Distribution Characteristics of δ3C during the Decomposition Process of Soil Organic Matters under Different Climates and in Different Vegetation Zones

摘要

[Objective]The research aims to study distribution characteristics of δ13C during the decomposition process of soil organic matters under different climates and in different vegetation zones. [Method]This essay measures the values of δ13 Corg in various soil profiles from different climatic zones and vegetation zones in order to obtain the precise corrected value. The 14 profiles of the following soil types in different zones are collected: brown earths in arid and semi-arid regions covered by C3 forests,yellow earths in humid zone covered by shrubs and forest,sandy loess from arid area covered by sparse vegetation,loess-paleosols in arid and semi-arid regions covered by C3/C4 grassland,yellow soils and paleosols in semi humid regions covered by C3/C4 grassland and yellow earths in humid areas covered by C3/C4 grassland. The measurement of δ13 Corg and standardized testing of the organic carbon are carried with above-mentioned profiles. An unified and skewed trend is not observed in the variation of δ13C values in these profiles. A discussion about the causes of distribution features is held in this essay. [Result]If the measurement of δ13C in the organic matters of paleosols is adopted in order to precisely rebuild the historical vegetation cover,the kinetic fractionation should be taken into consideration to calculate the δ13 Corg in the prolife from the soils that is exclusively covered by C3 plants; the δ13 Corg in the organic matters of the sand loess in the arid regions is affected by the contribution from basis; during the long-term decomposition of the organic matters in soils covered by C3/C4 grassland,the range of δ13 Corg is under 2‰. [Conclusion]In view of the mixed vegetation cover,the profile distribution of δ13 Corg in different geographic periods is more likely to indicate the ratio of C4 plants to C3 plants.