|Park, J-H: Dissolved Organic Matter Dynamics in a Deciduous Forest Floor: Controls Investigated by Field and Laboratory Manipulation Experiments in Bayreuther Institut für Terrestrische Ökosystemforschung (BITÖK): Bayreuther Forum Ökologie, Selbstverlag, 95, 1-110 (2002)|
The forest floor in temperate forests plays a crucial role in the retention of elevated inputs of dissolved inorganic nitrogen (DIN) and as a source of dissolved organic matter (DOM). The objectives of this study were to investigate the controls on the release of dissolved organic carbon (DOC) and nitrogen (DON) from the forest floor of a hardwood stand in northern Bavaria, Germany, and to explore the relationships between the limited availability of carbon sources and an elevated nitrogen leaching loss from the N-enriched forest floor. The role of resource availability and water flux as primary controls over DOM mobilization and N retention in the forest floor was investigated using manipulation approaches either in the field or in the laboratory. The field manipulation experiment was composed of litter removal, litter addition, glucose addition, and throughfall input doubling. Forest floor leachates (below Oi and Oa) were biweekly sampled and analyzed for DOC, DON, NH4-N, and NO3-N. In the laboratory leaching experiment, resource availability was manipulated using different types of treatments: exclusion of specific forest floor layers (no Oi; no Oe) and addition of carbon sources (glucose; cellulose; leaf; wood) and NH4NO3 (nitrogen). Resource availability constrained the production and mobilization of both DOM and DIN in the forest floor via intricately related processes. In particular, the amount and quality of available C played a key role for microbial activity and N immobilization mechanisms in this forest floor, presumably due to C limitation associated with unbalanced, high N supply at this site. An increase in the microbial production of DOM was not always reflected in the actual amount of DOC and DON released from the forest floor due to the concurrent microbial consumption or confounding effects of frequent leaching events. The results suggest that the actual DOM release from the forest floor may be largely explained by the magnitude of resource pools in different forest floor horizons and varying water fluxes.
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