Data_Sheet_1_Spiders indicate delivery of an agri-environment scheme at multiple diversity levels.docx

Agri-environment schemes (AES) are expected to counteract the negative impacts of intensive agriculture on biodiversity. These schemes were specifically designed to target farmland biodiversity and included, for instance, ecological focus areas (EFAs). In Switzerland, in order to qualify for direct payments, farmers must manage 7% or more of their land as biodiversity promotion areas (BPAs). BPAs encompass extensively managed and low intensity hay meadows, fallows (wildflower strips), traditional orchards with high-stem trees and hedgerows. Evaluation of AES delivery for biodiversity is of crucial importance but must be performed across several years and considering the various components of species diversity to avoid incomplete or wrong conclusions. From a complex study design comprising 478 fields in three regions and sampling over 7 years with four sampling times, spider assemblages of BPA habitats were compared to corresponding conventionally managed fields. A battery of investigations was performed including alpha- and beta-diversity analysis, multivariate dispersion, indicator species and species specificity to understand what BPAs deliver for spiders in the habitat scale and farming landscape. Results showed that alpha-diversity (average number of species) was usually higher in BPA habitats than in conventionally managed fields but the species composition (beta-diversity) had more power to perceive AES impact. Furthermore, the various environmental conditions of BPAs in the farming landscape led to highly diverse spider assemblages (multivariate dispersion) emphasizing that not only the agricultural management plays a role in determining species diversity but the environmental heterogeneity. Indicator (and rare) species were mostly found in woody BPAs (hedges and high-stem tree orchards) revealing the high importance of these BPA habitats for spider conservation. At regional scale, BPA hedges contributed most to the regional diversity of spiders in grassland and mixed regions while BPA meadows and wildflower strip BPAs were first delivering in the region of arable crops. Recommendations highlight the role of the woody habitats and of the environmental heterogeneity in the farming landscape as well as of regional planning to make AES effective.

农业环境计划（Agri-environment Schemes, AES）旨在抵消集约化农业对生物多样性带来的负面影响。此类计划专为保护农田生物多样性而设计，例如包含生态重点区域（Ecological Focus Areas, EFAs）。在瑞士，农户若要申领直接支付补贴，需将至少7%的耕地用作生物多样性促进区（Biodiversity Promotion Areas, BPAs）。BPAs涵盖粗放管理、低强度的干草甸、休耕地（野花带）、种植高干树的传统果园以及树篱。对AES实施效果进行生物多样性相关评估至关重要，但该评估需跨越多年开展，并兼顾物种多样性的各个维度，方可避免得出片面或错误的结论。本研究采用复杂的实验设计：在三个区域内选取478块样地，历时7年、分4次采样，对比了BPAs生境与常规管理农田的蜘蛛群落。研究开展了一系列分析，包括α多样性与β多样性分析、多元离散度分析、指示物种分析以及物种特异性分析，以探究BPAs在生境尺度与农田景观尺度上对蜘蛛群落的影响。研究结果显示，BPAs生境的α多样性（物种平均丰富度）通常高于常规管理农田，但物种组成（β多样性）更能体现AES的实施效果。此外，农田景观中BPAs所处的多样环境条件造就了高度多样化的蜘蛛群落（多元离散度结果印证了这一点），这表明不仅农业管理方式会影响物种多样性，生境的环境异质性同样发挥着重要作用。指示物种（及稀有物种）大多集中在木本型BPAs（树篱与高干树果园）中，凸显了此类BPAs生境对蜘蛛保护的重要价值。在区域尺度上，BPAs树篱对草地与混合农业区域的蜘蛛区域多样性贡献最大，而BPAs草甸与野花带则在耕地作物区发挥首要的保护作用。本研究建议，应重视农田景观中的木生生境与环境异质性，同时加强区域规划，以提升AES的实施成效。