Release of nitrogen and phosphorus from loblolly pine forest floor in a post-harvest microclimate
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Loblolly pine (Pinus taeda L.) plantations grown on nutrient deficient soils in the southeastern U.S. require nitrogen (N) and phosphorus (P) fertilization to increase growth (Albaugh et al., 2007; Fox et al., 2007). Fertilization increases growth by increasing foliar nutrients and leaf area (Albaugh et al., 1998) which also results in higher litterfall mass. Nutrients sequestered in foliage eventually accumulate in the forest floor. As a loblolly pine stand ages forest floor mass increases (Switzer and Nelson, 1972). Nitrogen and P content also increase (Switzer and Nelson, 1972) due to an accumulation of N and P as the litter decomposes (Piatek and Allen, 2001; Sanchez, 2001) suggesting a forest floor sink. In fertilized systems, the forest floor sink is magnified due to higher inputs from litterfall and increased foliar N and P concentrations (Will et al., 2006). When a stand is harvested, forest floor decomposition increases due to changes in environmental conditions. Since next rotation seedling nutrient demand is not great enough to capture nutrient released through forest floor decomposition (Fox et al., 2007), a significant amount of site nutrient capital could be lost. Our objectives were to: (1) determine whether fertilization results in a forest floor N and P sink and (2) quantify N and P release from decomposing forest floor material in a post-harvest microclimate.