A component model of decomposition of Spartina alterniflora in a New Jersey salt marsh

Abstract

Spartina alterniflora decomposition was monitored in the high and low salt marsh in litter bags (2-mm mesh). The detritus formed in this process was analyzed at various times for ash-free dry weight (AFDW) (combustion at 550 °C), total carbon (wet combustion to CO2), and total nitrogen (Kjeldahl digestion). A mathematical component model predicting the change of these parameters was developed to explain these data.The first-order decay equation Xt = X0 e−kt was used to explain AFDW and carbon changes. The k values ranged from 0.004 to 0.02 per day for data from the high and low marsh, respectively, for New Jersey. Nitrogen fluxes are described by four functions. Three of these are decay functions which theoretically model (1) loss of soluble nitrogen, (2) loss of recalcitrant nitrogenous plant material, and (3) loss of microbial nitrogen. The fourth is a logistic function which describes the microbial incorportaion of nitrogen into the detritus. Nitrogen and C/N ratio values calculated with these equations simulated values obtained from field data.