Effects of large herbivores on grassland arthropod diversity

Both arthropods and large grazing herbivores are important components and drivers of biodiversity in grassland ecosystems, but a synthesis of how arthropod diversity is affected by large herbivores has been largely missing. To fill this gap, we conducted a literature search, which yielded 141 studies on this topic of which 24 simultaneously investigated plant and arthropod diversity. Using the data from these 24 studies, we compared the responses of plant and arthropod diversity to an increase in grazing intensity. This quantitative assessment showed no overall significant effect of increasing grazing intensity on plant diversity, while arthropod diversity was generally negatively affected. To understand these negative effects, we explored the mechanisms by which large herbivores affect arthropod communities: direct effects, changes in vegetation structure, changes in plant community composition, changes in soil conditions, and cascading effects within the arthropod interaction web. We identify three main factors determining the effects of large herbivores on arthropod diversity: (i) unintentional predation and increased disturbance, (ii) decreases in total resource abundance for arthropods (biomass) and (iii) changes in plant diversity, vegetation structure and abiotic conditions. In general, heterogeneity in vegetation structure and abiotic conditions increases at intermediate grazing intensity, but declines at both low and high grazing intensity. We conclude that large herbivores can only increase arthropod diversity if they cause an increase in (a)biotic heterogeneity, and then only if this increase is large enough to compensate for the loss of total resource abundance and the increased mortality rate. This is expected to occur only at low herbivore densities or with spatio‐temporal variation in herbivore densities. As we demonstrate that arthropod diversity is often more negatively affected by grazing than plant diversity, we strongly recommend considering the specific requirements of arthropods when applying grazing management and to include arthropods in monitoring schemes. Conservation strategies aiming at maximizing heterogeneity, including regulation of herbivore densities (through human interventions or top‐down control), maintenance of different types of management in close proximity and rotational grazing regimes, are the most promising options to conserve arthropod diversity.     

Do weaver ants affect arthropod diversity and the natural‐enemy‐to‐pest ratio in horticultural systems?

High biodiversity is an important component of sustainable agricultural systems, and previous studies have found that increases in the diversity of the natural enemies of pests are associated with decreases in pest populations. Weaver ants are well known for their highly territorial and aggressive behaviour and for their control efficiency of many insect pests in tropical crop trees. Because of this, the ants have been used as a key component in integrated pest management (IPM) programmes for tropical crop trees. In implementing the IPM programmes, we received a number of enquiries related to whether weaver ants have negative effects on arthropod diversity and other natural enemies in orchard systems due to their aggressive behaviour. To answer these questions, we regularly sampled canopy arthropods in cashew and mango orchards in the Northern Territory of Australia in 1996, 2002 and 2003. We sampled, using a vacuum sampler, orchards with and without weaver ants. Cashew and mango plots with abundant weaver ants had similar or higher canopy arthropod and natural enemy diversity and similar ratios of natural enemies to insect pests, compared with plot where the weaver ant was absent. The study also showed that the application of insecticides reduced arthropod diversity and the ratio of natural enemies to insect pests in a mango orchard. However, insecticide spray did not affect natural enemy diversity and abundance, which may be related to a high immigration rate of natural enemies in small plots surrounded by areas that were not sprayed.     

半自然农田边界与相邻农田步甲和蜘蛛的时空分布

分别于小麦、玉米收获前后,采用陷阱法调查了华北地区典型农业景观中具有不同植被结构的农田边界及其相邻农田中两类重要天敌类群步甲和蜘蛛的多样性.通过比较农田生境及相邻农田边界间两类天敌群落的时空分布格局及其与相邻半自然生境植被群落的相关关系,探讨半自然农田边界对两类天敌类群的保护作用.结果表明: 整个取样季节农田边界处蜘蛛的多度显著高于农田内部;而步甲多样性在农田与边界间无显著性差异,仅呈现不同的群落结构;作物收获后蜘蛛分科数在边界处的增加以及在农田的减少,显示了蜘蛛在农田和边界之间的迁移活动.边界植被结构对蜘蛛和步甲多样性有不同影响:边界较高的草本层盖度和较低的乔木层盖度有利于增加农田中某些步甲优势种的多样性;而较高的草本层盖度有利于增加皿蛛科蜘蛛的多样性.因此,半自然生境的存在可以通过天敌在农田和边界之间的迁移运动促进农田天敌多样性的维持;但不同类型半自然生境植被群落结构可能影响其对不同天敌群落多样性的维持和保护作用.为促进农业景观对天敌的保护作用,提高其害虫控制功能,需要深入了解不同天敌的生境需求及食物需求,精心设计有利于天敌多样性维持的半自然生境.     

Tree diversity drives diversity of arthropod herbivores,but successional stage mediates detritivores

The high tree diversity of subtropical forests is linked to the biodiversity of other trophic levels. Disentangling the effects of tree species richness and composition, forest age, and stand structure on higher trophic levels in a forest landscape is important for understanding the factors that promote biodiversity and ecosystem functioning. Using a plot network spanning gradients of tree diversity and secondary succession in subtropical forest, we tested the effects of tree community characteristics (species richness and composition) and forest succession (stand age) on arthropod community characteristics (morphotype diversity, abundance and composition) of four arthropod functional groups. We posit that these gradients differentially affect the arthropod functional groups, which mediates the diversity, composition, and abundance of arthropods in subtropical forests. We found that herbivore richness was positively related to tree species richness. Furthermore, the composition of herbivore communities was associated with tree species composition. In contrast, detritivore richness and composition was associated with stand age instead of tree diversity. Predator and pollinator richness and abundance were not strongly related to either gradient, although positive trends with tree species richness were found for predators. The weaker effect of tree diversity on predators suggests a cascading diversity effect from trees to herbivores to predators. Our results suggest that arthropod diversity in a subtropical forest reflects the net outcome of complex interactions among variables associated with tree diversity and stand age. Despite this complexity, there are clear linkages between the overall richness and composition of tree and arthropod communities, in particular herbivores, demonstrating that these trophic levels directly impact each other.     

Structural complexity of arthropod guilds is affected by the agricultural landscape heterogeneity generated by fencerows

Intensive farming imposes harsh conditions impeding the persistence of most arthropod species within crop fields. Hence, arthropods surviving the unfavourable conditions prevailing within crop fields may disperse towards nearby uncropped margins, such as fencerows. Here, we evaluate the influence of landscape heterogeneity on the abundance of different guilds, particularly herbivores and their natural enemies. Said heterogeneity mostly derives from fencerow network density. Hence, we developed an approach based on fitting linear‐mixed models to elucidate the effects of landscape heterogeneity and field position (fencerows and crop interiors) on arthropod diversity. Mixed models were fitted to arthropod data obtained by pitfall trap samplings in 36 crop fields. Arthropod communities were structurally and functionally more complex along fencerows than within nearby crop interiors. Arthropods abundance was modulated by landscape heterogeneity, increasing the abundance of natural enemies as the landscape heterogeneity increased. On the contrary, herbivores abundance decreased as landscape heterogeneity increased. Consequently, the ratio between herbivores and natural enemies also decreased as landscapes became more heterogeneous. Natural enemies with larger body sizes, mostly carabid beetles, were more sensitive to landscape homogenisation. Our study reveals that, despite the coarse‐grained landscapes in the Rolling Pampa, fencerow density appears as a key factor for structuring complex arthropod guilds in intensively farmed agricultural mosaics. In landscapes with higher density of fencerows, arthropods tend to concentrate along them, thus increasing the community structural complexity as well as the predation pressure over herbivores. This structural complexity of upper trophic levels enhances the ‘top‐down’ regulation of herbivore populations, consequently decreasing the probability of pest outbreaks within crop fields.     

Utilisation of plant functional diversity in wildflower strips for the delivery of multiple agroecosystem services

Increased plant diversity in cropping systems can play an important role in agriculture by enhancing arthropod‐mediated ecosystem services, including biological control and pollination. However, there is limited research investigating the concurrent influence of plant functional diversity within cultivated systems on different arthropod functional groups, the provision of multiple ecosystem services, and crop yield. During a field experiment, repeated over 2 years, we measured the effect of increasing plant functional diversity on community structure of arthropod visitors, the abundance of multiple pests and induced crop damage, and fruit production in two varieties of tomato. Plant resources (floral and extra‐floral nectar and pollen) were included within experimental plots in four levels, with each level increasing the plant functional group richness, based on floral morphology and availability of resources, in a replacement series. The presence of sown flower mixtures in experimental plots was associated with increased abundance and diversity of natural enemy functional groups and an enhanced abundance of bees (Hymenoptera: Apiformes). However, we only detected relatively small variability in arthropod visitors among types of mixtures, and increased abundance of natural enemies did not translate into stronger pest suppression or reduced crop damage. Lepidoptera pest damage was significantly higher in plots adjacent to wildflower strips, an ecosystem disservice, but a significantly higher crop productivity was recorded from these plots. Our results provide evidence that inclusion of non‐crop plant resources in agroecosystems can improve the conservation of beneficial arthropods and may lead to increased crop productivity.     

Agroenergy Crops Influence the Diversity, Biomass, and Guild Structure of Terrestrial Arthropod Communities

Expanded production of contemporary bioenergy crops (e.g., corn) is considered a threat to the conservation of biodiversity, yet next-generation perennially based crops (switchgrass, mixed-grass?Cforb prairie) may represent an opportunity for enhancing biodiversity in agricultural landscapes. We employed a multi-scaled approach to investigate the relative importance of feedstock selection, forb content, patch size, and landscape-scale habitat structure and composition as factors shaping the diversity and abundance of terrestrial arthropod communities and the biomass of functional groups of arthropods associated with the provisioning of ecosystem services. Compared to intensively managed annual corn fields, switchgrass and mixed-grass?Cforb prairie plantings were associated with a 230% and 324% increase in arthropod family diversity and a 750% and 2,700% increase in arthropod biomass, respectively. Biomass of arthropod pollinators, herbivores, predators, and parasites were similarly the highest in mixed-grass?Cforb prairie, intermediate in switchgrass plantings, and the lowest in cornfields. Community-wide biomass and that of several functional arthropod groups were positively linked to increasing forest cover and land cover diversity surrounding biomass plantings, while pollinator and detritivore biomass was lower in smaller fields. Results not only suggest that the choice of biomass feedstock will play an important role in shaping within-field arthropod diversity but also indicate an important role for the composition of this surrounding landscape. Collectively, our results suggest that selection of perennially based biomass feedstocks along with careful attention to crop placement have important potential to enhance biodiversity conservation and the provisioning of ecologically and economically important arthropod-mediated ecosystem services in future agricultural landscapes.     

Effects of insecticide-treated and Lepidopteran-active Bt transgenic sweet corn on the abundance and diversity of arthropods

A field study was conducted over 2 yr to determine the effects of transgenic sweet corn containing a gene from the bacterium Bacillus thuringiensis (Bt) on the diversity and abundance of nontarget arthropods. The Bt hybrid (expressing Cry1Ab endotoxin for lepidopteran control) was compared with near-isogenic non-Bt and Bt hybrids treated with a foliar insecticide and with a near-isogenic non-Bt hybrid without insecticides. Plant inspections, sticky cards, and pitfall traps were used to sample a total of 573,672 arthropods, representing 128 taxonomic groups in 95 families and 18 orders. Overall biodiversity and community-level responses were not significantly affected by the transgenic hybrid. The Bt hybrid also had no significant adverse effects on population densities of specific nontarget herbivores, decomposers, and natural enemies enumerated at the family level during the crop cycle. As expected, the insecticide lambda-cyhalothrin had broad negative impacts on the abundance of many nontarget arthropods. One insecticide application in the Bt plots reduced the overall abundance of the natural enemy community by 21-48%. Five applications in the non-Bt plots reduced natural enemy communities by 33-70%. Nontarget communities affected in the insecticide-treated Bt plots exhibited some recovery, but communities exposed to five applications showed no trends toward recovery during the crop cycle. This study clearly showed that the nontarget effects of Bt transgenic sweet corn on natural enemies and other arthropods were minimal and far less than the community-level disruptions caused by lambda-cyhalothrin.     

Do arthropod assemblages display globally consistent responses to intensified agricultural land use and management?

Aim To determine whether arthropod richness and abundance for combined taxa, feeding guilds and broad taxonomic groups respond in a globally consistent manner to a range of agricultural land‐use and management intensification scenarios. Location Mixed land‐use agricultural landscapes, globally. Methods We performed a series of meta‐analyses using arthropod richness and abundance data derived from the published literature. Richness and abundance were compared among land uses that commonly occur in agricultural landscapes and that represent a gradient of increasing intensification. These included land‐use comparisons, such as wooded native vegetation compared with improved pasture, and a management comparison, reduced‐input cropping compared with conventional cropping. Data were analysed using three different meta‐analytical techniques, including a simple vote counting method and a formal fixed‐effects/random‐effects meta‐analysis. Results Arthropod richness was significantly higher in areas of less intensive land use. The decline in arthropod richness was greater between native vegetation and agricultural land uses than among different agricultural land uses. These patterns were evident for all taxa combined, predators and decomposers, but not herbivorous taxa. Overall, arthropod abundance was greater in native vegetation than in agricultural lands and under reduced‐input cropping compared with conventional cropping. Again, this trend was largely mirrored by predators and decomposers, but not herbivores. Main conclusions The greater arthropod richness found in native vegetation relative to agricultural land types indicates that in production landscapes still containing considerable native vegetation, retention of that vegetation may well be the most effective method of conserving arthropod biodiversity. Conversely, in highly intensified agricultural landscapes with little remaining native vegetation, the employment of reduced‐input crop management and the provision of relatively low‐intensity agricultural land uses, such as pasture, may prove effective in maintaining arthropod diversity, and potentially in promoting functionally important groups such as predators and decomposers.     

Plant Diversity Impacts Decomposition and Herbivory via Changes in Aboveground Arthropods

Loss of plant diversity influences essential ecosystem processes as aboveground productivity, and can have cascading effects on the arthropod communities in adjacent trophic levels. However, few studies have examined how those changes in arthropod communities can have additional impacts on ecosystem processes caused by them (e.g. pollination, bioturbation, predation, decomposition, herbivory). Therefore, including arthropod effects in predictions of the impact of plant diversity loss on such ecosystem processes is an important but little studied piece of information. In a grassland biodiversity experiment, we addressed this gap by assessing aboveground decomposer and herbivore communities and linking their abundance and diversity to rates of decomposition and herbivory. Path analyses showed that increasing plant diversity led to higher abundance and diversity of decomposing arthropods through higher plant biomass. Higher species richness of decomposers, in turn, enhanced decomposition. Similarly, species-rich plant communities hosted a higher abundance and diversity of herbivores through elevated plant biomass and C:N ratio, leading to higher herbivory rates. Integrating trophic interactions into the study of biodiversity effects is required to understand the multiple pathways by which biodiversity affects ecosystem functioning.     

Cascading ecological effects of landscape moderated arthropod diversity

Understanding the mechanisms regulating the diversity and distribution of arthropods is essential to understanding food web interactions and ecosystem functioning. Local arthropod diversity is known to be linked to features of surrounding landscapes, including the area of human‐developed land. Yet, how such landscape moderation of diversity affects processes within local sites remains understudied. We report on a study that 1) measured the impacts of human development surrounding old‐field habitats of arthropods on arthropod food web structure within those habitats and 2) determined if these shifts were associated with cascading impacts on the plant community. We sampled the arthropod community in 16 old‐fields that span an urban‐rural gradient throughout southern New England, USA. In each field, we also established paired mesocosms enclosing vegetation, one of which allowed arthropod herbivory while the other excluded such interactions, to isolate impacts of arthropod herbivory on three functional groups of plants: grasses, goldenrod and non‐goldenrod forbs. Biomass of both herbivorous and predatory arthropods were positively related to the proportion of natural area surrounding a field early in the growing season (June). This relationship persisted later into the season for predatory arthropods (through July), but not for herbivorous arthropods. We found no evidence that the biomass of predators was related to the abundance of herbivorous arthropods in a field; or that biomass of herbivores was correlated to change in plant biomass between the two types of mesocosms. We did, however, find that in fields with low predator abundance there was greater herbivory on grasses (nutritious host), but that in high predator fields goldenrod was increasingly impacted (safe host), as is predicted by past work in old‐field ecosystems. The findings support the generalizability of landscape moderated biodiversity to non‐agricultural systems and suggests that observed shifts in food webs have implications for community and ecosystem dynamics.     

麦蚜的不同防治方法对麦田节肢动物功能团的影响

【目的】本文从功能团的角度研究了不同的麦蚜防治方法对小麦田节肢功能团的影响,为进一步研究小麦田内生物多样性提供了基础。【方法】本试验采用黄板、诱虫灯、糖醋液及3种方法综合使用的方法防治麦蚜,系统调查了这些防治方法对小麦田节肢功能团的影响。【结果】综合使用黄板、诱虫灯、糖醋液防治麦蚜能够提高昆虫群落和蚜虫亚群落的稳定性,降低小麦蚜虫种类和天敌种类丰盛度,采用防治措施的小麦田内捕食性天敌的群落稳定性均较差,单一防治措施的使用对麦田内昆虫群落相对丰盛度、蚜虫亚群落稳定性、捕食性天敌群落稳定性也有一定影响。【结论】在农田生态系统中,不同的防治方法对昆虫群落的影响不同。在实际应用中我们应合理搭配使用麦蚜的防治方法。     

Resource-Mediated Indirect Effects of Grassland Management on Arthropod Diversity

Intensive land use is a driving force for biodiversity decline in many ecosystems. In semi-natural grasslands, land-use activities such as mowing, grazing and fertilization affect the diversity of plants and arthropods, but the combined effects of different drivers and the chain of effects are largely unknown. In this study we used structural equation modelling to analyse how the arthropod communities in managed grasslands respond to land use and whether these responses are mediated through changes in resource diversity or resource quantity (biomass). Plants were considered resources for herbivores which themselves were considered resources for predators. Plant and arthropod (herbivores and predators) communities were sampled on 141 meadows, pastures and mown pastures within three regions in Germany in 2008 and 2009. Increasing land-use intensity generally increased plant biomass and decreased plant diversity, mainly through increasing fertilization. Herbivore diversity decreased together with plant diversity but showed no response to changes in plant biomass. Hence, land-use effects on herbivore diversity were mediated through resource diversity rather than quantity. Land-use effects on predator diversity were mediated by both herbivore diversity (resource diversity) and herbivore quantity (herbivore biomass), but indirect effects through resource quantity were stronger. Our findings highlight the importance of assessing both direct and indirect effects of land-use intensity and mode on different trophic levels. In addition to the overall effects, there were subtle differences between the different regions, pointing to the importance of regional land-use specificities. Our study underlines the commonly observed strong effect of grassland land use on biodiversity. It also highlights that mechanistic approaches help us to understand how different land-use modes affect biodiversity.     

Arthropod diversity and community composition on wild and cultivated rice

• 1 Most crop plants are grown far from their region of origin and have been significantly altered by human selection. Given the importance of biodiversity in ecosystem function, surprisingly little is known about the effect of domestication on arthropod diversity and community composition.
• 2 Arthropod diversity and species abundance were compared with three genotypes of cultivated rice Oryza sativa L. and two genotypes of wild rice O. rufipogon Griff. in southern Luzon, the Philippines.
• 3 Domestication had a small but positive effect on total arthropod diversity. Arthropod species richness was highest on the cultivar IR64 and lowest on one of the O. rufipogon genotypes, although arthropod community composition was similar across rice genotypes.
• 4 Total arthropod abundance and the relative abundance of guilds did not differ between wild and cultivated rice. All common herbivores, however, responded to rice domestication. Stem‐boring moths and several sap‐sucking herbivores benefited from domestication, although domestication reduced densities of the wolf spider Pardosa pseudoannulata Boesenberg et Strand.
• 5 By contrast to previous assumptions, crop domestication may not always decrease arthropod diversity. We did not detect any changes in biodiversity or community composition suggesting that rice domestication has altered the capacity of the arthropod community to regulate herbivores.

     

Agroecological transition increases arthropod diversity and decreases herbivore abundance on field margins

1. In peri-urban areas, many farmers are transitioning from conventional agriculture to agroecological practices to reduce pesticide input and preserving ecosystem services such as natural pest control. Field margins represent a stable habitat for arthropods, but community structure depends on many factors, including management type and vegetation features.
2. We studied the effects of agroecological transitions and vegetation features on arthropods of horticultural field margins, focusing on three feeding guilds (herbivores, predators and parasitoids). We sampled arthropods using the beat-sheet method in five conventional fields and five under agroecological transition. We also measured vegetation height, richness, flower abundance and plant cover.
3. Our results showed that arthropod diversity was higher in agroecological fields whereas herbivore abundance was lower, with a consistent pattern across most taxonomic orders. Vegetation features displayed multiple effects among functional and taxonomic groups. Herbivores did not respond to most vegetation variables whereas predators correlated with several, with similar trends among orders.
4. We conclude that agroecological transitions and field margins with high vegetation richness and floral resources influence arthropod communities with potential benefits regarding pest regulation. These practices might be more effective if considered alongside other methods that enhance biodiversity and if they are consistent at a landscape scale.

     

茶园间作不同绿肥对节肢动物群落结构和多样性的影响

【目的】研究在茶园中合理间作绿肥对茶园节肢动物群落结构和多样性的影响。【方法】本文在茶园中分别设间作铺地木兰+罗顿豆、圆叶决明+白三叶、白三叶+平托花生3种不同绿肥组合处理,并设不间作绿肥、常规除草的茶园为对照。【结果】间作不同绿肥均能提高茶园节肢动物群落的物种丰富度和群落多样性,提高茶园捕食性天敌昆虫、蜘蛛和寄生性天敌在茶园冠层群落的比率;不同处理茶园冠层节肢动物Shannon-wiener多样性指数(H)、Simpson指数(D)和均匀度指数变化趋势基本一致;茶冠层的节肢动物群落多样性指数在4类不同处理茶园间差异显著;间作绿肥增加了茶园的生物多样性,4类不同处理茶园茶冠层群落相似性系数在0.741~0.892之间,表明4类不同处理茶园冠层群落在物种组成上有较高的相似性。4类不同处理茶园害虫与天敌两类群功能团的丰盛度之间成显著的正相关,表明天敌对害虫的空间数量跟随效应强,主要表现为二者数量间的相互作用。灰色关联度分析表明在4类不同处理茶园中的群落节肢动物物种数/个体数、天敌物种数/害虫物种数、害虫丰富度与多样性指数和均匀度指数的关联系数较高,反应了群落的多样性和稳定性。【结论】间作增强了茶园群落的生物多样性,提高害虫天敌的种类和个体数,有利有效发挥天敌对有害生物的生态控制。     

Urban greenspace composition and landscape context influence natural enemy community composition and function

Conservation research has historically been aimed at preserving high value natural habitats, but urbanization and its associated impacts have prompted broader mandates that include the preservation and promotion of biodiversity in cities. Current efforts within urban landscapes aim to support biodiversity and diverse ecosystem services such as storm water management, sustainable food production, and toxin remediation. Arthropod natural enemies provide biocontrol services important for the ecosystem management of urban greenspaces. Establishing habitat for these and other beneficial arthropods is a growing area of urban conservation. Habitat design, resource inputs, management, and abiotic conditions shape the value of greenspace habitats for arthropods. In general, larger patches with diverse plant communities support a greater abundance and diversity of natural enemies and biocontrol services, yet opposing patterns or no effects have also been documented. The surrounding landscape is likely a contributor to this variation in natural enemy response to patch-scale habitat design and management. Looking across rural–urban landscape gradients, natural enemy communities shift toward dominance by habitat generalists and disturbance tolerant species in urban areas compared to rural or natural communities. These changes have been linked to variation in habitat fragmentation, plant productivity and management intensity. In landscape-scale studies focusing solely within cities, variables such as impervious surface area and greenspace connectivity affect the community assembly of natural enemies within a patch. Given these findings, a greater mechanistic understanding of how both the composition and spatial context of urban greenspaces influence natural enemy biodiversity–biocontrol relationships is needed to advance conservation planning and implementation.     

不同邻作作物对玉米田节肢动物多样性的影响

为探明不同邻作对云南普洱地区玉米田节肢动物多样性的影响.采用目测法和粘虫板等多种诱集法对邻作咖啡、水稻、李树及单作的玉米田节肢动物群落进行系统调查,分析不同邻作作物对玉米田节肢动物群落的影响.结果表明:不同邻作玉米田天敌亚群落主要为双翅目和膜翅目,其中玉米单作田赤池信息量准则(AIC)值最低为-16.858,最优模型为...     

不同作物布局方式对转基因抗虫棉田节肢动物群落结构的影响

比较了不同作物布局下转基因抗虫棉田节肢动物的群落结构.结果表明,与单作棉田相比,蔬菜-棉花、果树-棉花及花生-棉花布局的棉田节肢动物群落、植食性害虫亚群落和天敌亚群落的物种数均增加,中性节肢动物的数量均有增加;蔬菜-棉花和花生-棉花布局的棉田植食性害虫个体数量增加;蔬菜-棉花和果树-棉花布局的棉田天敌个体数量增加.花生-棉花和果树-棉花布局棉田的节肢动物群落相似性最大;而单作棉田与蔬菜-棉花布局棉田的节肢动物群落相似性最小.R啨nyi多样性指数表明,与单作棉田相比,蔬菜-棉花布局棉田节肢动物群落多样性较低,害虫亚群落多样性较低;果树-棉花布局棉田节肢动物群落多样性较高,天敌亚群落多样性较高;花生-棉花布局棉田节肢动物群落多样性较高,害虫亚群落多样性较高.果树-棉花布局是值得推广的转基因抗虫棉田布局方式.     

Ecological intensification to mitigate impacts of conventional intensive land use on pollinators and pollination

Worldwide, human appropriation of ecosystems is disrupting plant–pollinator communities and pollination function through habitat conversion and landscape homogenisation. Conversion to agriculture is destroying and degrading semi‐natural ecosystems while conventional land‐use intensification (e.g. industrial management of large‐scale monocultures with high chemical inputs) homogenises landscape structure and quality. Together, these anthropogenic processes reduce the connectivity of populations and erode floral and nesting resources to undermine pollinator abundance and diversity, and ultimately pollination services. Ecological intensification of agriculture represents a strategic alternative to ameliorate these drivers of pollinator decline while supporting sustainable food production, by promoting biodiversity beneficial to agricultural production through management practices such as intercropping, crop rotations, farm‐level diversification and reduced agrochemical use. We critically evaluate its potential to address and reverse the land use and management trends currently degrading pollinator communities and potentially causing widespread pollination deficits. We find that many of the practices that constitute ecological intensification can contribute to mitigating the drivers of pollinator decline. Our findings support ecological intensification as a solution to pollinator declines, and we discuss ways to promote it in agricultural policy and practice.