Variations in delta 13C values among major plant community types in the Xilin River Basin, Inner Mongolia, China.

摘要

The delta 13C values of 51 plant species selected from eight plant communities along a moisture gradient were measured. Our results showed that all the community types that we investigated are dominated by C3 species in the Xilin River Basin. Large variations in the average 13C natural abundance of different communities were detected, and the magnitude of delta 13C values showed the following trend: typical steppe (-23.0 per mil) > degraded steppe (-23.5 per mil) > sand dune (-25.0 per mil) > restoring degraded steppe (-25.8 per mil) > meadow steppe (-26.4 per mil) >= saline meadow (-26.5 per mil) > swamp meadow (-28.2 per mil). The major determinants of the biomass-weighted delta 13C values in a given community were the presence or absence of C4 plants, the intrinsic variation among species and the variation of the same species growing in different habitats with different soil-moisture regimes and disturbance history. These results suggested that different habitats support dominant species with different water-use efficiencies and a trend in the community-level delta 13C values was observed, as ascribed by the contribution of C4 plants and/or the variations among species or the response of water-use efficiency of the same species to different soil moisture conditions..