Spatio-temporal patterns and potential trade-offs in the promotion of aphid and seed predation in agroforestry systems

Abstract

Agricultural intensification and simplification compromise biodiversity and can destabilize populations of important ecosystem service providers. By promoting invertebrate and vertebrate predators that deliver important ecosystem services such as pest and weed control, agroforestry systems may reconcile ecological benefits and agriculture productivity, making them a promising land-use system for the transition towards sustainable agriculture. However, the spatio-temporal regulation of ecosystem services and potential disservices provided by predators in agroforestry systems remains poorly studied. We compared aphid, weed seed, and crop seed predation in the crop rows between temperate alley cropping systems and open croplands without trees. In addition, we analyzed the extent to which effects of tree rows extended into the crop rows at two different time periods in spring. Aphid predation was higher at sampling locations close to the tree rows. Seed predation was spatially more variable but showed, similar to aphid predation, particularly low rates in open croplands. The distance-dependence of aphid and crop seed predation changed in magnitude across sampling periods, while weed seed predation was more temporally constant. Moreover, crop seeds were consumed nearly twice as much as weed seeds, indicating varying food preferences among invertebrate and vertebrate seed predators and a potential trade-off between ecosystem services and disservices. Our results suggest that alley cropping agroforestry benefits pest and weed control. However, differences in spatio-temporal patterns of aphid and seed predation indicate varying dependencies of different predator groups on the tree rows, while high crop seed predation suggests a concurrent promotion of a disservice. Our study emphasizes that understanding the spatial and temporal patterns of predation-related ecosystem services and disservices is needed to develop management practices promoting natural pest control and reducing the amount of plant protection products used in agriculture. Therefore, knowing how and when to support beneficial organisms and at the same time control pests is key for the development of sustainable agricultural systems.