Unequal contributions of species’ persistence and migration on plant communities’ response to climate warming throughout forests

Abstract

Community reshuffling is lagging behind climate warming for many taxa, thereby generating a climatic debt. However, only few studies have attempted to assess the underlying factors that explain this debt. Here I examine how effects of species’ migration and persistence on the current climatic debt vary spatially in forest herbaceous communities throughout the French territory. I show that Mediterranean communities are responding to climate warming through both high species’ migration and persistence effects, while alpine forest is the only ecosystem where species’ migration overtakes species’ persistence mechanisms. Such an approach seems promising in assessing the underlying mechanisms of the biodiversity response to climate change locally, and it can be applied for conservation issues to assess biodiversity sensitivity and optimize its management.

Climatic distribution of tree species in the Atlantic Forest

“…It is not new that climate change is shifting biodiversity by causing shifts in species distributions, community composition, and ecosystem function (Bertrand et al, 2016;Peterson et al, 2019;Zimmermann et al, 2009). The persistence of species under future climate depends on their tolerance to climatic stresses, on the capacity to shift their climatic niche (Bertrand, 2018), and on the ability to migrate fast enough to keep pace with the rapidly changing climate (Alexander et al, 2018;Renwick & Rocca, 2015). Climate change scenarios project an increase in rainfall irregularities (i.e., longer drought periods) over the next decades (IPCC, 2021).…”

“…Therefore, species composition and diversity of tree communities, especially due to changes in incidence and density, may substantially change in the long term (Raymundo et al, 2019) with a steady decrease in the density of cold-affiliated species in the subtropical region and wetaffiliated species in the tropical region. However, predicting future distributions and abundances of tropical and subtropical species remains uncertain (Bertrand, 2018), especially because evolution could alter species responses to climate change at the edge of the range and since these regions are often the first to experience novel selection (Nadeau & Urban, 2019;Rehm et al, 2015). Furthermore, an increase in the density of generalist species is expected, potentially leading to biotic homogenization of biodiversity along with the remnants of forests (Zwiener, 2017).…”

Lags in the response of plant assemblages to global warming depends on temperature-change velocity

“…Including abundance data and functional groups might help to give a more detailed picture of the shifting dominance of functional groups and species within assemblages and subsequently to understand the consequences of assemblage reorganizations in response to global warming (Kullman, 2004;Rumpf et al, 2019). Finally, we highlight that, although we focus in our study on temperature change, combined effects with other climatic factors, such as precipitation (Feeley et al, 2020) or vegetation structure (Richard et al, 2021) and non-climatic factors, such as landuse change or populations dynamics (Bertrand, 2019), are needed in future studies to achieve a holistic perspective of drivers of the thermal lags in plant assemblages.…”

“…As a result, plant species may only need to shift short distances to find thermally suitable habitats in areas with low temperature-change velocity when climate is changing. On the other hand, if species migration is limited by dispersion and high temperature velocities occur, a greater thermal lag is more likely (Bertrand, 2019;Bertrand et al, 2016;Jump, Mátyás, & Peñuelas, 2009;Lenoir et al, 2020). Therefore, we expect the magnitude of thermal lag to be positively related to both temperature change (magnitude and rate of change) and the spatial distance plant species need to migrate to find analogous thermal conditions (i.e.…”

“…stand age) and natural and anthropogenic disturbances modulate thermal lags in understory forest assemblages by altering microclimate conditions. However, we still need a better understanding of the spatio-temporal patterns of thermal lags to assess the impact of global warming on biodiversity and ecosystem functioning (Bertrand, 2019;Blonder et al, 2015;Svenning & Sandel, 2013).…”