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Title: The impact of timber harvest on surface soil microbial community activity in clearcut Missouri Ozark Forest Ecosystem project plots
Author: Spratt, Henry G., Jr.
Publication: In: Shifley, S. R.; Kabrick, J. M., eds. Proceedings of the Second Missouri Ozark Forest Ecosystem Project Symposium: Post-treatment Results of the Landscape Experiment. Gen. Tech. Rep. NC-227. St. Paul, MN: U.S. Dept. of Agriculture, Forest Service, North Central Forest Experiment Station. 196-211.
Abstract: Transformations of carbon (C), sulfur (S), nitrogen (N), potassium (K), and magnesium (Mg) were determined for Oa+A- and EB-horizon soils collected from 12 permanent subplots located in MOFEP sites 1 and 3 from May 1995 to June 1999. Six of the subplots were clearcut in 1996, and six were left undisturbed. Mineralization of 14-C lignocellulose (of Quercus alba) was used as a measure of microbial catabolic activity in the soils. Quercus alba is the predominant overstory tree species on MOFEP plots. Incorporation of 35SO4 into organic sulfur compounds was used as a measure of microbial anabolic activity in the soils. Total C, N, and S (TC, TN, and TS) were determined by elemental analysis. Exchangeable K and Mg were determined using ammonium acetate extraction followed by atomic absorption spectrophotometry. After harvest, Oa+A-horizons from clearcut sites initially had higher rates of lignocellulose mineralization than controls, but these had declined by 2 years post-harvest. Organic S production rates were reduced to a large extent (by 80 to 90 percent, t-test, p<0.05) for soils from plots both high and low in the landscape. Concentrations of TC in Oa+A-horizons were lower in clearcut soils than controls on all dates beginning 1 year post-harvest (declining by as much as 35 percent compared with pre-treatment soils). Total S of both Oa+A-horizons decreased by nearly 40 percent after clearcutting, while EB-horizons tended to show an increase in TS following clearcutting (up nearly 73%). The TS content of litter falling into clearcut sites increased by nearly 50 percent 2 years post-harvest. Total N was lowest in clearcut plots. Exchangeable K concentrations in Oa+A-horizons from clearcut plots declined by nearly 75 percent 2 years post-harvest. Trends in exchangeable Mg concentrations in Oa+A-horizons were not easily determined for the clearcut plots 2 years post-harvest.
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