A Study On The Impact Of Land Use Data On Carbon Sources And Sinks In China's Terrestrial Ecosystems Simulated By Dynamic Vegetation Models

One of the main characteristics of global climate change is global warming.The main factor that causes this warming trend is the radiation forcing effect brought by the greenhouse gas is CO₂.The study of carbon cycle is to clarify the carbon pools and the fluxes between them.Terrestrial ecosystem is the core of global change research and its Carbon cycle process is significantly affected by human activities and climate change.Vegetation is an important part of the terrestrial carbon cycle.Between ground and atmospheric systems,vegetation plays an important role in climate,hydrology and biological cycle by significantly affecting the energy balance through photosynthesis.Land use/cover change can alter carbon,water and nutrient cycles in terrestrial ecosystems by affecting vegetation.Under the background of the intensification of global climate change and the increasing frequency of human activities,it is of great practical significance to study the impact of land use/cover change on the carbon cycle process,and to evaluate the regional environment and carbon source and sink effects..Dynamic vegetation model is an effective tool for the impact of land use/cover change on the carbon cycle of terrestrial ecosystems.In this study,we first analyzed the changes and trends of carbon pools in terrestrial ecosystems in China from 1980 to 2015 using the results of multi-model simulations.Then,the sensitivity of carbon cycle model to land use data in the driving data is further studied.Since most model generally adopt the Global land use data Hyde(Historical Database of the Global Environment)as default landuse data,which there is often a large error in China.Therefore,the applicability of multi-source data to Hyde in China during1980-2015 was evaluated,and the land use driving field of Hyde model was further modified.The VEGAS model was selected to conduct comparative simulation of the ecosystem carbon cycle in China.The main results are as follows:(1)Analysis of carbon source and sink changes in China's ecosystem from 1980 to 2015based on multiple modelsThe carbon source and sink changes in China can be divided into two stages:1980-1990and 1990-2015.From 1980 to 1990,China was a carbon source as a whole,which was mainly caused by the decline of carbon storage in vegetation carbon pool.During this period,China released about 0.17-2.7Gt C,equivalent to about 0.017-0.27Gt C/yr of carbon source size.From1990 to 2015,China showed a carbon sink as a whole.The growth of vegetation carbon pool and soil carbon pool jointly contributed to the carbon sink in China.During this period,the ecosystem in China absorbed about 0.35-4.78Gt C in total,which is about 0.014-0.19Gt C/yr.The carbon sinks in China mainly occur in the big and small Xing'an Mountains,Changbai Mountains,and in the southwest and southeast hilly areas.From 1980 to 1990,the carbon sources in China mainly occurred in the traditional agricultural areas such as Sanjiang Plain,Songnen Plain,North China Plain and Sichuan Basin.From 1990 to 2015,China's carbon sources mainly occurred in the Sanjiang Plain and Songnen Plain.(2)The applicability of HYDE land use data in ChinaHYDE does not accurately and timely grasp the dynamic changes of total arable land and urban area in China from 1980 to 2015.In terms of spatial distribution,HYDE underestimates the expansion of farmland in Northeast China,and overestimates the growth of farmland in Huang-Huai-Hai,the middle-lower reaches of the Yangtze River Plain,and even shows the direction of the change of farmland area contrary to the reality in some time periods and specific regions.(3)Simulation results of VEGAS model after optimizing the land use driving fieldDuring 1980-2015,the vegetation carbon pool decreased by 0.03Gt C,while the soil carbon pool increased by 1.51Gt C,and the total biological organic carbon pool increased by 1.49Gt C.Taking 2002 as the cut-off point,before 2002,the carbon storage of vegetation decreased,while that of soil increased.After 2002,the carbon storage of vegetation increased rapidly and significantly.The simulation results show that the carbon sink scale of terrestrial ecosystem in China is about 0.13Gt/yr,which can offset about about 9.1%of China's fossil fuel carbon emissions in the same period(calculated as the average of 2000s).The simulation results under the hypothetical future scenario show that China's terrestrial ecosystem will maintain the above scale of carbon sink by 2030,and the annual total carbon sink will be about 0.15Gt C/yr.