Recovery time of juniper trees is longer in wet than dry conditions on the Tibetan Plateau in the past two centuries

Abstract

The recovery time of trees after extreme events may vary over space and among individuals, affecting the accuracy of predicting forest vulnerability to climate change. However, it remains unclear how different regional moisture conditions modulate the recovery time of trees in the long term. Here, we address this problem by examining 747 juniper trees at 24 sites on the Tibetan Plateau (TP). Tree-growth recovery time after extreme events was defined when reduced tree-ring indices returned to one, and site-level recovery time was assessed by calculating the time required to reach two levels of recovery, that is, 50% and 90% of trees recovered. We found that, in general, 50% of trees have recovered within three years following extreme events in the past two centuries; it took approximately 16 years for 90% of trees to recover. The recovery time for juniper trees increased from the northeastern TP to the southern TP and showed a significant positive correlation with the local latitudinal gradient of moisture conditions, particularly for the timespan at which 90% of trees recovered. Our study demonstrates that within certain moisture conditions, juniper trees on the TP recover faster after extreme events in dryer rather than wetter conditions, suggesting that juniper trees long established in dry conditions may have developed a greater ability to adapt to extremes than those in wet conditions. These findings highlight the importance of considering different performances of individuals in evaluating recovery time. In addition, the long-term influence of moisture conditions on tree recovery should be considered in the future when assessing the vulnerability of this high-elevation forest ecosystem.