Research On Spatiotemporal Changes And Influencing Factors Of Vegetation Carbon Sequestration Capacity In The Beijing Tianjin Sandstorm Source Control Area

Since the 20th century,global carbon emissions have grown rapidly,and the global carbon balance has been constantly disrupted.Vegetation is the main body of terrestrial ecosystems and plays a crucial role in regulating global carbon balance and slowing down global warming.Protecting and repairing the structure and function of terrestrial ecosystems is an important way to achieve"dual carbon"and is the cleanest,safe,economical,and effective way to increase carbon sinks.How to quantify the vegetation carbon sequestration capacity of terrestrial ecosystems is a common scientific issue in the research fields of terrestrial surface ecosystems and ecology.Net Ecosystem Productivity(NEP)is a key flux that characterizes the carbon sequestration capacity of vegetation and an important indicator of ecosystem health.The Beijing Tianjin sandstorm source control project area is one of the most serious engineering control areas for ecological environment problems in the semi-arid regions of northern China.The quantitative analysis of NEP can provide the important basis for understanding the carbon cycle process in arid areas and formulating reasonable ecological control measures.In this research,the Beijing Tianjin sandstorm source control area was taken as the research area.Firstly,this study analyzed the temporal and spatial pattern and variations of NEP in the sandstorm source control area of Beijing and Tianjin from 2000 to 2020by using remote sensing data.Then,this research used the change rate and amount of vegetation coverage to identify the ecological engineering areas with carbon sequestration benefits in the Beijing Tianjin sandstorm source control area,and analyzed the temporal and spatial dynamics of NEP.Furthermore,the natural factors and human activities affecting NEP were clarified quantitatively.The main results are as follows:(1)In 2020,the average NEP of the Beijing Tianjin sandstorm source control project area was 110.09 g C/(m~2·a),mainly a carbon sink area,with an area of approximately 3.591×10~5 km~2,accounting for 78.80%of the total area of the research area.From 2000 to 2020,the NEP in the Beijing Tianjin sandstorm source control project area showed an increasing trend,with an interannual change rate of 4.118g C/(m~2·a).Among them,the area with an increasing trend of NEP accounted for 74.91%of the total area,and the significantly increased area was mainly distributed in the southern part of the study area,accounting for 55.16%of the total area;only 0.15%of the regions showed a downward trend in NEP,mainly distributed in the northern arid grassland desertification control area,and distributed in patches.The NEP of different ecosystems in descending order was forest land,farmland,and grassland.Among them,forest land has a strong carbon sequestration effect,and its NEP showed an upward trend,indicating a greater potential for carbon sequestration in the future.The grassland area accounted for 70%of the research area,and its total carbon sequestration was much higher than other types,showing an increasing trend.(2)The area of ecological engineering area in 2000-2005,2006-2010,2011-2015 and 2016-2020 were 76324 km~2,43172 km~2,92642 km~2 and 71118 km~2respectively.As time goes by,the ecological engineering area expanded from the southern and northern regions to the middle regions.The ecosystem in the ecological engineering area was dominated by grassland,forest and farmland.The forest area showed an increasing trend,the grassland area fluctuated,and the farmland area showed a downward trend.The average value and growth rate of NEP in the ecological engineering area in 2000-2005,2006-2010,2011-2015 and 2016-2020 were greater than those in the overall study area.(3)The primary influencing factor of NEP in Beijing Tianjin sandstorm source control project area was annual precipitation.Secondly,the implementation of ecological engineering was also an important influencing factor of NEP.The impact of factors on the NEP in the Beijing Tianjin sandstorm source control project area was not independent,but rather manifested as mutual or nonlinear enhanced interactions.