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The effects of harvesting intensity on soil CO2 efflux and carbon content in an east Texas bottomland hardwood ecosystem
Abstract
Soil respiration rates have been used as an indicator of soil community activity around the world. An increasing number of studies have been performed using soil respiration rates as a measure of man's impacts on the environment, including forest land. I examined the effects of harvest intensity on in situ and mineral soil respiration, along with total soil and soluble organic carbon, were examined in a bottomland hardwood forest. Treatments included a clearcut, a partial cut, and a non-harvested control. I hypothesized that respiration rates would vary directly with harvest intensity. The sodalime absorption technique was used for determining in situ respiration and the wet alkali method was used for measuring mineral soil respiration in the lab. Soil temperature and moisture content were also measured. Sampling occurred between 6 and 22 months after harvesting. Total soil and soluble organic carbon analyses were performed every three sampling periods beginning with period 6. Total soil organic carbon content was determined by the Walkley-Black method, an acid digest procedure. Soluble organic carbon content was determined from cold-water extracts analyzed with a total organic carbon analyzer. Results indicated that harvesting significantly (a=0.05) increased in situ respiration during most sampling periods. This effect was attributed to the revegetation of the site creating an increase in live root and associated microflora activity in the soil following harvesting. In situ respiration varied directly with soil temperature and inversely with soil moisture. Harvesting effects on mineral soil respiration were less clear and showed trends in only some months. Harvesting significantly (a=0.05) increased the amount of total organic carbon in the top 15 cm, whereas overall soluble organic carbon levels were not significantly affected. I feel that even though harvesting has significantly effected soil respiration rates, this increase will not adversely affect atmospheric C02 levels. Published data show that when temperate forests are allowed to regrow immediately after harvest, carbon assimilated in growing vegetation is greater than the C02 lost from the soil.
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Citation
Londo, Andrew James (1995). The effects of harvesting intensity on soil CO2 efflux and carbon content in an east Texas bottomland hardwood ecosystem. Master's thesis, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1995 -THESIS -L65.
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