Variations of mean sensitivity of tree rings in Asia and their influencing factors.

Mean sensitivity (MS) of tree ring is a key index representing the sensitivity of tree rings to climate. Understanding the variation of MS and its influencing factors at a large area is helpful to understand the interaction between tree growth and climate. We used 573 tree-ring width chronologies in Asia from the International Tree Ring Date Bank (ITRDB) to examine the variation of tree-ring sensitivity and potential influencing factors. The results showed that the MS of trees was high in the arid regions and cold regions. Precipitation was more important than temperature in diriving MS. Consistent with the pattern of up-down-up for precipitation, MS showed a down-up-down fluctuation with increasing altitude, indicating that precipitation affected by altitude was a key climate factor for the MS. MS had great difference due to different physiological traits among tree species. Light-adapted species, such as Juniperus przewalskii and Pinus gerardiana, had high MS due to drought tole-rance. Shade-adapted species, such as Picea and Abies, had low MS. Old trees may have high MS.