Changes in selected soil quality indicators in forested soils following sawlog harvests

by

Kathleen M. Hatch, Keith W. Goyne, John M. Kabrick, Robert J. Kremer

USDA-ARS, Kathleen.Hatch@ars.usda.gov. 573-884-9065

Abstract – The highly weathered, nutrient-deficient soils of the Missouri Ozarks are vulnerable to degradation, necessitating improved understanding of forest harvest impacts on soil quality. The objective of this study was to investigate changes in selected soil quality indicators following sawlog harvests. The research was conducted at the Missouri Ozark Forest Ecosystem Project (MOFEP) sites of southeast Missouri. Pre- and post-harvest soil samples were collected at 0-10 and 10-20 cm from sites harvested using clearcutting (CC) and single-tree selection (STS), as well as no harvest (NH) management sites. Samples were collected from low (<20 % base saturation in diagnostic subsoil horizons) and medium (20-50 % base saturation) soil nutrient status (SNS) soils. Indicators examined were total organic carbon (TOC), total nitrogen (TN), KMnO4 oxidizable carbon, water extractable organic C and N (WEOC and WEN, respectively), soil pH, soil microbial enzyme activities of β-glucosidase and β-glucosaminidase, and water stable aggregate (WSA) content. Few differences in soil quality parameters were observed in the ~1.5 years after harvest. However, β-glucosaminidase activity decreased significantly in CC treatments at the 0-10 cm depth within low SNS soils post-harvest (collected January 2013) when compared to NH values and pre-harvest NH and CC treatment values collected January 2011. The CC treatment values in low SNS soils collected January 2013 post-harvest had significantly less WEN than NH treatment values and pre-harvest (January 2011) NH values. Changes in soil quality indicators after harvest, were most pronounced in CC harvested sites, though there were few significant differences between CC and STS sites.