Water Quality Effects of Clearcut Harvesting and Forest Fertilization with Best Management Practices

Abstract

Nine small (2.5 ha) and four large (70-135 ha) watersheds were instrumented in 1999 to evaluate the effects of silvicultural practices with application of best management practices (BMPs) on stream water quality in East Texas, USA. Two management regimes were implemented in 2002: (i) conventional, with clearcutting, herbicide site preparation, and BMPs and (ii) intensive, which added subsoiling, aerial broadcast fertilization, and an additional herbicide application. Watershed effects were compared with results from a study on the same small watersheds in 1981, in which two combinations of harvesting and mechanical site preparation without BMPs or fertilization were evaluated. Clearcutting with conventional site preparation resulted in increased nitrogen losses on the small watersheds by about 1 additional kg ha(-1) each of total Kjeldahl nitrogen (TKN) and nitrate-nitrogen (NO(3)-N) in 2003. First-year losses were not significantly increased on the large watershed with a conventional site preparation with BMPs. Fertilization resulted in increased runoff losses in 2003 on the intensive small watersheds by an additional 0.77, 2.33, and 0.36 kg ha(-1) for NO(3)-N, TKN, and total phosphorus, respectively. Total loss rates of ammonia nitrogen (NH(4)-N) and NO(3)-N were low overall and accounted for only approximately 7% of the applied N. Mean loss rates from treated watersheds were much lower than rainfall inputs of about 5 kg ha(-1) TKN and NO(3)-N in 2003. Aerial fertilization of the 5-yr-old stand on another large watershed did not increase nutrient losses. Intensive silvicultural practices with BMPs did not significantly impair surface water quality with N and P.

U.S. Billion-Ton Update: Biomass Supply for a Bioenergy and Bioproducts Industry

“…Wood ash, created during wood combustion for energy, can be safely used to replace calcium and other basic cations removed through biomass harvesting (Pitman, 2006). Concerns related to the impact of forest fertilization on water quality have generally been unfounded (Binkley et al, 1999), even in intensively managed systems (McBroom et al, 2008) or when biosolids are applied (Pratt and Fox, 2009). …”

Forest fertilization: Trends in knowledge and practice compared to agriculture

“…Modern navigational methods aid the selection and recording of ground or flight paths for fertilizer application, which in-turn improves the uniformity of application, and improves the ability of pilots to avoid buffers and other areas that are not to be fertilized (e.g. McBroom et al 2008). …”

Nutrient concentration dynamics in an inland Pacific Northwest watershed before and after timber harvest

“…Often site preparation (e.g., broadcast prescribed burning, mechanical treatments, herbicides) or other management practices (e.g., competition release sprays, fertilization, roads) confound our ability to determine the specific practice(s) contributing to changes (Fredriksen, 1973;McBroom et al, 2007). These changes may be shortlived or persistent and must be assessed in relation to management stages across a watershed, as well as compared to natural disturbance events, to gain a better understanding of the processes that control nutrient dynamics.…”