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Littlefield, Caitlin Emily

Natural Resources

2012

MS

Demand for forest bioenergy fuel is increasing in the northern forest region and beyond, but the ecological impacts -particularly on habitat -of bioenergy harvesting remain poorly explored. In this thesis research, I evaluated the harvesting impacts upon stand structural complexity; a concurrent study is investigating the short-and long-term carbon dynamics of bioenergy harvesting. Our field crew collected stand structure data from 35 recent harvests, pairing harvested areas with unharvested reference areas. I analyzed biometrics generated from field data using a multi-tiered nonparametric uniand multi-variate statistical approach.
In analyses comparing harvested to reference areas, sites that had been whole-tree harvested (WTH) demonstrated significant differences (relative negative contrasts; p<0.05) in snag density, large live tree density, well decayed downed coarse woody debris (DCWD), and structural diversity index values while sites that had not been whole-tree harvested (non-WTH) did not demonstrate significant differences. My classification and regression tree (CART) analyses suggested that the strongest predictors of structural retention were harvesting treatment and equipment type rather than the proportion of harvested volume allocated to bioenergy uses. In general, harvesting impacts were highly variable across the 35 sites we sampled, supporting a role for harvesting guidelines aimed at encouraging retention of ecologically important structural attributes.