Responses Of Tree Radial Growth And Vegetation Index To Climate Change In Cold Temperate Forests In The Northern Hemisphere

As one of the largest terrestrial ecosystems in the world,cold-temperate forest ecosystem plays an important role in global climate regulation and carbon cycle,and is valued globally because of its various service functions for society.However,due to the strong influence of climate change,the characteristics of tree changes in cold temperate forest ecosystems and their driving factors are not yet clear.In this study,the response of tree growth to climate change in cold-temperate forests in the Northern Hemisphere from 1901 to 2000 was investigated by statistical analysis using 62253 tree ring data from 1232 sample sites of five different genus of trees in cold-temperate forest in ITRDB,satellite NDVI data and CRU meteorological data.The main results of this study are as follows:(1)Tree radial growth in several genus of cold-temperate forests had a significant decreasing trend after 1945 when there was a significant abrupt change in climate at most of the study sample sites(Larix:52%,Picea:63.2%,Pinus:52.4%,Tsuga:73.5%).Moreover,the negative correlation between tree radial growth with summer temperature,the positive correlation with precipitation and PDSI for several genus trees in cold temperate regions increased significantly after 1945.(2)The results of Pearson correlation analysis showed that with the increase of summer temperature,the negative correlation between summer temperature with tree radial growth and NDVI in the cold temperate zone was significantly enhanced.With the increase of spring minimum temperature,the positive correlation between spring minimum temperature with tree radial growth and NDVI in cold temperate regions gradually strengthened.The increase in winter temperature will have a significant impact on the NDVI.Summer temperature may be the main climatic factor causing tree growth decline.(3)The response relationship between tree radial growth and NDVI to climate will change obviously over time,and the changing trend may vary with tree species.After 1960,the positive correlations between temperature and radial growth of Larix,Pseudotsuga and Tsuga trees in most seasons were enhanced,while the positive correlation between temperature with the radial growth of Picea and Pinus trees decreased.Overall,after 1981,the positive correlation between NDVI at the location of Larix and Picea trees with temperature gradually increased,while the positive correlation between NDVI at the location of Tsuga,Picea and Pseudotsuga trees with temperature slightly decreased.Except for Larix trees,the positive correlation trend between NDVI at the location of other tree species and precipitation gradually increased.(4)The main climatic factors affecting tree radial growth and NDVI are different.From 1981 to 2000,temperature was the main climatic factor affecting NDVI in the cold temperate zone.Temperature and PDSI were the main climatic factors affecting tree radial growth.In summary,the study reveals the response of radial growth and vegetation index of cold-temperate forest trees to climate and the trend of change over time using a large amount of actual tree annual rings and NDVI remote sensing data,and compares the main climate factors affecting the change of radial growth and vegetation index of trees in cold-temperate regions in several genus.This study provides a lot of empirical analysis results and theoretical support for solving the dynamic response process of forests in the context of global climate change and predicting the tree growth trend under global climate change conditions.