Response Of Rock Weathering Carbon Sink To Climate And Vegetation Changes In China

The Rock Chemical weathering Carbon sink（RCS）has been included in one of the technical pathways for removing atmospheric carbon dioxide by the Intergovernmental Panel on Climate Change（IPCC）,alongside marine and vegetation carbon sinks.At the same time,RCS is also an important part of the global carbon sink and plays an important role in the global carbon cycle and climate change.However,the spatiotemporal pattern and evolution trend of RCS in China since the21st century are not clear.In addition,the impacts of climate change and vegetation change on China’s RCS are not clear,which affects the in-depth understanding of China’s carbon cycle.Therefore,based on high-precision hydrometeorological data from2000 to 2020,using the Suchet and Hartmann model,combined with pixel based univariate regression trend analysis,partial correlation analysis,and spatial relative contribution rate analysis,this study conducted a systematic and quantitative study of the magnitude,spatiotemporal pattern,and response to climate change and vegetation change in RCS.The results show that:（1）The spatio-temporal pattern and evolution trend of various influencing factors are revealed.In terms of spatiotemporal evolution,the difference between temperature,soil water,precipitation,and actual evapotranspiration showed a slight downward trend,while precipitation,actual evapotranspiration,solar radiation,and leaf area index showed an upward trend.On a multi-year average scale,the average temperature in China from 2000 to 2020 was 13.07℃,the precipitation was 979.88 mm yr^-1,the actual evapotranspiration was 412.82 mm yr^-1,the water profit and loss was 517.04 mm yr^-1,the soil water level was 0.2 m³m^-3,the solar radiation level was 771.11 Wm²,and the leaf area index was 14.72 m²m^-2.On a provincial scale,Hainan Province has the highest average temperature and evapotranspiration,Guangdong Province has the highest average precipitation,the difference between precipitation and actual evapotranspiration,Shanghai has the highest soil water level,Yunnan Province has the highest solar radiation magnitude,and Fujian Province has the highest leaf area index.（2）Based on the support of Suchet model and Hartmann model,the magnitude of China’s RCS in pixel scale and latitude direction is calculated,and a set of China’s 1km×1km high-resolution RCS data set from 2000 to 2020 is formed.It was found that the Rock weathering carbon Sinks Flux（RCSF）and Full Rock weathering carbon Sinks（FRCS）of in China were 3.46 t km^-2yr^-1and 17.32 Tg C yr^-1,respectively.China’s FRCS(17.32 Tg C yr^-1)account for 8.33%-10.53%of the net carbon sink of China’s terrestrial ecosystems(0.19-0.24 Pg C yr^-1).And gradually decreases with increasing latitude.It is mainly concentrated in the eight provinces in Southwest China and the south of Hu Line.The south area is mainly larger than 4 t km^-2yr^-1,while the Hu line is mainly between 3-4 t km^-2yr^-1.（3）RCS in China are spatially heterogeneous on a large regional scale.Chinese RCS are mainly distributed in the karst areas of eight provinces in southwest China with Guizhou as the core,especially in the border areas of Yunnan,Guizhou,Guangxi,Guizhou,Hunan and Hubei.Carbonate rocks with faster widespread weathering rate have a much higher carbon sink capacity than other regions in China.Compared with silicate rocks,SC,SM（76%）and MT（75%）rocks with higher carbonate weathering ratio are mainly distributed in this region.（4）In the carbonate rock with SC as the typical representative calculated in the study,its weathered carbon sink during the study period is 9.47 t km^-2yr^-1.It is higher than SU(1.46 t km^-2yr^-1),VB(1.71 t km^-2yr^-1),PB(1.63 t km^-2yr^-1)and other rocks.（5）Eight provinces in southwest China are high concentration areas of RCS.Guizhou Province contributed the most RCSF with 11.79 t km^-2yr^-1.Guangxi Autonomous Region contributed the most FRCS,and its FRCS(0.21 Tg C yr^-1)accounted for 11.83%of the national total(1.73Tg C yr^-1).In terms of the evolution trend of provinces,China’s FRCS fluctuated,with the two periods of maximum FRCS from 2003 to 2005and 2015 to 2017,and the FRCS were at a low level from 2009 to 2011,with the trough of 2004 and 2011 as the main factors.In addition,there are also great differences in FRCS among provinces.Guangxi Autonomous Region has the largest contribution to FRCS in China,followed by Guizhou Province,Sichuan Province,Hunan Province and Yunnan Province.（6）During the study period,Chinese RCS increased in a state of fluctuation,with a growth rate of 2.76 kg km^-2.By 2020,RCSF and FRCS increased by 0.31 t km^-2yr^-1and 2.11 Tg C yr^-1,respectively.During the study period,the peaks of 6 troughs and 7 peaks of FRCS were all above 20 Tg,with the highest value in 2016（22.5 Tg）.The troughs were all between 14.7 Tg and 18.8 Tg,with the lowest value appearing in 2011（14.7 Tg）.（7）From 2000 to 2020,precipitation（r=0.92）,evapotranspiration and temperature（r=0.30）are the key driving factors for the change of RCS in China.The warm and humid climate is conducive to the chemical weathering of rocks,and the evapotranspiration is negatively correlated with the chemical weathering rate of rocks（r=-0.68）.In addition,although vegetation overall has a negative correlation with RCS in China,regional comparison shows that in most vegetation restoration areas,especially in southwest karst areas,there is a significant positive correlation between them.（8）During the study period,precipitation contributed the most to the change of RCS in China,with a relative contribution rate of 35.02%.The relative contribution rates of each factor to RCS change in China from high to low are as follows:precipitation（35.02%）>actual evapotranspiration（25.38%）>air temperature（13.11%）>vegetation（9.21%）>soil water（8.78%）>and solar radiation（8.49%）.Again,it is revealed that precipitation,especially the final runoff remaining on the surface and underground after actual evapotranspiration,is the key factor affecting RCS.In addition to precipitation,actual evapotranspiration and air temperature,vegetation contributes significantly to the growth of RCS in China.Current vegetation restoration not only directly provides carbon sinks in terrestrial ecosystems,but also indirectly provides RCS.In conclusion,this study constructed a set of high-resolution carbon sinks of rock chemical weathering in China from 2000 to 2020,revealed the response of carbon sinks of rock chemical weathering in China to climate change and vegetation change,and quantified the relative contribution rates of climate change and vegetation change to carbon sinks of rock chemical weathering in China.It provides data and theoretical support for China’s carbon cycle,solving the problem of"carbon missing"and realizing the goal of carbon neutrality.