Abstract: The “divergence problem” of tree radial growth-climate relationship arose in the 1990s. Initially, tree-ring researchers found the phenomenon that the temperature sensitivity of tree’s radial growth decreased at Alaska’s alpine timberline. Then, similar reports appeared in many regions of the mid and high latitudes in the northern hemisphere. This discovery raises a challenge to the established basic hypothesis in dendrochronology-“uniformity principle” of relationship of radial growth-climate, and to the scientificity of data derived from ring index based on the hypothesis. Despite extensive research published, there are lots of arguments about the causes and mechanisms of the formation of “divergence problem”. To clarify the formation mechanism of “divergence problem”, this review sorted the related research in the literature into location, tree species, driving factors and analyzed the misjudgment induced by research methods. The results showed that the tree species involved in “divergence problem” are growing mainly in the regions of midhigh latitude and high altitude, and sensitive to moisture and temperature. The climate warming and drying in these regions resulted in soil water deficit (exceeding the water threshold) or temperatureinduced physiological changes of trees (exceeding the temperature threshold of normal growth or dormancy). Consequently, climate sensitivity or tree growth decreased. There are some other explanations for the formation mechanism, including the change of atmospheric CO₂ concentration, the influence of anthropogenic activities; however, the threshold hypothesis is the most possible explanation for the formation mechanism of “divergence problem”.

Key words: global change, soil microorganism, field manipulative experiment, carbon and nitrogen cycle.