parametric tests, such as Mann-Whitney U tests and Kruskal-Wallis analysis of variance using ranks, were employed using multiple comparison tests (Dunn’s tests) where relevant. Similarly, non-parametric correlations (Spearman’s rank correlation coefﬁcient) were used to examine possible relationships 6 H.J. Read et al.

between variables. Chi square analysis and likelihood ratio analysis (G test) were used to identify possible associations between frequency distributions. All non-parametric analyses were done using StatView (V5.0.1). For simplicity of understanding, all averages are given as mean values ^ standard errors. Ordination (non-metric multidimensional scaling using the Gower distance measure) was used to seek patterns in the complex data set produced using PAST (V1.65).

Results Trees generally responded well to cutting with relatively high mean numbers and lengths of new shoots (see Table 2). However, one tree had died and another was moribund in 2009 and there was considerable variation between the responses of individual branches. There was a signiﬁcant difference between the extension growth (distance between terminal bud scars) before and after the 2007 cutting event on the uncut, retained branches of the four trees examined. Measurements for the three years before cutting were signiﬁcantly shorter (60–80 mm per year) than for the three years after cutting (150– 230 mm: ANOVA, F5,280 ¼ 19.515, p , 0.0001). The increment core samples taken from seven trees at two sites indicated a reduced ring in 2007, the growth season following cutting; generally seen as a disappearance of late wood (that laid down in the summer) rather than spring wood. This is compatible with previous work showing a reduction in ring size after pollarding followed by a subsequent gradual increase (Slotte, 2000). One core from a tree at Leitza showed an event 69 years ago resulting in subsequent very poor growth which may have been the last time the tree was pollarded.

Effects of location There were signiﬁcant differences between the responses of trees from different locations (see Table 3). In all instances, trees at Aiako Harria were poorer than the three locations at Leitza, having fewer new shoots, more dead branches, less and poorer quality callus and more dieback of the bark below the cut.

Table 2. Characteristics of branches cut in 2007 and responses of 38 pollarded beech trees from four sites, three growing seasons after pollarding (2009).

Range Factor Minimum Maximum Mean Standard error

Downloaded by [Guildhall Library], [Helen Read] at 09:00 02 January 2013 For individual branches Stub length (mm) (n ¼ 345) 0 3200 449.05 22.70 Stub diameter (mm) (n ¼ 345) 40 825 207.10 6.02 No. new shoots* (n ¼ 345) 0 14 1.28 0.10 No. clusters (n ¼ 345) 0 9 0.79 0.74 Distance cut to new shoot (mm) (n ¼ 185) 0 950 165.02 15.52 Length of longest shoot (mm) (n ¼ 184) 5 1800 663.07 25.73 Length of dieback (mm) (n ¼ 329) 0 10000 218.66 34.29 For the whole tree No. of new shoots* (n ¼ 38) 0 48 11.6 1.75 No. clusters (n ¼ 38) 0 41 7.1 1.31 Total length of longest shoots (mm) (n ¼ 38) 0 3080 704.4 81.19

Note: *Includes number of clusters. Arboricultural Journal: The International Journal of Urban Forestry 7

Table 3. Comparisons of tree responses to pollarding at the four sites.

Kruskal- Comments based on multiple comparison Factors Wallis H df P (Dunn’s) tests Number of new shoots 9.91 3 0.019 Pastain Borda had more new shoots than either Aiako Harria or Urkizu Number of clusters 7.90 3 0.048 Marginal differences found with no separation identiﬁed between sites Length of dieback 49.52 3 ,0.0001 Aiako Harria had the most dieback and Areso had the least, with Pastain Borda and Urkizu being intermediate Factors Chi-square df P Comments

Number of dead Aiako Harria had more dead, while Urkizu had branches 42.96 3 ,0.0001 fewer dead Aiako Harria had more callus, while Urkizu had Presence of callus 30.88 3 ,0.0001 fewer callus Aiako Harria had poorer callus health, while Health of callus 21.05 3 ,0.0001 Urkizu had better callus health

Comparison of pollard restoration techniques Basque-style cut branches had significantly longer stub lengths (Mann-Whitney U tests z ¼ 2.833, P ¼ 0.005) and larger diameters (z ¼ 6.454, P , 0.0001) compared with the gradual pollard restoration method which had significantly more branches with a diameter of less than , 100 mm (z ¼ 3.798, P ¼ 0.0001). Basque-style cutting produced significantly more clusters of shoots (z ¼ 2.493, P ¼ 0.013), although not overall numbers of shoots, but had significantly more dieback (z ¼ 2.442, P ¼ 0.015). Trees with gradual pollard restoration cuts were less likely to have epicormic growth on the bolling compared to Basque-style cut trees (Chi-Squared ¼ 11.667, df ¼ 1, P , 0.0006) and shorter epicormic growth on the bolling (Mann-Whitney U, z ¼ 3.141, P ¼ 0.0017). Gradual pollard restoration cut trees had significantly more growth from dormant buds and significantly less adventitious bud growth (but more of both types together) than Basque- style-cut trees (likelihood ratio, G ¼ 7.087, df ¼ 2, P ¼ 0.029).

Comparison of cutting tools Branches cut with an axe had signiﬁcantly longer stubs (z ¼ 3.464, P ¼ 0.0005), a smaller diameter to length ratio (z ¼ 3.685, P ¼ 0.0002), more new shoots (z ¼ 2.648,

Downloaded by [Guildhall Library], [Helen Read] at 09:00 02 January 2013 P ¼ 0.0081), more clusters (z ¼ 2.942, P ¼ 0.0033), and more callus (Chi- square ¼ 7.138, df ¼ 1, P ¼ 0.007). Trees cut with a chainsaw were less likely to have epicormic growth on the bolling (Chi Squared ¼ 21.467, df ¼ 2, P , 0.0001) or growth on the base (Chi Square ¼ 6.622, df ¼ 2, P , 0.036). Trees cut with an axe had longer epicormic growth on the bolling than those cut with a chainsaw (Kruskal-Wallis H ¼ 12.628, df ¼ 2, P ¼ 0.0001). There was no signiﬁcant difference in growth types (from dormant buds or adventitious) for the different tools. No signiﬁcant differences were found in the responses of branches on those trees cut with both an axe and a chainsaw.

Impact of shade and orientation Canopy shade (in 2009) was only signiﬁcantly associated with three factors: shade was positively correlated with the distance between the cut and ﬁrst shoot (Spearman rho ¼ 0.405, 8 H.J. Read et al.

n ¼ 345, P ¼ 0.0002), whilst lower amounts of callus (Mann-Whitney U test, z ¼ 23.21, P ¼ 0.0013) and less healthy callus (z ¼ 22.78, P ¼ 0.005) were found with increased shade. Branch orientation had no signiﬁcant impact on branch response, dieback or epicormic growth. Neither was there any pattern identiﬁed relating to branch orientation when an ordination of the branch data (n ¼ 343) was carried out employing non-metric multidimensional scaling using Gower distance measurements.

Stub length and tree response In previous studies stub length has been linked to tree response. The impacts of this and stub diameter are shown in Table 4. Although longer stubs seem to increase the numbers of shoots and clusters arising, little variation was associated with the stub length (R 2 ¼ 10.2). This was investigated further by comparing situations where few (0 or 1) or multiple (2 or more) new shoots arise. Figure 2 indicates that stubs of 550 mm or more had a 50% or greater chance of producing multiple shoots per stub, whereas stubs of 300 mm or less had a 50% chance of producing none or just one shoot.

Discussion Growth patterns The results from increment core samples indicated reduced wood growth, whilst retained branch lateral growth rates showed increased canopy growth after cutting. Both results are compatible with previous studies (Le Sueur, 1931; Slotte, 2000). The generally accepted pattern of growth following cutting is that the annual increment is reduced while the tree produces callus growth around the margins of the wound and juvenile foliage. In the years following cutting the balance gradually shifts from leaf production into wood production (Fay & Bengtsson, 2011). This pattern of regeneration and the growth of physiologically younger growth on an ancient tree is discussed in more detail by Fay (2002). Carbohydrates in trees that have been heavily pruned have also been shown to migrate to the pruning points and away from the main trunk; sometime after cutting the concentrations at the pruning points gradually reduce (Clair-Maczulajtys, Le Disquet, & Bory, 1999).

Comparison of pollard restoration techniques Larger diameters were expected from the Basque-style cutting on out-of-cycle pollards because branches were cut closer to the bolling to get the tree quickly back into a regular Downloaded by [Guildhall Library], [Helen Read] at 09:00 02 January 2013 cutting cycle. In contrast, gradual pollard restoration cutting results in shorter stubs, being carried out higher in the crown, on more branches, closer to the tips of the branches, and where a retained branch is likely to be closer to the cut. These differences may have significant consequences; for example, greater dieback may occur with larger diameter cuts (see also Sisitka, 1991). Significantly more dormant buds were activated on gradual pollard restoration trees presumably because the cuts were higher in the canopy with younger bark. However, the Basque-style cuts may induce more response from the cambium resulting in adventitious growth and increasing quantity and length of epicormic growth on the bolling. This may be related to an increase in light levels (Collet, Lanter, & Pardos, 2002; Cochard, Coste, Chanson, Guehl, & Nicolini, 2005), as bigger branches were removed, and the influence of greatly reduced apical dominance. Greater light levels may also produce larger numbers of shoot clusters. Downloaded by [Guildhall Library], [Helen Read] at 09:00 02 January 2013 roiutrlJunl h nentoa ora fUbnForestry Urban of Journal International The Journal: Arboricultural

Table 4. Correlations between successful growth and stub length and diameter of cut branches sampled three years after cutting from 38 beech trees in four sites in the Basque Country, Spain.

Stub variable Successful growth factor Spearman’s rho P Comment Stub length (n ¼ 345) Number of new shoots 0.319 ,0.0001 More new shoots with longer stub lengths Stub diameter (n ¼ 345) Number of new shoots 20.077 0.0076 Fewer new shoots with larger diameters Stub length (n ¼ 345) Number of clusters 0.417 ,0.0001 More clusters with longer stub lengths Stub diameter (n ¼ 345) Number of clusters 0.153 0.390 No signiﬁcant correlation Stub diameter: length ratio (n ¼ 336) Number of new shoots 20.286 ,0.0001 More new shoots with smaller diameter: length ratios Stub diameter: length ratio (n ¼ 336) Number of clusters 20.176 ,0.0001 More clusters with smaller diameter: length ratios 9 10 H.J. Read et al.

1200

1000

800

600

400 STUB LENGTH mm

200

0 0 1

Figure 2. Box and whisker plot of stub length (mm) and growth of new shoots of 345 cut branches from 38 trees across four locations, where class 0 indicates1 or fewer, and class 1 indicates multiple (.1) new shoots per stub.

Comparison of cutting tools Axe-cut branches had significantly longer stubs and shorter diameter: length ratios which were potentially confounding factors when branch responses were examined. In practice, longer stubs are more likely on axe-cut branches because of the difficulty in cutting close to retained branches. Axe-cut branches produced significantly more shoots and clusters and more callus than those cut with a chainsaw. This needs further experimentation to tease out the impact of the tool used from the influence of stub length itself. Axe cuts also increased the quantity and length of epicormic growth on the bolling and the quantity of growth on the base of the tree. It is worth noting that axe-cut trees were all cut using the Basque-style which increased the light levels to the bolling, whereas all gradual pollard restoration cut trees were cut by chainsaw. Cuts made using different tools have different characteristics (see Table 5) and tool sharpness is likely to be very important for both axes and chainsaws. In relation to the response of branches to cutting, moisture levels and extent of wood dysfunction may be the two most important aspects. Previous studies have only looked at the impact of different tools on coppiced trees. Rackham (1975) suggested that there was no difference Downloaded by [Guildhall Library], [Helen Read] at 09:00 02 January 2013 between axes and saws at Hayley Wood, but Tanasescu (1939 cited in Mitchell, 1989) found edged tools better (the tree species was not noted). Different growth rates and growth patterns were reported on sweet chestnut coppice cut with axes and chainsaws (Phillips, 1971); the initial height of growth from axed stools was greater than for sawn stools but by the end of the first growing season after cutting there was no such difference. Axe-cut stool shoots grew more evenly than sawn stool shoots, which varied more in the number produced in the first year. However, by the end of the second year, the percentage of living shoots dropped sharply on sawn stools. He concluded that chainsaws induced more sporadic growth surges through the season than axes, and stimulated initial shoot production, but that this had an adverse effect on the number of viable shoots in later growing seasons. Chainsaw-cut stools tended to produce new shoots 1–2 inches (2.5–5 cm) below the cut surface whereas axe-cut stools produced shoots close to the cut. Arboricultural Journal: The International Journal of Urban Forestry 11

Table 5. Characteristics of cutting with different tools that could lead to different growth responses in trees and which merit further investigation. Axe Chainsaw Comments/references Less chance of “pollution” “Pollution” via oil Pollution may damage adventitious buds and reduce regrowth “Clean” cut Torn cells and ragged cut Philips (1971) suggested that saws separate the bark disturbing the cambial layer Stub left as series of cuts Stub usually horizontal Sloping cuts may shed water better and on an angle have greater surface area to promote adventitious buds Higher possibility for Less chance of water Higher moisture retention and less desic- water retention on stub retention cation may be beneﬁcial in encouraging growth in drier climates Cutting rocks trees/- Cutting produces micro Rocking tree branches may be more similar branches vibration to a natural break and may provoke a physiological response Cutting is less controlled, Cutting is better planned, Uncontrolled cutting may remove branches more ad hoc more controlled or parts of branches that would be better retained Lower tendency to cut big Easier to cut big branches Usually stated (see E. E. Green, 1996) but branches not the situation in this study Less friction – less heat More heat via friction If occurs, this might be the reason for less damage callus growth on chainsaw branch cuts

This difference was attributed to the tendency of the bark to separate from the stool in saw- cut stools, disturbing the cambial layer. No such difference was found in the current study. Ducrey and Turrel (1992) compared the growth of holm oak coppice stools cut with a chainsaw, with an axe, and from breaking stumps. Although cutting with tools yielded better growth than stump breaking, no difference was detected between the tool type. There have been no studies comparing tools on the growth of beech or of pollards. Patterns of growth within the three growing seasons were not followed in the current study, and it will be interesting to see if the results obtained after three growing seasons are maintained over the long term.

Shade and orientation Shading or exposure has little impact on tree responses, but increased shade detrimentally affects the health of the branches. The lack of significant findings with orientation is surprising. Clarke (1992) found much more dieback of the pollard trunks of hornbeam Downloaded by [Guildhall Library], [Helen Read] at 09:00 02 January 2013 (Carpinus betulus L.) on the south side of the tree, but noted that this was less statistically significant than thought from observation, and suggested that a combination of factors was involved. Mitchell (1989) listed shade as a factor to consider when restoring lapsed pollards but suggested it might be more important for oak than beech or hornbeam, and be more influential in the long term rather than in the initial production of shoots. Experience at Burnham Beeches (e.g. Read et al., 1991) suggests that avoiding too much shade may be very important in beech, despite the species being shade tolerant. The same seems to be the case for hornbeam pollards at Epping Forest (Dagley, unpublished data). Lack of a significant effect in the current study may be due to higher rainfall in the Basque Country compared with south-east England, reducing water-stress and the impact of drying out after cutting. Beech is relatively susceptible to water-stress and its growth is positively correlated with rainfall (Power, 1994). Around San Sebastian, monthly rainfall in April to 12 H.J. Read et al.

June averages 125 mm (Agencia Estatal de Meteorologia – AEMET, www.aemet.es/), twice that of south-east England, for example 54 mm at Rothamsted, 30-year average 1971–2000 (Meteorological Office, www.metoffice.gov.uk). In comparison, average air temperatures (also important for growth), are similar with average July air temperatures between 18.6–218C (AEMET and Met Office). Cutting the trees may not have significantly altered the micro-climate around them because they were mostly open-grown trees within grazed landscapes with few younger trees around them. However, restoration of lapsed pollards in southern Britain often requires clearance of dense competing vegetation before cutting, for example, at Epping Forest where beeches and hornbeams grow at high densities and trees seem to have reduced vigour when on the edge of clearance plots (Dagley, personal observation). These site differences could influence how trees respond, particularly under water-stress (Cermak, Matyssek, & Kucera, 1993). Furthermore, bark death and the influence of aspect/shade on shoot survival may take longer than three years to manifest itself after cutting.

Stub length This study shows that to encourage new shoots in lapsed beech pollards the stub length should be at least as long as the diameter of the branch and stubs should be over 500 mm (see Figure 2). This finding is probably counter intuitive to most arboriculturists. For restoration pollarding, Mitchell (1989) recommended stub lengths varying from 150 mm to 600 mm in a range of species to improve the response to pollarding. He stated that, stubs are not encouraged normally but that “the need for younger bark from which more buds may grow, and the tolerance of heart-rot, could justify this departure from arboricultural practice” (p. 135). This importance of stub length agrees with fieldwork on lapsed beech at Burnham Beeches (Read et al., 1991, Read et al., 1996; Read et al., 2010) and Le Sueur (1931) noted that in beech coppice the shoots appearing some distance from the cut are generally the strongest. Le Sueural also suggested that, historically when beech pollards at Burnham Beeches were cut they were “lopped to short stumps and never completely pollarded” (Le Sueur, 1934). Even in 1838, Loudon reported that beech, if cut close to the trunk, does not send out new shoots. It is very likely that “traditional” cutting techniques in Britain were more similar to those in the Basque Country than to the gradual pollard restoration method. The historical literature about pollarding techniques is very sparse so it is not always easy to identify what the “traditional” practice was in England or the Basque Country. Gradual restoration pollarding is carried out in Britain on lapsed beech trees because the removal of large branches close to the bolling is almost certain to kill the trees Downloaded by [Guildhall Library], [Helen Read] at 09:00 02 January 2013 (Read et al., 1996; Dagley & Burman, 1996). Lonsdale (1993) studied the impact of arboricultural cutting techniques on callus production and wound wood (but not shoot production) in young beech trees. Leaving stubs resulted in poor callus growth and slow wound occlusion and he considered that they should be avoided on the grounds of delayed occlusion, not because they encouraged decay, although cambial decay in stub cuts extended to the stub base. Lonsdale (1996), however, noted that cuts made close to the stem of the tree allow little chance of barriers in existing tissue to function. Stub length in restoration pollarding was studied by Warrington and Brookes (1998) on hornbeam trees with five treatments (stubs lengths from none to 1–3 m) but found no significant differences. A similar result was found for hornbeam in Epping Forest (Dagley & Burman, 1996). However, Sisitka (1991) noted that, at Hatfield Forest, Arboricultural Journal: The International Journal of Urban Forestry 13

regrowth of hornbeam took place from a considerable distance behind the cut and that cuts made close to the original bolling were not beneﬁcial. He also noted that it appears logical to leave long stubs on larger diameter branches because larger ones suffered more dieback. It has been pointed out (Lonsdale, personal communication, October 19, 2011) that the impact of the length of stub retained may relate to where the nearest node is on that branch. If a cut is made just above the node, then growth may occur with little dieback. If a cut is made just below a node, then there may be a greater length of dieback as there may not be live dormant buds below it. Balie´ (1933), in a history of pollarding in the French Basque Country, describes oak pollards with “tirants de se`ve” (sap risers) left during cutting which gave excellent results when used to try to counter the impacts of a disease on the trees. This method has also been used in recent years in northern France (Dominique Mansion, personal communication, October 21, 2004).

Impact of tree condition prior to cutting Tree condition prior to cutting is likely to be important. Data from this study indicate that measures of vitality and soil compaction were important predictors of the quality of the responses. In general, the trees selected for this study were in better condition, as judged by crown architecture and canopy scores (Roloff, 1985; Fay & De Berker, 1996), than pollards at Epping Forest and Burnham Beeches. However, there was sufficient variation in condition to indicate that estimated higher vitality and lower crown loss in 2007 were linked to better callus growth and more regrowth shoots in 2009 respectively. Increased soil compaction was linked to greater dieback length in stubs; trees with more branches greater than 100 mm diameter had more branches with new shoots. Although it is logical that trees in better health should respond better, and that trees that responded well to an earlier cutting event should grow better than those that did not, the limited amount of data did not allow firm conclusions to be drawn. Increased awareness of the value of old pollarded trees in the Basque Country has stimulated a range of new initiatives in the area. An EU LIFE project is comparing cutting techniques for the creation of new pollards as well as restoring older ones. Guidelines have been produced (in Spanish) directly as a result of the current study to assist future work. In addition, economic conditions are encouraging the cutting of more lapsed pollards for firewood. At least in the mountains closer to Madrid, trees are being cut again primarily for this reason and, although numbers are regulated, there are no guidelines on how to cut, resulting in both sympathetic and non-sympathetic techniques being used (A´ . Quiro´s, personal communication, March 24, 2012). Further exchanges of information between England and Spain based on information gathered here will help to inform this process. In Downloaded by [Guildhall Library], [Helen Read] at 09:00 02 January 2013 addition, the trees examined here need to be revisited after further growing seasons to compare longer term responses.

Conclusions The response of lapsed pollards to a range of restoration cutting techniques is under- reported in the literature. Even regular pollarding of trees has not been well studied. The current study has conﬁrmed the importance of factors highlighted in a previous investigation into pollard restoration at Burnham Beeches (Read et al., 2010), whilst indicating new lines of inquiry for research on restoring lapsed pollards. Further research, evaluating the same trees over a longer period will be needed to rule out short-term effects, whilst more quantitative assessments of tree vitality and work on factors such as age and 14 H.J. Read et al.

size of branches, timing of cuts and type of cutting tool would be helpful. For future conservation work, ensuring that trees are healthy before cutting, with good forms (e.g. many branches), adequate light levels and good soil conditions should be the starting point. From the current study, a range of factors have been identified (see Table 6). There may be advantages in cutting trees with an axe rather than a chainsaw, although, successful axe cutting is potentially hazardous at height. The possible advantages of using a bladed tool needs to be explored further but it is unlikely that this will be an option for many people wanting to restore pollards. Cutting branches leaving a long stub (at least 500 mm) may be significant for the successful growth of new shoots on beech. This is not standard arboricultural practice and arboriculturists are taught target pruning (Shigo, 1986), with branches cut immediately above a retained side branch and no stub left. In the current study, gradual pollard restoration cut trees had shorter stubs than Basque-style cut trees and this practice needs to be further researched to separate out the effects. Cutting beech branches older than 30 years means that they are at an age where the ripe wood starts to die and is less able to callus over wounds; cutting old beech wood can cause catastrophic decay and failure (Lonsdale, personal communication, October 19, 2011). So, although traditional Basque-style cutting encourages trees to produce more clusters of regrowth, cutting also results in greater dieback which could kill the trees. Survival of the Basque trees may be due to higher moisture levels from higher rainfall. In addition, the Basque pollards were last cut more recently than those in England and were less affected by infill, so may be acclimatised to more open conditions prior to cutting (Cermak et al., 1993). Nonetheless, some trees cut in the Basque-style are giving some cause for concern. One tree in the present study died, another was moribund in 2009, whilst four trees in three locations exhibited leaf death during the summer of 2011, although some recovered following late summer rain.

Table 6. Summary of techniques for restoring old beech pollards (see also Read et al., 2010, for more guidelines). Characteristics Known success Comments

Many branches . 50 mm* Yes High vitality* Yes Low root compaction* Yes Low crown loss* Yes High light levels pre-cut* Yes Lots of epicormic growth Possibly Trees with large bollings Yes Downloaded by [Guildhall Library], [Helen Read] at 09:00 02 January 2013 Trees in a group (cut 1–2 ﬁrst) Yes Precautionary approach Traditional Basque-style cuts* Possibly but not Do not attempt where few trees and/or not in UK demonstrated to work nearby Pollard restoration cuts* Yes Expensive, technical: working at height Cut with axe* Yes Cut with chainsaw* Yes Reduce exposure of bark on cut Possibly Consider branch orientation – southern branches (Clarke, 1992) exposures might cause drying and bark death If trees are in dense shade, Yes See Cermak, et al., 1993 release slowly Leave stub of at least 500 mm* Yes Avoid cutting large diameter Yes branches*

Note: * Results from present study. Arboricultural Journal: The International Journal of Urban Forestry 15

Gradual pollard restoration cutting can be more difficult and take longer to cut each tree, hence becoming more expensive. However, less photosynthetic area is removed, so trees are less likely to die, and can produce a greater response from dormant buds. This method is appropriate where there are smaller numbers of trees of high conservation or cultural value. However, more cutting events are required to produce a “regular” pollard shape, which may not be possible in some instances. Second cuts on gradually restored lapsed pollards are now being made at Burnham Beeches, some of which will result in large diameter cuts which may present the problems with dieback described above. The future of old lapsed pollards does not have to be bleak. There is increased awareness of their value for conservation, as cultural and landscape features, and cutting techniques are being refined. Once re-started with further regular cutting, without a lapse, these pollards could be extremely long-lived. However, such work remains expensive and is not always viewed as important within nature conservation because such heavily managed trees are not considered “natural”. This perception is changing, but lack of resources is a significant constraint, including for the creation of new pollards that are essential soon to ensure continuity in sites where old pollards remain.

Acknowledgements This work would not have been possible without the immense help we have had in both the Basque Country and in England, in particular from the organisations who gave permission for the work to be done and funded it: The Mayor of Leitza, The Mayor of Areso and the respective Town Councils and Forestry Service (Navarra); The Director and the Natural Park staff in Aiako Harria; Trepalari; The City of London Corporation (Open Spaces Dept.). We thank all who that gave their time and expertise in cutting and measuring the trees, data entry and discussing aspects of pollard cutting and restoration: Inãki Aizpuru, Jose Ignacion Martıńez Alejos, Alvaro Aragoń, Estibalitz Arbelaitz, Ian Barker, Miguel Barriola, John Clarkson, Allan Davies, Caroline Davies, Kevin Davies, Michael Elgood, Migel Mari Elosegi, Nev Fay, Roy Finch, Tom Fradd, Mikel Gomez, Martin Hartup, David Humphries, Susie Latchford, David Lonsdale, Dominique Mansion, Xabier Nieto, Raul Ortiz, Juan Jose Perurena, Martin Proelss, Angel Quiros, Samuel Alvarez, Kepa Urionabarrenetxea, Jeremy Young, Juan Mari Zabaleta, Pako Zufiaur.

Notes on contributors Helen Read is Conservation Ofﬁcer for the City of London at Burnham Beeches where she has worked closely with old trees and pollards for over 20 years. She has travelled throughout Europe comparing pollarding techniques in different countries. Jeremy Dagley is Conservation Manager for the Conservators of Epping Forest (City of London Downloaded by [Guildhall Library], [Helen Read] at 09:00 02 January 2013 Corporation). He has worked in nature conservation for 25 years focusing on the management of veteran trees and the biodiversity of wood-pasture habitat. He is a member of the UK Wood-pasture & Parkland Biodiversity Action Plan Technical Advisory Group. Jose´ Miguel Elo´segui is an amateur naturalist and ethnologist living in the Basque Country. He has been involved in actions to protect and restore forests and ancient trees. He is now retired, but keeps working for nature conservation. Alvaro Sicilia is a forester, tree surgeon and arboriculturist working in England and Spain. He is also an English-Spanish interpreter and translator for the Ancient Tree Forum and an active member of Trepalari (Basque association of Arboriculture). Phil Wheater is Professor of Environmental and Geographical Sciences at Manchester Metropolitan University. He has been researching in the ﬁelds of countryside management, human impacts on the environment, and the conservation of both habitats and species for over 30 years. He also has an interest in the statistical analysis of environmental data. 16 H.J. Read et al.

References Aragon Ruano, A. (2001). El bosque guipuzcoano en la Edad moderna: aprovechamiento, ordenamiento legal y conflictividad [The Guipuzkoan forest in the modern age: Exploitation, legal legislation and conflict]. Munibesuplemento 14. San Sebastian: Sociedad de ciencias aranzadi zientzadi elkartea. Balie´, P. (1933). Les foreˆts de cheˆnes teˆtrads du Pays Basque [The pollard oak forests of the (French) Basque country]. Revue des Eaux et Foreˆts. Novembre, 1933, 825–833. Cermak, J., Matyssek, R., & Kucera, J. (1993). Rapid response of large, drought-stressed beech trees to irrigation. Tree Physiology, 12, 281–290. Clair-Maczulajtys, D., Le Disquet, I., & Bory, G. (1999). Pruning stress: Changes in the tree physiology and their effects on the tree health. Acta Horticulturae, 496, 317–324. Retrieved from http://www.actahort.org/books/496/496_39.htm Clarke, A. (1992). The effect of sunlight on the renovation of ancient neglected pollards (Unpublished project submitted toward an HND). Seale Hayne Agricultural College, Plymouth, UK. Cochard, H., Coste, S., Chanson, B., Guehl, J. M., & Nicolini, E. (2005). Hydraulic architecture correlates with bud organogenesis and primary shoot growth in beech (Fagus sylvatica). Tree Physiology, 25, 1545–1552. Collet, C., Lanter, O., & Pardos, M. (2002). Effects of canopy opening on the morphology and anatomy of naturally-regenerated beech seedlings. Trees, 16, 291–298. Dagley, J. R., & Burman, P. (1996). The management of the pollards of Epping Forest: Its history and revival. In H. J. Read (Ed.), Pollard and veteran tree management II (pp. 29–38). London: Corporation of London. Dagley, J. R. (2007). Les trognes de la foreˆt d’Epping. In Maison Botanique (Ed.), Les trognes en Europe (pp. 46–52). Vendoˆme: Boursay. Ducrey, M., & Turrel, M. (1992). Influence of cutting methods and dates on stump sprouting in Holm oak (Quercus ilex L.) coppice. Annals of Forest Science, 49(5), 449–464. Edlin, H. L. (1971). Woodland note book: Goodbye to the pollards. Quarterly Journal of Forestry, LXV, 157–165. Fay, N., & Bengtsson, V. (2011). Literature review for evaluating veteran tree rejuvenation and management techniques. London: Internal report for the City of London. Fay, N., & De Berker, N. (1996). English Nature veteran trees initiative specialist survey method. Retrieved from http://frontpage.woodland-trust.org.uk/ancient-tree-forum/atfresources/im ages/ssm_HandBook.pdf Fay, N. (2002). Environmental arboriculture, tree ecology and veteran tree management. Arboricultural Journal, 26(3), 213–238. Frater, M. (1995). A study of the growth response of beech trees after pollarding (Unpublished MSc thesis). Manchester Metropolitan University, UK. Green, E. E. (1996). Thoughts on pollarding. In H. J. Read (Ed.), Pollard and veteran tree management II (pp. 1–5). London: Corporation of London. Green, T. (1996). Pollarding – Origins and some practical advice. British Wildlife, 8(2), 100–105. Ismay, J. (2001). The flies (Diptera) of Epping Forest. Essex Naturalist, 18,(new series) 105–112. Le Sueur, A. D. C. (1931). Burnham Beeches. A study of pollards. Quarterly Journal of Forestry,

Downloaded by [Guildhall Library], [Helen Read] at 09:00 02 January 2013 1931, 12–25. Le Sueur, A. D. C. (1934). The care and repair of ornamental trees in garden, park and street. London: Country Life. Lonsdale, D. (1993). A comparison of ‘target’ pruning, versus ﬂush cuts and stub pruning. Farnham: Arboricultural Advisory and Information Service. Lonsdale, D. (1996). Pollarding success of failure; some principles to consider. In H. J. Read (Ed.), Pollard and veteran tree management II (pp. 100–104). London: Corporation of London. Loudon, J. C. (1838). Arboretum et fruticetum Britannicum. London. Mitchell, P. L. (1989). Re-pollarding large neglected pollards: A review of current practice and results. Arboricultural Journal, 13, 125–142. PAST (Version 1.65) [Computer software]. Oslo: University of Oslo. Phillips, J. B. (1971). Effect of cutting techniques on coppice re-growth. Quarterly Journal of Forestry, 65, 220–223. Power, S. A. (1994). Temporal trends in twig growth of Fagus sylvatica L. and their relationships with environmental factors. Forestry, 67(I1), 13–30. Arboricultural Journal: The International Journal of Urban Forestry 17

Rackham, O. (1975). Hayley Wood: Its history and ecology. Cambridge: Cambridgeshire and Isle of Ely Naturalists’ Trust. Read, H. J. (2000). Veteran trees: A guide to good management. Peterborough: English Nature. Read, H. J. (2007a). Bref tour d’horizon des arbes tetards et des practiques d’e´teˆtage en Europe. In Maison Botanique (Ed.), Les trognes en Europe (pp. 12–18). Vendoˆme: Boursay. Read, H. J. (2007b). Health cuts. The Horticulturist, Summer 2007, 9–12. Read, H. J. (2007c). Pollarding beech trees in the Basque Country. Unpublished report of work carried out in February 2007. Read, H. J., Frater, M., & Noble, D. (1996). A survey of the condition of the pollards at Burnham Beeches and results of some experiments in cutting them. In H. J. Read (Ed.), Pollard and veteran tree management II (pp. 50–54). London: Corporation of London. Read, H. J., Frater, M., & Turney, I. S. (1991). Pollarding in Burnham Beeches, Bucks.: A historical review and notes on recent work. In H. J. Read (Ed.), Pollard and veteran tree management (pp. 11–18). London: Corporation of London. Read, H. J., Wheater, C. P., Forbes, V., & Young, J. (2010). The current status of ancient pollarded beech trees at Burnham Beeches and evaluation of recent restoration techniques. Quarterly Journal of Forestry, 104(2), 109–120. Roloff, A. (1985). Schadstufen bei der Vuche. Forst-Holzw, 5, 131–134. Shigo, A. L. (1986). A new tree biology. New Hampshire: Shigo and Trees Associates. Sisitka, L. (1991). Pollarding experiences at Hatﬁeld Forest, Essex. In H. J. Read (Ed.), Pollard and veteran tree management (pp. 19–21). London: Corporation of London. Slotte, H. (2000). Lo¨vtakt I Sverige och pa˚ A˚ land [Harvest of leaf-hay in Sweden and A˚ land Island. Methods used and impact on landscape]. (Doctoral thesis, Swedish University of Agricultural Sciences, Sweden). Published in Acta Universitatis Agriculturae Sueciae, 236. SPSS (Version 8) [Computer software]. Armonk, NY: IBM Corporation. StatView (Version 5.0.1) [Computer software]. Cary, NC: SAS Institute Inc. Warrington, S., & Brookes, R. C. (1998). The recovery of Hornbeam Carpinus betulus following the reinstatement of pollard management. Forest and Landscape Research, 1, 521–529. Watkins, C. (1998). ‘A solemn and gloomy umbrage’: Changing interpretations of the ancient oaks of Sherwood Forest. In C. Watkins (Ed.), European Woods and Forests: Studies in cultural history (pp. 93–111). Wallingford: CAB International. Downloaded by [Guildhall Library], [Helen Read] at 09:00 02 January 2013