Changes in arthropod communities mediate the effects of landscape composition and farm management on pest control ecosystem services in organically managed strawberry crops

AbstractLandscape composition and local diversification practices such as polyculture, cover cropping, and hedgerows may promote natural pest control by benefiting natural enemy communities on farms. Our study employs piecewise structural equation modeling (PSEM) to test causal hypotheses regarding the effects of landscape composition and local diversification practices on arthropod communities and pest control ecosystem services. We sampled 27 organic strawberry fields in California’s Central Coast region in 2015 and 2016 (17 repeated between years) for a total of 37 distinct sites across years. The sites were selected along orthogonal gradients of landscape composition and local diversification practices. We also investigated the effects of two common pest management practices. At each site, we sampled arthropod communities using a hand-held vacuum and performed sentinel prey experiments using the pest species Lygus hesperus to estimate pest control levels. At the landscape scale, proportion woods increased natural enemy abundance; at the local scale, diversification practices increased natural enemy diversity. Insecticides and tractor vacuuming, aimed at controlling pests, were indirectly detrimental to pest control services. Both practices decreased natural enemy abundance, and while insecticides also decreased pest abundance, vacuuming did not. Natural enemy abundance and diversity increased pest control levels, while pest abundance had the opposite effect. The PSEM results confirmed our hypotheses that landscape and local effects on pest control are mediated through changes in arthropod communities. Synthesis and applications: At the landscape scale, higher proportions of woody habitat are associated with greater natural enemy abundance, which increases pest control levels.  When promoting pest control ecosystem services is a policy goal, regional planners should prioritize the conservation and restoration of woodlands in agricultural landscapes. At the local scale, decisions of individual growers can impact pest control services. For many growers, adopting practices that promote on-farm plant diversity may be a feasible solution for increasing pest control levels while avoiding the environmental and economic costs imposed by insecticide application and tractor vacuuming.   , MethodsPlease refer to the Methods section of the paper., Usage notesPlease refer to readme file.

摘要：景观格局与当地多样化种植模式（如混作、覆盖作物种植、绿篱种植）可通过助力农田天敌群落，提升自然虫害防控效果。本研究采用分段结构方程模型（PSEM），针对景观格局、当地多样化种植模式对节肢动物群落及虫害防控生态系统服务的影响检验因果假设。本研究于2015年与2016年在加利福尼亚中央海岸区域采样了27块有机草莓田（其中17块在两年间重复采样），跨年度共计37个独立样点。样点选取沿景观格局与当地多样化种植模式的正交梯度展开。本研究同时探究了两种常见害虫治理措施的影响。在每个样点，研究人员采用手持式真空采样器采集节肢动物群落，并以害虫物种西美盲蝽（Lygus hesperus）开展哨兵猎物实验，以此估算虫害防控水平。在景观尺度上，林地占比提升了天敌种群数量；在样地尺度上，多样化种植模式提升了天敌群落多样性。旨在防控害虫的杀虫剂与拖拉机牵引式真空除虫措施，实则间接损害了虫害防控生态服务功能。两类措施均降低了天敌种群数量，其中杀虫剂同时降低了害虫种群数量，但真空除虫无此效果。天敌种群数量与群落多样性提升了虫害防控水平，而害虫种群数量则产生相反作用。分段结构方程模型的结果验证了本研究的假设：景观与样地尺度对虫害防控的影响，是通过节肢动物群落的变化实现介导的。综合与应用：在景观尺度上，木本生境占比越高，天敌种群数量越多，进而提升虫害防控水平。若将提升虫害防控生态服务功能列为政策目标，区域规划者应优先保护并修复农业景观中的林地。在样地尺度上，种植户的个体决策可对虫害防控服务产生影响。对多数种植户而言，采用有助于提升农田植物多样性的措施，或许是在规避杀虫剂施用与拖拉机真空除虫所带来的环境与经济成本的同时，提升虫害防控水平的可行方案。方法：请参阅论文的方法部分。使用说明：请参阅readme文件。