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Isotope Tracing Of Soil Organic Carbon Dynamics In The Grassland

Posted on:2006-01-30Degree:DoctorType:Dissertation
Country:ChinaCandidate:Z TaoFull Text:PDF
GTID:1100360155464464Subject:Institute of Geochemistry
Abstract/Summary:PDF Full Text Request
High-resolution sampling, measurement and analysis of root content, organic matter content, 14C specific activity, δ13C and magnetic susceptibility of selected all 6 soil profiles in Haibei Research Station of Alpine Meadow Ecosystem in the Tibetan Plateau and Inner Mongolia Grassland Ecosystem Research Station, CAS, were made in an attempt to detect the soil organic carbon dynamics of grassland. The results as follows:The soil organic carbon storage in the alpine meadow in the Tibetan Plateau is pronounced larger than that in Inner Mongolia grassland ecosystem. Organic matter content of topsoil (0-10cm) in Haibei Station is two times higher than that of Inner Mongolia Station.Soil organic matter consists of fast component, slow component and passive component. The vertical distribution of soil root content is that root content(060cm) comprises some 90% of root content of total the profiles.The roots of the natural soils are mainly in the upper soil horizons and rapidly decrease with depth; there are less roots in the disturbed soils and gradually decrease with depth.The soil CO2 flux ranges from 73.3 gC m-2a-1 to 181 gC m-2a-1 and 390 g m-2a-1 to 866 gC m-2a-1 (Wang gengchen et al 2004) for the alpine meadow and for Inner Mongolia typical grassland, respectively. The latter is about 5 times as high as the former. The CO2 emitted from the surface soil comprises an important part for the soil CO2 flux of the alpine meadow soil profiles.The soil CO2 flux has negative correlation with elevation.δ13C values of soil organic matter increase with depth. Their vertical changes are divided into three segments: rapidly increase segment, gradually increase segment andless increase or slightly fluctuation variable segment. The extent of 13C enrichment of soil organic matter in Inner Mongolia Station is larger than that in Haibei Station.Vegetation types control the soil organic carbon dynamics.Soil organic carbon dynamics can be reflected to some extent by the soil quality magnetic susceptibility and root content.The powerful measures for increasing the capacity of soil reservoir in the flimsy grassland consist of forbiding overgrazing, not disturbing of the surface soil horizons, introducing of deep-rooted plants, and controlling the loss of water and soil.
Keywords/Search Tags:soil organic carbon dynamics, carbon isotope, grassland ecosystem, soil CO2, global change
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