高寒草原土壤有机碳及土壤碳库管理指数变化研究

Abstract

The alpine steppe plays a vital role in the stability of alpine ecosystem. To understand the variation of soil organic carbon( SOC) and active soil organic carbon( ASOC) in alpine steppe,and the influence of grassland degradation on soil carbon pool,We initially investigated the SOC and ASOC in the surface soil( 0—10 cm) and subsurface soil( 0— 20 cm) in normal steppe,light degraded steppe,severely degraded steppe in The Northern Tibet Plateau. The results showed that:( 1) The SOC and ASOC all declined with different degree in each layer soil in mildly degraded steppe and severely degraded steppe. The decline of SOC in surface soil were much higher than that in subsurface soil in these degraded steppe,and the decline of SOC in each layer soil decreased with the steppe degradation.. But the decline of ASOC in surface soil was much lower than subsurface soil,and which in severely degraded steppe was much higher than that in mildly degraded steppe.( 2) The distribution ratio of ASOC in surface soil in normal steppe,mildly degraded steppe and severely degraded steppe were 16. 8%,21. 3% and 16. 6%,respectively,and which in the subsurface were 21. 8%, 18. 1 and 16. 0%,respectively. Besides that,the variation tendencies of soil carbon pool activities were consistent with the distribution ratio of ASOC. So that,the SOC in the surface soil in the mildly degraded steppe is unstable.( 3) The soil carbon management index( CMI) in the surface soil and subsurface soil all significantly declined in degraded steppe,the decline of CMI in surface soil much lower than subsurface soil. The CMI in each layer soil of mildly degraded steppe were much higher compared to severely degraded steppe.( 4) The negative correlation was observed between SOC and ASOC in each layer soils in normal steppe,mildly degrade steppe and severely degraded steppe in alpine grassland. This result suggests that the effects of soil microorganism on SOC,ASOC might be different.