Seed banks of temperate deciduous forests during secondary succession

Question: (i) How does former land use and land use intensity affect seed bank development during post‐agricultural succession? (ii) How does time since the last clear‐cut change seed bank composition during post‐clear‐cut succession? Methods: One data set was compiled per succession type using the following selection criteria: (i) the data set included a successional series, (ii) plots were located in mesotrophic forest plant communities and (iii) vegetation data were available. The post‐agricultural succession data set comprised 76 recent forest plots (eight studies); the post‐clear‐cut succession data set comprised 218 ancient forest plots (three studies). Each data set was analysed separately using either linear mixed models or generalized linear models, controlling for both environmental heterogeneity and variation between study locations. Results: In the post‐agricultural succession data set, land use and time significantly affected nearly all the studied seed bank characteristics. Seed banks on former arable land recovered poorly even after 150 year of restored forest cover, whereas moderate land use intensities (grasslands, heathlands) yielded more rapid seed bank recovery. Time was a significant determinant of all but two soil seed bank characteristics during post‐clear‐cut succession. Seed banks in managed ancient forest differed strongly in their characteristics compared to primary forest seed banks. Conclusions: Forest seed banks bear the marks of former land use and/or forest management and continue to do so for at least 150 years. Nevertheless, time since the last major disturbance, being either former land use or clear‐cutting, remains a significant determinant of the seed bank.     

Does the method of set-aside establishment affect its use by wood mice?

The set-aside scheme, whereby land is removed from arable production, is primarily aimed at manipulating agricultural surplus within the European Community, but has potentially great consequences for biodiversity and wildlife management (Feber et al ., 1995; Macdonald et al ., 1998; Sotherton 1998). Managed inappropriately, set-aside could prove environmentally damaging by reducing biodiversity and directly harming certain species, such as ground-nesting birds (Thompson, 1993). Conversely, appropriately managed set-aside could foster desirable ecological communities, with enhanced populations and biodiversity.     

Comparative nesting and feeding ecology of skylarks Alauda arvensis on arable farmland in southern England with special reference to set-aside

1. A study of skylark Alauda arvensis L. breeding ecology in relation to crop type was carried out from April to August 1992 on arable land in southern England. Set-aside land was included in this comparative study.
2. Territory density averaged 0·15 ha⁻¹. It was 2–3 times higher in fields of set-aside and grass, especially permanent pasture, than in winter and spring-sown cereals.
3. Territory size was nearly twice as large in fields of winter cereals (4·5 ha) than in other crop types (2·5 ha). Where set-aside was present on one farm, territory size in set-aside (1·7 ha) was a third lower than in cereals and grass.
4. Nesting began in set-aside and permanent pasture in April and peaked in late May. Nesting was not detected in spring barley until late May and in silage grass until early June. The density of successful nests in set-aside fields was more than double that in any of the arable crop types.
5. Average clutch size at hatching was 3·91 eggs in fields of set-aside, over 15% higher than in silage grass (3·40) and in spring barley (3·27).
6. Fledging success did not differ according to crop type, but productivity, expressed as the number of fledglings produced per hectare, was 0·50 in set-aside, 0·13 in silage grass, and 0·21 in spring barley. Nests with chicks were not found in fields of winter cereals. The causes of chick death were thought to be predation in set-aside fields, farming practices in silage grass fields, and suspected starvation in spring cereals.
7. The potentially high nesting success of skylarks in set-aside implies that sympathetic set-aside management could play an important part in reversing its decline across the European Union.     

Succession of bee communities on fallows

Wild bee communities were studied on one- to five-year-old set-aside fields with naturally developed vegetation (n = 20). and old orchard meadows (n = 4) to analyse effects of secondary succession on species diversity, resource use and associated life history traits. General theory predicts a steady increase of species richness with age of succession. In contrast, we found a first maximum in species richness of bees on two-year-old set-aside fields and a second on old meadows. Successional changes of bee communities were related to changes of vegetation. The transition from pioneer successional stages, dominated by annuals, to early successional stages, dominated by perennials, resulted in the highest species richness of flowering plants in the second year within the first five years of succession. Species richness of flowering plants was the best predictor variable for species richness of bees, whereas the cover of flowering plants correlated with the abundance of bees. Annual plants were visited more often and perennials less often than expected from their flower cover. Halictidae tended to prefer flowers of annuals, whereas Megachilidae. Apidae and Anthophoridae significantly preferred perennials. In departure from successional theory, body size, proportion of specialised bees and proportion of parasitic bees did not significantly increase with successional age, but number of generations and the proportion of soil-nesting bees decreased with successional age. Comparison of different management types showed that set-aside fields with naturally developed vegetation supported much more specialised and endangered bee species than set-aside fields sown with Phacelia tanacetifolia.     

Clear‐felling effects on colonization rates of shade‐tolerant forest herbs into a post‐agricultural forest adjacent to ancient forest

Question: Does clear‐felling influence forest herb colonization into post‐agricultural forest? Location: A stand of poplar cultivars with a dense understorey of Acer pseudoplatanus in Muizen forest (northern Belgium), planted in 1952 on farmland adjacent to ancient forest and clear‐felled in 1997. Methods: Shade‐tolerant forest herbs were surveyed in 112 grid‐based sample plots: just before clear‐felling, and 5 and 10 yr afterwards. Shade‐tolerant herbs were subdivided into ancient forest species (AFS) and other shade‐tolerant species (OSS). Effects of clear‐felling on species number per plot, total cover per plot and colonization rate of species groups were compared using non‐parametrical tests. Species number per plot was modelled by means of generalized linear mixed models (GLMMs), with inventory time, distance to the nearest parcel edge, and cover of light‐loving species (LS) as explanatory variables. The C‐S‐R signature (competitive, stress‐tolerant and ruderal strategies, respectively) shift of sample plots was calculated on the selected shade‐tolerant species. Results: Frequency of most species increased during the 10‐yr period. Number of OSS increased more and faster than that of AFS. OSS increased to the level of the adjacent forest, but was lower where LS cover remained high. There was a positive correlation between the change of the colonization rate and the competitive plant strategy. Conclusions: We assume that clear‐felling stimulated generative reproduction of shade‐tolerant herbs, whereas quickly emerging woody species controlled competitive exclusion by LS. Succession of dark and light phases, such as provided by an understorey managed as a coppice, could promote colonization of shade‐tolerant herbs into post‐agricultural forest.     

Temporal changes in species diversity and composition in abandoned fields in a <Emphasis Type="Italic">trans</Emphasis>-Himalayan landscape,Nepal

Secondary succession is an increasing phenomenon due to global changes in agriculture policies and practices. The empirical findings are biased towards the temperate zone. Abandonment of agriculture fields is less frequent in the subtropical and tropical zones where agriculture areas are, in general, expanding. But there are exceptions; a rapid rate of abandonment of agricultural fields have taken place in the arid trans-Himalayan region, due to today’s globalization of economy. We analysed agriculture fields that were abandoned between 1950 and 2003 in a large u-valley in central Nepal (3400 m a.s.l.). The potential forest vegetation is dominated by Pinus wallichina and shrubs of junipers and cotoneaster species. We tested the intermediate richness hypothesis in relation to vegetation cover, soil development and whether old-field succession is convergent or divergent with species data from 242 1 m² plots in 5 age-classes. The main species compositional turnover expressed by Detrended Correspondence Analyses (DCA) correlated, as expected, with time after abandonment. Fields that were abandoned a long time ago are closer to forest at the periphery of the agricultural landscape. Moisture of the soil significantly increased with age of abandonment, but total vegetation cover and pH were negatively related to age. Beta diversity expressed in DCA SD-units showed an increasing trend with age of abandonment, supporting the divergence pattern in old-field succession. The reason why the succession is not converging may be due to browsing by domestic animals that prevent a closed canopy of pines and juniper to develop. There was a significant hump-shaped pattern in species richness along the temporal gradient, which agrees with the intermediate species-richness hypothesis. There was a rapid increase in species richness in plots close to the villages that were used for haymaking which increased the seed input significantly.     

The movements of the Kittiwake

Capsule During winter songbirds were far more abundant in game cover crops than conventional agricultural habitats.

Aims To quantify game crop use during winter by farmland songbirds when compared with conventional farmland at a regional scale.

Methods Songbirds were counted on 20 farms in eastern Scotland. The number of songbirds using game crops was compared with a sample of nearby conventional crops – with particular emphasis on set-aside and cereal stubbles.

Results Game crops supported up to 100 times as many birds per hectare, of significantly more species, than the other two habitat categories. Many of these species were those currently causing concern because of their declining populations.

Conclusion Game crops could provide opportunities for increasing food resources to songbirds whose populations may be limited by food availability and possibly arrest population declines. At present, the only measures likely to facilitate this are the government's various agri-environment schemes.     

Density and productivity of breeding Skylarks Alauda arvensis in relation to crop type on agricultural lands in western France

Capsule Small field size and the maintenance of set-aside and lucerne are important to ensure high breeding pair densities and productivity.

Aims To investigate the effects of crop types and their attributes on density and productivity of breeding Skylark.

Methods At each of four selected study sites in western France, territory density, vegetation height, vegetation cover and field size was estimated by field and attempts were made to find nests. Crop types included winter and spring cereals, oilseed rape, sunflower, maize, grass, lucerne, set-aside, and bare ground.

Results About 80% of Skylark territories included more than one crop type. Birds preferred small fields and territory density decreased with increasing field size. Density was highest in crops with low vegetation height and cover. Set-aside, lucerne and grass supported highest territory density. Fledging productivity was highest in set-aside and lucerne, and was zero on bare ground. Skylark density decreased throughout the breeding season (-26% in 1999 and -29% in 2000), suggesting an instability in territory distribution or activity in intensive farmland.

Conclusions Farming systems that decrease field size and increase set-aside and lucerne instead of oilseed rape, maize and sunflower will benefit Skylark and other declining farmland species.     

Long‐term effectiveness of sowing high and low diversity seed mixtures to enhance plant community development on ex‐arable fields

Questions: How is succession on ex‐arable land affected by sowing high and low diversity mixtures of grassland species as compared to natural succession? How long do effects persist? Location: Experimental plots installed in the Czech Republic, The Netherlands, Spain, Sweden and the United Kingdom. Methods: The experiment was established on ex‐arable land, with five blocks, each containing three 10 m × 10 m experimental plots: natural colonization, a low‐ (four species) and high‐diversity (15 species) seed mixture. Species composition and biomass was followed for eight years. Results: The sown plants considerably affected the whole successional pathway and the effects persisted during the whole eight year period. Whilst the proportion of sown species (characterized by their cover) increased during the study period, the number of sown species started to decrease from the third season onwards. Sowing caused suppression of natural colonizing species, and the sown plots had more biomass. These effects were on average larger in the high diversity mixtures. However, the low diversity replicate sown with the mixture that produced the largest biomass or largest suppression of natural colonizers fell within the range recorded at the five replicates of the high diversity plots. The natural colonization plots usually had the highest total species richness and lowest productivity at the end of the observation period. Conclusions: The effect of sowing demonstrated dispersal limitation as a factor controlling the rate of early secondary succession. Diversity was important primarily for its‘insurance effect’: the high diversity mixtures were always able to compensate for the failure of some species.     

Assessing German farmers’ attitudes regarding nature conservation set-aside in regions dominated by arable farming

This paper presents an analysis of the attitudes of farmers towards a policy approach that combines the instrument of set-aside of farmland with agri-environmental measures under the Common Agricultural Policy (CAP) for achieving nature goals. One of the stated objectives of current agricultural and environmental policies is to give greater consideration to issues of nature conservation in agricultural landscapes. To fulfil this objective, there is an urgent need to develop approaches that, on the one hand, are capable of delivering tangible improvements in the ecological situation and nature conservation in agriculture and, on the other hand, are structured in such a way that farmers are willing to put them into practice. In addition, such approaches need to be economical and affordable for society. The Leibniz-Centre for Agricultural Landscape Research (ZALF) has developed the concept of ‘nature-conservation set-aside’, especially for landscapes that are under predominantly arable use. Conservation set-aside refers to parts of arable farmland especially well suited to nature conservation, which are mandatorily withdrawn from agricultural production (for those who claim payment) and on which ecologically valuable habitats are created through specific management activities. To determine what kind of problems might arise for farmers in the course of implementing this concept as an agri-environmental measure, a survey was carried out in four largely arable regions of Germany. The results of this survey show the attitudes of German farmers regarding set-aside farmland for nature conservation in regions dominated by arable farming, and they demonstrate which factors influence the implementation of conservation set-aside.     

覆盖作物的种植现状及其对下茬作物生长和土壤环境影响的研究进展

覆盖作物指的是在农业生产间隙种植,使土壤在时间或空间上减少或避免裸露的一种作物。其能使农田土壤免受风蚀、水蚀和人为扰动的影响,被认为是一种新型的保护性耕作方式。本文简要介绍了农田覆盖作物的种植管理情况,包括种植品种、耕作模式和绿肥作物的灭生还田方式等,可为推广覆盖作物在农田休闲期的高效大面积种植提供参考。基于国内外研究综述了绿肥种植对经济作物、土壤质量、杂草抑制、温室气体排放和土壤微生物等的影响及研究进展,阐明了覆盖作物对农田生态系统的诸多益处。尽管覆盖作物存在局限性,例如短期收益不明显、管理措施不当会造成作物减产等,但其在改善土壤质量、实现农业可持续发展方面仍然具有重要的应用价值。     

Habitat Quality Following Mid-Rotation Treatment in Conservation Reserve Program Pines

ABSTRACT Evaluation of habitat management practices at mid-rotation is needed for pine (Pinus spp.) plantations enrolled in cost-share programs. Plantations established in abandoned agricultural fields may have different understory plant communities than those with a long history of forest cover. Mid-rotation pine plantations often have a hardwood midstory that limits development of early succession habitat components important to white-tailed deer (Odocoileus virginianus; deer) and northern bobwhite (Colinus virginianus; bobwhite). We treated with imazapyr herbicide and prescribed burning (HB) 11 thinned, 13–22-year-old pine plantations in the Upper East Gulf Coastal Plain of Mississippi, USA, enrolled in cost-share programs, and we sampled plant community response during the summers of 2003 and 2004, years 1 and 2 posttreatment. The HB treatment created a more open structure with greater coverage of debris and herbaceous plants than in controls. Increased forb coverage in HB plots yielded a more seasonally diverse foraging base for deer. Horizontal screening cover developed slowly in HB plots and was more abundant in control plots. Autumn and winter food-plant coverage for bobwhite was provided by either treatment, but accessibility was improved in HB plots relative to controls. Bobwhite nesting cover was improved by HB relative to controls but was still of marginal quality. Brood-rearing habitat was precluded in both treatments due to lack of bare ground. Our results indicate that imazapyr followed by prescribed fire is a beneficial tool for creating early succession habitat for deer and bobwhite in mid-rotation pine plantations with a history of agricultural use. Continued management with periodic prescribed fire and overstory thinning should be instituted to maintain and perhaps improve these conditions.     

Spontaneous succession in limestone quarries as an effective restoration tool for endangered arthropods and plants

1. The view of post-mining sites is rapidly changing among ecologists and conservationists, as sensitive restoration using spontaneous succession may turn such sites into biodiversity refuges in human-exploited regions. However, technical reclamation, consisting of covering the sites by topsoil, sowing fast-growing herb mixtures and planting trees, is still commonly adopted. Until now, no multi-taxa study has compared technically reclaimed sites and sites left with spontaneous succession.
2. We sampled communities of vascular plants and 10 arthropod groups in technically reclaimed and spontaneously restored plots in limestone quarries in the Bohemian Karst, Czech Republic. For comparison, we used paired t -tests and multivariate methods, emphasizing red-list status and habitat specialization of individual species.
3. We recorded 692 species of target taxa, with a high proportion of red-listed (10%) and xeric specialist (14%) species, corroborating the great conservation potential of the quarries.
4. Spontaneously restored post-mining sites did not differ in species richness from the technical reclaimed sites but they supported more rare species. The microhabitat cover of leaf litter, herbs and moss, were all directly influenced by the addition of topsoil during reclamation.
5. Synthesis and applications. Our results show that the high conservation potential of limestone quarries could be realized by allowing succession to progress spontaneously with minimal intervention. Given the threat to semi-natural sparsely vegetated habitats in many regions, active restoration measures at post-mining sites should be limited to maintenance of early successional stages, instead of acceleration of succession.     

The role of fallow in habitat use by the Lesser Kestrel during the post-fledging period: inferring potential conservation implications from the abolition of obligatory set-aside

The maintenance of fallows has been shown to prevent the loss of farmland biodiversity caused by agricultural intensification. These are mainly introduced as part of both obligatory and voluntary set-aside schemes. However, the obligatory set-aside has recently been abolished by the Common Agricultural Policy Health Check. In this study, we examine the role of fallow in fine-grained habitat use by a threatened farmland bird (Lesser Kestrel) during summer in northwestern Spain. To analyze Lesser Kestrel occurrence, we used generalized linear models, a theoretic-information approach and a hierarchical partitioning analysis. The best AIC-based models explaining occurrence of Lesser Kestrels showed that fallow was the more important habitat type followed, to a lesser extent, by dry cereal stubble and field margin. In contrast, irrigated crops negatively influenced occurrence. Heterogeneity of crop mosaic was not important in explaining occurrence of Lesser Kestrel. Fallows, like dry cereal stubbles and field margins, seem to be suitable for foraging given the abundance of high food resources and their availability due to shorter vegetation cover. The abolition of the obligatory set-aside could reduce the total surface of fallow land (approximately 40.9%), likely affecting habitat use by Lesser Kestrel through an increase of other non-preferred crops (e.g., irrigated crops) or by decreasing food resources. Agri-environment schemes focusing on the maintenance of low-intensive farming systems with a mosaic of crops and semi-natural habitats interspersed should be promoted in premigratory areas to maintain Lesser Kestrel.     

Effects of landscape composition on farmland and red-listed birds in boreal agricultural-forest mosaics

Farmland birds have declined in large areas of western and northern Europe. This decline has been connected with changes in the agricultural landscape. We studied the effects of landscape composition on birds in a boreal agricultural-forest mosaic in SW Finland. This study was carried out with a grid-based approach: bird pairs were counted in 105 grid squares of 25 ha within an area of 26.25 km². The total density of farmland birds and density of red-listed species were related to the land cover variables using generalized linear modelling (GLM). Farmland birds consist of a variable group of species either breeding or feeding in agricultural land. The model explained a moderate proportion (49%) of the variation in the total density of farmland birds in the landscape. In a regression analysis cover of non-arable agricultural land (semi-natural grasslands, built-up areas) explained a much higher proportion (r²=0.49) of the variation in farmland bird density than that of arable land (cultivated fields and set-aside fields, r²=0.04). Semi-natural grasslands, which have drastically declined throughout NW Europe, and built-up areas (mainly farmyards) had the most significant positive effects on the density of red-listed species. The results emphasize the significance of semi-natural grasslands for the declining red-listed farmland bird species. Birds are usually not restricted to certain patches of habitat but use several patches in their home range. Thus, when studying bird-landscape relations for land use planning, we also recommend grid-based approaches covering the whole landscape variation.     

Forecasting the Effects of Land Use Scenarios on Farmland Birds Reveal a Potential Mitigation of Climate Change Impacts

Climate and land use changes are key drivers of current biodiversity trends, but interactions between these drivers are poorly modeled, even though they could amplify or mitigate negative impacts of climate change. Here, we attempt to predict the impacts of different agricultural change scenarios on common breeding birds within farmland included in the potential future climatic suitable areas for these species. We used the Special Report on Emissions Scenarios (SRES) to integrate likely changes in species climatic suitability, based on species distribution models, and changes in area of farmland, based on the IMAGE model, inside future climatic suitable areas. We also developed six farmland cover scenarios, based on expert opinion, which cover a wide spectrum of potential changes in livestock farming and cropping patterns by 2050. We ran generalized linear mixed models to calibrate the effects of farmland cover and climate change on bird specific abundance within 386 small agricultural regions. We used model outputs to predict potential changes in bird populations on the basis of predicted changes in regional farmland cover, in area of farmland and in species climatic suitability. We then examined the species sensitivity according to their habitat requirements. A scenario based on extensification of agricultural systems (i.e., low-intensity agriculture) showed the greatest potential to reduce reverse current declines in breeding birds. To meet ecological requirements of a larger number of species, agricultural policies accounting for regional disparities and landscape structure appear more efficient than global policies uniformly implemented at national scale. Interestingly, we also found evidence that farmland cover changes can mitigate the negative effect of climate change. Here, we confirm that there is a potential for countering negative effects of climate change by adaptive management of landscape. We argue that such studies will help inform sustainable agricultural policies for the future.     

Migration of herbaceous plant species across ancient–recent forest ecotones in central Belgium

1 We studied the migration of forest plant species using their percentage cover and frequency in 197 plots distributed over 26 transects across ecotones between ancient and recent deciduous forests in the Meerdaal forest complex in central Belgium. The recent forest stands varied in age between 36 and 132 years, and all occurred on silty, well-drained soils.
2 The total cover, number and diversity of field layer species did not differ significantly between ancient and recent forest stands.
3 The number and cover of the ancient forest plant species and of ant-dispersed species correlated positively with the age of the recent forest and negatively with both the duration of its former agricultural land use and the distance to the ancient forest. This implies a slow colonization of the recent forest stands by these species; all species were, however, able to migrate across the ecotones.
4 The cover of four species ( Anemone nemorosa , Lamium galeobdolon , Convallaria majalis and Polygonatum multiflorum ) declined along the transect, suggesting that they are limited by seed dispersal. Their colonization rates, calculated from the occurrence of the farthest individual, ranged from < 0.05 to 1.15 m year⁻¹ and for other measures from < 0.05 to 0.65 m year⁻¹. Anemone and Lamium appeared to colonize the recent forest by establishment of isolated individuals, while Polygonatum and Convallaria expanded populations from existing patches on the border between ancient and recent forest.
5 Several forest species were able to colonize the recent forest rapidly, where some of them even reached a higher abundance, due to the increased availability of colonization sites with a higher nutrient content and a thinner organic layer.     

Restoration of a species‐rich fen‐meadow after abandonment: response of 64 plant species to management

Abstract. Eleven years of abandonment of a species‐rich fen‐meadow under undisturbed environmental conditions resulted in transformation into areas with tall herb‐, sedge‐ and rush‐dominated communities and areas with Alnus thicket. Species cover was measured in permanent plots in both community types and succession was monitored during 14 yr of restoration following reintroduction of management. The annual increase in accumulated species number followed a log‐log‐time linear regression during 10 yr of grazing management. The expected number of years taken before this annual rate was equal to annual extinction, i.e. a stable situation according to species density, was up to six. The response of 64 species to management was evaluated through paired statistical tests of changes in cover and frequency over time. In total, 55 species could each be allocated to one unique response model (monotone or non‐monotone, concave models) independently of the importance value used (cover or frequency) and type of management (grazing following felling or mowing and mowing without grazing). Species which increased in response to grazing had the most persistent seed banks and CR‐strategies, while species decreasing in response to grazing had less persistent seed banks and CS‐strategies. Some of the species which increased due to grazing followed a model with a local maximum in cover and frequency. The results are discussed in relation to management of species with high cover value during restoration succession.     

Low-Intensity Agricultural Landscapes in Transylvania Support High Butterfly Diversity: Implications for Conservation

European farmland biodiversity is declining due to land use changes towards agricultural intensification or abandonment. Some Eastern European farming systems have sustained traditional forms of use, resulting in high levels of biodiversity. However, global markets and international policies now imply rapid and major changes to these systems. To effectively protect farmland biodiversity, understanding landscape features which underpin species diversity is crucial. Focusing on butterflies, we addressed this question for a cultural-historic landscape in Southern Transylvania, Romania. Following a natural experiment, we randomly selected 120 survey sites in farmland, 60 each in grassland and arable land. We surveyed butterfly species richness and abundance by walking transects with four repeats in summer 2012. We analysed species composition using Detrended Correspondence Analysis. We modelled species richness, richness of functional groups, and abundance of selected species in response to topography, woody vegetation cover and heterogeneity at three spatial scales, using generalised linear mixed effects models. Species composition widely overlapped in grassland and arable land. Composition changed along gradients of heterogeneity at local and context scales, and of woody vegetation cover at context and landscape scales. The effect of local heterogeneity on species richness was positive in arable land, but negative in grassland. Plant species richness, and structural and topographic conditions at multiple scales explained species richness, richness of functional groups and species abundances. Our study revealed high conservation value of both grassland and arable land in low-intensity Eastern European farmland. Besides grassland, also heterogeneous arable land provides important habitat for butterflies. While butterfly diversity in arable land benefits from heterogeneity by small-scale structures, grasslands should be protected from fragmentation to provide sufficiently large areas for butterflies. These findings have important implications for EU agricultural and conservation policy. Most importantly, conservation management needs to consider entire landscapes, and implement appropriate measures at multiple spatial scales.     

Leaf miner assemblies: effects of plant succession and grazing management

Abstract. 1. Changes in leaf-miner assemblies during 4 years of secondary succession, under different controlled sheep-grazing treatments, are described and compared to the miner fauna of older grazed grassland nearby.
2. Multivariate analyses were used in conjunction with examination of individual common species to assess the independent effects of time, grazing treatment, plant species composition and architecture on the leaf-miner assemblies.
3. Leaf-miner species composition was strongly related to plant species composition, but was modified by plant structure under different grazing treatments. There was a strong successional trend in miner assemblies, even when the effects of changes in plant composition had been taken into account. Conversely, local variation in miner species composition generally reflected foodplant distribution alone.
4. Grazed treatments had fewer mines than controls, but there were also species specializing in grazed areas, despite the abundance of their foodplants elsewhere. There was a weak indication that miner species in grazed treatments were more likely to fluctuate in abundance than those in controls.
5. The results are discussed in relation to the assembly of grassland insect communities during succession, and the use of 'indicator groups' in management for nature conservation.