Effects of Clearfelling and Site Preparation on Nitrogen Mineralization in a Southern Pine Stand
1984
Burger, J. A. | Pritchett, W. L.
A clearcut forest site (45-year-old natural stand of Pinus elliottii Engelm. and Pinus palustris Mill.) was subjected to different intensities of site preparation to determine management impacts on N availability. Using a laboratory aerobic soil incubation technique, N mineralization potentials (N mineralizable over time) (Nₒ) were determined to be 25.0, 23.3, and 17.7 µg/g for soils from an uncut control area; a burned and chopped area; and a bladed, disced, and bedded area, respectively. The Nₒ of soil from the intensively treated area was significantly lower than the others when measured in the laboratory; however, simulations of field conditions indicated that more N may be mineralized in soils from intensively treated sites due to more favorable soil moisture and temperature conditions. Mineralization rates for these three areas, however, were not significantly different, and C/N ratios (28 and 26 for the chopped and bladed sites, respectively) for the clearcut and prepared areas did not suggest a difference in N availability. Ratios of organic matter/soluble carbon (OM/Cₐ) increased from 79 to 136 with treatment intensity and suggest that the N associated with the organic matter remaining on the most intensively treated site may be more resistant to decomposition. Nitrogen availability is a function of substrate quality and microenvironmental conditions. Harvesting and site treatment affected both of these. Laboratory determinations of Nₒ appear to be a better index of nitrogen availability than C/N, Cₛ, or total N, but do not adequately account for differences in mineralization due to treatment-induced changes in the soil environment.
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