【摘要】 碳交换是影响草地生态系统碳汇功能的关键过程,对气候变暖极为敏感。青藏高原分布着大面积的高寒草原,其碳汇功能对气候变暖的响应对区域碳循环过程具有重要的影响。为探究高寒草原生态系统碳交换过程对增温的响应,2012—2014年,在青藏高原班戈县进行了模拟增温对高寒草原生态系统碳交换过程影响的研究。结果表明,增温对高寒草原碳交换各组分的影响存在年际差异,但总体上对碳交换存在负面影响。3年平均结果显示,增温显著降低了高寒草原地上生物量、总生态系统生产力(GEP)、生态系统呼吸(ER)和净生态系统碳交换量(NEE)(P<0.05),平均降幅分别为15.1%、36.8%、19.2%和51.5%。增温条件下3年平均土壤呼吸(SR)较对照无显著变化(P>0.05),但2013年增温显著降低了SR(P<0.05),降幅达18.1%。增温对SR与ER的比值具有一定的促进作用,最高增幅达到40.0%。GEP、ER、SR和NEE与土壤温度和土壤水分无显著相关(P>0.05),而GEP、ER和NEE与空气温度呈显著的负相关关系(P<0.05)。增温引起的干旱胁迫以及地上生物量降低是导致高寒草原NEE降低的主要原因。研究表明,全球变暖会一定程度降低青藏高原高寒草原的碳汇功能。更多还原

【Abstract】 Carbon exchange is a key process that affects the carbon sink capacity of grassland ecosystems and is very sensitive to climate warming. The Tibetan Plateau is covered by large areas of alpine steppe, which is the main carbon pool and fundamental in regional carbon cycling. The present study investigated the effects of warming on carbon exchange in an alpine steppe ecosystem in Baingoin County, Tibetan Plateau from 2012 to 2014. The results showed that there are interannual differences in the effects of warming on the components of carbon exchange in alpine steppes, but there is a negative effect on carbon exchange as a whole. Three-year average results showed that warming significantly reduced the above-ground biomass, gross ecosystem productivity(GEP), ecosystem respiration(ER), and net ecosystem carbon exchange(NEE) in the alpine steppe(P<0.05), with an average decrease of 15.1%, 36.8%, 19.2%, and 51.5%, respectively. Three-year average soil respiration(SR) did not change significantly(P>0.05) compared with the control under warming conditions, but warming in 2013 significantly reduced SR(P<0.05), by 18.1%. Warming has a certain role in promoting the ratio of SR to ER, with the highest increase reaching 40.0%. GEP, ER, SR, and NEE had no significant correlation with soil temperature and soil moisture(P>0.05), whereas GEP, ER, and NEE showed a significant negative correlation with air temperature(P<0.05). A decrease in drought stress and above-ground biomass caused by warming were the main factors for the decrease of NEE in the alpine steppe. In summary, our study showed that global warming may reduce the carbon sink capacity of alpine steppes in the Tibetan Plateau.更多还原