Abstract: The aim of this study was to clarify the elemental C∶N∶P stoichiometric ratios and carbon density distribution patterns of the herb layer under forest in ecosystems in China’s Qinghai Province. Forest surveys and laboratory analyses of samples collected were carried out in 2011. Determinations included elemental concentrations of C, N, and P, together with their stoichometric ratios, C∶N, C∶P, and N∶P, and C reserves (g·kg^-1) of the herb layers under seven dominant species (Betula platyphylla, Populus tomentosa, Betula albo-sinensis, Picea wilsonii, Populus davidiana, Sabina chinensis, Picea asperata). The results show: the aboveground carbon content [(419.9±1.44) g·kg^-1] of S. chinensis forest was significantly higher than that of other forest types, but the underground carbon content [(364.6±8.33) g·kg^-1] was significantly lower than that of other forest types; the nitrogen content of S. chinensis and P. asperata forests was significantly higher than that of other forest types. There was no significant difference in phosphorus content between different forest types. The C∶N and C∶P stoichiometric ratios of S. chinensis and P. asperata forests were significantly lower than other forest types, while the N∶P ratio was significantly higher than other forest types. In addition, the biomass and carbon density of S. chinensis forest underground herb layer, both aboveground and belowground were significantly higher than that of other forest types. Correlation analysis of the stoichiometric data for these seven dominant tree species in Qinghai Province showed that the carbon density of the herb layer was correlated with its stoichiometric characteristics, and the carbon density could be estimated based on the carbon content. Taking altitude as an environmental factor, it was found that the carbon density of the herb layer under S. chinensis and P. asperata forest was distributed at higher altitude, while other species were distributed at lower altitude. Therefore, understanding the ecological stoichiometric characteristics of nutrient elements for the above and below ground parts of the herb layer, as well as estimating the carbon reserves of the herb layer, is very important to understanding the nutrient status and biochemical cycling processes of forest ecosystems in Qinghai Province.

Key words: herb layer, dominant species, stoichiometric character, the biomass, the density of carbon, carbon reserve