Biological weed control by seed predators is an ecosystem service reducing weed population densities in agricultural landscapes. Drivers of seed predation are manifold and may change with spatial scales considered. We aimed at identifying the functional identity of seed predators, food web interactions and feeding links between weed and wheat seeds, considering the causal relationships between local and landscape-scale patterns. We investigated direct and indirect effects of local management intensity in winter wheat fields (organic vs. conventional farming), local crop characteristics (wheat density and height), edge effects, landscape composition (measured as land-use diversity) and configuration (edge length) on carabid beetles of different body size (large vs. small carabids), and removal of weed and wheat seeds. We showed the importance of indirect local- and landscape-scale effects for weed seed removal via the activity density, but not assemblage composition, of large, but not small carabids, which was driven by few ubiquitous species. The activity density of large carabids increased with decreasing wheat density and increasing wheat height, which was highest in organic fields and in landscapes with low compositional and configurational heterogeneity. Further, the availability of nutrient-rich wheat seeds enhanced weed seed removal rates. We found highest weed seed removal via large carabids in organic fields in large-scale agricultural landscapes. Predator body size and species identity as well as the availability of additional food items need to be taken into account for better predicting the biological weed control potential and reducing the use of plant protection products.

中文翻译：

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大型甲虫可促进有机田地和大规模而非小规模农业中的杂草种子去除

种子捕食者的生物杂草控制是一种生态系统服务，可减少农业景观中的杂草种群密度。种子捕食的驱动因素是多方面的，可能会随着空间尺度的考虑而变化。考虑到当地和景观尺度模式之间的因果关系，我们旨在确定种子捕食者的功能特性、食物网相互作用以及杂草和小麦种子之间的饲养联系。我们调查了冬小麦田当地管理强度（有机耕作与传统耕作）、当地作物特征（小麦密度和高度）、边缘效应、景观组成（以土地利用多样性衡量）和配置（边缘长度）的直接和间接影响) 对不同体型的甲虫（大与小甲虫），以及杂草和小麦种子的去除。我们通过活动密度，而不是由少数普遍存在的物种驱动的大型但非小型carabids的活动密度，展示了间接局部和景观规模效应对杂草种子去除的重要性。大型甲虫的活动密度随着小麦密度的降低和小麦高度的增加而增加，在有机田和组成和构型异质性低的景观中最高。此外，营养丰富的小麦种子的可用性提高了杂草种子去除率。我们发现在大型农业景观中的有机田中通过大型甲虫去除杂草种子的效果最高。