The Characteristics And Mechanisms Of Stable Carbon Isotope In Degraded Grasslands

The experiment was carried out in the seven types of Chinese grasslands in August 2014,and analyzed samples within the next year.We attemped to investigate the stable carbon isotopes(?¹³C)variation characters of leaves,roots and soil in degraded grassland,and to reveal the mechanism of factors effecting on ?¹³C values:grazing?grazing treatment and grazing intensity?and geographical factors?longitude,latitude and altitude?.This experiment provides a new idea and method for monitoring grassland degradation.The results are as follows:?1?The ?¹³C range values of leaves,roots and soils in all types of grassland were unique.The variation degree of ?¹³C1eaf range value at different families and the range value of ?¹³Croot were both increased after grazing,and the later become more negative.While the variation of ?¹³Csool range values at different depths and after grazing were both not in one direction.?2?Overgrazing caused most ?¹³Cleaf values decreasing and the photosynthetic pathway of three species converting,but have little effect on ?¹³Croot values.The four factors,grazing treatments,depths,regions,the interaction between grazing treatments and regions,were significantly effected the ?¹³Csoil values.?3?With the graze intensity increasing,the variation trends of ?¹³Cleaf,?¹³Croot and?¹³Csoil were declined.But the ?¹³Croot value showed a trend of increasing first and then decreasing.The ?¹³Croot value riched down along the plant axis:?¹³Csoil ??¹³Croot??¹³Cleaf.?4?The values of ?¹³Cleaf,?¹³Croot and ?¹³Csoil showed a regular variation trends with the elevation gradient.The ?¹³Croot and ?¹³Csoil values showed a significant regression relationship with geographical factors before and after grazing.?5?The difference gap between ?¹³Croot and ?¹³Csoil at OG and NG plots??r-sOG,?r-sNG?.showed significant linear correlation.