Dissolved Nitrogen Release Research Articles

Erratum to: Dissolved nitrogen release from coarse and amphipod-produced fine particulate organic matter in freshwater column

Dissolved nitrogen (DN) is essential for primary production in aquatic systems. We investigated total DN (TDN) and nitrate and nitrite (NO3 − + NO2 −) releases from particulate organic matter (POM) by incubating POM of various sizes and chemical characteristics in stream water over a 2-week period. Large- and medium-sized fine POM (L-FPOM, 250–500 μm, and M-FPOM, 100–250 μm) were prepared by feeding five types of coarse POM (CPOM) to shredding amphipods in laboratory aquaria. For CPOM, the TDN release rate was greatest during the first day of the experiment while L-FPOM continued to release TDN during the experimental period, and the TDN release rate from L-FPOM in the second week was higher than those from the other size fractions. In addition, TDN release on the first day from FPOM was significantly affected by FPOM chemical qualities, with a negative correlation to lignin content and lignocellulose index. The present study indicates the importance of source and chemical quality of POM in the instream TDN release and the significance of amphipod-produced FPOM as a nitrogen source in streams despite being recalcitrant to microbial decomposition.

Dissolved nitrogen release from coarse and amphipod-produced fine particulate organic matter in freshwater column

Dissolved nitrogen release from coarse and amphipod-produced fine particulate organic matter in freshwater column

Dissolved nitrogen release from coarse woody debris of different tree species in the early phase of decomposition

In forest ecosystems, coarse woody debris (CWD) can represent a large stock of organic matter that contributes to the C and N cycling in forest ecosystems. Here we investigated the net release of dissolved organic N (DON), NH4 and NO3 from CWD of different tree species in the early phase of decomposition. Logs of 13 tree species were exposed in the winter 2008/2009 on the soil in a temperate Fagus sylvatica L. forest in Germany. Runoff solutions were periodically collected underneath logs for 17months from June 2011 to November 2012 in the third to fourth year of decomposition. The net release of N was calculated for each log on an annual scale as difference of N fluxes in runoff and throughfall.Nitrogen was net released from CWD of all tree species with DON as the dominant N form, but leaching of NH4 and NO3 was also observed. Differences in total N release between tree species were not statistically significant due to high intra-specific variation. The net release of N ranged from 0.42 (Pseudotsuga) to 1.39 (Carpinus) gNm−2 log projection area yr−1 The variation in net release of N was not related to the initial C/N ratio of bark and sapwood of the different species. The DOC/DON ratios in runoff were positively related to the initial C/N ratio of bark and sapwood. Net release of NH4 was larger in the dormant than in the growing season, opposite to the release of NO3, but no seasonality was found for DON release. Average ratios of NH4/NO3 in runoff from CWD did not significantly differ between species. Precipitation amount and temperature had only minor effect on the total N release, suggesting other dominating drivers.Our results demonstrate that CWD is a source of solute N, even in the early phase of decomposition.