Effects of forest ecosystem restoration treatments on leaf litter decomposition and nutrient turnover in mixed-oak forests in Southern Ohio, USA

In 2004 we began a three year litter decomposition experiment at the Ohio Hills Fire and Fire Surrogate site in order to produce predictive models of the effects of the restoration on nutrient turnover. We considered soil/climate characteristics, the quality of the decomposing litter, the influence of dormant season fire at historical frequencies, and landscape position as factors. Decomposition rates and N and P dynamics were determined by using leaf litterbags incubated in situ packed with site-specific litter mixes and standard litter types. We compared mass, N, and P loss among treatments between leaf fall in autumn 2004 and early spring 2005, and found that mass loss was unaffected by treatment; but, N release was greater in burned than unburned plots (with or without thinning) and P release was greater in burn-only and thin-only plots than in the control. We compared the first four months of decomposition of litter from burned plots harvested in 2004 (4th post-fire year) and 2005 (1st year after second fire). Loss of mass, N, and P were significantly greater from the 1st post-fire year than the 4th post-fire year litter. Estimates of annual decay rates (k) suggest that spatial variability in decomposition within a treatment was considerably greater in burned or burned+thinned plots than in control or thinned plots. Once the final harvest in completed in July 2007 we will utilize structural equation modeling approaches to develop predictive models for C, N, and P turnover in relation to landscape position, litter source, and restoration treatments.