The influence of elevated nitrate concentration on rate of leaf decomposition in a stream

SUMMARY. Leaf decomposition was compared in two streams at the Coweeta Hydrologic Laboratory, North Carolina. U.S.A. One stream drains an undisturbed hardwood watershed, while the other drains a successional watershed subject to an insect outbreak. The successional watershed has elevated nitrate concentrations in the streamwater. Both black locust (Robinia pseudo‐acacia) and sweet birch (Betula lenta) leaf litter decomposed 2.8 times more rapidly in the stream with high nitrate concentrations. The more rapid decay rates appeared to be partly due to accelerated microbial processing in response to nitrate enrichment, because microbial biomass (as ATP) was higher in the nitrate‐enriched stream. At each point in time, nitrogen and phosphorus content of the litter was lower in the high nitrate stream; however, there was no significant difference in nitrogen or phosphorus content at the same state of leaf decay in the two streams.