Soil carbon (C), nitrogen (N) and phosphorus (P) are the three most important chemical elements in ecosystems. Circulation of C, N and P is inextricably linked with the ecological structure of ecosystems, including their processes and functioning. Consequently, the dynamic ratios of C, N and P (e.g. C:N, C:P and N:P) might reflect ecosystem characteristics.

In wetland ecosystems, hydrological regimes (e.g. duration of submergence, sedimentation and water-table fluctuations) alter the composition, structure and functioning of wetland ecosystems by influencing nutrient concentrations, aeration conditions and the size of substrate particles. However, the characteristics of soil C, N and P stoichiometry in freshwater wetlands remain poorly understood.

Scientists from the Institute of Subtropical Agriculture (ISA) of the Chinese Academy of Sciences (CAS) studied the patterns of the spatial distribution and stoichiometry of soil carbon (C), nitrogen (N) and phosphorus (P), with 123 soil samples, along a small-scale elevation gradient in the wetland of East Dongting Lake, China.

The spatial distributions of plant nutrient concentrations (C, N and P) and stoichiometry (C:N, C:P and N:P ratios) were evaluated geostatistically with regression kriging, entailing estimation of regression parameters by generalized least squares and ordinary kriging of the residuals.

The researchers found that the ratios of C:P and N:P had similar patterns of distribution to soil organic carbon (SOC) and total nitrogen (TN). The SOC, TN, C:N, C:P and N:P ratios increased with increasing elevation, whereas total phosphorus (TP) showed no marked change. Furthermore, SOC, TN, C:N, C:P and N:P decreased considerably with increasing duration of submergence, soil moisture and pH.

In the East Dongting Lake wetland, elevation appeared to influence the distribution of plant nutrients and stoichiometry as a result of changing soil moisture and duration of submergence.

The research was supported by the National Natural Science Foundation of China, the Open Funding Project of the Key Laboratory of Aquatic Botany and Watershed Ecology, Chinese Academy of Sciences, the Key Research Program of the Chinese Academy of Sciences and the Youth Innovation Promotion Association of CAS.

The study entitled "Spatial distribution and stoichiometry of soil carbon, nitrogen and phosphorus along an elevation gradient in a wetland in China" was published in European Journal of Soil Science.