Extreme climate events counteract the effects of climate and land‐use changes in Alpine tree lines

Abstract

1. Climate change and extreme events, such as drought, threaten ecosystems worldwide and in particular mountain ecosystems, 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 of Alpine treelines 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 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 than 2 years). 4. Furthermore, intense and frequent drought accelerated the rates of taxonomic change and resulted in overall higher taxonomic spatial heterogeneity of the ecotone than would be expected under gradual climate and land-use changes only. 5. The results from our model show that intense and frequent drought counteracts forest expansion driven by climate and land-use changes in the forest-grassland ecotone of Alpine treelines. We argue that land-use planning must consider the effects of extreme events, such as drought, as well as climate and land-use changes, since extreme events might interfere with trends predicted under gradual climate warming and agricultural abandonment.

A three decade assessment of climate‐associated changes in forest composition across the north‐eastern USA

“…In recent decades, climate-associated shifts in forest composition have been increasingly reported (e.g. Rigling et al 2013;Bernhardt-R€ omermann et al 2015;Barros et al 2017). The key factors identified have included elevated temperature, increased atmospheric CO 2 concentration and greater frequency of prolonged drought (Hansen et al 2001;Cavin & Jump 2017).…”

Sampling strategies for high quality time-series of climatic variables in forest resource assessment

“…Under future climate changes a fundamental role will be played by extreme events, recognized as a high peak or depression after and before an almost stable climatic situation. Actually extreme events have been demonstrated to have a fundamental role for forest systems and plants communities even in Mediterranean areas (Eilmann & Rigling 2012, Lelieveld et al 2012, Barros et al 2017, Ummenhofer & Meehl 2017 and such rare and unpredictable events will require even more accurate and gap-free time-series to understand the effects of these events on forest ecosystems.…”

Biodiversity and ecosystem services in forests: management and restoration founded on ecological theory

“…The papers in this Special Feature focus on the profound potential of research on forest biodiversity and ecosystem services by summarizing the present state of the art (Mori, Lertzman & Gustafsson ) and adopting modern analytical tools and approaches to quantify issues of concern (Barros et al . ; Chamagne et al . ; Fujii et al .…”

“…The topics and study regions in this Special Feature are diverse. The original studies include field-based work from different forests (Chamagne et al 2016;Fujii et al 2016) and ecological modelling of tropical, temperate, boreal and high-elevation forest landscapes (Barros et al 2016;Law et al 2016;Thom et al 2016;Triviño et al 2016). Our hope is that societies around the world can benefit from the wealth of such observational, experimental and theoretical works in forest ecosystems to help realize sustainable forest management.…”

“…Thom et al (2016) report on spatiotemporal trajectories of biodiversity in temperate forests in response to changing climate and to the accompanying changes in forest disturbance regimes. Barros et al (2016) analysed synergetic influences between climate change and land-use change on plant communities in timberline forest-grassland ecotones, with explicit considerations of different types of climate impacts including climate extremes. Both studies demonstrate that the disturbance effects are variable and complicated and often have substantial impacts on biodiversity, depending on possible changes in the frequency and severity of disturbance under the changing climate.…”