Linking restoration to the wider landscape: A study of a bracken control experiment within a upland moorland landscape mosaic in the Peak District, UK

Landscape and Urban Planning 78 (2006) 115–134

Linking restoration to the wider landscape: A study of a bracken control experiment within a upland moorland landscape mosaic in the Peak District, UK C. Tong a,b,∗ , M.G. Le Duc a , J. Ghorbani a,c , R.H. Marrs a,∗ a

c

Applied Vegetation Dynamics Laboratory, School of Biological Sciences, University of Liverpool, PO Box 147, Liverpool L69 7ZB, UK b College of Geography Science, Fujian Normal University, Fuzhou 350007, China Department of Rangeland and Watershed Management, Faculty of Natural Resources, University of Mazandaran, PO Box 737, Sari, Iran Received 25 January 2005; received in revised form 15 June 2005; accepted 15 June 2005 Available online 31 August 2005

Abstract The reasons for choice of restoration target are often driven by policy objectives such as the requirements of Agri-environment schemes or Biodiversity Action Plans, where the target community may not reflect the characteristics of the surrounding landscape. Here, we relate the results of a restoration experiment designed to reverse succession by controlling bracken (Pteridium aquilinum) and restoring moorland within the context of the surrounding landscape. Our study included three parts: (1) we tested the effects of the bracken control/restoration treatments within a relatively long-term experiment; (2) we used high spatial resolution aerial photography to produce a map of the landscape surrounding with 13 component land classes, and then estimated the composition and configuration of the landscape; (3) we compared the species in standing vegetation and soil diaspore bank and the vegetation communities in the experimental area and the wider landscape. The restoration treatments applied experimentally showed varying degrees of success. The bracken cover was reduced to varying degrees and for various periods by control, and the species number and cover increased over the 10 years. The vegetation communities (UK NVC classes) produced showed a mixture of responses, some close to the target and some not; these varied from dense bracken stands through to well-established Calluna and grass-heath mosaics, with some woodland communities. Comparison of the experiment with the landscape indicated that the restoration work had successfully created some of the target communities. However, it also showed that within the experiment there were some unwanted communities typical of disturbed habitats, there was a lack of mire communities, which were prevalent in the wider landscape, and there were some developing woodland communities. The latter result suggests it may have been more sensible to choose a woodland target on this site rather than moorland. The wider landscape had a fine-grained texture, was

∗ Corresponding authors at: Applied Vegetation Dynamics Laboratory, School of Vegetation Dynamics Laboratory, University of Liverpool, Liverpool L69 7ZB, UK. Tel.: +44 151 795 5172; fax: +44 151 795 5171. E-mail addresses: [email protected] (C. Tong), [email protected], [email protected] (R.H. Marrs). URL: http://www.appliedvegetationdynamics.co.uk/.

0169-2046/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.landurbplan.2005.06.004

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highly fragmented and had an intermixed distribution of many communities, with mires having a more complex structure than communities on drier soils. © 2005 Elsevier B.V. All rights reserved. Keywords: Mapping; High-resolution aerial photography; Remote sensing; Geographical Information System (GIS); Plant communities; Bracken; Restoration; Scale

1. Introduction Ecological restoration is often focussed around policy objectives or on a perceived need to change a landscape towards a preconceived notion of what that landscape should look like. Where restoration has been linked to the surrounding landscape this has usually been done in an ad hoc manner using brief landscape surveys, Environmental Impact Assessments, or a consideration of the species pool and communities found in the surroundings. Few attempts have been made to consider the restoration process within a framework of landscape ecology, where the spatial pattern of the vegetation is considered in the context of the wider landscape (Ludwig and Tongway, 1996; Bell et al., 1997; Radeloff et al., 2000; Briggs, 2001). In this paper we assess success of restoration treatments, designed to implement current agricultural and conservation management policies, but tested within an experimental design. Specifically, we assess whether the communities that have developed over an 11-year period within a restoration experiment are typical of the wider area, and whether the correct restoration targets were chosen. In addition we consider simple simulations of restoration success fit into the wider landscape.

1.1. The restoration problem The control of bracken (Pteridium aquilinum) and the restoration of heathland/moorland is a priority in the UK (Pakeman and Marrs, 1992), mainly within the policy context of Agri-environment schemes and Biodiversity Action Plans (BAP: Anon., 1995a,b; MAFF, 1993, 1996). Bracken (Pteridium aquilinum) infestation reduces the area and increases the fragmentation of these priority BAP communities, and is a particular problem in upland Britain. This restoration process can be viewed as succession reversal (Marrs et al., 2000). (Following common practice Pteridium aquilinum will

be referred to as bracken – otherwise nomenclature follows Stace, 1997.) The Peak District in England is one area where bracken encroachment is a serious problem and there is funding under the North Peak Environmentally Sensitive Area (ESA) Agri-environment scheme to control bracken and restore moorland. We chose this area to investigate links between restoration success and the surrounding landscape because we had an ongoing experiment, which had been investigating bracken control and moorland restoration over an 11-year period (1993–2003). The experiment represents a typical situation where a landowner might wish to control bracken and restore moorland. The original restoration target for this site was moorland, and was based on the policies within the ESA scheme. No attempt had been made to consider the implications of this restoration within the wider landscape setting. The experiments have been monitored annually for bracken frond performance and vegetation recovery (Le Duc et al., 2000); information on rhizome performance and developing diaspore banks has also been recorded on single occasions (Le Duc et al., 2003; Ghorbani, 2005). 1.2. Assessing the landscape Usually information on landscape composition, pattern and configuration is derived through remote sensing (Chen et al., 2001; Rogova et al., 2000; Zak and Cabido, 2002). However, although both aerial photography and satellite imagery have been used to estimate the size of bracken stands at both regional and local levels (Marrs et al., 1986; Birnie and Miller, 1986; Weaver, 1986), bracken is a particularly difficult plant to map accurately from remotely-sensed data. The reasons for this difficulty is that bracken (a) occurs over a wide range of contexts and spatial configurations (i.e. from isolated fronds to dense patches or complete coverage of entire hillside), and (b) shows marked seasonal changes in its appearance (Birnie et al., 2000). Indeed,

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in a UK-wide survey of land cover using Landsat Thematic Mapper (TM) satellite imagery (Barr et al., 1993), the mapping accuracy for bracken was shown to be very poor, indeed the worst of all classes measured (Pakeman et al., 1996). Accordingly, we used high-resolution, aerial imagery to detect pattern in the landscape surrounding the restoration experiment. This approach has been used successfully to describe pattern in urban environments, grassland and salt marsh (Lobo et al., 1998; Smith et al., 1998; Akbari et al., 2003). However, there have been few attempts to develop this technique to assess plant communities in upland moors, or to relate ecological restoration treatments to the pattern of communities found in the wider landscape. The aims for this paper were to develop methods for comparing vegetation between local experimental and wider landscape scales. In order to do this, we compared species composition of both vegetation and the diaspore bank. The diaspore bank was included as it represents a measure of developing ecosystem function during the restoration process (Ghorbani et al., 2003). We also classified all the vegetation samples from the experiment and landscape into the UK National Vegetation Classification system (NVC; Rodwell, 1991a,b, 1992, 2000), as it is the most widely used classification in the UK. Part of the reasons for this work was to develop a baseline for the study area, and partly to develop methodology. Part of the wider aim was to provide a methodology to test simple simulations of restoration treatment within the context of the wider landscape. The simulations were simple, but they provide policy makers and vegetation managers to assess at a glance the potential landscape impact of their restoration work.

2. Methods 2.1. Study area The study (120 ha area 1.2 km × 1.0 km) focussed around an existing long-term bracken control/ moorland restoration experiment (1 ha) at Hordron Edge in the North Peak ESA, Derbyshire, UK (1◦ 41 W, 53◦ 23 N, National Grid Reference SK 2187). This area is situated between two hills with elevation ranging between 280 and 400 m, the central area is relatively flat with an aspect between west and northwest. In

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2000, the annual total precipitation was ca. 1050 mm and the soils are acid podzols/gleys. Bracken infestation is very obvious, and there is a considerable pattern with mosaics of Calluna moorland, bracken-dominated land, grassland and woodland. Recently sheep grazing has been relatively low under the regime imposed by the ESA prescriptions (ca. 0.5 sheep ha−1 , Pakeman et al., 2000), and parts of the moorland landscape are burned routinely as part of a management program for grouse (Lagopus lagopus). 2.2. The experiment A bracken control/moorland restoration experiment was established in 1993 as part of an extensive set of experiments established in four different locations within Great Britain. Full methodological details are provided by Le Duc et al. (2000, 2003) so only a brief description is given here. The experiment was set up in an area of dense bracken with a deep litter layer (>30 cm) and a very depauperate flora. An experimental split–split-plot design was used, necessitated by the nature of the cutting operations (main treatments) and stock fencing (sub-treatments). There were three blocks (replicates) of 70 m × 40 m. The blocks were divided into six main-plots each of 10 m × 40 m with 2 m buffer zones; each main-plot then was divided into two sub-plots 10 m × 18 m with 2 m buffers. Finally, the sub-plots were divided into three sub-sub-plots of 10 m × 5 m with 2 m buffers. Thus each block comprised 36 sub-sub-plots making 108 treatments and sampling units; all treatments were applied randomly at the appropriate stratum in the experiment. The main treatments (applied randomly, within blocks, to main plots) were: (1) untreated experimental control; (2) cut once per year in June; (3) cut twice per year, June and August; (4) sprayed with asulam (Asulox, Bayer plc.); (5) asulam application in the first year of treatment, followed by a single cut in the second year; (6) cut in the first year, asulam in the second. The sub-treatment was stock fencing to exclude sheep or free range grazing (<0.5 sheep ha−1 ), and the sub-sub-treatments were designed to test methods of Calluna restoration; these were: no addition, Calluna brash addition (cut stems ca. 20 cm long, applied at 13.2 t ha−1 ) or Calluna-moorland litter addition (sucked using an industrial vacuum cleaner from under a nearby mature Calluna moorland, and applied

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at 1.2 t ha−1 ). Both seed addition treatments included Agrostis castellana as a nurse crop, with seed applied at 12 kg ha−1 . All seed treatments were applied in 1993. Monitoring was carried out annually, from 1993 to 2002, in June and in August when bracken fronds were fully expanded. Sampling positions were sampled by selecting randomly, without replacement, the intersections of a 1 m grid within each of the 108 units. Two were selected in June and one in August. In June a 1 m2 quadrat was examined and we estimated cover of all species, including bryophytes and lichens, bracken litter depth, cover of litter of other species, bare ground and rock cover. At the same time cover, density and length of bracken fronds were measured (Le Duc et al., 2000). In August, the time of maximum frond expansion, only bracken frond measurements were made. As we were interested in quantifying the diaspore bank that could contribute to ecological restoration, we designed a protocol to sample the persistent seed bank, recognizing that species with transient seeds will be under-represented. The soil diaspore bank (seeds, spores and bryophyte fragments) was sampled in April 2002 thus ensuring that seeds had been chilled/stratified over winter (Ghorbani, 2005). Five cores (6 cm diameter, 7 cm depth) were taken from each unit and divided into three depth classes (bracken litter section, 0–5 and 5–10 cm); the five portions from each depth class were then combined. After removing bracken rhizomes, roots and large stones the material was spread over a 1 cm deep layer of horticultural sand in a seed tray (21.5 cm × 16 cm). All trays were placed in a glasshouse in random positions on benches fitted with capillary matting, which was kept saturated. Trays were given additional surface mat watering where needed. Some trays, containing sand only, were used as controls to measure potential diaspore contamination. Seedling counts for higher plants and ferns were expressed in numbers m−2 . The presence and absence of species was recorded for bryophytes. 2.3. Assessing the wider landscape Remote sensing was used to produce a vegetation map and Digital Elevation Model (DEM) for the landscape surrounding the experiment. Four colour aerial digital images were obtained from the Simmons Aerofilms (Cheddar, Somerset, UK). The images were taken on 5 September 1999 and had a ground resolution

of 25 cm × 25 cm; the path/row numbers are SK2186, SK2187, SK2286 and SK2287 (upleft 421100, 387500; lowright 422300, 386500). The images were georeferenced to Great Britain National Grid coordinates using ERDAS IMAGINE 8.6 remote sensing software, and then combined into a single image using its MOSAIC function. The final map covered a 1.2 km × 1 km study area surrounding the experiment. A Digital Elevation Model (DEM) with a spatial resolution of 10 m for the study area was obtained, also from Simmons Aerofilms. The TOPOGRAPHIC and GIS ANALYSIS functions in ERDAS IMAGINE 8.6 were used to produce a slope map and the SPATIAL MODELER function used to analyse the relationship between main vegetation types and slope. This changed the raster data to vector form. A vegetation polygon map was then produced in ARCVIEW 3.2 GIS by visual interpretation of the digital image supplemented with reference to data collected in a field survey in August 2002. In this survey 50 sample positions were chosen randomly from the intersections of a 100 m × 100 m grid overlying the study area. These positions were located using GPS, and at each point the species composition (5 m × 5 m quadrat) and abundance of each species (1 m × 1 m quadrat) was estimated. A soil sample was also collected during this survey and an estimate of the persistent diaspore bank composition was made using an identical procedure to that used for the experiments (see above). A second vegetation survey was then done in mid-June 2003 to ground reference the vegetation map and assess the accuracy of the vegetation map. Any misclassifications were identified and corrected. 2.4. Data analysis The vegetation data were available at a range of levels. First, the vegetation and diaspore bank data collected in the experiment were analysed by both univariate repeated measures analysis of variance with polynomial contrasts (Le Duc et al., unpublished), and multivariate analysis of variance using Redundancy Analysis (RDA: Marrs, 2003). Second, 13 land cover types were delineated on the vegetation map. Third, the vegetation data collected in both the experiment (n = 108) and the landscape (n = 50) were allocated a National Vegetation Classification (NVC) class using TABLEFIT (Hill, 1996).

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In addition, selected landscape metrics were quantified from the vegetation map was using FRAGSTATS v 3.0 spatial pattern analysis software (McGarigal et al., 2002); these were: (a) the proportion of each land cover type in the landscape, (b) the number of different patch types (NP), and (c) size of patch and mean perimeter length for each land cover type, and (d) a range of indices of landscape complexity. Most indices for landscape complexity gave similar conclusions so only the Interspersion and Juxtaposition Index is discussed further here; this index measures the extent to which patches are interspersed (0: poor interspersion; 100: high interspersion). During this process the vector image was converted to a raster one and a cell size less than half the narrowest dimension of the smallest patch was selected (1 m × 1 m cell size) when converting to avoid disjunct patches joining, and vice versa (McGarigal et al., 2002).

3. Results 3.1. Vegetation change within the experiment The species detected within the overall experiment (i.e. all sampling units pooled) showed that there was an approximate doubling of species almost immediately after the experiment was established, thereafter as the experiments progressed species cover increased (Table 1). Areas were sampled much less frequently in the first year, but this was partly because there were so few species present, and the bracken vegetation was relatively uniform. The reason for the increase in species pool was because of the treatments applied. The effect on bracken was considerable. Canopy cover measurements in both June and August showed that bracken responded significantly to control treatment (Fig. 1). Treatments involving herbicide application produced the greatest effect until 1998 (June), and 1997 (August). After those dates the cut twice per year treatment was most successful, resulting in the canopy being reduced to less than 10% of the experimental control by 2002. Cutting once per year had little effect on the June performance and had only mixed results compared to other treatments in August. In August (Fig. 1b) there was a significant minimum of around 1% with cut twice per year treatment in 1998 and 1999, but this canopy recovered to over 10% in 2000. The lat-

Fig. 1. Effect of bracken control treatments on Pteridium aquilinum cover (%) in (a) June and (b) August (data for 1994 and 1995 not available), for the experiment at Hordron Edge, Derbyshire. Treatments are: circle – no treatment; grey square – cut once per year; black square – cut twice per year; open triangle – herbicide only; grey diamond – herbicide in first year, cut in second; black diamond – cut in first year, herbicide in second. Statistics are for polynomial contrasts with Bonferroni corrected significance level: ** 0.00023 ≥ p > 0.000023. Error bars are 2 × SED of the means, plotted using the left-hand transformed scale.

ter recovery was not noticeable until August, as there had been a significantly poorer performance in June for all treatments, including no treatment (experimental control). A first order, linear, response was found for the June performance (Fig. 1a). The gradients of treatment responses were all positive, implying cover recovery over the period, except for cut twice per year, which was negative. The multivariate analysis of variance showed that all treatment effects and interactions were significant (P < 0.002) except for the seeding sub-subtreatment. The four-way interaction term relating bracken control × fencing × Calluna addition × time

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Table 1 The species complement in June of the bracken control/moorland restoration experiment at Hordron Edge, Derbyshire, UK Species

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

Agrostis capillaris Agrostis castellana Agrostis gigantean Agrostis vinealis Anthoxanthum odoratum Barbilophozia floerkei Betula pendula Betula seedling/sp. Brachythecium rutabulum Calluna vulgaris Campylopus introflexus Campylopus pyriformis Carex pilulifera Carex seedling/sp. Cerastium fontanum Chamerion angustifolium Cladonia pyxidata/coccifera Cladonia sp. Deschampsia flexuosa Dicranella heteromalla Dicranum majus Dicranum scoparium Digitalis purpurea Epilobium montanum Erica tetralix Eurhynchium praelongum Festuca ovina Festuca rubra Galium saxatile Holcus lanatus Holcus mollis Hypnum jutlandicum Hypochaeris radicata Juncus effusus Leptodontium flexifolium Lophocolea bidentata Luzula campestris Luzula multiflora Mnium hornum Nardus stricta Non-cladonia lichen Pinus sylvestris Pleurozium schreberi Poa annua Poa pratensis Poa trivialis Polytrichum formosum Potentilla erecta Pseudoscleropodium purum Pteridium aquilinum Ptilidium ciliare Quercus seedling/sp. Rhytidiadelphus squarrosus

I(0.1) – – I(0.1) – – – – – – – – I(0.1) – – – – – IV(12.5) I(<0.1) – I(<0.1) – – – – I(0.5) – II(0.7) – I(<0.1) II(0.6) – – – I(<0.1) I(<0.1) – – I(<0.1) – – – – – – – II(0.5) – V(67.7) – – I(<0.1)

I(0.2) I(0.1) – I(<0.1) I(<0.1) – – I(<0.1) I(<0.1) I(<0.1) I(<0.1) I(0.1) I(<0.1) I(<0.1) – I(<0.1) I(<0.1) I(<0.1) V(10.7) I(<0.1) I(<0.1) I(0.1) – – I(<0.1) I(<0.1) II(1.5) – III(2.0) I(<0.1) I(<0.1) III(1.2) I(<0.1) – I(<0.1) I(<0.1) I(<0.1) – – I(0.3) I(<0.1) – – I(<0.1) – – – II(0.4) I(<0.1) IV(5.8) – – I(0.1)

I(0.1) I(0.1) I(<0.1) I(<0.1) I(<0.1) I(<0.1) I(<0.1) – I(<0.1) I(<0.1) I(<0.1) I(0.1) I(<0.1) – – I(<0.1) – I(<0.1) V(10.3) – – I(0.1) – I(<0.1) I(<0.1) I(<0.1) II(0.6) I(0.5) III(1.7) – I(0.1) III(0.4) I(<0.1) – – I(<0.1) I(<0.1) I(<0.1) – I(0.3) – I(<0.1) I(<0.1) – I(<0.1) – I(<0.1) II(0.3) – IV(4.7) I(<0.1) – I(<0.1)

I(0.2) I(0.2) I(<0.1) I(<0.1) I(<0.1) – – I(<0.1) – I(<0.1) I(<0.1) II(0.2) I(0.1) – – I(<0.1) – – V(12.9) – I(<0.1) I(0.1) – – I(<0.1) I(<0.1) II(0.8) I(0.7) III(1.9) I(<0.1) I(0.1) III(0.6) – – I(<0.1) I(<0.1) I(<0.1) I(<0.1) I(<0.1) I(0.3) – I(<0.1) I(<0.1) I(<0.1) – – – II(0.4) I(<0.1) IV(3.3) I(<0.1) I(<0.1) I(<0.1)

I(0.2) I(0.1) – I(0.1) I(<0.1) – – I(<0.1) I(<0.1) I(0.1) II(0.4) I(0.1) I(0.1) – – I(<0.1) I(<0.1) I(<0.1) V(13.2) – – II(0.2) – – I(<0.1) I(<0.1) I(0.1) III(2.2) III(2.8) – I(0.1) III(0.9) I(<0.1) – I(<0.1) I(<0.1) I(<0.1) – – I(0.5) – I(<0.1) I(<0.1) I(<0.1) I(<0.1) – I(<0.1) II(0.3) – V(5.9) I(<0.1) – I(<0.1)

I(0.2) I(0.4) I(<0.1) I(0.2) I(<0.1) – – I(<0.1) – I(0.2) II(1.0) I(0.2) I(0.1) I(<0.1) I(<0.1) II(0.2) – I(<0.1) V(16.0) – – II(0.1) I(<0.1) – I(<0.1) – II(0.6) II(1.1) IV(6.1) – I(0.1) III(0.7) – – I(<0.1) I(<0.1) I(<0.1) I(<0.1) – I(0.3) I(<0.1) I(<0.1) I(<0.1) – I(<0.1) I(<0.1) – II(0.4) – V(14.6) I(<0.1) – I(<0.1)

II(0.8) I(0.3) – I(0.2) I(<0.1) – – I(<0.1) I(<0.1) II(0.2) II(0.8) I(<0.1) I(0.1) – – I(0.3) – I(<0.1) V(12.9) – – I(0.1) – I(<0.1) I(<0.1) – I(0.2) III(2.6) IV(7.2) I(<0.1) I(0.1) III(0.9) – I(<0.1) I(<0.1) I(<0.1) I(<0.1) – – I(0.3) – I(<0.1) I(<0.1) – I(<0.1) – I(<0.1) II(0.5) – V(14.7) – – I(0.1)

I(0.3) II(0.7) – I(0.2) I(<0.1) – I(<0.1) I(<0.1) I(<0.1) I(0.2) II(0.6) I(0.1) I(0.1) – – I(0.3) – I(<0.1) V(12.1) – – II(0.1) – – I(<0.1) – II(1.8) I(0.2) IV(2.8) I(<0.1) I(0.1) III(1.2) – I(<0.1) I(<0.1) I(<0.1) I(<0.1) – I(<0.1) I(0.3) – I(<0.1) I(0.1) – – I(<0.1) I(<0.1) II(0.4) – V(3.2) I(<0.1) – I(0.1)

I(0.5) I(0.3) – I(<0.1) I(<0.1) – – I(<0.1) I(<0.1) I(0.1) I(0.3) – I(0.1) – – I(0.4) – – V(11.2) – – I(0.1) – – I(<0.1) – II(1.8) I(0.2) IV(6.7) – I(0.1) II(0.6) – – I(<0.1) I(<0.1) I(<0.1) I(<0.1) – I(0.3) – – I(<0.1) – – I(<0.1) – II(0.5) – V(21.7) I(<0.1) – I(0.1)

II(1.1) – – I(0.2) I(<0.1) I(<0.1) – – I(<0.1) I(0.2) I(0.2) I(<0.1) I(<0.1) – I(<0.1) I(0.3) – – V(13.9) – – I(0.1) I(<0.1) – I(<0.1) – I(0.4) III(2.2) V(7.2) – I(0.2) III(1.3) – – – I(<0.1) I(<0.1) I(<0.1) – I(0.3) – I(<0.1) I(<0.1) – – – I(<0.1) II(0.5) I(<0.1) V(30.6) – I(<0.1) II(0.3)

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Table 1 (Continued ) Species

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

Rumex acetosella Sorbus aucuparia Vaccinium myrtillus Vaccinium vitis-idaea

– – II(0.5) I(<0.1)

– – II(0.2) I(<0.1)

– I(<0.1) II(0.3) I(<0.1)

– I(<0.1) II(0.3) I(<0.1)

– – II(0.1) I(<0.1)

I(<0.1) I(<0.1) II(0.3) I(<0.1)

I(<0.1) I(<0.1) II(0.4) I(0.1)

I(<0.1) I(<0.1) II(0.3) I(<0.1)

I(<0.1) – II(0.3) I(<0.1)

I(<0.1) – II(0.4) I(0.1)

Total species (note included)

18

42

52

42

41

41

41

43

35

41

Roman numerals are frequency per 1 m2 (n = 216 for all except 1993 when n = 45), I = 1–20%, II = 21–40%, III = 41–60%, IV = 61–80%, V = 81–100%; figures in parentheses geometric mean cover (%) values; ‘–’: not found. Species occurring only in a single year are listed in the footnote. Additional species, found in only a single year are as follows: Agrostis stolonifera, Aira praecox, Barbilophozia atlantica, Barbula convoluta, Betula pubescens, Bryum sp., Campylopus paradoxus, Carex binervis, C. caryophyllea, C. nigra, Cirsium palustre, Cladonia chlorophaea, Crataegus monogyna, Dryopteris carthusiana, D. dilatata, D. filix-mas, Elytrigia repens, Epilobium sp., Eriophorum vaginatum, Festuca filiformis, Fraxinus excelsior, Hypnum cupressiforme, Juncus conglomeratus, J. squarrosus, Pilosella officinarum, Plagiothecium nemorale, Poltrichum juniperinum, Potentilla sterilis, Rumex acetosa, Stellaria media, Thuidium tamariscinum.

was significant so only the RDA from this analysis is discussed (Fig. 2a). Bracken increase is approximately orthogonal to the directions for increase in more desirable species; in the upper right hand quadrant the species of acid grassland and those of heath are increasing, and in the opposite direction to Deschampsia flexuosus. Nardus stricta increases in approximately the opposite direction to P. aquilinum. Festuca rubra increases with axis 1, and Chamerion angustifolium increases in the negative direction of axis 2. There are 36 potential treatment trajectories through time and essentially there are three types; representatives are illustrated (Fig. 2). The control plots centre around the bracken position (Fig. 2b); most treatments move to the opposite end of the bracken trajectory at the start close to Nardus stricta, indicating an initial reduction in bracken cover. This is followed by a recovery back to the bracken position, with some treatments going through a Deschampsia flexuosa phase (Fig. 2c). The most successful treatments were those where cutting was applied twice per year as they moved into the Calluna grass heath community (Fig. 2d). 3.2. Land cover types within the landscape The final map of the landscape surrounding the experiment (Fig. 3) illustrates the extent of the 13 land-cover types detected (Table 2); 10 land cover community types, and three others (bare rock, road infrastructure and the bracken control experimental site, which was delineated separately for calculation purposes). The results of the classification accuracy of map (Table 3), showed that for both the dense Calluna

vulgaris moorland (unburned and burned) and Pinus sylvestris plantation an agreement of 100% was found, and all classes show a high degree of accuracy. The characteristics of the land cover community types are: 1. Pteridium aquilinum–Agrostis capillaris–Festuca ovina community. In the study area, Pteridium aquilinum (bracken) covered either entire slopes or was present in dense, discrete patches. In this community, Pteridium aquilinum is always dominant with a high cover. Other species include Agrostis capillaris, Festuca ovina and Galium saxatile. In mid-June when the survey was done, the bracken fronds had expanded and a full canopy had formed. 2. Dense Calluna vulgaris moorland. Calluna vulgaris dominated-moorland is the most common community in the study area. There is a high cover of Calluna vulgaris; in most patches cover is >60% and the mean height is 30 cm. Other species include Deschampsia flexuosa, Nardus stricta and Eriophorum vaginatum. 3. Dense Calluna moorland subject to management burning. Here, the Calluna community occurs in various stages of post-fire regeneration. Immediately after burning the vegetation is reduced to burnt stems and bare soil; recovery occurs through re-sprouting from the burnt stems and colonisation from the soil diaspore bank (Gimingham, 1972). 4. Agrostis capillaris–Nardus stricta–Festuca ovina grassland. This grass community was mainly distributed on the rocky edges and in mosaics

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Fig. 2. (a) Biplot of the species in a redundancy analysis of the interaction between bracken control treatments × ±grazing × Calluna addition treatments × time in a multivariate analysis of variance; this analysis was significant (P < 0.001). Three example treatment trajectories are shown as examples: the same biplot as (a), but showing individual treatment interaction SDE’s for: (b) untreated plots; (c) sprayed in 1993, fenced with Calluna litter; (d) cut twice per year, grazed + Calluna brash. Species codes are 4 letter genus/specific name. Blue ellipses 1993–1997; green 1998–2000; purple 2001–2003.

between Calluna and Pteridium patches. Other associated species included Deschampsia flexuosa, Molinia caerulea, Rumex acetosella and Poa annua. 5. Eriophorum vaginatum mire. This community covered a large flat area in the middle of the study area; associated species included Molinia caerulea and Carex viridula ssp. oedocarpa.

6. Mixed Eriophorum vaginatum–Juncus effusus mire. In this community, Eriophorum vaginatum and Juncus effusus occurred in equal proportions. They occur in intimate mixtures and it was impossible to separate or delineate them on the map. 7. Mixed Calluna vulgaris–Eriophorum vaginatum community. This community is a mixture of the

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123

Fig. 3. Map of the plant communities within the study area at Hordron Edge, Derbyshire, UK; produced from digital aerial photographs.

Calluna vulgaris-dominated dense stands, and the Mixed Eriophorum vaginatum–Juncus effusus mire. It was obviously different from these two other communities. 8. Pinus sylvestris plantation. Pinus sylvestris is the main tree species in this plantation with a dense understory of Pteridium aquilinum. This community occurs at the foot of the hill, and was present in a belt close to the road. 9. Juncus effusus flushes. This community is found near wet flushes and areas of obvious natural drainage; associated species include Nardus stricta, Molinia caerulea, Festuca ovina and Carex viridula ssp. oedocarpa. 10. Quercus–Betula woodland. This woodland is distributed mainly in the southwest corner of the study area. Quercus petraea, Betula spp. and Sorbus aucuparia form the canopy, and the ground cover

is mainly Deschampsia flexuosa, Agrostis capillaris, Pteridium aquilinum, Vaccinium myrtillus, Galium saxatile, and Holcus mollis. Topography appeared to be a major influence on land cover distribution. The topography of the study area was classified into four slope-degree categories; approximately half the area was classified as having zero slope (41%), and the greatest area (45%) was found within the 1–3◦ class, with a smaller proportion amounts in the steeper 4–6◦ class (13%) and 7–9◦ class (1%). The distribution of the five major land classes with respect to slope (Table 4) showed that four communities were found in the flattest areas, and their area reduced with increasing slope. The bracken community was the exception being present in the lowest slope class, having the greatest amount in the mid-slope section (1–3◦ class).

124

Table 2 The land cover types derived from the vegetation map of the Hordron Edge study area in Derbyshire, UK Area (ha)

Percentage of landscape

Number of patches (NP)

Minimum patch Maximum patch area (ha) area (ha)

Mean patch area (ha) ± S.E.

Mean patch perimeter (m)

Interspersion and juxtaposition index

Pteridium aquilinum–Agrostis capillaris–Festuca ovina community Dense Calluna vulgaris moorland (unburned) Dense Calluna vulgaris community (burned) Agrostis capillaris–Nardus stricta–Festuca ovina grassland Eriophorum vaginatum mire Mixed Eriophorum vaginatum–Juncus effusus mire Mixed Calluna vulgaris–Eriophorum vaginatum community Pinus sylvestris plantation Juncus effusus flushes Quercus–Betula woodland Bare rock Road Experiment site

34.61

28.6

63

0.01

16.99

0.55 ± 0.28

383.3

86.9

19.50

16.1

67

0.01

6.60

0.29 ± 0.10

262.5

71.5

8.45

7.0

8

0.10

2.84

1.06 ± 0.28

612.5

59.4

15.10

12.5

38

0.01

3.56

0.40 ± 0.12

398.0

72.2

14.83 9.05

12.3 7.5

10 3

0.07 0.27

12.15 8.44

2.47 ± 1.38 3.02 ± 2.22

625.1 2182.6

62.9 46.4

6.80

5.6

21

0.03

1.72

0.32 ± 0.09

405.2

66.5

4.18 3.66 1.88 1.51 1.03 0.27

3.5 3.0 1.6 1.2 0.9 0.2

11 6 7 2 1 3

0.03 0.03 0.02 0.06 0.16 1.03

3.16 1.49 1.16 0.10 1.35 1.03

0.38 ± 0.27 0.37 ± 0.16 0.27 ± 0.14 0.09 ± 0.01 0.76 ± 0.42 1.03

294.1 1217.8 261.5 148.7 1731.7 549.0

20.5 62.1 30.7 49.1 58.3 0.00

Landscape contextual and configuration information for each class is also presented; the values for patch number, area and perimeter were derived from the GIS vegetation map; IJI was derived from FRAGSTATS v 3.0.

C. Tong et al. / Landscape and Urban Planning 78 (2006) 115–134

Land cover class

Table 3 Classification accuracy assessment for standing vegetation map produced by visual interpretation Land cover

Classification

Pteridium aquilinum– Agrostis capillaris– Festuca ovina Dense Calluna vulgaris moorland (unburned) Dense Calluna vulgaris moorland (burned) Agrostis capillaris– Nardus stricta–Festuca ovina grassland Eriophorum vaginatum mire Mixed Eriophorum vaginatum–Juncus effusus mire Mixed Calluna vulgaris–Eriophorum vaginatum Juncus effusus flushes Pinus sylvestris plantation

Dense C. vulgaris moorland (unburned)

Dense C. vulgaris moorland (burned)

A. capillaris– N. stricta– F. ovina grassland

E. vaginatum Mixed E. Mixed C. mire vaginatum – vulgaris– J. effusus mire E. vaginatum

24

J. effusus flushes

P. sylvestris plantation

1

15 15 24

1

1

19 19

1

1

14

1

14 10

Total Error sample rate points (%) 25

4

15

0

15

0

25

4

20

5

20

5

15

6.7

15 10

6.7 0

C. Tong et al. / Landscape and Urban Planning 78 (2006) 115–134

P. aquilinum– A. capillaris– F. ovina

125

Note these data are slightly different from those in Table 2, this is because of differences associated with the use of raster data in the SPATIAL MODELER function in ERDAS IMAGINE 8.6 rather than calculated from the polygon attribution table in vector format. The experiment site was wholly within class 1–3◦ .

57.8 42.2 0 0 1.74 1.27 0 0

Area (ha) %

69.2 30.7 0.2 0 8.95 3.97 0.02 0

Area (ha) %

38.3 48.5 12.3 0.9 5.27 6.68 1.69 0.12

Area (ha) %

61.0 31.3 7.0 0.8 16.89 8.66 1.93 0.23

Area (ha) %

18.7 54.7 24.7 2.0

Area (ha)

6.30 18.42 8.31 0.67 0 1–3 4–6 7–9

Eriophorum vaginatum mire Agrostis capillaris–Nardus stricta–Festuca ovina grassland Calluna vulgaris moorland Pteridium aquilinum–Agrostis capillaris–Festuca ovina grassland Slope degree class (◦ )

Table 4 The area and percentage of main standing vegetation types in different slope sections at the Hordron Edge, Derbyshire, UK

%

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Juncus effusus flushes

126

3.3. Comparisons of species and communities types produced in the experiments and the wider landscape The species detected in the assessments of both diaspore bank and standing vegetation in the experiment and landscape (Table 5) are grouped on the basis of their presence in the seed bank and vegetation. The species found reflect the communities identified previously but species of the wetter parts are under-represented in both the seed bank and vegetation relative to the spatial area they cover, e.g. Eriophorum vaginatum. Thirteen species were present in reasonable amount in the seed bank and were also present in the vegetation, although four of these had only limited presence in the vegetation. Most of these species are common moorland species and represent the major species pool available for restoration. The four species present in the seed bank with limited amounts in the vegetation probably represent two different scenarios. Betula seed is shed from trees in the surrounding landscape, but presumably does not establish because of the grazing pressure and/or lack of disturbance. The other three (Carex pilulifera, Erica tetralix and Juncus effusus) have longlived seed banks (Grime et al., 1988), and no obvious means of dispersal over great distances, so may either be present as survivors from a previous establishment event, or establishing infrequently from the seed bank as conditions allow. A group of eight species were present in the vegetation with only a very small seed bank. Of these species, two (Agrostis canina, Stellaria uliginosa), and perhaps also Poa trivialis are plants commonly found in wet flushes. The others are mainly acid grassland species and their colonisation within the experiment was relatively limited (three of the eight), presumably because seed production must be limited by the low level of seed produced by small plant populations in the landscape. However, some colonisation of the experimental area by some species has occurred. For example, of the eight species found only in the vegetation, three were found in the wider landscape at low abundance, and four were found on the experiment but were not detected in the wider landscape. Agrostis castellana in the vegetation is a special case as it was introduced by seed as a nurse crop within the experiment. The occurrence of Chamerion angstifolium is not unexpected as it occurs in the wider area and has very

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Table 5 Cover (%) of above-ground vegetation and density of propagules in the diaspore bank in the experimental site and in the around landscape at Hordron Edge, Derbyshire in 2001 Main category

Minor category

Species

Species found in both seed bank and vegetation

Agrostis capillaris Agrostis vinealis Calluna vulgaris Deschampsia flexuosa Galium saxatile Nardus stricta Potentilla erecta Rumex acetosella Vaccinium myrtillus

Species that were abundant in seed bank but less common in vegetation

Betula pubescens Carex pilulifera Erica tetralix Juncus effusus

Species scattered in vegetation with limited seed bank

Festuca ovina Holcus mollis Anthoxanthum odoratum Agrostis canina Epilobium montanum Holcus lanatus Poa trivialis Stellaria uliginosa

Species restricted to the vegetation

Species more or less restricted to the seed bank

Experiment (n = 108)

Landscape (n = 50)

Diaspore bank

Diaspore bank

Standing vegetation 2.7 0.11 14.8 6.6 1.11 0.17 0.04 0.03 0.3

Standing vegetation

349 22 4352 23 39 5 27 2 1

0.15 + 0.04 9.5 4.77 0.08 0.18 0.01 0.11

218 27 12580 3 62 3 5 22 8

1 82 43 690

+ 0.03 0.01 –

109 17 66 798

– – 0.13

19 5 – – – – – –

0.64 0.02 0.01 – – – + –

– – 4 4 17 4 6 9

0.3 0.08 + + + + – + + 0.03 28.1 +

a

Both

Carex binervis Festuca rubra Pteridium aquilinum Vaccinium vitis-idaea

– – – –

+ 0.1 20.5 0.01

– – – –

Exp

Agrostis castellana Chamerion angustifolium Luzula campestris Luzula multiflora

– – – –

0.1 0.1 0.01 +

– – – –

– – – –

Land

Molinia caerulea Rubus fruticosus

– –

– –

– –

0.02 0.04

Both

Athyrium filix-femina Blechnum spicant Carex spp. Juncus bulbosus Juncus squarrosus Oreopteris limbosperma

3 133 0.5 2 59 12

– – – – – –

4 40 13 3 13 138

Exp

Dryopteris dilatata Juncus bufonius Luzula pilosa Rumex acetosa

2 0.5 1 1

– – – –

– – – –

– – – – – – 0.04 – – –

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C. Tong et al. / Landscape and Urban Planning 78 (2006) 115–134

Table 5 (Continued ) Main category

Minor category

Species

Land

Digitalis purpurea Poa pratensis Teucrium scorodium Urtica dioica

Experiment (n = 108)

Landscape (n = 50)

Diaspore bank

Diaspore bank

– – – –

Standing vegetation – – – –

11 3 4 4

Standing vegetation – – – –

Species have been categorised into response groups. Data are geometric means for cover values (%) and back-transformed means (Y = (Y + 0.5)0.5 ) for density (seeds m−2 ). +: <0.01%. Minor category – Both: found in experiment and landscape studies; Exp and Land: restricted to experiment and landscape study respectively. Additional species restricted to the vegetation of landscape with <0.01% cover and trees: Carex echinata, Carex nigra, Cirsium palustre, Dactylis glomerata, Empetrum nigrum, Epilobium palustre, Eriophorum angustifolium, Eriophorum vaginatum, Fagus sylvatica, Fragaria vesca, Fraxinus excelsior, Galium palustre, Geranium robertianum, Hydrocotyle vulgaris, Juncus conglomeratus, Oxalis acetosella, Picea abies, Pinus sylvestris, Quercus petraea, Ranunculus acris, Salix capraea, Sorbus aucuparia, Veronica chamaedrys. a Shows the presence of trees and the total basal area of trees was 152 m2 h−1 .

widely dispersed seeds which can colonise following the creation of any bare soil after disturbance, and has short lived seeds unlikely to be incorporated into a seed bank (Grime et al., 1988). It is interesting that, in addition to Pteridium and Chamaerion, Festuca rubra also appears to have a very limited capacity to enter the seed bank. The Luzula species are relatively inconspicuous and could have been missed in the wider landscape, but like their relatives the Juncus species, they have a long lived seed bank (Grime et al., 1988) and may have germinated on the experimental site following disturbance. As these species were not detected in the seed bank, presumably they have colonised from outside the area. Twenty-five species were present in the landscape, which had not colonised the experiment. Several of these are trees, either with limited means of dispersal (Fagus sylvatica) or of which seedlings are likely to be eliminated by grazing. Others are species of wet flushes, none of which occur in the experimental area, or are species of more mineral rich areas (e.g. Dactylis glomerata, Fragaria vesca). Several species were more or less restricted to the seed bank, six were found in both experiment and landscape; four were restricted to the experiment and four to the landscape. It is common to find species in the seed bank that are not found in the vegetation (Van Diggelen and Marrs, 2003). Of these the four ferns have very efficient long distance dispersal and are no doubt largely absent from the vegetation due to lack of suitable sites for sporeling establishment. The three non-Dryopteris

species also have long lived spore banks (Dyer and Lindsay, 1992). In addition to these three ferns Juncus effusus, Luzula spp., Carex spp., Urtica dioica, and Rumex acetosella, all have long lived seed banks (Grime et al., 1988). The NVC communities produced by restoration treatment compare favourably with those detected in the wider landscape (Table 6). Twenty NVC communities/sub-communities were found in the study within five broad categories: woodland (4), calcifugous grassland (7), open habitats (2), mires (4) and heaths (3) were detected. However, of these only seven NVC classes were found at both the experiment and landscape scale (W16, W16b, U2, U2a, U20, U20c, H10a, H10), only four were unique to the experiment (U4e, U5, OV27, OV27b) with the remainder found in the landscape (W10e, W24a, U2b, U20, U16c, M2, M20, M20a, M23). A χ2 -test comparing the numbers of communities (i.e. sub-communities pooled) between the experiment and landscape indicated no overall significant difference between the two datasets (χ2 = 10, P = 0.26). These results are encouraging in that community types have been created in the bracken control/moorland restoration experiment that are similar to types already present in the surrounding landscapes, for example U and U2a were found in the experiment and a similar community U2b in the wider landscape, the differences between these is a matter of minor species complement. However, there are some cautionary points. First, no mire communities were found

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Table 6 The distribution of National Vegetation Classes found in the experiment and the landscape at Hordron Edge, Derbyshire, expressed as a % of sites sampled NVC class

Type of community

W W10e

Woodland Acer pseudoplatanus–Oxalis acetosella sub-community of Quercus robur–Pteridium aquilinium–Rubus fruticosus woodland Quercus–Betula–Deschampsia flexuosa woodland Vaccinium myrtillus–Dryopteris dilatata sub-community of Quercus–Betula–Deschampsia woodland Cirsium arvense–Cirsium vulgare sub-community of Rubus fruticosus–Holcus lanatus underscrub Calcifugous grassland Deschampsia flexuosa grassland Festuca ovina–Agrostis capillaris sub-community of Deschampsia flexuosa grassland Vaccinium myrtillus sub-community of Deschampsia flexuosa grassland Typical sub-community of Festuca ovina–Agrostis capillaris–Galium saxatile grassland Species-poor sub-community of Luzula sylvatica–Vaccinium myrtillus tall-herb community Pteridium aquilinum–Galium saxatile Species-poor sub-community of Pteridium aquilinum–Galium saxatile Open habitats Chamerion angustifolium community Urtica dioica–Cirsium arvense sub-community of Chamerion angustifolium Mires Sphagnum cuspidatum/recuvum bog pool Eriophorum vaginatum blanket and raised mire Species-poor sub-community of Eriophorum vaginatum blanket and raised mire Juncus effusus/acutiflorus–Galium palustre rush-pasture Heaths Molinia caerulea sub-community of Calluna vulgaris–Deschampsia flexuosa heath Calluna vulgaris–Erica cinerea heath Typical sub-community of Calluna vulgaris–Erica cinerea heath

W16 W16b W24a U U2 U2a U2b U4e U16c U20 U20c OV OV27 OV27b M M2 M20 M20a M23 H H9e H10 H10a

Experiment scale (n = 108)

Landscape scale (n = 50)

0

2

28 1

4 2

0

2

24 19 0 5 0

16 6 6 0 2

0 18

6 20

2 1

0 0

0 0 0 0

6 2 8 8

0 2 1

2 2 2

Note two landscape quadrats contained only Pteridium and could not be allocated a NVC class (after Rodwell, 1991a,b, 1992, 2000).

in the experiment although they are abundant in the wider landscape. Second within the woodland there is a preponderance of W16 in the experiment, reflecting the ground flora and the presence of Betula trees. Whilst W16 is the most common woodland community in the experiment there was less proportionately of it in the wider landscape. Three other woodland types were also present in the landscape, two of which were not found in the experiment. 3.4. Land cover composition and configuration There were 240 land-cover patches in the landscape, with a mean patch size of 0.5 ha. The community type with the largest total area was

the Pteridium aquilinum–Agrostis capillaris–Festuca ovina community, followed by the dense Calluna vulgaris moorland (both burned and unburned), Agrostis capillaris–Nardus stricta–Festuca ovina grassland, and Eriophorum vaginatum mire; the others had less than 10 ha (Table 2). The ratio of recently burned to unburned dense Calluna vulgaris is 1:2.31, and the area ratio of the Pteridium aquilinum–Agrostis capillaris–Festuca ovina community to dense Calluna vulgaris moorland is 1:0.8. The percentage of the Pteridium aquilinum–Agrostis capillaris–Festuca ovina community and dense Calluna vulgaris moorland were 29 and 23 respectively, and for dense Calluna vulgaris moorland, the burned and unburned were 7 and 16. At the landscape

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scale the IJI = 73.1 suggests considerable complexity, indicating a relatively fine and intermixed grain texture, typical of moorland edge communities in the area. At the vegetation class scale the mean patch size varied over a 10-fold range, from 0.32 to 3.0 ha (Table 2). The land class with the largest mean patch size was the Mixed Eriophorum vaginatum–Juncus effusus mire, followed by the Eriophorum vaginatum mire. The next largest community was the dense Calluna vulgaris community, the others had relatively small mean patch sizes (<0.6 ha). The maximum patch size found, however, showed a different order; the greatest patch found was of the Pteridium aquilinum–Agrostis capillaris–Festuca ovina community at 16.9 ha followed by two Eriophorum mire communities, and the dense Calluna communities. The minimum patch size was relatively small for all communities, <0.3 ha for the mixed Eriophorum vaginatum–Juncus effusus mire, all others were <0.1 ha. The values for IJI show important differences between the land classes, separating those with relatively low values, the two woodland communities (<40%), from the others (>40%). This suggests that the pattern of the woodlands is more regular and may reflect planting (certainly the case for the Pinus sylvestris plantation), or other form of woodland management, perhaps for game. The other communities are interspersed, to a greater or lesser degree, in a fragmented mixture. But the Pteridium aquilinum–Agrostis capillaris–Festuca ovina had the highest value suggesting it is most interspersed.

4. Discussion Ecological restoration often tends to be focused towards either site-specific objectives, rare species (Red lists, Bakker et al., 2000) or a community based on conservation status (e.g. in the UK the NVC classes as idealised types, Rodwell, 1991a,b, 1992, 2000; or a phyto-sociological ideal; Bakker et al., 2000; Jansen et al., 2000). However, most restoration sites are part of an integrated wider landscape mosaic and there seems a need for a methodology that sets the restoration objective in a wider landscape context. The work presented here represents a first attempt to do this for an upland moorland ecosystem in the Peak District in the Eng-

land. A large part of this moorland has been colonised by Pteridium, and there is a policy objective to reverse this succession (Marrs et al., 2000) and establish moorland, a priority BAP community in the UK (Anon., 1995a,b). The restoration treatments applied experimentally show varying degrees of success. The bracken cover was reduced to varying degrees and for various periods by control treatment, and the overall species number and cover also increased over the 10 years. The NVC vegetation classes produced showed a mixture of responses, varying from dense bracken stands in untreated or unsuccessful treatments through to wellestablished Calluna and grass heath mosaics, with some woodland communities. 4.1. Mapping vegetation/land cover at fine scale In order to seriously consider the experiment within in a landscape context it was essential to produce a map of the plant communities of the area (Blackstock et al., 1994), and to be able to compare the vegetation produced in the experiment with that outside. The most economical way to develop accurate vegetation maps is to use remote sensing linked to field surveys. Finescale vegetation maps produced by remote sensing can be used to inform policy makers of the distribution of plant communities present for vegetation management and ecosystem restoration (Raal and Burns, 1996; Lobo et al., 1998; Kamada and Okabe, 1998; Treitz and Howarth, 2000; Verheyden et al., 2002). For vegetation mapping at a fine scale, remote sensing data with a high spatial and spectral resolution is needed. Here, the colour aerial photographs used had a ground resolution, of 25 cm × 25 cm, which means that very small areas (e.g. 0.005 ha) could be detected. Mapping resolution can be defined as the smallest area of vegetation that is recorded as a separate parcel on the map (Cherrill and McClean, 1999). However, as any map is a generalized, simplified abstraction of reality (Weibel and Jones, 1998), a compromise between very high spatial resolution and making maps too complex is needed. Here, we used a spatial resolution of mapping of ca. 0.01 ha, and the scale of delineating polygons on the image in ARCHVIEW 3.2 GIS was ca. 1:3000. We also used visual interpretation of the image to produce the map rather than a supervised classification method. Visual interpretation exploits both the contextual and

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textual information of the remote sensing data in addition to spectral information and can reduce the more fragmented polygon structure found when a pixel based classification system is used. This approach is particularly useful where the boundaries of each land cover patch are relatively clear-cut, as was the case here. However, it is a time-consuming method as it takes time to delineate each polygon of land-cover. Supervised classification will be more appropriate for large-scale, broad surveys (Cushman and Wallin, 2000; Tobler et al., 2003). The final map produced land classes at a relatively coarse scale, certainly coarser than that used in the standardised vegetation classification system typically used in the UK, i.e. the National Vegetation Classification (NVC) (Rodwell, 1991a,b, 1992, 2000). In order to compare the vegetation at the two scales objectively, we used the quadrat allocation algorithm TABLEFIT to fit the sampled vegetation data from both the experiment and the landscape to the standard NVC system. 4.2. Species and communities The comparison of both species and communities at the experiment and landscape scale produce some challenges for the manager and policy maker. On the one hand, positive results for many quadrats in the experiment showed that the species and communities produced after 10 years were typical of those found in the wider landscape (typically species of moorland and upland grassland, NVC communities U and H). Thus, the restoration goal has in many ways been achieved. On the other hand, however, there were three results that suggest problems and issues for policy discussion. First, some communities of open habitat were found in the experiment and not in the landscape, albeit at low frequency. This is probably an artefact of the disturbance applied during the experiment to control the bracken, by opening gaps and allowing ruderals such as Chamerion angustifolium – the main dominant of OV27 to invade (Rodwell, 2000). At the present level of occurrence this is not a problem here, but it is possible that in other situations these communities could predominate. Elsewhere, species such as Carex arenaria and Calamagrsotis epigejos have proved problematic after bracken restoration work in lowland Britain (Marrs et al., 1998).

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Second, there was a distinct lack of mire communities within the experiment, which are relatively common in the wider landscape. There are two possible reasons. The most likely is that the soil under bracken is probably relatively well-drained and aerated compared to soils under mire vegetation (Watt, 1976), thus when the bracken is controlled, the soil conditions will favour Upland grass (U) and Heath (H) communities rather than Mires (M). This is a likely scenario, but some areas of the bracken-infested area are locally wet, and it might be expected that pockets of mire vegetation might develop there. However, it is also possible that mire species are either not present in the seed bank, have poor dispersal abilities or do not compete well with species for grassland and heath communities. There is some evidence that seed banks of some species were low (e.g. Eriophorum vaginatum). However, to distinguish the most important constraints on the lack of mire species and communities require further experimentation. Finally, the presence of a relatively large number of quadrats in the experiment with woodland species and communities suggests that a woodland target may be more appropriate at this site. Woodland establishment may be easier as a result of species present in seed banks and dispersing from nearby sites. An upland wood option is not present in the current Agrienvironment schemes for this area, although it has been highlighted as a sensible future policy option for the uplands (Gimingham, 2002). A woodland option would probably require a restriction on sheep grazing at least during the establishment phase. This could be accommodated within the current ESA prescriptions for the North Peak through the new woodland tier, designed to encourage positive management and natural regeneration of small woods, particularly along ravines/gullies. These areas may include upland Quercus woodland, a priority BAP habitat. 4.3. Landscape pattern and configuration The aim of assessing the landscape pattern and configuration here was partly to provide a baseline against which future restoration success would be judged on a quantitative basis. It showed that the configuration of the land classes in the wider landscape was highlyfragmented, with a fine-grained pattern, and that the grain size was greater for the wetter mire communities

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than the drier ones. Presumably this increased grain size in wet communities to some extent reflects groundwater flows and drainage pathways, but this remains to be tested. In an ideal world we should have been in a position to compare the configuration of the vegetation developing within the experiment with that already present in the landscape. In principle, under a full-scale restoration scheme, the spatial pattern of the vegetation within the treated area could either be mapped using the high-resolution airborne imagery that was used in the landscape study here, or alternatively the vegetation could be mapped on the ground. This was not possible in this study because a spatially explicit, randomized experimental design was used, which by definition will produce spatial vegetation mosaics that are related to treatment applied. However, there is no a priori reason why the results from the landscape level cannot be used as a benchmark to judge success if full-scale restoration is attempted on this site. Thus, there is at least a potential mechanism for assessing success for restoration schemes in terms of landscape complexity. Irrespective, this approach allows these options to be considered as part of the restoration planning process and could aid future conservation and restoration issues being more efficiently incorporated in future.

Acknowledgements We thank the Department for Environment, Food and Rural Affairs, the UK Royal Society China Royal Fellowship Programme and the Royal Botanical and Horticultural Society for Manchester and the Northern Counties for funding this work. Professors J. Bakker, R. Birnie and R.J. Pakeman for helpful advice on this manuscript.

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Jamshid Ghorbani was a graduate student at the University of Liverpool, researching the role of seed banks in ecological restoration, with special reference to the restoration of grassland and moorland on bracken-infested sites.

Rob Marrs is the Bulley Professor of Applied Plant Biology at the University of Liverpool, where he teaches and researches in the theory and practice of manipulating successions towards desired endpoints.