LAUSR

PREMISE Seed germination is controlled by the soil microclimate; however, microclimate is expected to be changed by temperature increase and rainfall irregularity predicted for the future. As changes in soil characteristics directly affect species recruitment, vegetation dynamics and resilience, we investigated how caryopses of native grasses from dry and wet grasslands respond to water stress under current and future temperature regimes. METHODS Caryopses were collected from 10 grass species occurring in dry and wet grasslands, subjected or not to a fire event, and put to germinate under increasing osmotic potential (0 to -1.0 MPa) at current (17/27°C) and future (23/33°C) simulated (night/day) temperature regimes. RESULTS The viability and germination percentages of caryopses from both dry and wet grassland species were progressively reduced by increasing osmotic stress, irrespective of temperature regime. The viability of caryopses from wet grassland species was reduced when incubated under a future temperature regime, irrespective of osmotic potential. The slow-germination pattern presented by caryopses of dry grassland species under current temperature vanished when incubated under future temperature regime. CONCLUSIONS More intense water stress reduced the survival of caryopses for both dry and wet grassland species. Temperature regime predicted for the future reduced the viability of wet grassland species and affected the germination strategy of dry grassland species. These results indicate that increasing water stress and temperature predicted for the future may compromise the recruitment potential of dry and wet grassland species, thus directly impacting the dynamics and resilience of these ecosystems in a future scenario. This article is protected by copyright. All rights reserved.