The use of senescent plant biomass to investigate relationships between potential particulate and dissolved organic matter in a wetland ecosystem

The purpose of this research was to (1) determine if different species of wetland vegetation produced characteristically different dissolved organic matter (DOM) based upon both chemical and physical characteristics and (2) determine if any relationships exist between characteristics of DOM derived from freshly senescent tissues of different wetland plant species common to the Florida Everglades and characteristics of the senescent plant tissue itself. Senescent plant tissues were used to represent potential particulate organic matter (POM) and leachates derived from them through cold water extraction were used to simulate abiotically produced labile DOM. Leachate DOM was characterized by total phosphorus (TP), nitrogen (TN), and carbon (TC), total carbohydrate content (TCC), total phenolic content (TPC), E4/E6 ratios, stable isotopes (δ13C, δ15N) and molecular mass fractionation (MMF). Senescent plant tissue (POM) was characterized by TP, TN, TC, E4/E6 ratio, stable isotopes (δ13C, δ15N), and fiber fractionation analysis (soluble content, hemicellulose, cellulose, and lignin).Comparisons of DOM mean values for MMF, TCC, and TPC among species revealed significant differences, which was further supported by observed separation of species in principal components analysis. Regression analysis between POM and DOM characteristics suggests that POM N:P ratios are useful predictors of DOM N:P ratios (r2 = 0.83, P < 0.001) and that POM levels of soluble constituents and hemicellulose can be a significant predictors of DOM TC (r2 = 0.82, P < 0.001). Comparisons of E4/E6 ratios and stable isotopes (δ13C, δ15N) of DOM and POM, however, did not reveal significant relationships. The results of this study suggest that plant community structure may be a significant modulator of DOM quality and quantity through species specific contributions of characteristically different DOM and that plant tissue concentrations of nutrients and structural components can significantly influence chemical characteristics of DOM derived from them.