树轮-气候“分异问题”研究进展

Research Progress on the Divergence Problem of Tree Ring Growth-Climate Relationship

森林生态系统对全球气候变化响应一直是备受关注的问题。自20世纪中叶以来,在许多高纬度地区和高海拔地带的树木年轮宽度和密度记录中发现了森林生长指数和温度敏感性异常降低的现象,这一现象也被称为“分异问题”。“分异问题”对森林生态系统以及树轮古气候重建带来巨大影响。回顾了国内外关于“分异问题”的文献报道,从分异问题的发现(包括分异问题出现的地点和涉及的树种)出发,并对其发生的原因进行总结归纳。发现目前关于“分异问题”研究主要集中在中高纬度高寒地带以及高海拔地区,而中低纬度地区研究较少。目前对“分异问题”的成因解释还存在较大争议,主要包括干旱胁迫、“温度阈值”、“尾端效应”以及“北极变暗”等。因此,有必要进一步评估不同树种和不同地区对气候变化响应的稳定性,进一步确定“分异问题”发生的范围,与此同时对于已经确定的“分异问题”还需找到相应的解决办法,以提高树轮气候历史重建的准确性。

The response of forest ecosystems to global climate change has always been a concern.Since the middle of the 20th century,the abnormal decrease in forest growth index and temperature sensitivity have been observed in the records of tree ring width and density in many high-latitude and high-altitude areas,which is also known as the"divergence problem".The"divergence problem"has a significant impact on forest ecosystem and the reconstruction of tree-ring paleoclimate.This article reviews the literature reports on the"divergence problem"at home and abroad,starting from the discovery of the divergence problem(including the location of the divergence problem and the tree species involved),and summarizes its causes.It is found that the current research on"divergence problem"mainly concentrates in middle and high latitudes and high altitude regions,but less in the middle and low latitudes.At present,there are still significant controversies about the explanation of the causes of the"divergence problem",which mainly include drought stress,"temperature threshold","tail end effect",and"Arctic darkening".Therefore,it is necessary to further evaluate the stability of different tree species and different regions in response to climate change,and further determine the occurrence scope of the"divergence problem".At the same time,it is necessary to find corresponding solutions to the identified"divergence problem"to improve the accuracy of the reconstruction of tree-ring climate history.