| Popis: |
Biological crusts (Biocrusts) are important surface active coverings in arid and semi-arid regions, which affect the content of soil organic carbon (SOC), SOC labile fractions and stability of SOC through photosynthetic carbon fixation. At present, studies on the variation characteristics of SOC, SOC labile fractions and the stability of SOC in biocrusts are rather limited. In this study, two types of typical biocrusts (moss crusts and algae crusts) were selected along a precipitation gradient from northwest to southeast in the Mu Us Sandland (straight line distance 188 km) by measuring soil organic carbon (SOC), soil microbial biomass carbon (MBC), water soluble carbon (DOC), particulate carbon (POC), easily oxidizable carbon (ROC). We aimed to explore the effects of biocrusts on the stability of SOC and carbon decomposition across the precipitation gradient. Results showed that:1) Two types of biocrusts significantly increased the contents of SOC, MBC, DOC, POC, ROC and stability of SOC. Moss crusts increased SOC contents by 1.6 to 2.6 times as that of algae crusts. 2) The lowest SOC contents of the two types of biocrusts were 6.43 g·kg生物结皮是干旱半干旱地区重要的地表活体覆盖物,其通过光合固碳影响土壤有机碳、活性碳组分的含量及其稳定性。目前有关生物结皮中有机碳变化特征的研究非常有限。本研究在毛乌素沙地沿降水梯度从西北向东南选择了两类典型的生物结皮(苔藓结皮、藻结皮),直线跨度188 km,通过测定土壤有机碳(SOC)、微生物生物量碳(MBC)、可溶性有机碳(DOC)、颗粒态有机碳(POC)和易氧化有机碳(ROC),探讨生物结皮对土壤有机碳稳定性的作用及其对降水梯度的响应,并基于藓类植物凋落物分解试验解析降水变化对其碳分解过程的影响。结果表明: 1)两类生物结皮覆盖均显著提高了SOC和MBC、DOC、POC、ROC等活性碳组分含量及SOC稳定性,其中,藓结皮对SOC的提升作用为藻结皮的1.6～2.6倍。2)两类生物结皮SOC含量最低点均出现在西北样地(分别为6.43、14.50 g·kg |
