# Dynamic stability of climate-growth relationships in Picea crassifolia in the Qilian Mountains: the modulating role of elevation gradient and time-varying characteristics

## TL;DR

This study shows how climate change affects tree growth differently at various elevations in the Qilian Mountains, highlighting the need for adaptive forest management.

## Contribution

The study introduces a novel framework for understanding elevation-driven variability in tree-climate relationships under climate change.

## Key findings

- Lower elevation trees respond to summer temperatures and precipitation, while higher elevation trees are sensitive to winter conditions.
- Climate-growth relationships show nonstationary patterns, especially at mid- to high-elevation sites.
- Hydrothermal imbalances due to warming likely cause instability in tree growth responses.

## Abstract

Amid ongoing climate warming, Picea crassifolia in the arid and semi-arid Qilian Mountains has exhibited increasingly unstable growth responses to climatic variability, raising concerns regarding the resilience of high-elevation forests in this ecologically sensitive region. To elucidate the modulating effect of elevation gradients on the stability of tree-climate relationships, this study examined Picea crassifolia, the dominant conifer species in the region.

Tree-ring width chronologies were developed from samples collected across five elevation bands (2,900-3,300 m a.s.l.) within the Pailugou watershed of the Qilian Mountains. By integrating Climate Research Unit (CRU) gridded climate data and applying 30-year moving window correlation analyses, this study systematically evaluated the temporal stability of climate-growth relationships along the elevation gradient.

The results are as follows: (1) At lower elevations (2,900-3,000 m a.s.l.), tree growth was primarily limited by moisture availability and influenced by summer temperatures, exhibiting significant positive correlations (p < 0.01) with precipitation in January and September of the current year. In contrast, at higher elevations (3,200-3,300 m a.s.l.), trees exhibited greater sensitivity to winter conditions, demonstrating significant negative correlations (p < 0.05) with December precipitation of the previous year and June temperature of the current year. (2) Moving window correlation analyses between tree-ring chronologies and climate variables revealed nonstationary climate-growth relationships across all five elevation sites. Notably, trees at mid- to high-elevation sites (3,100-3,300 m a.s.l.) exhibited pronounced temporal variability in their climate-growth responses, particularly during the growing season (June-September) and adjacent months. This instability is likely attributable to intensifying hydrothermal imbalances driven by climate warming.

This study demonstrates that elevation gradients modulate the temporal stability of climate–growth relationships and underscores that the responses of alpine forest ecosystems to climate change are dynamic rather than static. These findings provide a novel framework for understanding the dynamic adaptive mechanisms of montane ecosystems in the Qilian Mountains under ongoing climate change and offer critical insights for designing adaptive forest management strategies in high-elevation cold regions.