Different diversity mechanisms underlying drought resistance in native and invaded communities

The decline of global biodiversity and the increasing spread of invasive
alien plants raise critical questions about how native species diversity
and biological invasions interact to influence community resistance to
disturbance, particularly global climate change.  To explore the
effects of native species diversity and biological invasions on community
resistance to drought, we established experimental plant communities with
varying species richness levels (1, 2, 4, 8, and 16 species), introduced
the invasive species Symphyotrichum subulatum into half of these
communities, and then subjected all communities to no, moderate, or
intense drought.  In both native and invaded communities,
community resistance to drought was negatively correlated with biomass of
the communities without drought, regardless of species richness.
Additionally, lower biomass of the communities without drought was
associated with smaller drought-induced increases in root:shoot ratio,
which in turn conferred higher community drought resistance. However, the
mechanisms underlying drought resistance differed between native and
invaded communities: changes in biomass triggered by complementarity
effects positively determined drought resistance in native communities,
but those triggered by selection effects governed drought resistance in
invaded communities.  Synthesis. These findings reveal distinct
mechanisms governing drought resistance in native communities and those
invaded by S. subulatum, offering valuable insights for managing the
invasion of this species in the context of global climate change.