Changes in Forest Floor and Water Quality Following Thinning and Clearcutting of 20‐Year‐Old Pine

Abstract

AbstractEffects of timber cutting on forest floor, sediment movement, and chemical quality of percolating water and of plot runoff are reported for pole‐size loblolly pine (Pinus taeda L.) plantations on fragile soils of the upper Coastal Plain. Treatments were clearcut, thin, and nocut. Water quality measurements were derived for runoff samples from 0.002‐ha plots and for percolating water from zero‐tension lysimeters at a 15‐cm depth. Forest floor on clearcut plots was reduced to near the minimum regarded as necessary for site protection within two years. Regardless of cutting treatment, more N and P were coming into the plots via precipitation than were leaving via plot runoff and percolation combined. More K appeared to be leaving the sites than was coming in via rainfall, regardless of cutting treatment. Sediment concentrations in plot runoff tended to be proportional to cutting intensity. Nutrient content in percolation waters was unrelated to cutting intensity. Nutrient concentrations in plot runoff were high compared to concentrations reported in stormflows from local, small catchments with similar characteristics, but plot runoff was <3% of annual rainfall.