The landscape context of trophic interactions : insect spillover across the crop-noncrop interface

Landscape structure influences local diversity and ecosystem processes, including cross-habitat fluxes of organisms coupling the dynamics of different habitats. The flow of organisms across system boundaries is known to occur between different natural habitats as well as across the crop¿noncrop interface. Several studies show how field boundaries can enhance predator populations invading arable crops and controlling pest populations. However, generalist arthropods may also spill over from land-use systems to natural areas (mainly grassland) modifying interactions therein. A view of land-use systems as sources and natural habitats as sinks is consistent with the idea that the direction of the organismsâ¿¿ fluxes is from high to low productivity systems, while noncrop habitats are important sources for recolonization of arable fields after they are cleared for harvest. From the perspective of landscape management, enhancement of population exchanges between crop and noncrop areas may include beneficial as well as unwelcome interactions