LANDSCAPE FEATURES ARE A BETTER CORRELATE OF WILD PLANT POLLINATION THAN AGRICULTURAL PRACTICES IN AN INTENSIVE CROPPING SYSTEM

Summary

Organic farming is commonly associated with increased pollinator diversity and abundance, but the net effects on pollination rates are less documented. Besides, organic farms are often surrounded by more diverse landscapes than conventional farms, such that the contributions of landscape diversity vs. farming practices to pollination rates are often confounded with each other. Here, the roles of local vs. landscape scale variables on pollination rates of experimental plants are examined in agricultural landscapes. To this end, fruit set and seed production were measured in the obligate insect-pollinated Lotus corniculatus. Plants were located in pairs of neighboring organic vs. conventional farms, which were characterized by contrasting landscape structures and compositions. Fruit set, a proxy for pollinator visitation rates, was significantly related to landscape variables: fruit set was higher in farms close to a patch of semi-natural habitat, but lower in landscapes with a high cover of semi-natural habitats. Fruit set also correlated with local variables, such as habitat type, but not with farming type. Identical pollination rates in conventional and organic farms are likely due to similar diversities of habitats, crops and weeds in both farming types of the study area. These results therefore confirm that habitat diversity prevails over pesticide-free practices to explain the higher pollinator abundances usually observed in organic vs. conventional farms.