The alpine grassland ecosystem can sequester a large quantity of carbon, yet its significance remains controversial owing to large uncertainties in the relative contributions of climate factors and grazing intensity. In this study we surveyed 115 sites to measure ecosystem carbon storage (both biomass and soil) in alpine grassland over the Qinghai Plateau during the peak growing season in 2011 and 2012. Our results revealed three key findings. (1) Total biomass carbon density ranged from 0.04 for alpine steppe to 2.80 kg C m-2 for alpine meadow. Median soil organic carbon (SOC) density was estimated to be 16.43 kg C m-2 in alpine grassland. Total ecosystem carbon density varied across sites and grassland types, from 1.95 to 28.56 kg C m-2. (2) Based on the median estimate, the total carbon storage of alpine grassland on the Qinghai Plateau was 5.14 Pg, of which 94% (4.85 Pg) was soil organic carbon. (3) Overall, we found that ecosystem carbon density was affected by both climate and grazing, but to different extents. Temperature and precipitation interaction significantly affected AGB carbon density in winter pasture, BGB carbon density in alpine meadow, and SOC density in alpine steppe. On the other hand, grazing intensity affected AGB carbon density in summer pasture, SOC density in alpine meadow and ecosystem carbon density in alpine grassland. Our results indicate that grazing intensity was the primary contributing factor controlling carbon storage at the sites tested and should be the primary consideration when accurately estimating the carbon storage in alpine grassland.
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机译：高寒草原生态系统可以吸收大量的碳，但是由于气候因素和放牧强度的相对不确定性很大，其重要性仍然存在争议。在这项研究中，我们调查了115个站点，以测量2011年和2012年生长期高峰期青海高原高寒草地的生态系统碳存储（生物量和土壤）。我们的结果揭示了三个关键发现。 （1）总生物量碳密度从高寒草原的0.04到高寒草甸的2.80 kg C m -2 不等。在高寒草地上，土壤有机碳（SOC）的中值估计为16.43 kg C m -2 。不同地点和草地类型的生态系统总碳密度在1.95至28.56 kg C m -2 之间变化。 （2）根据中位数估算，青海高原高寒草地的总碳储量为5.14 Pg，其中94％（4.85 Pg）为土壤有机碳。 （3）总体而言，我们发现生态系统的碳密度受气候和放牧的影响，但程度不同。温度和降水的相互作用显着影响了冬季牧场的AGB碳密度，高寒草甸的BGB碳密度和高寒草原的SOC密度。另一方面，放牧强度影响夏季牧场的AGB碳密度，高寒草甸的SOC密度和高寒草原的生态系统碳密度。我们的结果表明，放牧强度是控制受测地点碳储量的主要因素，也是准确估算高寒草地碳储量的主要考虑因素。
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