A global synthesis of the effects of diversified farming systems on arthropod diversity within fields and across agricultural landscapes

Agricultural intensification is a leading cause of global biodiversity loss, which can reduce the provisioning of ecosystem services in managed ecosystems. Organic farming and plant diversification are farm management schemes that may mitigate potential ecological harm by increasing species richness and boosting related ecosystem services to agroecosystems. What remains unclear is the extent to which farm management schemes affect biodiversity components other than species richness, and whether impacts differ across spatial scales and landscape contexts. Using a global metadataset, we quantified the effects of organic farming and plant diversification on abundance, local diversity (communities within fields), and regional diversity (communities across fields) of arthropod pollinators, predators, herbivores, and detritivores. Both organic farming and higher in‐field plant diversity enhanced arthropod abundance, particularly for rare taxa. This resulted in increased richness but decreased evenness. While these responses were stronger at local relative to regional scales, richness and abundance increased at both scales, and richness on farms embedded in complex relative to simple landscapes. Overall, both organic farming and in‐field plant diversification exerted the strongest effects on pollinators and predators, suggesting these management schemes can facilitate ecosystem service providers without augmenting herbivore (pest) populations. Our results suggest that organic farming and plant diversification promote diverse arthropod metacommunities that may provide temporal and spatial stability of ecosystem service provisioning. Conserving diverse plant and arthropod communities in farming systems therefore requires sustainable practices that operate both within fields and across landscapes.     

Trait-Specific Responses of Wild Bee Communities to Landscape Composition,Configuration and Local Factors

Land-use intensification and loss of semi-natural habitats have induced a severe decline of bee diversity in agricultural landscapes. Semi-natural habitats like calcareous grasslands are among the most important bee habitats in central Europe, but they are threatened by decreasing habitat area and quality, and by homogenization of the surrounding landscape affecting both landscape composition and configuration. In this study we tested the importance of habitat area, quality and connectivity as well as landscape composition and configuration on wild bees in calcareous grasslands. We made detailed trait-specific analyses as bees with different traits might differ in their response to the tested factors. Species richness and abundance of wild bees were surveyed on 23 calcareous grassland patches in Southern Germany with independent gradients in local and landscape factors. Total wild bee richness was positively affected by complex landscape configuration, large habitat area and high habitat quality (i.e. steep slopes). Cuckoo bee richness was positively affected by complex landscape configuration and large habitat area whereas habitat specialists were only affected by the local factors habitat area and habitat quality. Small social generalists were positively influenced by habitat area whereas large social generalists (bumblebees) were positively affected by landscape composition (high percentage of semi-natural habitats). Our results emphasize a strong dependence of habitat specialists on local habitat characteristics, whereas cuckoo bees and bumblebees are more likely affected by the surrounding landscape. We conclude that a combination of large high-quality patches and heterogeneous landscapes maintains high bee species richness and communities with diverse trait composition. Such diverse communities might stabilize pollination services provided to crops and wild plants on local and landscape scales.     

Effects of landscape cover and local habitat characteristics on visiting bees in tropical orchards

相似文献   

北京昌平区景观复杂度和局地管理对苹果园传粉蜂多样性的影响

传粉蜂为作物生产和粮食安全提供重要的生态系统服务。随着农业经济的不断发展,土地利用强度加剧,大量自然或半自然生境已经转变为农业用地。景观均质化和集约化管理导致野生蜂多样性下降,从而威胁到农业可持续生产。本研究以北京市昌平区苹果园为对象,探究景观复杂度(半自然生境比例)、局地管理强度(地表开花植物多样性和土壤全氮)及其交互作用对传粉蜂多样性的影响。结果表明: 共捕获传粉蜂8642头,其中人工蜂5125头,野生蜂分属5科14属49种3517头。传粉蜂多样性对景观复杂度和局地管理强度响应的最优尺度在500 m。样点半径500 m范围内,总传粉蜂和野生蜂多度随周围半自然生境增加均呈显著上升趋势。景观复杂度与开花植物多样性的交互作用对总传粉蜂和野生蜂物种丰富度有显著影响。当景观复杂度较低时(≤29.9%),总传粉蜂和野生蜂物种丰富度与开花植物多样性呈显著正相关;而当景观复杂度较高时(>29.9%),总传粉蜂和野生蜂物种丰富度与开花植物多样性呈显著负相关。此外,人工蜂多度随果园内局地开花植物多样性和土壤全氮增加呈显著升高趋势。土壤全氮与开花植物多样性的交互作用对人工蜂多度有显著影响。当土壤全氮含量较低时(≤1.9 g·kg^-1),人工蜂多度与开花植物多样性呈显著正相关;而当土壤全氮含量较高时(>1.9 g·kg^-1),人工蜂多度与开花植物多样性呈显著负相关。农业景观中半自然生境比例的增加有利于提高野生蜂多度,而地表开花植物多样性可以促进传粉蜂多样性,但是受到景观尺度(半自然生境比例)和局地尺度(氮肥施用)的影响。因此,农业景观中野生蜂多样性的维持需要综合考虑多尺度因素来制定保护策略。尽可能保留更高比例的耕地仍然是生产的长期需求,而保持中等景观复杂度,增加地表开花植物多样性,减少氮肥施用量将是促进苹果园传粉蜂多样性的有效方式。     

Organic farming promotes bee abundance in vineyards in Italy but not in South Africa

Although grapevine is a crop that produces fruit without insect pollination, vineyards may provide resources for bees and other pollinators. Flower resources such as pollen and nectar are provided by the vine plants as well as other flowering plants including cover crops grown between the vine rows. Little is known about how management and landscape context affects bee communities in pollinator-independent crop systems such as grapevine. This study investigates the effect of organic versus conventional management on bee species richness and abundance in vineyards in Italy and South Africa both having a Mediterranean climate. In each country, six pairs of organic and conventional vineyards were studied in simplified and complex agricultural landscapes. A total of 433 bee individuals from 25 species and 1049 individuals from 15 species were recovered in pan traps from Italy and South Africa respectively. Bee abundance showed region specific response to the effects of vineyard management. Flowering plants and proportion of uncultivated land mediated differences in bee abundance. Higher flowering plant species richness and flower density were found in organic vineyards compared to conventional vineyards in South Africa but these flowering plant indices were not significantly different between the two vineyard management types in Italy. This emphasizes the necessity for local and region specific studies for informing conservation, as even in the same crop system with a similar climate, the effects of farm management differed between countries.     

Agricultural landscapes with organic crops support higher pollinator diversity

Pollinators are traditionally thought to perceive non-flowering crop fields as hostile landscape matrix. In this study, we show that landscapes composed of higher proportions of organic crop fields support more bee species at greater abundances in fallow strips. An increase in organic cropping in the surrounding landscape from 5% to 20% enhanced bee species richness in fallow strips by 50%, density of solitary bees by 60% and bumble bee density by 150%. Bee species richness and bumble bee density responded strongest to organic cropping in landscape sectors with 500 m radius, solitary bee density in landscape sectors with 250 m radius. The most likely source of these results is that crop and noncrop habitats are strongly connected via bee foraging at the landscape scale. It seems likely that bees depending on nesting sites in fallow strips benefited from the more abundant flower resources provided by broadleaved weeds in organic crop fields. We conclude that the incorporation of organic crop fields into conventionally managed agricultural landscapes can provide food resources needed to sustain greater pollinator species richness in noncrop habitats.     

Landscape spatial configuration is a key driver of wild bee demographics

The majority of studies investigating the effects of landscape composition and configuration on bee populations have been conducted in regions of intensive agricultural production, ignoring regions which are dominated by seminatural habitats, such as the islands of the Aegean Archipelago. In addition, research so far has focused on the landscape impacts on bees sampled in cropped fields while the landscape effects on bees inhabiting seminatural habitats are understudied. Here, we investigate the impact of the landscape on wild bee assemblages in 66 phryganic (low scrubland) communities on 8 Aegean islands. We computed landscape metrics (total area and total perimeter–area ratio) in 4 concentric circles (250, 500, 750, and 1000 m) around the center of each bee sampling site including 3 habitat groups (namely phrygana, cultivated land, and natural forests). We further measured the local flower cover in 25 quadrats distributed randomly at the center of each sampling site. We found that the landscape scale is more important than the local scale in shaping abundance and species richness of bees. Furthermore, habitat configuration was more important than the total area of habitats, probably because it affects bees’ movement across the landscape. Phrygana and natural forests had a positive effect on bee demographics, while cultivated land had a negative effect. This demonstrates that phryganic specialists drive bee assemblages in these seminatural landscapes. This finding, together with the shown importance of landscape scale, should be considered for the management of wild bees with special emphasis placed on the spatial configuration of seminatural habitats.     

Spider diversity in cereal fields: comparing factors at local, landscape and regional scales

Aim Factors acting at various scales may affect biodiversity, demanding analyses at multiple spatial scales in order to understand how community richness is determined. Here, we adopted a hierarchical approach to test the contribution of region, landscape heterogeneity, local management (organic vs. conventional) and location within field (edge vs. centre) to the species richness and abundance of spiders in cereals. Location Three regions of western and central Germany: Leine Bergland, Soester Boerde, and Lahn‐Dill Bergland. Methods Forty‐two paired organic and conventional winter wheat fields were compared. Field pairs were located in areas ranging from structurally simple to structurally complex landscapes. In May and June 2003, spiders were sampled using pitfall traps. Linear mixed models were used to determine the relationship of spider diversity and abundance with regional spatial factors and landscape heterogeneity within a 500‐m radius, as well as with local management and within‐field location. Results Within‐field location of the traps and landscape heterogeneity were the best predictors of species richness: more species were found in field edges and in heterogeneous landscapes. Region and local management had no effect on species richness. Activity density was higher in field edges and differed among regions. Main conclusions The diversity of farmland spiders was influenced by differences at two of the spatial scales (edge vs. centre, simple vs. complex landscapes), but not at the two others (field management, region), emphasizing the importance of analyses at a variety of spatial scales for an adequate explanation of patterns in biodiversity. Our study suggests that promoting heterogeneity in land use at landscape scales is one of the keys to promoting spider diversity in agroecosystems.     

Interacting effects of landscape context and habitat quality on flower visiting insects in agricultural landscapes

Landscape context and habitat quality may have pronounced effects on the diversity of flower visiting insects. We investigated whether the effects of landscape context and habitat quality on flower visiting insects interact in agricultural landscapes in the Netherlands. Landscape context was expressed as the area of semi-natural habitats or the density of linear landscape features, and was quantified at spatial scales ranging from 250 to 2000 m. Habitat quality was determined as flower abundance. Species richness and abundance of hoverflies and bees were determined along 16 stream banks experiencing similar environmental conditions but situated in areas with contrasting landscape context. Only flower abundance and the area of semi-natural habitats within 500–1000 m were significantly related to species richness of hoverflies and bees and these factors had interacting effects on both species groups. Our results suggest that the regional area of semi-natural habitats had a positive effect on hoverfly species richness when flower abundance was relatively high, but not when flower abundance was low. Moreover, flower abundance had positive effects on hoverfly species richness only in areas with relatively many semi-natural habitats. Contrastingly, flower abundance had a more positive effect on bee species richness in landscapes with few semi-natural habitats compared to landscapes with more semi-natural habitats. Our results suggest that the importance of landscape context for the species richness of flower visiting insects depends upon the quality of the habitat patches.     

Local and landscape effects on bee communities of Hungarian winter cereal fields

• 1 Pollination is a key ecosystem service. Although bees are the most important pollinators, they are endangered by intensive agricultural practices. The present study investigated the effects of farmland management and environmental factors at local and landscape scales on bees in Central Hungary.
• 2 Bees were sampled in winter cereal fields that varied in the amount of applied fertilizer and insecticide use. Measurements included total, small and large bee species richness and abundance; stability of total species richness and abundance (coefficient of variation, CV); the nitrogen content of fertilizers; the number of insecticide applications; within‐field location; species richness and abundance of insect‐pollinated plants; and the percentage of semi‐natural areas in a 500‐m radius circle around the fields under study.
• 3 Increasing the amount of fertilizer decreased total and small bee abundance and increased the CV of total bee abundance. Insecticide use had a significant negative effect on total and small bee species richness and on large bee abundance. The percentage of semi‐natural habitats in a 500‐m radius did not influence bee species richness and abundance.
• 4 The results obtained confirms that the intensification of farmland management poses a threat to bee diversity, and thus may reduce pollination services. Recently‐introduced agri‐environment schemes are one potential approach for managing agricultural land use: reduced amounts of fertilizer and a cessation of insecticide application might lead to high bee species richness and abundance and ensure the pollination of wild plants and flowering crops.

     

Organic farming at local and landscape scales benefits plant diversity

Agri‐environment schemes (AES) have been suggested to counter negative effects of agricultural intensification and enhance farmland biodiversity, but evaluations have produced inconsistent results. We suggest that this is partly a consequence of scale‐dependence, i.e. that the consequence of organic farming will differ depending on the scale of uptake in a particular landscape. To test our hypothesis on diversity of forbs, we designed a landscape scale study using spatially explicit information about the Swedish AES for organic farming. The study system consisted of uncultivated field borders along paired fields (organic and conventional) in matched landscapes with either a high or a low proportion of organic faming, allowing separate tests of the effects of farming practice at the local and the landscape scale. The local effect of organic farming was consistently strong, with higher diversity in borders adjoining organic fields, most likely due to the lack of herbicide use on organically managed farmland. Thus, we show that not only the proportion of semi‐natural habitat is important for farmland biodiversity, but that also the management of cropland can influence the diversity in semi‐natural habitats. Furthermore, forb richness was also higher in borders situated in landscapes with a high proportion of organic land, irrespectively of local management, possibly as a result of dispersal of mainly annual plant species from the organically managed fields into the borders (mass effect). Our results demonstrate that farming practice at a local and a landscape scale independently can influence plant species richness, indicating that organic farming can influence diversity also at larger spatial scales and outside the organically managed land. Our study highlight the importance of studying multiple scales, including both local and landscape factors to provide a better understanding of biodiversity patterns.     

Railway Embankments as New Habitat for Pollinators in an Agricultural Landscape

Pollinating insect populations, essential for maintaining wild plant diversity and agricultural productivity, rely on (semi)natural habitats. An increasing human population is encroaching upon and deteriorating pollinator habitats. Thus the population persistence of pollinating insects and their associated ecosystem services may depend upon on man-made novel habitats; however, their importance for ecosystem services is barely understood. We tested if man-made infrastructure (railway embankments) in an agricultural landscape establishes novel habitats that support large populations of pollinators (bees, butterflies, hoverflies) when compared to typical habitats for these insects, i.e., semi-natural grasslands. We also identified key environmental factors affecting the species richness and abundance of pollinators on embankments. Species richness and abundance of bees and butterflies were higher for railway embankments than for grasslands. The occurrence of bare (non-vegetated) ground on embankments positively affected bee species richness and abundance, but negatively affected butterfly populations. Species richness and abundance of butterflies positively depended on species richness of native plants on embankments, whereas bee species richness was positively affected by species richness of non-native flowering plants. The density of shrubs on embankments negatively affected the number of bee species and their abundance. Bee and hoverfly species richness were positively related to wood cover in a landscape surrounding embankments. This is the first study showing that railway embankments constitute valuable habitat for the conservation of pollinators in farmland. Specific conservation strategies involving embankments should focus on preventing habitat deterioration due to encroachment of dense shrubs and maintaining grassland vegetation with patches of bare ground.     

Interactive effects of local and landscape factors on farmland carabids

相似文献   

Wild bees respond complementarily to ‘high-quality’ perennial and annual habitats of organic farms in a complex landscape

Agricultural intensification leads to large-scale loss of habitats offering food and nesting sites for bees. This has resulted in a severe decline of wild bee diversity and abundance during the past decades. There is an urgent need for cost-effective conservation measures to mitigate this decline. We analysed the impact of five different high-quality habitats on species richness and abundance of wild bees in a complex landscape of north-western Switzerland at six sites. The five habitat types included 45 plots situated on eight organic farms and were composed of 16 low-input meadows, six low-input pastures, seven herbaceous strips adjacent to hedges, five sown flower strips and eleven organic cereal fields. All of them are financially subsidised by the Swiss agri-environmental scheme. Wild bees were sampled between the end of April and end of August 2014 by using trio-pan traps and complementary sweep netting on these five habitat types. On 45 plots we recorded 3973 bee specimens, belonging to 91 species, 16 of which are red listed, revealing a high bee species richness in the study area. Wild bee species richness and abundance were best explained by habitat type, number of flowering plants and site. A strong relationship of increasing number of flowering plants and bee species richness and abundance was found. Grassland habitats, especially low-input meadows, harboured the highest species richness and abundances. Organic cereal fields showed a potential to conserve bee species relevant to nature conservation (harbouring exclusively two red list species and four rare species). Ordination analysis of the bee communities showed a relative dissimilarity between the habitat types and indicates their complementary effects to benefit the diversity of wild bees. Our results demonstrate that a matrix of low-input habitats are needed to sustain rich assemblages of wild bees in agroecosystems.     

Effects of landscape structure and land-use intensity on similarity of plant and animal communities

Aim Species richness in itself is not always sufficient to evaluate land management strategies for nature conservation. The exchange of species between local communities may be affected by landscape structure and land‐use intensity. Thus, species turnover, and its inverse, community similarity, may be useful measures of landscape integrity from a diversity perspective. Location A European transect from France to Estonia. Methods We measured the similarity of plant, bird, wild bee, true bug, carabid beetle, hoverfly and spider communities sampled along gradients in landscape composition (e.g. total availability of semi‐natural habitat), landscape configuration (e.g. fragmentation) and land‐use intensity (e.g. pesticide loads). Results Total availability of semi‐natural habitats had little effect on community similarity, except for bird communities, which were more homogeneous in more natural landscapes. Bee communities, in contrast, were less similar in landscapes with higher percentages of semi‐natural habitats. Increased landscape fragmentation decreased similarity of true bug communities, while plant communities showed a nonlinear, U‐shaped response. More intense land use, specifically increased pesticide burden, led to a homogenization of bee, bug and spider communities within sites. In these cases, habitat fragmentation interacted with pesticide load. Hoverfly and carabid beetle community similarity was differentially affected by higher pesticide levels: for carabid beetles similarity decreased, while for hoverflies we observed a U‐shaped relationship. Main conclusions Our study demonstrates the effects of landscape composition, configuration and land‐use intensity on the similarity of communities. It indicates reduced exchange of species between communities in landscapes dominated by agricultural activities. Taxonomic groups differed in their responses to environmental drivers and using but one group as an indicator for ‘biodiversity’ as such would thus not be advisable.     

Organic fields sustain weed metacommunity dynamics in farmland landscapes

Agro-ecosystems constitute essential habitat for many organisms. Agricultural intensification, however, has caused a strong decline of farmland biodiversity. Organic farming (OF) is often presented as a more biodiversity-friendly practice, but the generality of the beneficial effects of OF is debated as the effects appear often species- and context-dependent, and current research has highlighted the need to quantify the relative effects of local- and landscape-scale management on farmland biodiversity. Yet very few studies have investigated the landscape-level effects of OF; that is to say, how the biodiversity of a field is affected by the presence or density of organically farmed fields in the surrounding landscape. We addressed this issue using the metacommunity framework, with weed species richness in winter wheat within an intensively farmed landscape in France as model system. Controlling for the effects of local and landscape structure, we showed that OF leads to higher local weed diversity and that the presence of OF in the landscape is associated with higher local weed biodiversity also for conventionally farmed fields, and may reach a similar biodiversity level to organic fields in field margins. Based on these results, we derive indications for improving the sustainable management of farming systems.     

Temporal variation of the effects of landscape composition on lacewings (Chrysopidae: Neuroptera) in vineyards

1. Increasing landscape heterogeneity, both in terms of composition and configuration, can promote natural enemies and biological control in agricultural landscapes. However, relatively poor information exists about the effects of landscape heterogeneity on lacewings, which are a major group of predators. Furthermore, temporal changes of landscape effects on natural enemy dynamics remain largely unexplored.
2. Here, we investigated how landscape composition and configuration affect lacewings and their biological control potential on leafhoppers. Lacewings and leafhoppers were sampled from April to July in 10 vineyards located in southwestern France. The vineyards were selected along a gradient of a proportion of semi‐natural habitats in the landscape.
3. The proportion of semi‐natural habitats positively affected the abundance of adults and eggs, as well as species richness, of lacewings, alone or in interaction with the sampling month. Landscape configuration was never found to enhance abundance or species richness of lacewings. Finally, the predator–prey ratio increased through time but did not respond to landscape composition or configuration.
4. Our study highlights that the proportion of semi‐natural habitats increases both abundance and diversity of lacewings in vineyard landscapes but that this effect varies over time. This result indicates the need to assess the variability of landscape effects over time to maximize biological pest control services in agricultural landscapes.

     

Floral resources,body size,and surrounding landscape influence bee community assemblages in oak‐savannah fragments

相似文献   

Farming for bees: annual variation in pollinator populations across agricultural landscapes

相似文献   

Contrasting responses of arable spiders to the landscape matrix at different spatial scales

Aim Animal communities can be influenced by the composition of the surrounding landscape through immigration. Depending on habitat preferences, however, the effect of the landscape matrix can be positive or negative and can vary with scale. We tested this idea with arable spiders and tried to infer dispersal distances from relationships between local density and landscape composition at different spatial scales. Location Thirty‐eight landscapes around the cities of Göttingen and Giessen, Germany. Methods Spiders were captured with pitfall traps in one field of winter wheat in each landscape. Landscape composition around the fields was characterized at 11 scales from 95 m to 3 km radius by land‐use mapping and subsequent GIS analysis. Correlation tests were performed between landscape composition and local densities or species richness. Results In both study regions, local species richness was enhanced by non‐crop habitats on a landscape scale. The overall densities of wolf spiders (Lycosidae), long‐jawed spiders (Tetragnathidae), crab spiders (Thomisidae), and dwarf sheet spiders (Hahniidae) increased significantly in landscapes with high percentages of non‐crop habitats. Out of the 40 species tested, 19 responded positively to the percentage of non‐crop habitats in the surrounding landscape, and five responded negatively. Depending on the species, the spatial scales with the highest explanatory power ranged from 95 m to 3 km radius around the study fields, potentially reflecting dispersal distances. Main conclusions Arable spider species showed contrasting responses to the landscape context with respect both to the direction and to the spatial scale of the relationship. The variation in landscape requirements among species ensures high spider densities in a wide range of situations, which contributes to ecosystem resilience. However, species richness of arable spiders depends on heterogeneous landscapes with high percentages of non‐crop habitats.