高寒草原土壤有机碳及土壤碳库管理指数的变化

The changes of soil organic carbon and carbon management index in alpine steppe

高寒草原对高寒生态系统的稳定具有重大意义。为探明高寒草原土壤有机碳(SOC)、土壤活性有机碳(ASOC)变化,以及草地退化对土壤碳库稳定性的影响,对藏北高原正常、轻度和严重退化高寒草原表层(0—10 cm)、亚表层(10—20 cm)土壤进行了初步研究。结果表明:(1)轻度、严重退化草地各土层SOC、ASOC均呈不同程度的下降。其中,退化草地SOC的降幅均以表层最大,且各土层降幅均随草地退化加剧而下降;退化草地ASOC的降幅则均以亚表层最大,但各土层ASOC的降幅随草地退化加剧而提高。(2)正常草地、轻度和严重退化草地表层ASOC比率分别为16.8%、21.3%、16.6%,亚表层分别为21.8%、18.1%和16.0%;土壤碳库活度与ASOC比率的变化趋势完全一致。因此,轻度退化草地SOC的不稳定性主要体现在表层土壤。(3)退化草地表层、亚表层碳库管理指数(CMI)均呈显著下降,但表层降幅相对较低;与严重退化草地比,轻度退化草地不同土层CMI明显提高。(4)高寒草原环境中,正常草地、轻度和严重退化草地各土层SOC、ASOC间则均呈一定程度的负相关,表明土壤微生物对SOC、ASOC的影响和作用可能不同。

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.