穆棱东北红豆杉年轮-气候关系及其濒危机制

东北红豆杉是国家I级重点保护野生濒危植物,其径向生长与气候的关系对于探讨其种群濒危机制具有极其重要的意义。利用穆棱自然保护区内天然东北红豆杉树木年轮样本,建立了长300多年的树轮年表(1700—2005年)。分析径向生长特征发现东北红豆杉总体上呈波动式下降的生长方式,在1770年和1930年左右存在两个生长释放区,该地区调查的样本最大年龄达到370a左右。年表与气候变量之间相关分析表明,冬春季节最低气温、平均气温是树木生长的主要限制因子,其他气候因子也有一定的影响,但不起主要作用。1942年以后东北红豆杉年轮指数与Wilson重建的北半球气温变化吻合度降低,温度对东北红豆杉的径向生长限制性降低,这表明气候变暖可能有利于东北红豆杉的径向生长,但不足以说明气候变暖与东北红豆杉衰退的关系,其他气候因子的年轮气候响应分析也不能确定气候变化在东北红豆杉衰退中的主导作用。人为破坏可能是东北红豆杉衰退的主要因素,但气候变化在其中起到多大的贡献还有待深入研究。

Tree ring-climate response and endangered mechanism deliberation of Japanese yew (Taxus cuspidata) in Muling Nature Reserve

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.