Soil Nutrients and Stoichiometry Along Elevation Gradients in Shallow-lakes of Poyang Lake Wetland
Four types of wetland habitats, i.e. downland, high beach, low beach and swamp, were chosen as elevation gradients in 4 shallow - lakes in Nanjishan wetland nature reserve of Poyang Lake and the contents of soil C, N and P contents and their stoichiometry along the 4 elevation gradients were determined. The results showed that SOC content in 0–10 cm soil layer was lowest in the downland, TN and TP contents were ranked as downland >high beach > low beach > swamp, TN was positively correlated with TP content, SOC and TN contents were decreased with the depth of soil layer, mean ratios of C/N, C/P and N/P were 11.17, 52.74 and 5.03, respectively. In the study area, soil C/N was relatively stable, while C/P and N/P varied substantially either along elevation gradients or among shallow-lakes. NH4+-N content was ranked as downland < high beach < low beach < swamp, while NO3–-N content was ranked as high beach < low beach < downland < swamp. Furthermore, AP and TP contents were positively correlated. In short, soil nutrients in the study area exhibits large variations due to the seasonal dynamics of hydrology in Poyang Lake and TN was the primary limiting factor of N/P ratio.