Abstract
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.
Highlights
China’s terrestrial ecosystems have been estimated to have sequestered 20.8–26.8% of the carbon released in industrial CO2 emissions during 1981–2000 [1]
Estimating carbon storage in vegetation and soil is essential for understanding current levels of carbon pools, and for mapping how these terrestrial ecosystem carbon pools change over time, which is critical for evaluating the global carbon budget, the main predictor of climate change [9,10]
For the two alpine grassland types, the median ratio of Below-ground biomass (BGB) to above-ground biomass (AGB) was 20.40, and a higher median ratio of BGB to AGB was observed in the alpine meadow (21.38) (Table 1)
Summary
China’s terrestrial ecosystems (both vegetation and soils) have been estimated to have sequestered 20.8–26.8% of the carbon released in industrial CO2 emissions during 1981–2000 [1]. A large number of estimates of the forest ecosystem carbon stocks in China have been reported [3,4], but a comprehensive assessment of carbon storage in China’s grasslands is still lacking [5]. Estimating the level of carbon stored in living vegetation and soil organic matter in grassland. Estimating carbon storage in vegetation and soil is essential for understanding current levels of carbon pools, and for mapping how these terrestrial ecosystem carbon pools change over time, which is critical for evaluating the global carbon budget, the main predictor of climate change [9,10]
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