Soil organic carbon storage and soil CO2 flux in the alpine meadow ecosystem

Abstract

High-resolution sampling, measurements of organic carbon contents and 14 C signatures of selected four soil profiles in the Haibei Station situated on the northeast Tibetan Plateau, and application of 14 C tracing technology were conducted in an attempt to investigate the turnover times of soil organic carbon and the soil-CO 2 flux in the alpine meadow ecosystem. The results show that the organic carbon stored in the soils varies from 22.12×10 4 kg C hm −2 to 30.75×10 4 kg C hm −2 in the alpine meadow ecosystems, with an average of 26.86×10 4 kg C hm −2 . Turnover times of organic carbon pools increase with depth from 45 a to 73 a in the surface soil horizon to hundreds of years or millennia or even longer at the deep soil horizons in the alpine meadow ecosystems. The soil-CO 2 flux ranges from 103.24 g C m −2 a −1 to 254.93 gC m −2 a −1 , with an average of 191.23 g C m −2 a −1 . The CO 2 efflux produced from microbial decomposition of organic matter varies from 73.3 g C m −2 a −1 to 181 g C m −2 a −1 . More than 30% of total soil organic carbon resides in the active carbon pool and 72.8%-81.23% of total CO 2 emitted from organic matter decomposition results from the topsoil horizon (from 0 cm to 10 cm) for the Kobresia meadow. Responding to global warming, the storage, volume of flow and fate of the soil organic carbon in the alpine meadow ecosystem of the Tibetan Plateau will be changed, which needs further research.

Soil organic carbon and nutrients along an alpine grassland transect across Northern Tibet

“…SOC, TN, TP, AN and AP stocks in the upper 30 cm of soil in the alpine meadow are significantly higher (P < 0.05) than those in the alpine steppe. Compared to previous results, we found lower SOC stock in two alpine grasslands (Wang et al 2002;Tao et al 2007). The coefficient of variation (CV) was used to qualitatively describe the magnitude of spatial variability as weak when CV < 0.1, moderate if 0.1 < CV < 1, and strong when CV > 1 ).…”

Soil aggregate fraction-based 14C analysis and its application in the study of soil organic carbon turnover under forests of different ages

“…Torn et al [27] showed that the soil CO 2 flux will be underestimated by using the 14 C tracer method if treating all the carbon in bulk soil as homogeneous with respect to turnover times. The soil CO 2 flux in alpine meadow estimated by Tao et al [98] also exhibited relatively low values. This may be partly caused by not dividing soil organic matter into fractions with different intrinsic turnover times.…”

“…This may be attributed to the re-adaptation of microbes to soil environment. It has been shown that soil CO 2 flux gradually decreases with increasing depth along a soil profile, and the surface soil (0-10 cm) accounts for about 40%-80% of the whole soil profile [98]. Therefore, it can be inferred that the soil CO 2 in topsoil (0-5 cm) can contribute at least 20%-40% to whole soil profile.…”

Turnover Rate of Soil Organic Matter and Origin of Soil 14Co2 in Deep Soil from a Subtropical Forest in Dinghushan Biosphere Reserve, South China

“…With respect to SOC turnover rates, bomb 14 C is a unique tracer to evaluate the rate (Levin and Hesshaimer 2000). Cherkinsky and Brovkin (1993) presented a simple model to calculate turnover rates of SOC, which has been further developed to calculate the production of humus-derived soil CO 2 by Chen et al (2002b) and Tao et al (2007). Soil CO 2 is produced through biological process including organic matter decomposition and root respiration, then it transports to the overlying atmosphere via molec-ular diffusion (Amundson et al 1998).…”