Cellulose decay in natural and disturbed peatlands in North Carolina
Carbon cycling is central to nutrient dynamics and accretion rates in wetlands. Drainage and conversion of wetlands has been occurring at an accelerating rate. This paper compares decay rates in natural and disturbed peatlands in the southeastern USA and examines relationships between edaphic factors and decay rates. Cellulose decay rates (as tensile strength loss of cotton fibers) were used to compare decomposition potentials in these peatlands. A 1984 pilot experiment included undisturbed short pocosin and several sites under various stages of agricultural conversion. A spring 1987 experiment included an increasing nutrient availability gradient in undisturbed communities from short pocosin to tall pocosin to gum swamp, drained pocosin with natural vegetation remaining, and pocosin converted to pine forestry and agriculture. In the 1984 experiment, distrubed sites had decay rates approximately nine times greater than undisturbed pocosin. In the 1987 experiment, disturbed sites had decay rates from 1.8 to 10.3 times natural sites. The greatest decay rates occurred in the agricultural site with its high nutrients, less acidic conditions, and relatively low soil moisture. Drained pocosin had the next highest decay rates, although pH and nutrients were low. Pine (Pinus taeda L.) forestry had intermediate rates of decay, while undisturbed sites had low rates. The more nutrient-rich, but wet and low pH, gum swamp site had similar or slightly higher rates than the pocosin sites. Drainage, relieving excessive soil moisture and the resultant anaerobiosis, was the dominant factor explaining the greater decay rates in the disturbed sites. Other factors, such as nutrient availability and low pH, may have had secondary effects on cellulose decay. Rates were also compared to a global data set based on potential evapotranspiration. Natural sites have rates very close to those predicted, while disturbed sites have much higher rates (1.9-4.4X predicted).
Bridgham, SD; Richardson, CJ; Maltby, E; Faulkner, SP
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