Data from: Increasing the germination envelope under water stress improves seedling emergence in two dominant grass species across different pulse rainfall events

1. Demographic recruitment processes, such as seed germination and
seedling emergence, are critical transitional phases to the
re-establishment of degraded plant populations, but often fail due to
rainfall not supporting plant requirements. Using species from the
widespread arid Australian perennial grass genus Triodia, we investigated
the interactions of seeds in different dormancy states and their
functional germination envelope in response to water stress after
simulated pulse rainfall events. 2. Seed dormancy was alleviated in
Triodia species to varying degrees by wet/ dry cycling or by removing
floret structures from seeds. The seeds were then exposed to different
rainfall frequency and quantity events mimicking the 25th, median, 75th
and 95th percentile rainfall events found in natural habitats for the
study species in the north-west Australian arid zone. 3. Under 95th
percentile rainfall conditions recruitment was highest, but still limited
to 35% germination and 10% emergence of cleaned seeds (i.e. the least
dormant state evaluated). This was related to the functional germination
envelope as indicated by more negative base water potential thresholds
(Ψb50) for cleaned seeds (≥ -0.33 MPa) compared to intact florets (≥ -0.26
MPa). As a result the maximum cumulative time where soil water potentials
were optimal for germination (Ψsoil ≥ Ψb50) were 1.6–2.6 times longer for
cleaned seeds in large frequent rainfall events when compared to intact
florets. Furthermore, seed dormancy, that usually prolongs seed survival,
was linked to a short-term reduction in seed viability, which may further
reduce recruitment rates. 4. Synthesis and applications. Our findings
indicate that large frequent rainfall events raised soil water potentials
above critical thresholds for germination and are important for successful
plant establishment. If recruitment bottlenecks are a result of seed
dormancy and variable rainfall for arid grass species, then this study
shows benefits for alleviating seed dormancy prior to seeding in
restoration sites, as this increases the environmental envelope for
germination.