Effects of nitrate enrichment on leaf litter decomposition

aim: this study aimed to determine the effects of nitrate enrichment on leaf decomposition process and the kinetic parameters of decomposition model; methods: samples of water from a first-order stream and senescent leaves of the native tree species campomanesia xanthocarpa o. berg (myrtaceae) were collected in south of brazil. the leaves were oven-dried, grounded and for each experimental condition (control and enriched) 20 decomposition chambers were prepared with leaf fragments and unfiltered stream water (with and without nitrate addition), maintained under low and high oxygen conditions. in sampling days the particulate and dissolved organic carbon and total inorganic carbon concentrations were evaluated; results: the decomposition of particulate and dissolved organic carbon (poc and doc) was faster in nitrate enriched treatment under high dissolved oxygen condition. the doc mineralization coefficients (k3) were in average 283-fold higher than the rate constants for refractory poc (rpoc) mineralization, being the enriched k3 2.3-fold higher than the control k3; conclusions: the leaf litter decomposition was affected by dissolved nitrate concentration in the water and rpoc and doc decomposition was faster with nitrate enrichment than in reference natural conditions (without nitrate enrichment). thus, dissolved nitrate seems to be an important factor in controlling litter decomposition and its increase affects the leaf carbon processing in stream ecosystems.