| Maduo County in Sanjiangyuan district is"county of thousand lakes"and"China water tower".It is the hinterland of Qinghai Tibet Plateau.It is located in the National Nature Reserve of Sanjiangyuan and has an important ecological status.Maduo County is mainly composed of alpine grassland ecosystem with huge carbon storage,which is also the basis for the survival of local herdsmen and has great ecological production value.But its ecosystem structure is single and highly fragile,once destroyed,it is irreversible.Therefore,the quantitative evaluation of carbon storage and spatial distribution of alpine grassland ecosystem can provide the basis for the optimization of regional grassland utilization structure,provide reference for the next step of ecological compensation policy,and promote the harmonious development of local economic,social and ecological construction.In this paper,Maduo County in the source region of the three rivers was selected as the study area.The carbon storage function of Alpine Grassland Ecosystem in Maduo County was evaluated by invest model,and the NPP of grassland was calculated by improved CASA model to evaluate the carbon fixation function.Based on the measured grassland aboveground biomass and soil organic carbon basic data in2015,combined with the same period of remote sensing images,the grassland vegetation biomass estimation model based on remote sensing data was established,and the biomass carbon pool data and spatial distribution in the study area were retrieved by Arc GIS remote sensing.Based on the above research,the following conclusions are drawn:(1)Based on the remote sensing image extraction of normalized vegetation index(NDVI)raster data of Maduo County in the source region of Sanjiang River,the best inversion model between NDVI and aboveground biomass of grassland is cubic polynomial regression model:y=-1686x~3+2328.5x~2-907.57x+122.28(R~2=0.5986,n=70).In the formula,y is the estimated aboveground biomass(g/m~2),and x is the NDVI value.The results showed that the highest aboveground biomass was82.528g/m~2,the underground biomass was 653.623 g/m~2,and the total grassland biomass was 736.152g/m~2.(2)Based on the LUCC chart and the data of three carbon pools,invest model classified and evaluated the carbon storage of corresponding land types in each carbon pool.The results showed that the highest coverage of aboveground biomass,underground biomass,soil carbon storage and total carbon storage was 110 Mg/km~2,870 Mg/km~2,8110 Mg/km~2and 9090 Mg/km~2.The carbon storage of the aboveground part,underground part,soil carbon storage and total carbon storage were 80 Mg/km~2,630 Mg/km~2,7490 Mg/km~2and 8200 Mg/km~2.The carbon storage of aboveground part,underground part,soil and total carbon storage of low coverage grassland were70 Mg/km~2,540 Mg/km~2,6110 Mg/km~2and 6720Mg/km~2respectively,and the carbon storage of some lakes,glaciers and Gobi desert was 0.(3)The carbon storage of high coverage grassland is 7.7901 million tons,equivalent to 78 million US dollars;the carbon storage of medium coverage grassland is 137.8092 million tons,equivalent to carbon storage value of 1.378 billion US dollars;the carbon storage of low coverage grassland is 47.1341 million tons,equivalent to 471 million US dollars,and the total carbon storage is 192.7334 million tons,The total value of carbon storage is 1.927 billion US dollars,which has high ecological value.The average NPP of grassland in Maduo County is 125.36 g C/m~2,the total amount is 27.8556 million tons,and the carbon sequestration value is 279million US dollars. |
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