| The terrestrial ecosystem carbon cycle is an important part of the global carbon cycle.It is the life subsystem and basic energy source of human life.It quantitatively and qualitatively evaluates the potential of regional ecosystem carbon sinks through indicators,and provides scientific research for global climate change and carbon cycle mechanism research.With the frequent human activities and the rapid development of the tertiary industry,the content of greenhouse gases such as carbon dioxide in the atmosphere is exacerbated and the land-atmospheric carbon balance is destroyed.The Western Sichuan Plateau is a typical ecological climate sensitive area in China,and is a key area in the spatial distribution of the ecological protection red line in Sichuan Province.Its high mountains,valleys,plateaus and other landforms coexist,geological disasters occur frequently.the territory contains rich biological species and vegetation type.This paper takes the western Sichuan plateau as the research area,based on MODIS data and surface meteorological observation data.Using the CASA model and regression model to estimate the ecological net primary productivity(NPP)and soil respiration(Rh)of the Western Sichuan Plateau,calculate the NEP.To further determine the carbon source/sink of regional ecosystems,and explore the spatial and temporal distribution characteristics and changes of carbon sources/sinks in the western Sichuan Plateau.Under the condition of not considering the natural factors,from the altitude,slope,aspect,meteorological factors,vegetation types and other natural factors to explore the western Sichuan plateau ecosystem evolution process of carbon source/carbon sink structure and its impact mechanism.This provides a theoretical basis for the management of the ecological environment in the western Sichuan Plateau.The following conclusions were initially obtained:(1)From 2000 to 2015,the NEP of the Western Sichuan Plateau showed a spatial pattern of high southeast and low northwest,showing the area of carbon sink(NEP>0)with an area of about 217,700km2,accounting for 87.8%of the total area of the Western Sichuan Plateau The area of the carbon source(NEP<0)accounts for about 12.2%of the total area of the western Sichuan Plateau.The average cumulative carbon sequestration in the study area from 2000 to 2015 was 2443.36 gC/m2,and the total carbon sequestration in the entire study area was about 0.687 PgC;the average cumulative carbon emissions in the western Sichuan Plateau in the past 16 years was 1153.28 gC/m2,and the carbon emissions Reached 0.035 PgC.Different administrative regions present different carbon source and carbon sink functions.Jiuzhaigou County,Mao County,Luding County,Danba County,Heishui County,Li County,Malkang County,and Xiaojin County have stronger carbon sink functions,and Shiqu County has relatively higher carbon sink capacity Weaker.Overall,the western Sichuan Plateau mainly exhibited carbon sequestration from 2000 to 2015,and the NEP ecosystem in the Western Sichuan Plateau showed an increasing trend,indicating that the area around the western Sichuan Plateau rich in vegetation has a gradual improvement in the amount of carbon sequestration in the surrounding environment.(2)According to the NEP long-term sequence changes in the Western Sichuan Plateau ecosystem from 2000 to 2015,the average NEP is 125.52 gC·m-2·a-1 and the maximum and minimum values appear in 2009 and 2000,The range is 38.76 gC·m-2·a-1.In general,the carbon sink capacity of the western Sichuan Plateau is enhanced,and the enhancement rate is 1.008 gC·m-2·a-1.Choosing 2006 and 2012 as time nodes,NEP showed a trend of increasing first and then decreasing between 2000-2006 and 2006-2012.Among them,NEP reached the maximum value in 2004 and 2009,and the carbon sink capacity was the strongest.They are 179.36 gC·m-2·a-1 and 180.06 gC·m-2·a-1 According to the spatial distribution of monthly average NEP in the Western Sichuan Plateau from 2000 to 2015,the monthly average of NEP from January to December showed the same growth pattern as vegetation.In the best period of vegetation growth,the carbon sequestration capacity accumulates rapidly,and the maximum NEP appears in July at 35.58 gC·m-2·a-1,with the most significant carbon sink effect.(3)In the past 16 years,NEP and precipitation in the western Sichuan Plateau have been positively correlated,with a regional average correlation coefficient of 0.18.The area of NEP and precipitation is 129,700 km2,accounting for 51.80%of the total area,and the area of negative correlation is 127,700 km2,Accounting for 48.2%of the total area of the Western Sichuan Plateau.The impact of precipitation on the NEP in the western Sichuan Plateau is mainly in two aspects.On the one hand,in terms of precipitation promoting regional vegetation growth,such as the region itself has less rainfall,and the terrain is relatively flat,without considering other factors,with the increase of precipitation Soil moisture increases,which promotes vegetation growth and development,thereby improving carbon sequestration capacity.On the other hand,from the perspective of precipitation inhibition of regional vegetation growth,for alpine canyons,increased precipitation promotes regional natural disasters and has a destructive effect on vegetation.In the past 16 years,NEP has a positive correlation with annual average temperature in the Western Sichuan Plateau.The regional average correlation coefficient is 0.16.The temperature has a limited effect on NEP.The reason may be that the temperature affects the photosynthesis and respiration of vegetation in the Western Sichuan Plateau to a certain extent.The upper limit is related to vegetation growth.The area where solar radiation is positively correlated with NEP in the Western Sichuan Plateau is 184,200 km2,accounting for 73.52%of the total area.In terms of precipitation and temperature,some areas in the study area are more sensitive to solar radiation.(4)The value of NEP in the western Sichuan Plateau increases first and then decreases with altitude.The number of carbon source grids in the study area has a linear relationship with altitude,and increases with altitude.The number of carbon sink grids increases with altitude.The altitude changes fluctuatingly,with the altitude increasing first and then decreasing.The NEP in the western Sichuan Plateau shows a trend of decreasing first and then increasing with the slope.The slope affects the types of regional vegetation.With the increase of the slope,the transition from grassland to woodland,because the distribution of vegetation type makes the NEP value of this slope zone increase obviously.The number of sink grids shows increasing-decreasing-increasing-decreasing fluctuations with increasing slope;the slope direction has little effect on NEP in the western Sichuan Plateau.According to different vegetation types,carbon sequestration capacity is different.Vegetation NEP has obvious stratification.Among them,deciduous forest,coniferous forest and mixed forest have stronger carbon sink capacity,corresponding to higher NEP value;corresponding to different land use types in the study area NEP is:forest land>cultivated land>grassland>unused land>water area. |
PDF Full Text Request