Nov 14, 2012 - ecological patterns of vegetation formation and distribution during the different stages of the delta cycle are well described for coastal alluvial ...
Ecosystems DOI: 10.1007/s10021-013-9727-3 ! 2013 Springer Science+Business Media New York
Nutrient Biogeochemistry During the Early Stages of Delta Development in the Mississippi River Deltaic Plain Kelly M. Henry* and Robert R. Twilley Department of Oceanography and Coastal Sciences, School of the Coast and Environment, Louisiana State University, Baton Rouge, Louisiana 70803, USA
ABSTRACT Nutrient biogeochemistry associated with the early stages of soil development in deltaic floodplains has not been well defined. Such a model should follow classic patterns of soil nutrient pools described for alluvial ecosystems that are dominated by mineral matter high in phosphorus and low in carbon and nitrogen. A contrast with classic models of soil development is the anthropogenically enriched high nitrate conditions due to agricultural fertilization in upstream watersheds. Here we determine if short-term patterns of soil chemistry and dissolved inorganic nutrient fluxes along the emerging Wax Lake delta (WLD) chronosequence are consistent with conceptual models of long-term nutrient availability described for other ecosystems. We add a low nitrate treatment more typical of historic delta development to evaluate the role of nitrate enrichment in determining the net dinitrogen (N2) flux. Throughout the 35-year chronosequence, soil nitrogen and organic matter content significantly increased by an order of magnitude, whereas phosphorus exhibited a less
pronounced increase. Under ambient nitrate concentrations (>60 lM), mean net N2 fluxes (157.5 lmol N m-2 h-1) indicated greater rates of gross denitrification than gross nitrogen fixation; however, under low nitrate concentrations (
