Tree-rings δ13C different responses to environmental factors in angiosperms and gymnosperms at global scale

Tree-rings, was an extraordinary information base of climate. The global climatic change has been modifying ecosystem, it is important to understand mechanism of how plants respond to climate change. The carbon isotope composition of tree-rings corrected to the value before industrial revolution (δ¹³C_ring) can provide climatic information and carbon and water balance relationship of plants. However, it was still a challenge to disentangle the influence of different environmental parameters on δ¹³C_ring among different tree types. We collected published data of δ¹³C_ring from published papers and study how angiosperms and gymnosperms responsed to different environmental parameters. The results showed that the δ¹³C_ring of angiosperms and gymnosperms were significantly different and there was a decrasing trend in δ¹³C_ring of angiosperms and gymnosperms. In this study, we found that atmospheric concentration (C_a) was not the mainly factor to influence the δ¹³C_ring, and the MAT and PRE were the most important environmental parameters to influence the decreasing trend of δ¹³C_ring for angiosperms and gymnosperms, respectively. Additionally, the global isoscapes of δ¹³C_ring were not established, in this study, three machine learning methods to predict the spatial distribution of δ¹³C_ring were done, the results showed that RF was the best model to established the isoscapes of δ¹³C_ring.