Authors: Marja, Riho; Klein, Alexandra-Maria;Viik, Eneli;Batáry, Péter;

Plant and pollinator diversity has declined concurrently in Europe in the last half-century. We studied plant–bumblebee food webs to understand the effects of two Estonian agri-environmental schemes (AES; environmentally-friendly management and organic farming) vs. conventional farming, landscape structure (homogeneous, heterogeneous) and seasonality (June–August) interactions. We found that both AES and landscape structure influenced the generality (redundancy in the use of flower resources) of food webs. In homogeneous landscapes, environmentally-friendly management, including restrictions on the application of glyphosates, enhancement of bumblebee habitats (permanent grassland field margins), the allocation of a minimum of 15% of arable land to legumes, contributed to a higher number of visited plant species in July, whereas organic farming did so in August. Therefore, both AES are important to support plant–bumblebee food webs. Food webs generality and Shannon index are affected by a significant interaction between seasonality and landscape structure: food web diversity varied in homogeneous landscapes between the three survey months, whereas food webs were more diverse in heterogeneous landscapes. In homogeneous landscapes, resource limitation is an issue for bumblebees in certain time periods. For supporting bumblebees, avoiding resource limitation is important and this can be secured with a combination of AES management practices.