Tree ring-climate response and endangered mechanism deliberation of Japanese yew (Taxus cuspidata) in Muling Nature Reserve
穆棱东北红豆杉年轮-气候关系及其濒危机制

Japanese yew (Taxus cuspidata) is a national key protected species and an endangered wild tree. Understanding the relationship between tree growth and climate is important for understanding why the species is endangered. We developed a 300-year chronology for Japanese yew in Muling Japanese yew Nature Reserve spanning years from 1700-2005. We describe the radial growth curve of Japanese yew as a fluctuating descendent spline function. The growth rate was faster around 1770 and 1930. Correlation analysis between tree-ring width (used to index growth rate) and climatic variables showed that minimum and mean monthly temperatures in winter and spring were the main factors influencing Japanese yew radial growth, while other climatic factors had less pronounced effects. The correlation between the tree-ring index of Japanese yew and reconstructed northern hemisphere temperatures (Wilson ADD DATE) declined after 1942, showed a decreasing effect of temperature on radial growth. This suggests that global warming could be favorable to the growth of Japanese yew. However, the data did not enable elucidation of the relationship between global climate change and the regional decline of Japanese yew abundance. Other climatic factors showed the same results. Based on our analysis of the climatic and human impacts on the contracting abundance and distribution of Japanese yew, we conclude that excessive timber harvest could be the most important factor, while further analyses are needed to fully quantify the contribution of climate change.