The impact of altered rainfall on flowering phenology in an annual
grassland and its implications for coexistence
Abstract
Shifts in the timing of life history events, or phenology, have been
recorded across many taxa and biomes in response to global change. These
phenological changes are likely to have cascading effects on biotic
interactions and community structure, but untangling the realized
demographic consequences of these shifts is challenging. Focusing on an
annual grassland plant community, we examined how experimental changes
in precipitation affect flowering phenology in a community context and
explore the implications of these shifts for competitive interactions
and species coexistence. We found that changes in rainfall shift some
species flowering phenology, but sensitivity differed among neighboring
species. Four of seven species we studied started and/or peaked
flowering earlier in response to reduced water availability. The
idiosyncratic shifts in flowering phenology we observed have the
potential to alter existing temporal dynamics that may be maintaining
coexistence, such as temporal separation of resource use amongst
neighbors. We show how rainfall induced phenology changes may have
impacted competition outcomes between species pairs due to differences
in their response to reduced water availability. More research on the
effects of phenology changes on coexistence and the community level
repercussions they cause due to changes in competitive interactions is
essential for mitigating the impacts of climate change.