Review of Researches on Biomass Carbon Stock in Grassland Ecosystem of Qinghai-Tibetan Plateau

It is critical to know Qinghai-Tibetan Plateau’s grassland biomass carbon(C) stock and its dynamics in order to study the regional C cycle and sustainable use of grassland resources.After reviewing the publications,the authors present a summary of methods and results in the studies of biomass C stock in grassland ecosystem of Qinghai-Tibetan Plateau.(1) Four methods are mainly used in this field: searching in literature and documents,field measurement,remote sensing of vegetation/vegetation indices,and process modeling.In the practice,methods of estimation,quality standards for sample collection,and underground biomass estimation are the most important factors impacting the results.(2) According to the published literature,biomass C density of Qinghai-Tibetan Plateau’s grasslands is approximately 223g/m2,and can be translated to a total grassland biomass C stock of 277 Tg C(1Tg=1012g).(3) The estimation results based on remote sensing indicate that the biomass C stock of Qinghai-Tibetan Plateau’s grasslands increased over the past 20 years,suggesting that alpine grasslands might have functioned as a biomass C sink.(4) The above ground biomass C stock of Qinghai-Tibetan Plateau’s grasslands is strongly affected by precipitations,while the role of temperature is unclear.In addition,human activities are considered to be a crucial factor affecting grassland biomass C stock as well.Problems remain in the studies of biomass C stock in grassland ecosystem of Qinghai-Tibetan Plateau;more thorough investigations are needed in the fields such as data acquirement in the basic field measurements,optimization of algorithms for remotely-sensed vegetation indices,and process modeling of carbon-nitrogen-water coupling cycle in the alpine ecosystem.