Vegetation Growth Simulation of the Community Land Model in the Southwest China

Under the background of global warming， the temperature has increased frequently in the southwest， and the ecosystem in the southwest is vulnerable and sensitive to climate change in the past few decades.The southwest region is an important carbon sink area in China.Monitoring and simulation of vegetation variations is of great significance for an in-depth understanding of the carbon cycle mechanism and promoting sustainable economic development.Leaf Area Index （LAI） and Gross Primary Productivity （GPP）， as indicators of vegetation health and ecosystem stability， can be used to quantify vegetation studies and characterize dynamic changes of vegetation.Vegetation dynamic Model is one of the important means to study vegetation growth and change.Community Land Model （CLM） is one of the earliest land model with the function of vegetation dynamic simulation， the most developed and widely used land model in the world.Model evaluation is an indispensable part of model development， which provides a basis for model development and improvement.This study uses the Community Land Model version5 （CLM5） to simulate and analyze the spatial and temporal variations of the leaf area index （LAI） and total primary productivity （GPP） in the southwest region across 2000 -2016， and compare it with multiple sets of remote sensing data to evaluate LAI and GPP simulations of CLM5 in the southwest.The results showed that CLM5 could well simulate the seasonal variation of LAI and GPP in southwest China， but overestimated LAI in growing season.The CLM5 can reasonably simulate LAI of temperate deciduous broadleaf shrubs， LAI， GPP of alpine C3 meadow and GPP of C3 meadow.CLM5 could capture the spatial distribution pattern of LAI and GPP in the southwest， which is decreasing from southeast to northwest， but CLM5 overestimates LAI in the whole southwest region， especially in the karst landform area of Guizhou.Contrary to the overestimation of LAI simulation， CLM5's overall simulation of GPP in Southwest China is low， especially in Yunnan province.In addition， CLM5 has a poor simulation of LAI and GPP trend in the southwest.Especially in most parts of Yunnan， remote sensing data mainly shows an upward trend， while CLM5 simulation shows a downward trend.In a word， CLM5 can simulate the seasonal change and spatial distribution of LAI and GPP in the southwest， but the simulation of the trend in some areas of Yunnan and Guizhou is poor， and more in-depth parametric schemes for the development of farmland in Sichuan Basin， Yunnan forests， and karst vegetation in Guizhou are needed to improve the simulation.