Incorporation of local and neighborhood trophic cascades highly determine ecosystem function along a nitrogen subsidy gradient.

The spatial distribution of an ecological subsidy can change local trophic cascades and create differences among locations; however, its contribution to shaping large-scale ecosystem functions is less well known. Here, using a multi-scale hierarchical design along a nitrogen input gradient, we assessed both local (within field level) and neighborhood (inter-field level) differences in soil nutrients and plant-arthropod communities to explain variation in landscape-scale crop productivity and biocontrol service. We found that the average importance of neighborhood factors increased, approached and even exceeded local factors in explaining the variance in the predator-to-aphid abundance ratio, wheat yield and parasitism rate. Compared to models with only local factors, both local and neighborhood factors when integrated into linear models explained an extra 67% and 18% of the variation in wheat yield and parasitism rate, respectively. Preserving the abundance and variability of biological resources on a specific spatial scale using targeted nitrogen subsidies may be a promising strategy for sustaining multiple ecosystem functions under intensified land use. [ABSTRACT FROM AUTHOR]