Data from: Drought effects on the stability of forest-grassland ecotones under gradual climate change

Plant communities in forest-grassland ecotones of the European Alps are
already suffering from gradual climate change and will likely be exposed
to more frequent and intense drought periods in the future. Yet, how
gradual climate change and extreme drought will affect the stability of
these plant communities is largely unknown. Here, we investigated how
drought modulates the effects of gradual climate change on the long-term
structural stability of these ecotone communities using a multidimensional
approach. Using a spatially explicit landscape vegetation model, we
simulated three drought scenarios, on top of gradual changes of climate
variables, and their impacts on the dynamics of 24 plant functional
groups, distinguishing between forests and grasslands, as well as
different land uses. We then used n-dimensional hypervolumes to define
community states under the different drought scenarios, and compared them
to initial conditions to assess changes in community structural stability.
In general, added drought effects did not counteract the long-term
consequences of gradual climate changes, although they resulted in
quantitatively different effects. Importantly, drought and climate change
had non-negligible consequences for taxonomic and functional structure
that differed between communities and land-use regimes. For instance,
forest taxonomic structure was more overall more stable than grassland’s,
despite the observed functional shifts towards more warm-adapted species
compositions. Conversely, unmanaged grasslands were the least stable,
suffering the loss of characteristic alpine species. Also, while frequent
and severe drought regimes caused forests to become more variable in time,
they had the opposite effect on grasslands. Our results agree with
observations of drought- and climate-driven changes in mountain
communities of the Alps, and we discuss their relevance for ecosystem
management. Importantly, we demonstrate the utility of this
multidimensional approach to study community stability for analysing
cross-community and cross-disturbance responses to global change.