Data Sheet 1_Four decades of drought impacts on Swiss protective forests: a vanishing altitudinal gradient.pdf

In declining stands, fundamental resilience thresholds appear to be exceeded independently of altitude, while the specific resilience component signaling decline shifted from resistance to recovery over time, suggesting a progressive compositional adaptation that nonetheless proved insufficient to prevent continued decline. Drought stress reshaped individual tree growth drivers before inducing stand-scale reorganization.

The vulnerability of large, dominant individuals to drought were observed broadly across most periods, although a structural shift in stand growth partitioning toward smaller trees was detectable only in declining stands at the highest altitude and only in the most recent periods, alongside with higher average tree growth rates in that belt. These findings emphasize the urgent need for adaptive management strategies that promote structural heterogeneity, sufficient stem density, and the transition toward drought-tolerant tree cohorts to sustain the forest protective function under intensifying drought.</p>