Abstract
As interest in wood bioenergy increases, the demand for woody residues also increases leading to ecological concerns about soil productivity and site sustainability. Removal of woody residue after harvesting can reduce litter decomposition rates by altering physical conditions of forest surface and N input. Thus, I studied the effects of biomass (a.k.a residue) retention levels from thinning forests on changes in site physical conditions (e.g., temperature and moisture) and changes in litter decomposition and nutrients dynamics. In addition, I examined the compensating effect of fertilizer N additions. Decomposition was measured using a 172-day litterbag experiment in two forest stands which were thinned in 2013 and fertilized in 2014. Woody residue retention levels were: normal (1x), doubled (2x), or removed (0x), and there were adjacent unthinned control plots. The litterbags were placed on the forest floor in 2016.
The 0x retention level had litterbags with the lowest moisture and respiration, but the highest decomposition rate (k) and mass loss as compared to the control. Litterbag nitrogen (N) had the greatest losses in the 0x retention plots. There was no evidence that fertilization increased litterbag decomposition rates. This litterbag study indicates that removal woody residues from conifer forests in northern Idaho will not alter litterbag decomposition rates.