DOI: 10.5061/dryad.br8s9
title: Data from: Increasing the germination envelope under water stress improves seedling emergence in two dominant grass species across different pulse rainfall events

description: 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.
description: Lewandrowski et al.
 JAPPL2016-00640This data file contains
 five spreadsheets of the data described in Lewandrowski et al.
 JAPPL2016-00640.R1. The first worksheet contains the validation experiment
 for the different seed treatments tested in Triodia epactia and Triodia
 wiseana under optimal germination conditions. The second worksheet is the
 data used to quantify b50-thresholds under water stress of the different
 seed treatments using three parameter nonlinear functions.The third
 worksheet comprises the field recruitment data under the various rainfall
 events tested, along with the fourth spreadsheet containing the average
 soil water potential and temperature for the trial period. The last
 worksheet contains the modelled cumulative mean time parameters according
 to the b50 water potential thresholds. All methods and materials are
 described in the manuscript. For further information, please contact the
 authors, or wolfgang.lewandrowski@bgpa.wa.gov.au for
 assistance.