Response Of Weathered Carbon Sinks And Soil Formation To Climate Change And Ecological Restoration In China

China is one of the countries where carbonate rocks are widely distributed in the world.The chemical weathering process of carbonate rocks not only forms weathering carbon sinks,but also forms soils.However,some key issues have not been solved.It is mainly manifested in the following aspects:First,the previous research on the chemical weathering carbon sink and soil formation rate of carbonate rocks was mostly based on long-term positioning observations at single or multiple profile scales,but due to the lack of monitoring data at the regional or national scale,what is the karst carbon sink generated during the chemical weathering of carbonate rocks at the regional or national scale?A series of problems that plague the development of karst areas,such as soil formation rate,have not been answered scientifically,and it is difficult to match the regional or national scale research in the practical application process.Secondly,the change process of climate,soil moisture and vegetation in carbonate rock areas is special and complicated,but the interaction between climate change,soil moisture and vegetation and weathering processes is still unclear.In this paper,firstly,using lithology,climate data and vegetation data,the climatic and environmental factors affecting the carbon sink of chemical weathering of carbonate rocks and their evolution characteristics are discussed,and based on the correlation between published data of ion concentration stations in different river basins in China and climate and vegetation data,the spatial image metadata of calcium ion activity coefficient(γCa²⁺)and bicarbonate ion activity coefficient（γHCO₃^-）in China are inversed.Secondly,based on the classical thermodynamic dissolution model,the carbon sink of chemical weathering of carbonate rocks is calculated by using the inversion data ofγCa²⁺andγHCO₃^-.Thirdly,the chemical weathering rate of carbonate rock is calculated according to different dissolution rate,acid insoluble content,carbonate content,bulk density of carbonate rocks and soil formation rate of non-carbonate rocks.Finally,based on the Lindeman-Merenda-Gold（LMG）method,the relative importance of factors such as precipitation（MAP）,evapotranspiration（ET）,soil water（SM）and normalized vegetation index（NDVI）on the changes of chemical weathered carbon sink（CCSF）and soil formation rate（SFR）of carbonate rocks is quantified,and the results are as follows.（1）China’s CCSF is 22.76 t CO₂/km²/yr,higher than the global average（15.77 t CO₂/km²/yr）,the total CCS is 4772.67×10⁴t CO₂/yr,and China contributes 14.91%of the global CCS with a carbonate area of 252.98×10⁴km².The SFR flux was 18.79t/km²/yr,of which SFR_HCwas 10.82t/km²/yr,SFR_CIwas 42.15 t/km²/yr,and SFR_CAwas up to 92.18t/km²/yr.（2）In terms of spatial distribution,the overall CCSF and SFR in China gradually decreased from southeast to northwest,among which the CCSF in the karst area in the south was 33.14 t CO₂/km²/yr,and the SFR was located at 6～65 t/km²/yr,and the flux was 19.51 t/km²/yr;The CCSF in the northern karst zone was 7.27 t CO₂/km²/yr,and the SFR was located at 6～62 t/km²/yr,with a flux of 15.82 t/km²/yr.The CCSF in the karst area of Qinghai-Tibet was 12.93 t CO₂/km²/yr,and the SFR was located at 6～61t/km²/yr,with a flux of 20.04 t/km²/yr.（3）The chemical weathering process of different types of carbonate rocks was obvious,among which the limestone area was 184.50×10⁴km²,the CCSF was 21.51 t CO₂/km²/yr,and the CCS was 2222.63 t CO₂/yr,accounting for 61.26%of China’s CCS.The area of dolomite was 7.08×10⁴km²,CCSF was 23.57 t CO₂/km²/yr,CCS was 135.76 t CO₂/yr,accounting for 3.74%of China’s CCS.The mixed rock area is61.41×10⁴km²,the highest CCSF is 25.59 t CO₂/km²/yr,and the CCS is 1136.71 t CO₂/yr,accounting for 31.32%of China’s CCS.（4）The weathering soil formation rate of different carbonate rocks are also very different.The soil formation rate of continuous carbonate rock（HC）,Carbonate rocks are sandwiched with clastic rock combination（CI）and Combination of carbonate rocks and clastic rocks（CA）are 10.82 t/km²/yr,42.15 km²/yr and 92.18 t/km²/yr,respectively.（5）The contributions of MAP,ET,SM and NDVI to CCSF were 55.7%,41.3%,1.6%and 0.96%,respectively,among which the increase of MAP was the main contributor to the rise of CCSF in China in the past 30 years,and the enhancement of evaporation offset the positive contribution of some precipitation increase to CCSF.MAP,SM and NDVI contributed positively to the increase of SFR,among which the contribution rates of MAP to SFR_HC,SFR_CIand SFR_CAwere 47.64%,48.14%and44.90%,respectively,which were the factors that contributed the most to SFR among all the factors considered.The contribution rates of SM to SFR_HC,SFR_CIand SFR_CAwere 8.07%,7.30%and 8.26%,respectively.The contribution rate of NDVI to SFR_HC,SFR_CIand SFR_CAwas relatively low,8.87%,7.11%and 7.47%,respectively.The increase of ET to SFR_HC,SFR_CIand SFR_CAwas mainly negative,with contribution rates of 34.93%,37.94%and 39.38%,respectively.In a word,we evaluate the chemical weathering carbon sink potential and soil formation rate of China carbonate rocks.What is the magnitude of karst carbon sinks produced during the process of chemical weathering of carbonate rocks in a regional or national scope?A series of problems that puzzle the development of karst areas,such as the rate of soil formation.The contribution of climate change and ecological restoration factors to carbon sink and soil formation rate of chemical weathering of carbonate rocks is analyzed quantitatively.It solves the problem that the interaction between climate change,soil moisture,vegetation and weathering processes is not clear.This work has certain reference value and significance for the diagnosis of carbon neutrality in China and the world and the study of ecological environment management in karst areas.