Theses and Dissertations Collection

A lack of forest management has led to millions acres of overstocked forests in the northwest United States. Thinning forests increases stand resistance to wildfire, pests, and disease. Traditional forest management leaves thinned trees on site as slash. Forest slash provides stable conditions and supplies nutrients to the soil. Biomass removal from thinning can be used for cellulosic biofuel production. Biomass removal can provide environmental, financial, and ecosystem benefits, though biomass removal may decrease forest productivity and disrupt soil biological properties. Soil amendments can be used to mitigate effects of biomass removal by altering soil properties to increase forest productivity. Biochar is an amendment that adds carbon to the soil and increases water-holding capacity, while fertilizer can improve forest production and replace nutrients removed in biomass. This thesis examines the effect of post-thinning biomass retention levels on forest growth, as well as responses to fertilizer and biochar soil amendments.