Projected Future Changes In Vegetation Over The Tibetan Plateau In The Twenty-first Century

The alpine vegetation ecosystem over the Tibetan Plateau(TP)is sensitive to climate change.In this study,the natural vegetation over the TP in response to projected future climate change is investigated by long-term simulation of CLM4.5-CNDV,NCAR Commninty Land Model coupled with a vegetation dynamic model and Carbon-Nitrogen model driven by the constructed low layer meteorological data built up based on historical NCAR atmospheric data and projected variations under a high Representative Concentration Pathway(RCP8.5)from 19models participating in the Coupled Model Inter-comparison Project Phase 5(CMIP5).We firstly evaluate the future climate change over TP and investigate the possible causes based on the CMIP5 outputs,then projected the future vegetation change in response to climate change under RCP8.5,finally,we discussedthe linkage of vegetation change to climate change.Main conclusions we have drawn are listed as following:(1)the TP is generally getting wetter and warmer in future.The moisture convergence aroused by mean flow change plays a key role for moister TP,which contributes to 53%P-E increase,and mainly works over the southern,southwestern and northwestern TP.The much more abundant moisture because of the global warming contributes positively over three rivers' source(TRS).(2)CLM4.5-CNDV generally reproduces the spatial distribution pattern of leaf area index(LAI)and its linear trend of satellite data,but with overestimated LAI as shown in CMIP5 models due to the seriously overestimated tree coverage and underestimated grasscoverage.The shrub coverage over the TP is well represented.It can basically simulate the spatial distribution of various plant functional types(PFTs).(3)TP projects to begreening in the late 21st century.A significant LAI increasing belt(including the TRS)have been found from southwest to northeast,which is related to the"warm upgrading" of vegetation type.The PFT migration is obvious in the future,the boreal broadleaf deciduous shrub,the boreal needle leaf evergreen tree,the temperate broadleaf deciduous tree and the broadleaf deciduous tree extend to the drier and colder places such as northern and western TP.Needleleaf evergreen tree and broadleaf evergreen tree coverage expandin southeastern TP.(4)The significant increase area of future vegetation well correspondsto the absorbed solar radiation and shallow soil water content,implying the projected future vegetation change over TP is also closely related to the increase of soil moisture,besides temperature rising.