Data from: 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, landuse 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.

集约化土地利用是众多生态系统生物多样性衰退的关键驱动因素。在半自然草原中，刈割、放牧与施肥等土地利用活动会影响植物与节肢动物（arthropods）的多样性，但不同驱动因子的联合效应及其完整作用链条目前仍未明确。本研究采用结构方程模型（structural equation modelling），分析人工管理草原中的节肢动物群落对土地利用的响应特征，并探究此类响应是否通过资源多样性或资源量（生物量，biomass）的变化实现介导。植物被视作植食性动物（herbivores）的食物资源，而植食性动物自身又构成捕食性动物（predators）的食物来源。研究于2008年至2009年间，在德国境内三个区域的141块草甸、常规牧场及刈割牧场中开展采样，对植物与节肢动物（包括植食类群与捕食类群）的群落组成进行调查。总体而言，土地利用强度提升通常会提高植物生物量并降低植物多样性，该效应主要由施肥强度增加所主导。植食性动物的多样性随植物多样性下降而降低，但对植物生物量的变化无明显响应。由此可见，土地利用对植食性动物多样性的影响是通过资源多样性而非资源量介导的。而土地利用对捕食性动物多样性的影响，则同时通过植食性动物多样性（即资源多样性）与植食性动物生物量（即资源量）两条路径介导，其中通过资源量产生的间接效应更为显著。本研究结果凸显了评估土地利用强度与模式对不同营养级（trophic levels）生物群落的直接与间接效应的重要性。除整体效应外，不同研究区域间还存在细微差异，这体现出区域特异性土地利用特征的重要价值。本研究印证了学界普遍观测到的草原土地利用对生物多样性的强烈影响，同时也证实了机制性研究方法有助于我们深入理解不同土地利用模式对生物多样性的作用机制。