Vegetation-Climate Change In Northeast China Based On Eco-Geological Divisions

As an indicator of climate change research,the vegetation distribution is not only constrained by geological-geomorphological conditions,but also influenced by climate change.The long-term relatively stable spatial pattern of geology-geomorphology serves as the basis for the existence of vegetation ecosystems,while significant and multi-periodic climate changes are important driving forces for vegetation variations.Northeast China is an important ecological barrier and commodity grain base in northern China.Study on vegetation-climate change is of great ecological and strategic significance to regional ecological security,food security,and sustainable development.Most existing studies have focused on analyzing the dynamic changes of vegetation and its response to climate change for a certain vegetation parameter based on vegetation types or climate zoning,with little consideration of the impact of geological-geomorphological conditions,as well as a lack of comprehensive research on vegetation-climate change on recent and long-term scales.This paper conducts research on vegetation-climate change and its coupling coordination relationship in Northeast China from the perspective of Earth system science,utilizing remote sensing and geographical information technologies,based on clarifying the spatial coupling coordination relationship between geology-geomorphology and ecology.This paper takes vegetation and climate in Northeast China as the research object,divides it into nine eco-geological divisions according to the spatial clustering characteristics of eco-geological factors,and uses the Coupling Coordination Degree(CCD)model to quantitatively evaluate the spatial coupling coordination relationship between geology-geomorphology and ecology in different divisions.Based on temperature and precipitation data from 1901 to 2020,it systematically analyses the spatial and temporal variation characteristics of the background climate and recent climate in Northeast China.Based on vegetation types,MOD13A1-NDVI and GIMMS NDVI3g data,it analyses the distribution changes of vegetation types in the Northeast China from 1982 to 2020,reconstructs the Normalized Difference Vegetation Index(NDVI)of time series,extracts three vegetation phenological parameters:Start of Season(SOS),End of Season(EOS),and Length of Season(LOS),and uses the improved CASA model to estimate the Net Primary Productivity(NPP)of vegetation.It discusses the spatial and temporal changes of vegetation NDVI,phenology,and NPP in Northeast China under different spatial and temporal scales.Using Pearson correlation coefficient and p-value testing methods,it analyses the response and time-lag and-cumulative effects of vegetation on climate change in Northeast China from 1982 to 2020.Using multiple linear regression and residual analysis methods,it macroscopically evaluates the impact and contribution rate of two types of driving factors,including climate change and human activities,on vegetation changes.Based on the significant correlation between vegetation and climate,it constructs a comprehensive evaluation index system of vegetation-climate,and uses game theory comprehensive weighting method and CCD model to analyse the spatial and temporal changes of vegetation-climate coupling coordination relationship in nine eco-geological divisions in the five periods of 1982,1990,2000,2010,and 2020.This article explores vegetation-climate change from the perspective of eco-geological divisions,elevating the issue of vegetation-climate change to the dimension of Earth system science,providing a new perspective for comprehensive research on vegetation-climate change,and achieving theoretical innovation.It establishes coupling coordination models for geology-geomorphology and ecology,vegetation and climate,promoting methodological innovation in the study of the coupling coordination development of natural system elements.This article also possesses certain advantages in terms of systematicness,comprehensiveness,pertinence,and time length in vegetation-climate change research.The main conclusions of this article are as follows:(1)The nine eco-geological divisions are:Ⅰ Sanjiang Plain,Ⅱ Changbai Mountain,Ⅲ Lesser Khingan Mountains,Ⅳ Eastern Songliao Plain,Ⅴ Central and Western Songliao Plain,Ⅵ Low Mountain and Hilly Area in Western Liaoning,Ⅶ Central and Northern Greater Khingan Mountains,Ⅷ Southern Greater Khingan Mountains,and Ⅸ Eastern Inner Mongolia Plateau.The CCD model evaluation shows that the overall level of coupling coordination between geology-geomorphology and ecology in these nine divisions is high,but with significant spatial differentiation.There are 2 divisions with high-level coupling coordination development,3 divisions with medium-level,3 divisions with low-level,and 1 division with mild imbalance.The coupling coordination levels in the eastern plain divisions are high,while those in the western plateau and southern mountainous areas are low.(2)From 1901 to 2020,the climate showed a warming and humidifying trend,with average change rates of 0.15℃/10a for temperature and 1.70mm/10a for precipitation.Specifically,in 1985,there was an increasing mutation in temperature throughout the region.Between 1982 and 2020,the climate displayed a significant warming and drying trend,with average change rates of 0.22℃/10a for temperature and-2.51mm/10a for precipitation.In 2015,there was a a warming mutation in temperature across the entire region.(3)From 1982 to 2020,the vegetation NDVI was higher in the northern and eastern parts in Northeast China,and lower in the central and western parts,showing a highly significant spatial clustering distribution(P<0.01).The average center shifted from northeast to southwest,and the NDVI of the entire region increased year by year,with an increasing mutation occurring in 2002.The SOS in mountainous and plateau divisions was earlier than that of the plain areas,while the EOS of the central divisions was later than that of the east and west sides,and the LOS of the plain divisions was shorter than that of the mountainous and plateau divisions.The phenological periods advanced and the growing season shortened.Divisions Ⅴ,Ⅶ and Ⅸ experienced mutations in SOS and LOS.The NPP was higher in the east and lower in the west,higher in mountains and lower in plains and plateaus.The average center moved from northeast to southwest,and the NPP of the entire region increased year by year,with an average annual change rate of 2.59 gC/m2/a.Divisions Ⅴ,Ⅵ and Ⅸ experienced increasing mutations in NPP.(4)Vegetation has a significant response to climate change,and the correlation between vegetation parameters and temperature in each division is stronger than that between vegetation parameters and precipitation,with a wider distribution range.On an annual scale,NPP and NDVI are significantly positively correlated with precipitation and temperature,while SOS,EOS,and LOS are significantly positively correlated with precipitation and significantly negatively correlated with temperature.The time-lag effect of precipitation is strong,and the time-cumulative effect of temperature is significant.The impact of climate change and human activities on NDVI and NPP is mainly to promote,and the contribution rate of human activities is higher than that of climate change.(5)The vegetation-climate in each division is highly coupled,and the spatiotemporal differences of coupling coordination level varies significantly.The coupling coordination levels in the eastern divisions are higher than that in the central and western regions,and in 2020,they are higher than the previous four periods,with overall positive development over time.The climate conditions limit the high-level coupling coordination development of vegetation and climate in the eastern and northern divisions,while the vegetation status leads to the imbalance and decline of the vegetation-climate system in the central and western divisions.The coupling coordination level of Division Ⅸ is the lowest,and it is a sensitive area for vegetation-climate change.(6)Eco-geological factors affect regional vegetation-climate change trends and characteristics through multi-level and multi-factor spatiotemporal coupling.For Divisons Ⅴ,Ⅷ,and Ⅸ that are sensitive to vegetation and ecology,ecological management should be strengthened and climate adaptation strategies should be focused on.For Division Ⅱ with complex geological-geomorphological conditions and Division Ⅵ with unstable eco-geological conditions,regional natural system conditions should be fully considered when carrying out national spatial planning and vegetation ecological protection related work.