Estimating Net Primary Productivity And Carbon Storage Of Vegetation In Ili River Basin Based On CASA Model During 2000–2016

The description and understanding of the response and feedback of terrestrial ecosystem carbon storage to climate variables is essential for modeling exercises.Therefore,many methods based on modeled or locally measured data have been developed to assess the carbon storage between the biosphere and the atmosphere.Comparing biogeochemical models with terrestrial ecosystem carbon storage measurements,potential modeling constraints can be identified in the integrated framework of models and data.From this perspective,considering the initial equilibrium conditions of the ecosystem carbon pool level is a universal process that has potential impact on the estimation of net carbon flux and overall model development.Based on quantitative remote sensing and geographic analysis techniques,this study used CASA model to invert the NPP values from 2000 to 2016 in Ili Valley,and used the empirical model to calculate the vegetation carbon storage,and analyzed the temporal and spatial distribution characteristics of vegetation carbon storage in the Ili Valley.We discussed the influencing factors from some aspects such as nature and society.The results show:(1)The average annual net primary productivity of vegetation in the Ili Valley between 2000 and 2016 varies from 180 to 230 gC/(m~2·a),with the maximum occurring in 2016(south of Chapchal County),with the average value of 228.04gC/(m~2·a);the lowest value occurred in 2008(southern Xinyuan County),with an annual average of 182.55 gC/(m~2·a).(2)From the correlation coefficient,the correlation between vegetation net primary productivity and total annual precipitation,total summer precipitation,total spring precipitation is relatively large,indicating that the total annual precipitation is the main factor which affects the vegetation NPP;There is a negative correlation between the highest average temperature in summer and vegetation NPP,indicating that the higher the highest average temperature in summer,the lower is the vegetation NPP.(3)The carbon density in the study area showed a trend of decreasing first and increasing later.The highest value appeared in 2016,and the lowest value appeared in2008.From the vegetation type,the vegetation type with the highest average carbon density was the arbor garden(139.45).g/m~2),followed by deciduous broadleaf forest(133.97 g/m~2),and the lowest is the shrub swamp(92.82 g/m~2).(4)During the period from 2000 to 2016,the vegetation carbon storage in the Ili Valley was generally increased at a speed of 2.021×10~4 tC/a.Among them,the fastest was grassland,and the lowest was sparse grassland.