Hedgerow Characteristics Research Articles

How do hedgerow characteristics alter the dispersal of Pseudocercospora fijiensis propagules?

Hedgerows represent an agroecological lever for pest management. To date, few studies have shown that they can be used as a lever for the control of aerial fungal diseases, especially as a barrier to dispersal. On banana production, the main disease is black leaf streak disease (BLSD), which is a fungal disease caused by Pseudocercospora fijiensis. This pathogen disperses through two types of spores: ascospore and conidia. The aim of this study was to observe and to quantify the effect of hedgerows on BLSD dispersal. Trap plants were placed at the same distance to an artificial source of inoculum with a hedgerow on one side. Lesions were counted to establish the daily lesion density of each trap plant. The combination of hedgerow characteristics such as height, width, and optical porosity were used to evaluate its potential capacity to intercept spores. When ascospores were used as a source of inoculum, the lesion density on traps plant decreased up to 50% between the hedgerow with the lowest interception capacities and the one with the highest interception capacities. For conidia, hedgerow height and side of the trap plants (with or without hedgerow between them and the source) were not significant, but low porosity of the hedgerow reduced the lesion density. On the contrary, for ascospore, the hedgerow effect was anisotropic; the trap plants on hedgerow side had less lesions. Our study is the first experimental proof of the effect of hedgerows on P. fijiensis dispersion, both on conidia and ascospore. We showed that hedgerow characteristics impact the capacity of interception of the hedgerow. © 2023 Society of Chemical Industry.

Effects of hedgerows on the preservation of spontaneous biodiversity and the promotion of biotic regulation services in agriculture: towards a more constructive relationships between agriculture and biodiversity

ABSTRACT Central to the agroecological transition is biodiversity, which, once restored in agroecosystems, should provide multiple ecosystem services that result from the interactions between different organisms. However, the diversity of expected services raises questions about the capacity of agroecosystems to simultaneously provide many of them as well as the possible existence of synergies and antagonisms. In particular, the relationships between crop-associated biodiversity (i.e. biodiversity in action in crops) and spontaneous biodiversity (i.e. biodiversity not directly related to agriculture) remain unclear. In this article, we analyse the impact of hedgerows on the preservation of spontaneous biodiversity, on the promotion of biotic regulation services such as pollination and pest control in agriculture, and on the interactions between spontaneous and associated biodiversity. Our analysis of the scientific literature shows that hedgerows are unique assets for the preservation of spontaneous biodiversity, while they also provide biotic regulation services to adjacent crops but only under specific conditions, which need to be better understood. We propose a functional conceptual framework of the ecological effects of hedgerows on associated biodiversity and we highlight the possible synergistic and antagonistic effects related to hedgerow characteristics and the life-history traits of the organisms under consideration. Our analysis therefore seeks to overcome the cleavage between associated biodiversity and spontaneous biodiversity. This approach is in keeping with a more harmonious relationship between agriculture and biodiversity.

Hedgerows support rich communities of harvestmen (Opiliones) in upland agricultural landscape

Hedgerows play important roles in agricultural landscapes and they increase biodiversity by providing habitat refugia for species sensitive to agricultural disturbance. We have studied the characteristics of the communities of harvestmen (Opiliones) inhabiting hedgerows. Harvestmen are terrestrial arachnids associated with soil surface and subsurface and sensitive to land-use and disturbance. We were specifically interested in quantifying how hedgerow characteristics (e.g., elevation, length, width, connectivity, and plant diversity) affect harvestman diversity and community composition. We expected harvestman diversity and community composition to be positively related to both hedgerow size (area, length, width) and biological attributes of hedgerows (e.g., connectivity, plant community diversity). We surveyed hedgerow characteristics and harvestman communities of 20 hedgerows in an upland agricultural landscape in the Western Carpathians. Hedgerow characteristics were measured in the field or derived from GIS layers and we used correlation and ordination methods to relate them to harvestman community metrics. We found surprisingly high taxonomic richness of harvestmen within the studied hedgerows (15 species). Importantly, the Shannon index of harvestman communities was positively related to hedgerow length and hedgerow tree layer species richness and diversity. Harvestman community composition varied with hedgerow area and width. Despite their small total area, hedgerows represented an important habitat for diverse harvestman communities and hedgerow attributes such as size and tree diversity significantly affected the composition and the Shannon index of harvestman communities. Thus, greater lengths and widths of hedgerows can provide habitats for a higher Shannon index of harvestman communities, within surrounding agricultural landscapes.

Maize‐field complexity and farming system influence insectivorous birds’ contribution to arthropod herbivore regulation

AbstractThe contribution of insectivorous birds to reducing crop damage through suppression of herbivory remains underappreciated, despite their role as cropland arthropod predators. We examined the roles of farming system, crop cover pattern, and structural configuration in influencing assemblage composition of insectivorous birds and their herbivorous arthropod prey across maize fields, and determined how bird exclusion affects crop herbivory levels. To achieve these objectives, we collected data across a sample of organic and conventional small‐scale non‐Bt maize farms in western Kenya. Assessments of abundance, diversity, and richness of insectivorous birds and abundance of their arthropod prey were compared between organic and conventional small‐scale non‐Bt maize on monocultured and inter‐cropped farms. We also employed bird exclusion experiments to assess impacts of bird predation on herbivorous arthropod abundance. Results showed that higher structural heterogeneity supported higher insectivorous bird richness, particularly under organic systems, dense trees, large woodlots, and thick hedgerows. Bird abundance further increased with crop diversity but not in relation to cropping method, hedgerow type, or percent maize cover per se. Conversely, herbivorous arthropod abundance and richness increased on conventional farms and those with higher percent maize cover, but were unaffected by cropping methods, tree, or hedgerow characteristics. Birds’ arthropod prey was more abundant under completely closed experimental plots compared with open or semi‐closed plots, confirming a significant linkage between birds and herbivorous arthropod suppression. In this study, we demonstrate importance of structural heterogeneity in agricultural landscapes, including diverse croplands and on‐farm trees to maximize insectivorous birds’ contribution to reducing crop arthropod herbivory.Abstract in Swahili is available with online material.

Economic impact of predatory piscivorous birds on small-scale aquaculture farms in Kenya

This study assessed the economic loss due to pond-fish predation by piscivorous birds in small-scale aquaculture systems in western Kenya. Piscivorous birds were surveyed in the field through daily focal scan sampling to record abundance and species richness. Overall fish damage by birds was quantified from known daily feeding rates, and economic-loss estimates were projected for a six-month production season. The influence of farm habitat features on bird diversity and frequency was also evaluated. These features included hedgerow characteristics, size of fallow areas, presence of woodlots, tree density and pond proximity to dwellings. Thirteen piscivorous bird species were identified. Their abundances increased with increasing tree density and pond distance from houses, except when exotic hedgerows were present. Total seasonal fish damage by birds, mainly large waders, across all farms was estimated at 2.141 tonnes per production season valued at USD 12,845, representing 15% of the projected production. This corresponded to an average loss of 33 kg of fish (worth USD 165) per pond, and is a substantial and challenging setback for rural aquaculture. Urgent action through habitat management and capital support is required as a necessary step for reducing investment losses and sustaining the local food supply while at the same time protecting wildlife.

The Relative Effects of Local and Landscape Characteristics of Hedgerows on Bats

The role of hedgerows in maintaining biodiversity in areas of intensive agriculture is well known, particularly for bats. However, few studies have addressed the importance of the intrinsic characteristics of hedgerows for bats and disentangled the relative effects of local and landscape characteristics of hedgerows on bat activity. In an acoustic survey, we assessed bat activity by recording bat calls using detectors and manually verified all calls using spectrogram analysis. The parameters used to determine local hedgerow structures were the length of the line of trees, of shrub hedgerows, of wooded hedgerows without shrubs and of hedgerows including the three strata (tree, shrub and herb) at a local scale. We assessed the influence of hedgerow structure and on bat activity with an approach considering both species and community, comparing two different scales, the local and the landscape. We highlighted the importance of hedgerow characteristics for bats on both the local and landscape scales even though responses differ between species and spatial scales. We found that the presence of trees in hedgerows exerts a generally positive influence on bat activity and that hedgerows with the three strata had lower bat activity than hedgerows with trees. In our study, some bats seemed to prefer agricultural landscapes dominated by wooded hedgerows and, on the local scale, hedgerows that include trees with little diversified among strata, except for gleaning species. Our study shows that in terms of hedgerow management, conservation efforts must be designed and undertaken on both the local and landscape scales.

Myriapod (Chilopoda, Diplopoda) communities in hedgerows of upland agricultural landscape

AbstractIt is well established that hedgerows provide habitats, which cannot be found in otherwise coherent agricultural landscape. However, different organisms vary in their response to various environmental variables of hedgerows. The aim of this paper is to study how are the myriapod species richness and community composition related to biological and morphological parameters of farmland hedgerows. We expected diversity to be related to size of hedgerows and community composition to be primarily affected by their biological attributes. We studied myriapod communities in 20 hedgerows located in close vicinity of Žibritov village (the Carpathians, Slovakia) in Central European upland farmland. Characteristics of the hedgerows were either measured in the field or derived from GIS layers. We used univariate and multivariate correlation methods to investigate the effect of hedgerow characteristics on diversity and composition of myriapod communities. Surprisingly high taxa numbers of myriapods were found within small area. Richness of millipedes showed negative relationship with hedgerow plant community diversity, hedgerow length and soil depth and weak positive relationships with a degree of shrub layer defoliation. Centipede richness was mainly related to diversity of hedgerow tree layer. We did not find any significant relationship between centipede communities’ composition and environment. Length of hedgerows was the only variable showing significant relationship with millipede communities’ composition. Despite small area, hedgerows represent important habitats for several species of centipedes and millipedes and show specific composition of their taxocoenoses determined by hedgerows attributes. Farmland hedgerows appear to be important habitats for soil organisms, which may be further beneficial for surrounding landscape.

Long-term Effect of Intra-Row Spacing on Growth and Productivity of Super-High Density Hedgerow Olive Orchards (cv. Arbequina).

Intra-row spacing is known to determine early productivity of super-high density olive orchards depending on growing conditions, cultivar growth characteristics, planting geometry and subsequent pruning management but few experiments have been carried out in this olive hedgerow orchard design. In 2008 an experiment of 4-m spaced hedgerows was established with 8 intra-row spacings (from 1.0 to 2.5 m) in Toledo (Spain) resulting in orchards of density ranging from 2,500 to 1,000 trees ha−1. Tree growth was evaluated as height, trunk diameter and leaf area during the first 4 years. Hedgerow porosity was calculated from the 4th until the 9th year. In the 8th year hedgerow height, width, leaf area and branch angles were measured. Olives were harvested from 3rd to 9th year for measurements of fruit characteristics and productivity. Tree growth was not affected by intra-row spacing during the first 4 years. In the 8th year leaf area, external surface area and volume per tree were significantly greater in the more spaced trees; but hedgerow characteristics of leaf area per hectare, number of effective leaf layers horizontally through the hedgerow, and leaf density were not affected. In the more spaced trees insertion angles of branches to the vertical were significantly greater, mainly in the lower canopy. Intra-row spacing did not affect fruit characteristics. Oil production ha−1 decreased linearly with spacing during the first 4 harvests while production per tree increased significantly with spacing after the 3rd harvest. As a result, oil production ha−1 from the seven harvests combined only increased for tree spacing less than 1.2 m; wider spacing had no effect. Annual oil production ha−1 increased linearly as porosity was reduced by greater tree density and canopy development along the seasons.

Effects of hedgerows on bats and bush crickets at different spatial scales

Biodiversity is threatened by the loss and fragmentation of habitats. The role of hedgerows in maintaining biodiversity is well established, but few studies have addressed the importance for biodiversity of the intrinsic characteristics of hedgerows and the quality of hedgerow networks along a spatial scale. We examined three quality indices providing information at different territorial levels: density in the landscape, structural diversity and wood production. We performed an acoustic survey in a grassland to estimate the species abundance and community composition of bats (9 taxa) and bush crickets (11 species). Using an approach based on species and traits, we assessed how hedgerow quality influenced the activity of these taxa at different spatial scales (from 50 to 1000 m) and focused on three types of traits: bush cricket mobility ability, bat foraging strategy and habitat specialization. In general, our results showed the importance of hedgerow quality for bats and bush crickets, but the strength of the association between taxa and hedgerows varied substantially among the species and the spatial scales. Although it depends on the taxa, the production, density and structural diversity of hedgerows each had an overall positive effect. Our results suggested that these effects were generally more important at large scales. The scale effect of the production index is the best predictor of activity for bat and bush cricket taxa and traits. Our results showed the importance of hedgerow quality for the ecology of bat and bush cricket communities and could be used to improve conservation management.

Farmland conservation in West Africa: how do hedgerow characteristics affect bird species richness?

Capsule The value of farmland for birds at a site in Nigeria, West Africa, was highly dependent upon the habitat structure, with wider and more continuous hedges supporting more bird species. Aim To understand the value of hedges in Nigerian farmland to bird species richness. Methods We used line transects to survey birds and vegetation on 166 systematically selected hedgerows on fallow, cultivated and harvested fields in Jos East, Nigeria. Results Wider hedges supported higher species richness. Plant species composition was a weak predictor of bird species richness compared to hedge width. There was no observed difference in distribution of bird richness across field types, suggesting that the value of hedgerows for biodiversity is comparable, regardless of farming method. Continuous hedgerows (hedgerows with vegetation gap < 1.5 m) held higher species richness compared with discontinuous (hedgerows with vegetation gap > 1.5 m) hedges. Conclusion This result suggests that hedge size and structure, rather than plant species composition, is an important predictor of avian species richness in hedgerows surrounding farmland. Therefore, the value of farmland for birds in this part of Africa is highly dependent upon the habitat structure, with wider and more continuous hedges supporting more bird species.

The influence of pheasant releasing and associated management on farmland hedgerows and birds in England

Hedgerows are an integral part of the farmed landscape and are important habitats for many birds and other wildlife. Game managers recognize the importance of hedgerows for gamebirds, both in the nesting season for wild birds and as dispersal routes from woodland release pens for reared pheasants in late summer. Conservationists are interested in the potential impacts of pheasant releasing on wildlife and habitats. The aim of this study was to assess the impact of gamebird management on hedgerow structure and the density and connectedness of hedgerows at the landscape level by comparing sites with and without gamebird releasing. We surveyed 150 sites in southern and eastern England: 97 were on pheasant shoots while the others were on farms where there had been no pheasant releasing for at least 25 years. Using a combination of field survey, satellite imagery and GIS software, we determined hedgerow abundance and their structural characteristics. We also measured the extent of hedgerow connectedness. We found that the hedgerow structure was similar on farms with and without game shoots. However, hedgebanks were between 17% and 36% wider on game estates. Game estates also had between 10% and 65% more hedgerow per square kilometre than farms with no game shoot. We found no strong evidence that game management influenced bird numbers associated with individual hedgerows. We conclude that structural characteristics of hedgerows on sites with pheasant releasing do not differ from hedgerows on farms where there is no pheasant releasing undertaken. The tendency for wider hedgebanks and greater hedgerow abundance on game estates is likely due to the recognition of game estate managers of the value of hedgerows as habitats for gamebirds. The results of this study need to be considered within the context of other studies which have highlighted the potential negative effects of large pheasant releases on hedgerow vegetation.

Effects of hedgerow characteristics on intra-orchard distribution of larval codling moth

The spatial distribution of diapausing larvae of codling moth ( Cydia pomonella), a common pest species, was analysed in several commercial orchards during 3 consecutive years. Extent and location of the clustering of diapausing larval codling moth were first assessed in each orchard. The between year differences in clustering patterns were then checked. The relation of clustering patterns to characteristics of neighbouring hedgerow was finally tested. Clustering was detected in 16 orchards out of 53 (30.2%) in 2006, in 10 orchards out of 50 (20%) in 2007, and in 13 orchards out of 40 (32.5%) in 2008. The clustering pattern was generally similar between years. There was a consistent influence of neighbouring hedgerows on the spatial distribution of individuals. The number of larvae was lower – depending on the year – in areas either closest to hedgerows or under the influence of hedgerow shadow or wind protection depending on the year. Further, in one of the years, the number of larvae was negatively correlated with the floral diversity of the nearby hedgerow. This study suggests that hedgerows influence codling moth population dynamics and may play a key role in reducing the abundance of this species within orchards.

Evaluating hedgerow corridors for the conservation of native forest herb diversity

The maintenance of connecting habitats such as hedgerows in production landscapes could become increasingly critical as species migration is expected to accelerate with climate change. Species of particular conservation interest that could benefit from connecting habitats especially in agroecosystems are native forest herbs. It is still unclear, however, which hedgerow habitats have the best potential of supporting diverse forest herb communities, making it hard to target particular structures for conservation. Our objective was to identify the local and landscape characteristics of hedgerows that could help predict their potential at maximizing the richness, abundance, and diversity of native forest herbs of temperate deciduous forests of North-East America. We used multiple regression, Moran’ I correlograms, and conditional autoregressive models to assess the effect of landscape and historical variables (hedgerow age, amount of adjacent forest cover, connection to forests and other hedgerows) and of local variables (hedgerow width, canopy cover, cover of other species) on the response variables. The results show an increase in forest herb diversity and abundance in hedgerows with time and with increasing nearby forest cover. Local factors such as greater width and reduced cover of other species also relate to a greater abundance and diversity of forest herbs in linear habitats. The fact that forest herb communities can reassemble in hedgerow corridors with time implies that there could be long-term benefits in maintaining and even creating linear habitats where there is a pool of dispersing forest herbs.

Influence of management regimes of adjacent land uses on the woody plant richness of hedgerows in Spanish cultural landscapes

Hedgerows are an important component of the cultural landscape and may have an invaluable role in maintaining biological diversity. Adjacent land use potentially has an important influence on the species composition of hedgerows. In the Mediterranean region, hedgerows are considered as remnants of past practices and their function may be linked with the prevailing agrarian systems, in turn related to societal change. In this paper, the characteristics of hedgerows in Central Spain, and their interactions with adjacent fields were studied in order to understand their contribution to maintaining woody plant species richness in the cultural landscape. The hedgerow typology of the region were found to respond jointly both to environmental and livestock farming-related variations in adjacent land uses. The variation in the management intensity of the landscape is reflected in the composition of the woody plant species of hedgerows, varying from species of open landscape to woodland species. Moderate degrees of grazing allow for higher values of woody plant richness in hedgerows compared with those hedgerows separating systems subjected to a higher livestock loads or to abandonment processes. Thus, hedgerows potentially contribute to the functionality of these cultural landscapes and provide a basis of important ecological and historical value in landscape conservation planning. These conclusions have important implications in the development of landscape conservation and protection policies.

Tree-crop interactions in hedgerow intercropping with different tree species and tea in Sri Lanka: 1. Production and resource competition

Incorporation of tree hedges along contours has been proposed as a means of reducing soil erosion and increasing soil fertility of tea (Camellia sinensis (L.) O. Kuntz) plantations on sloping terrain in high-rainfall zones of Sri Lanka. Tea yields in these hedgerow intercrops are determined by the balance between the positive (i.e., increased soil fertility) and negative (i.e., resource competition) effects of hedgerows. Therefore, the objectives of the present study were to determine: (a) the net effect of six different hedgerow species (Calliandra calothyrsus Meissner, Senna [Cassia] spectabilis (DC.) H. Irwin and Barneby, Euphatorium innulifolium (R.M. King and H. Rob.) H.B.K., Flemingia congesta Aiton F., Gliricidia sepium (Jacq.) (Kunth.) Walp. and Tithonia diversifolia (Hemsl.) A. Gray) on long-term tea yields; (b) the effect of incorporating hedgerow prunings as mulch; and (c) the relationship between hedgerow characteristics (i.e., biomass production, canopy and root growth) and tea yield variation. Tea yields, measured over one complete pruning cycle from October 1998 to September 2001, showed reductions relative to a sole tea crop under all hedgerow species except Euphatorium. The yield reductions ranged from 22 to 40%. Tea yields under Euphatorium showed increases up to 23% relative to the sole crop control. Addition of hedgerow prunings as mulch increased tea yields in all hedgerow intercrops. The yield increases ranged from 11 to 20%, with the highest being under Euphatorium. Tea yields showed a negative relationship (R2=0.38) with the pruned biomass of hedgerows. Limitation of environmental resources (e.g., water and light) and hedgerow characters which intensified resource competition (i.e., greater canopy lateral spread and height and greater root length densities, especially in the top soil layer) were responsible for observed tea yield reductions in hedgerow intercrops.

Hedgerows as habitat for woodland plants

For hedgerows to act as corridors for woodland plants they must provide habitat conditions to suit species’ autecological requirements. This supposition was tested by examining differences in the habitat and autecological characteristics of woodland plants according to their relative frequency in hedgerows and woodlands using a novel Habitat Preference Index (HPI). Indicator values for habitat and autecological characteristics of plant species were derived from Ellenberg and other published sources. Analyses were done separately for three main types of landscape in which hedgerows are found in Britain: (1) Lowland Arable; (2) Lowland Pastural; and (3) Marginal Upland. The relative frequency of plant species across all three landscape types was similar and significant differences between HPIs and environmental indicators were found for all three landscape types. Plants more frequently found in hedgerows had significantly higher indicator scores for soil fertility, temperature, continentality together with reduced soil acidity, in comparison to those species more frequent in woodlands. Analyses of autecological indicators failed to show similar consistent trends across landscape types except for the number of woodland types of the National Vegetation Classification (NVC) in which species occur. Plants more frequently found in hedgerows were associated with fewer woodland communities suggesting that hedgerows contain only a narrow range of recognised woodland NVC stand types. Also, a significantly higher proportion of ancient woodland indicators were found in the group of plants that were more frequent in woodlands. Overall, results suggested that the environments of hedgerows are more similar to woodland edges than interiors. Qualitative differences between the environmental characteristics of hedgerows and woodlands are such that certain woodland plant species are highly likely to be limited in their capacity to use hedgerow networks. Implications for conservation of biodiversity are considered.

The Distribution of Passerine Birds in Hedgerows During the Breeding Season in Relation to Characteristics of the Hedgerow and Adjacent Farmland

1. Passerine birds were surveyed during the breeding season in hedgerows on 46 farms in lowland England. The incidence of each species was recorded in 50-m lengths of hedgerow and various attributes of these hedgerow sections were also recorded. 2. Logistic regression models were fitted to the data to describe the effects on the incidence of 18 bird species of the number of trees, hedge height and width, dominant plant species in the woody hedge, under the hedge and adjacent to the hedge in the uncultivated strip, the number of woody species in a standard length and other hedgerow characteristics. The effects of adjacent land use and cropping, reduced use of pesticides on cereal field edges and the geographical location of the study farms were also included in the models. 3. Most bird species preferred tall hedges with many trees, but there were some (dunnock, willow warbler and lesser whitethroat) which preferred tall hedges with few trees and others (whitethroat, linnet, yellowhammer) which preferred short hedges with few trees. 4. The differences among bird species in response to a sevenfold reduction in the height of hedges estimated from the models showed good agreement with the variation among species in the effects of severe hedge cutting on bird populations at one farm observed in an independent study. 5. The incidence of six bird species was positively influenced by the number of woody species in a standard length of hedgerow. 6. The incidence of two bird species was significantly affected by the identity of the dominant woody plant species in the hedge and one species by the identity of the dominant plant species at the base of the hedge. 7. Land use adjacent to the hedgerow, categorized as grass, tillage and roadside, had a significant influence on the incidence of five species. However, there was no evidence of consistency among species in the direction of effects. 8. The crops grown on tilled land adjacent to the hedgerow had a significant influence on the incidence of the blackbird. There was a significant degree of consistency among bird species in the ranking of crops, with oil-seed rape the most preferred and spring-sown cereal the least preferred. 9. The incidence of greenfinch, robin and song thrush was significantly lower in hedgerows adjacent to autumn-sown cereals which had received reduced levels of spraying of pesticides than in those adjacent to autumn-sown cereals which were fully sprayed. Most of the other species showed non-significant differences in the same direction. Most of the species studied also showed a non-significant tendency towards higher incidence in hedgerows adjacent to spring-sown cereals with reduced spraying than in those adjacent to fully sprayed spring-sown cereals.

The scientific management of temperate communities for conservation. The 31st symposium of the British Ecological Society, Southampton, 1989: I. F. Spellerberg, F. B. Goldsmith & M. G. Morris, (Blackwell Scientific, for British Ecological Society), ISBN (hardback) 0 632 02976 5, (paperback) 0 632 03186 7, price £45.00, £26.50, 1991, 566 pp, indexes.

In this review, we discuss the role of hedgerow structure and condition in determining the value of hedgerow habitat for biodiversity conservation within an agricultural context, to inform and evaluate hedgerow management decisions and policy. Through a systematic literature review, narrative synthesis and vote counting, key structural condition indicators were identified for a range of conservation priority taxa. Abundance, survival or fecundity of ground vegetation, birds, mammals and invertebrates were affected by height, width, woody biomass, foliar quality and quantity, and gappiness of hedgerows. Although general patterns may not occur, a response to a particular structural feature can vary both within and between taxonomic groups, many responses are synergistic and interdependent. In conclusion, the definition of a “good quality” hedgerow for biodiversity conservation should be expanded to include all those key structural features which are important across taxa. Furthermore, the importance of heterogeneity in hedgerow structural condition is highlighted, where no fixed set of hedgerow characteristics were found to benefit all taxa. If uniform hedgerow management is overprescribed, as has been the tendency with some agri-environment schemes, some species (including those of conservation concern) are likely to be adversely affected by a loss of suitable habitat or resource decline.

Effect of Hedgerow Characteristics on Partridge Breeding Densities

(1) The influence of the quantity and quality of nesting habitat (field boundaries, including hedgerows) on the breeding density of grey and red-legged partridge was examined on ten arable farms in Britain. (2) The length of permanent field boundary was found to correlate closely with the breeding density of both species of partridge within study farms; between farms it did not. (3) In a multiple regression analysis the amount of dead grass present in the base of the hedge was the best predictor of grey partridge breeding density within farms after the length of the field boundary was taken into account. A similar analysis for red-legged partridges showed that the amount of nettle present at the base of field boundaries was the only variable related to breeding density after the overall length was taken into account. Between farms, the breeding density of both species was unrelated to the hedgerow characteristics. (4) The importance of hedges and hedgerow management to partridges is discussed. It is suggested that hedgerow characteristics are important in determining the local spacing of breeding partridges but they may not determine overall population size.