Data from: Demographic rate directional change and its determinants reveal how plant species win in a patchy landscape with frequent droughts

Relative growth rate (RGR) has been a core demographic performance trait
in community ecology because its species-specific divergent responses to
light often determine community structure and dynamics. Nevertheless, how
divergent responses of plant species in RGR to water stress govern
community assembly, alongside the mechanistic basis of inter- and
intra-specific variations in functional traits, remains elusive. We
propose a theoretical framework for describing how directional change of
RGR across dry and wet patches drives community assembly in a landscape
with frequent droughts. The framework was applied to a subtropical
understory shrub community where rock fragment content, an important proxy
for water stress, shows strong spatial variability. Our empirical evidence
demonstrated that RGR directional change (RGRdir change) was more robust
than RGR in wet patches, RGR in dry patches, and the mean RGR in
predicting species’ dominance hierarchy. Intraspecific variation in
functional traits contributed equally to interspecific variation in
mediating shifts in species’ RGRdir change. Species with increasing RGR as
substrate water availability decreased were dominant (with higher relative
abundance and importance). Dominant species generally had acquisitive
roots and hydraulically safe stems. In response to decreasing substrate
water availability, dominant species further increased their leaf drought
tolerance and optimized root specific length, which not only contributed
to their faster radial stem growth but also likely to their release from
light competition. Our results highlight the roles of RGR directional
change across contrasting water-stress situations in driving community
assembly in patchy landscapes with frequent droughts and may improve our
understanding of how global climate change-related droughts shape plant
community assembly.