Spatial-temporal Simulation Of Vegetation Carbon Sink And Its Influential Factors In Shiyang River Basin From 2000 To 2015

Since the industrial revolution,the greenhouse gas content in the atmosphere has increased dramatically,causing the global carbon balance to be severely damaged.The terrestrial carbon cycle is an important part of the global carbon cycle.It is the most basic source of energy for human production and living,and it is most vulnerable to climate change and human activities.The Shiyang river basin is a typical inland river basin in the arid region of northwestern China,and it is also one of the most densely populated watersheds in the inland river basin of China,with the highest utilization of water resources and the most serious ecological environment problems.Therefore,taking the surface vegetation in Shiyang river basin as the research object,using remote sensing image data,meteorological data,DEM data and land use data,we calculated the vegetation carbon sink of the ecosystem in Shiyang river basin by modified CASA model and soil microbial respiration equation.Comprehensively study the temporal and spatial distribution of vegetation carbon sinks and their changing patterns in the Shiyang river basin from both time and space perspectives,and explore its influencing factors from multiple perspectives.To study and explore the causes of spatio-temporal changes in the structure of the carbon sink and the total amount of carbon sinks during the evolution of the river basin ecosystem,thus providing a theoretical basis for the governance of the ecological environment in the Shiyang river basin.The preliminary conclusions are as follows:(1)From 2000 to 2015,the annual NEP spatial distribution of the Shiyang river basin shows a trend of decreasing from southwest to northeast.In the desert area north of Liangzhou,the NEP is low,and most of the areas are below-100 g C·m-2·a-1.The NEP of the Qilian mountain area in the south of Liangzhou is higher than the 300 g C·m-2·a-1 in most areas.The lowest areas of NEP are mainly distributed in the two desert areas of Badan Jilin and Tenggeli,which are located next to Minqin.The highest areas of NEP are mainly concentrated in the mountains area in the southwest,suah as Leng Long Ling and Maomao mountains.Showing the whole distribution,and the north south high-low level.The spatial distribution of NEP in the Shiyang river basin is generally high in the south and low in the north.From 2000 to 2015,75% of the area of Shiyang river basin showed an increase in NEP,of which the area with a significant increase of 2500km2,mainly distributed in the middle reaches of the Shiyang river basin,Liangzhou district and surrounding areas,and the area with extremely significant growth of NEP was 820km2,scattered and distributed in the upper and middle reaches of the Shiyang river basin.The growth of the NEP in the study area indicates that the ecological environment in the Shiyang river basin has gradually improved over the past decade and the growth of vegetation has improved.(2)Overall speaking the distribution of carbon sources and sinks in the Shiyang river basin is simple,performing a striped pattern.Carbon sources are mainly distributed in the desert areas around Minqin oasis.The low carbon sinks areas are mainly distributed in Hexi plain.The high carbon sinks areas are mainly distributed in Qilian mountain area.The spatial distribution of the carbon sources and sinks exhibites significant vertical zonal characteristics.From 2000 to 2015,the area of vegetation carbon sinks in the Shiyang river basin has gradually increased,and the area of carbon sources has gradually decreased.These changes indicate that the carbon sequestration capacity of the vegetation ecosystem in the Shiyang river basin is continuously increasing.(3)The spatial distribution of carbon sources and sinks in the Shiyang river basin is linear with the change in altitude.The carbon sources in the basin are mainly distributed in the middle altitude areas.With the increase of altitude,the carbon source areas are gradually reduced.The carbon sink areas are mainly distributed in the high altitude areas.With the increase of altitude,the carbon sink shows the trend of increasing first and then decreasing.The topographic factors such as slope and aspect can reflect the spatial differences of natural resources such as light,temperature,water and nutrients,then impact carbon sources and sinks indirectly.The carbon sources are mainly distributed in the plain and micro slopes regions,and the carbon sinks are mainly distributed in the slope region.Studies have shown that from 2000 to 2015,the area of vegetation carbon sinks in all areas of elevation,slope,and aspect of the study area showed an increasing trend,and the area of carbon sources showed a decreasing trend.(4)The correlation analysis was made to the temperature,precipitation,solar radiation,NDVI,latitude and longitude,elevation,slope,aspect and monthly average NEP from 2000 to 2015.The results show that the correlation coefficient of temperature,precipitation,solar radiation,NDVI,and NEP are relatively high in the Shiyang river basin,and their spatial distribution characteristics of the correlation coefficients are basically the same.They all show that they are low in the south,high in the north,and from south to north the spatial distribution characteristics of the correlation coefficients that gradually transition from positive correlation to negative correlation.The order of longitude,latitude,altitude,slope and NEP correlation in the basin is “altitude>latitude>slope>longitude”,where elevation and slope are positively correlated with NEP,and longitude,latitude are negatively correlated with NEP,and aspect is not related to NEP.Research shows that from 2000 to 2015,33.42% of the Shiyang river basin area,the trend of human activities on vegetation carbon sink positively influence,and the type of land use in this region is mainly cultivated land.Under the influence of human activities in the study area,with an average annual growth value of NEP was 23367214.35 g C·m-2·a-1;There are 66.58% regions in Shiyang river basin.The human activities have a negative impact on vegetation carbon sinks,and the land use types in the region are mainly deserts and grasslands.Under the action of human activities,the annual average reduction in NEP in the study area is 28906337.12 g C·m-2·a-1.