Seasonal variations in decomposition processes in a valley-bottom riparian peatland.

A year-long field survey was carried out at a valley-bottom riparian peatland site in North Wales, UK from January 2002 to December 2002 to examine the seasonal variation of decomposition processes and dissolved organic carbon (DOC) concentrations. Peat temperature, physicochemistry, organic carbon pools, basal CO(2) respiration and extracellular enzyme activities (beta-glucosidase, phosphatase, sulphatase and phenol oxidase) were monitored monthly. The results of a principle component eigenanalysis of field data show that concentrations of basal CO(2) respiration, soil solution DOC and phenolics were positively correlated to soil temperature (P<0.01, F=12.25; P<0.001, F=59.8; P<0.001, F=141.27) with Q(10) responses of 2.29, 6.42 and 14.42, respectively. Extracellular enzyme activities, however, were more strongly associated with seasonal changes in ion concentrations and did not correspond significantly to temperature alone suggesting limitations attributable to a combination of continuous anaerobiosis and/or the suppressive compounds. Restraints on soil enzyme activities may limit the loss of CO(2) from the microbial community that is dependent on soil enzyme activities for nutrient availability. The seasonal effect of temperature on DOC may be explained by increased plant rhizodeposition and microbial activity. These results do not imply that the long-term increasing trend in DOC export is explainable by temperature increase but suggest that temperature may be a key factor regulating the seasonal variation in DOC concentrations. Thus, seasonal temperature effects on DOC may represent an important component of long-term models of DOC export.