青藏高原北麓河流域不同退化程度高寒草甸土壤呼吸特征

Alpine meadows at different levels of degradation in the Beiluhe Basin of Tibetan Plateau Characteristics of soil respiration

土壤呼吸是陆地生态系统碳循环的重要环节之一,而青藏高原高寒草甸的大面积退化对土壤呼吸及碳循环造成重要影响。为了进一步探明高寒草甸退化对土壤呼吸的影响,对北麓河区不同退化程度高寒草甸土壤呼吸及其相关因子进行了测定,分析了土壤呼吸与生物量、地下净初级生产力以及土壤温度的关系。结果表明:1)不同退化程度高寒草甸土壤呼吸在生长季均表现出相似的动态特征,随退化程度加剧呈先增加后降低的变化趋势,在中度退化程度达到最大值,且在生长季中期变化显著(P <0.05)。2)土壤呼吸和地上、地下生物量及地下净初级生产力均显著线性正相关(P <0.05)。3)土壤温度与土壤呼吸之间呈指数关系,但不同退化程度下土壤呼吸对土壤温度的敏感性不同,土壤呼吸敏感性在轻度退化(Q_(10)=3.26)和中度退化程度(Q_(10)=3.22)大于未退化(Q_(10)=2.66),而在重度退化(Q_(10)=2.49)和极度退化程度(Q_(10)=1.96)小于未退化;这主要是由不同退化程度土壤温度、地下生物量以及土壤有机碳含量的差异造成。研究的结果有助于进一步认识退化草地的碳循环过程。

Soil respiration is one of the most important components of the carbon cycle in terrestrial ecosystems.The widely distributed degradation of the alpine meadows on the Tibetan Plateau will impact the soil respiration and carbon cycle.In order to further explore the effects of degradation on the soil respiration of alpine meadows,we measured the soil respiration and related factors of alpine meadows under different levels of degradation in the Beiluhe area,and the relationships between soil respiration and biomass,belowground net primary productivity(BNPP)and soil temperature was analyzed.Our results showed that:1)Soil respiration of alpine meadows at different levels of degradation showed similar dynamic characteristics during the growing season.Soil respiration increased first and then decreased along the degradation gradient,which reached the maximum under moderate degradation and significantly changed in the middle of the growing season(P<0.05);2)There was a significant positive linear correlation between the soil respiration and the aboveground biomass,belowground biomass,and BNPP(P<0.05);3)The soil respiration is exponentially correlated with the soil temperature.The temperature sensitivity of the soil respiration changed with the degradation.The Q10 under slight(Q10=3.26)and moderate degradation(Q10=3.22)was higher than that under non-degraded soils(Q10=2.66);however,under severe(Q10=2.49)and extreme degradation(Q10=1.96),this was lower than that under no degradation.The change in the temperature sensitivity is mainly caused by differences in the soil temperature,belowground biomass,and soil organic carbon content under different degradation levels.The results of this study will help further the understanding of the carbon cycle process of degraded grasslands.