Influence of strip thinning on nutrient outflow concentrations from plantation forested watersheds

Abstract

AbstractNutrient concentrations in stream water, rainfall, throughfall, stemflow, surface flow and ground water were compared before, during and after strip thinning (intensive 50%) in plantation forested watersheds in Tochigi, Japan. Influences were evaluated comparing four thinning‐applied and two reference basins for 1 year before, 6 months during and 1 year after the thinning. Results show that this strip thinning significantly increased dissolved total phosphorus, total phosphorus and dissolved organic carbon (0.01, 0.04 and 0.53 mg l−1, respectively) during the thinning period and dissolved total nitrogen and total nitrogen (0.34 and 0.46 mg l−1, respectively) after the thinning in stream waters relative to the unthinned basins. The increased phosphorus during thinning indicated ground disturbances by the strip thinning, with a concomitant increase in dissolved organic carbon. Changes in biotic and abiotic conditions resulted in increased nitrogen after the thinning, particularly in the dissolved pool. Changes in hydrological processes due to thinning, for example, a change in flow distributions (less high nutrient stemflow and more low nutrient throughfall) and an increase in water discharge in stream water, possibly weakened the direct influences of thinning on nutrient concentrations. Copyright © 2015 John Wiley & Sons, Ltd.