Effects of forest management intensity on carbon and nitrogen content in different soil size fractions of a North Florida Spodosol |
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| Authors: | D V Sarkhot N B Comerford E J Jokela J B Reeves III |
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| Institution: | (1) Department of Soil and Water Science, University of Florida, PO Box 110290, Gainesville, FL 32611-0290, USA;(2) School of Forest Resources and Conservation, University of Florida, PO Box 110410, Gainesville, FL 32611-0410, USA;(3) Environmental Management and Byproducts Utilization Laboratory, ARS, USDA, Bldg 306, Rm. 101, Beltsville Agricultural Research Center East, Beltsville, MD 20705, USA |
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| Abstract: | Pine plantations of the southeastern USA are regional carbon (C) sinks. In spite of large increases in woody biomass due to
advanced growing systems, studies have shown little or even negative effects on the C content of the extremely sandy soils
of this region. Hence, it is important to understand the mechanisms that determine the impact of intensive forest management
on soil organic carbon (SOC) sequestration. This study was conducted to examine the C profile in a 4-year-old loblolly pine
(Pinus taeda L.) plantation managed under two levels of management intensity (chemical understory control and fertilizer inputs). Soil
organic C and nitrogen (N) pools were evaluated using two size fractionation methods, dry and wet sieving (2000–250 μm, 250–150 μm,
150–53 μm and <53 μm). Dry sieving was preferred over wet sieving for soil size fractionation, as it preserved more structure
and water-soluble SOC components such as esters and amides and did not affect the N distribution. Diffuse Reflectance Infrared
Fourier Transform Spectroscopy (DRIFTS) spectra were used to examine the chemical composition of the size fractions, which
showed the presence of recently added organic matter in the largest sand fraction, as well as more decomposed organic matter
in the <53 μm fraction. Intensive forest management reduced SOC in all three 2000–53 μm fractions, most likely due to reduced
root input of understory plants that were controlled using herbicides. The 2000–250 μm fractions contained nearly half of
the total SOC and showed a 23% decrease in C content due to the intensive management regime. Results from this study indicated
the significance and responsiveness of sand size SOC fractions in Florida Spodosols. Results also showed that reductions in
SOC due to intensive management occurred after four years and highlighted the need to understand the long-term impacts and
the mechanisms responsible.
Responsible Editor: Barbara Wick |
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| Keywords: | Carbon sequestration DRIFTS Fertilization and chemical weed control Intensive silviculture loblolly pine Pinus taeda Size fractionation |
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