Soil C, N and P stoichiometry of Deyeuxia angustifolia and Carex lasiocarpa wetlands in Sanjiang Plain, Northeast China

The theory of ecological stoichiometry has improved understanding of nutrient circulation processes in ecosystems. The purpose of this work was to study ecological stoichiometric characteristics of carbon, nitrogen and phosphorus in wetland soils of Sanjiang Plain, northeast China. A Deyeuxia angustifolia wetland (swamp meadow) and a Carex lasiocarpa wetland (marsh) were chosen for collection of soil cores (0-30 cm depth). Soil organic carbon, total nitrogen and phosphorus were analyzed to study patterns of C/N (R (CN)), C/P (R (CP)), N/P (R (NP)), and C/N/P (R (CNP)) in wetland soils. Soil carbon, nitrogen and phosphorus stoichiometry differed between the two wetlands. Soil R-CN (0-30 cm depth) in the D. angustifolia wetland was close to that in C. lasiocarpa wetland (12.97 and 12.80, respectively), but R (CP) and R (NP) in C. lasiocarpa soils were significantly higher than those in D. angustifolia soils. R (CN) changed little within soil profile, without obvious trends in both wetlands. Both R (CP) and R (NP) decreased with depth from the surface, and both R (CP) and R (NP) were higher at every depth interval in C. lasiocarpa soils compared to D. angustifolia soils. R (CN) in surface soil (0-10 cm, organic-rich Lo layer) was not significantly different from R (CN) in the entire profile (0-30 cm, La layer) of D. angustifolia wetland, while R (CP) and R (NP) were both significantly different between the Lo and La layers. In Carex lasiocarpa wetland, R (CN), R (CP) and R (NP) in Lo layer were significant higher than those in La layer. R (CNP) in La layer of D. angustifolia and C. lasiocarpa wetlands were 65:5:1 and 163:13:1, respectively. Soil R (CN) was relatively consistent, while R (CP) and R (NP) reflected P limitation in wetlands of Sanjiang Plain. Further research is needed to determine whether these ratios hold among other wetland ecosystems.