Abstract:

To scientifically evaluate the carbon sequestration effects of ecosystem in Lhasa under the background of global warming, account for the benefits of carbon sequestration in ecological projects, and explore the improvement path for carbon sequestration in future, NPP was used to measure the dynamic level of carbon sequestration of ecosystem systems in Lhasa. The study carried out a quantitative analysis of carbon sequestration in the Lhasa ecosystem based on the CASA model, and collected multi-source data such as land use, vegetation types, meteorology and NDVI, remote sensing images in Lhasa. Using MRT, ArcGIS, and ENVI software, we performed batch processing on remote sensing images, including mosaic, projection conversion, factor conversion and cropping, and the maximum synthesis method (MVC) was used to obtain monthly and year-by-year NDVI data in the Lhasa River Basin from 2000 to 2020. The results showed that the overall carbon sequestration capacity of vegetation in Lhasa was between 50-400 g C/m². From the county scale, it was found that the average carbon sequestration capacity of Linzhou County, Dazi District and Mozhu Gongka County was relatively high, and the average net primary vegetation productivity remained at 150 g C/m² and above all year round. Forests were the main source of carbon sink in Lhasa, fixing 55% carbon dioxide, followed by grasslands and wetlands, which provided 23% and 21% of carbon sink contributions, respectively. The overall average vegetation carbon sequestration capacity in Lhasa was 218 g C/m², and the increase in temperature mainly increased the carbon sequestration capacity of vegetation at high altitudes. In conclusion, it reveals the carbon sequestration process, rate and benefits of typical ecological engineering, clarifies the change of carbon reserves and carbon neutralization contribution under ecological restoration, such as Lhasa's north-south mountains, degraded grasslands, Lhasa River and important wetlands, compares the differences and impact mechanisms of ecosystem carbon reserves under the implementation of different ecological projects, and gives suggestions on the improvement pathway of the synergy of ecological carbon sequestration and functional restoration, aiming to help the construction of ecological civilization in Lhasa and even the whole Tibet with scientific and technological innovation, and provide technical support for achieving the goal of carbon peak and carbon neutralization.

Key words: climate change, carbon sequestration benefits, comprehensive analysis