Plant diversity and arthropod communities: Implications for temperate agroforestry

Polyculture in crop agroecosystems has been examined in numerous studies with the aim of reducing pest populations by increasing diversity among insect populations over those found in traditional monoculture. Resource concentration and enemies hypotheses predict decreased pest populations in more diverse plant communities. Although results have been mixed, insect diversity has been generally increased in polyculture over traditional monoculture. Maintaining natural insect diversity in managed forests to limit possible pest outbreaks has been the goal in forestry systems. Increased arthropod diversity with increased tree diversity has been observed, though fewer studies have been conducted in forestry compared to agriculture. Agroforestry holds promise for increasing insect diversity and reducing pest problems because the combination of trees and crops provides greater niche diversity and complexity in both time and space than does polyculture of annual crops.