The impacts of bioenergy pine plantation management practices on bee communities.
Abstract
Cultivation of bioenergy feedstocks is a growing land-use world-wide, yet we have a poor understanding of how bioenergy crop management practices affect biodiversity. This knowledge gap is particularly acute for candidate cellulosic bioenergy feedstocks, such as tree plantations, and for organisms that provide important ecosystem services, such as pollinators. We examined bee communities in 83 sites across three states in the southeastern United States-Alabama, Florida and Georgia. We compared bee abundance and diversity in 66 pine plantation sites that reflect management with and without potential bioenergy feedstock production. At least three bioenergy feedstock production methods have been proposed for this region: (a) converting conventional timber stands to short-rotation bioenergy plantations; (b) harvesting feedstock by thinning conventional plantations; and (c) harvesting of woody debris residues after plantations have been clear-cut. We found that bioenergy-associated management practices including younger plantations (relative to older) and woody debris removal (relative to debris unremoved) in clear-cut plantations were associated with reduced bee diversity. Removing ground debris in clear-cut plantations also drastically increased bee abundance, though this effect was largely driven by strong dominance of just two bee species. Clear-cut plantations had lower beta diversity than standing plantations. Synthesis and applications. Management practices associated with bioenergy feedstock production can have negative effects on bee community diversity. In particular, harvesting of debris in clear-cut plantations dramatically reduces bee diversity. Large-scale bioenergy feedstock production that increases the prevalence of young and clear-cut stands may cause landscape-level beta diversity to decline. Nevertheless, bioenergy pine plantations likely support higher bee diversity than corn fields, an alternative bioenergy feedstock.