Tree-ring width series of synchronously growing trees' classes effectively optimizes their climatic signal

The high variability in forest responses to climate changes is often due to the different ways in which individual trees transmit climate signals. This raises the problem that tree-ring chronologies sometimes lack a strong explanation for climate variations. This study aims to efficiently optimize the climatic signals from tree rings based on the method of classifying trees according to their synchronous growth.

Following dendroclimatological methods, we obtained tree-ring data from 190 juniper (Juniperus przewalskii) samples in the Qilian Mountains, northeast of the Qinghai-Tibetan Plateau. To explore the growth-climate relationship, we classified trees into high- and low-synchronous groups based on their synchrony of annual radial growth. We found that the tree growth of those two groups has different responses to climate factors.

The results showed that the chronology of high-synchronous growth was significantly and positively correlated with precipitation and moisture conditions during the early summer, while the chronology of low-synchronous growth was significantly and positively correlated with winter maximum temperatures. Compared with the regional standard chronology, the classified chronologies enhanced the extraction of climate information.

Synthesis. We utilize the growth inconsistency among individual trees to develop a classification method more effectively selects upstream trees, thereby capturing the key climatic signals embedded in tree radial growth. This approach enables a more precise exploration of the relationship between tree-ring growth and climatic factors, with potentially significant implications for improving the accuracy of future climate reconstructions.