Data from: Extreme climate events counteract the effects of climate and land-use changes in Alpine treelines

1. Climate change and extreme events, such as drought, threaten ecosystems worldwide and mountain ecosystems in particular, where species often live at their environmental tolerance limits. In the European Alps, plant communities are also influenced by land-use abandonment leading to woody encroachment of subalpine and alpine grasslands.
2. In this study, we explored how the forest-grassland ecotone will respond to gradual climate warming, drought events and land-use change in terms of forest expansion rates, taxonomic diversity and functional composition. We used a previously validated dynamic vegetation model, FATE-HD, parameterised for plant communities in the Ecrins National Park in the French Alps.
3. Our results showed that intense drought counteracted the trends of forest expansion at higher elevations driven by land-use abandonment and climate change, especially when combined with high drought frequency (occurring every 2 or less years).
4. Furthermore, intense and frequent drought accelerated the rates of taxonomical change and resulted in overall higher taxonomical spatial heterogeneity of the ecotone, than would be expected under gradual climate and land-use changes only.
5. Synthesis and applications: we argue that land-use planning must consider the effects of extreme events, since they might interfere with trends predicted under climate change and agricultural abandonment.