Recruitment for many arid-zone plant species is expected to be impacted by the projected increase in soil temperature and prolonged droughts associated with global climate change. As seed dormancy is considered a strategy to avoid unfavourable conditions, understanding the mechanisms underpinning vulnerability to these factors is critical for plant recruitment in intact communities, as well as for restoration efforts in arid ecosystems. This study determined the effects of temperature and water stress on recruitment processes in six grass species in the genus Triodia R.Br. from the Australian arid zone. Experiments in controlled environments were conducted on dormant and less-dormant seeds at constant temperatures of 25, 30, 35 and 40°C, under well-watered (Psi_soil = -0.15 MPa) and water-limited (Psi_soil = -0.35 MPa) conditions. Success at three key recruitment stages – seed germination, emergence and survival– and final seed viability of un-germinated seeds was assessed. For all species, less dormant seeds germinated to higher proportions under all conditions, however, subsequent seedling emergence and survival was higher in the more dormant seed treatment. An increase in temperature (35–40°C) under water-limited conditions caused 95–100% recruitment failure, regardless of the dormancy state. Ungerminated seeds maintained viability in dry soil, however, when exposed to warm (30-40°C) and well-watered conditions, loss of viability was greater from the less dormant seeds across all species. This work demonstrates that the transition from seed to established seedling is highly vulnerable to microclimatic constraints, and represents a critical filter for plant recruitment in the arid-zone. As we demonstrated temperature and water stress-driven mortality between seeds and established seedlings, understanding how these factors influence recruitment in other arid-zone species should be a high priority consideration for management actions to mitigate the impacts of global change on ecosystem resilience. The knowledge gained from these outcomes must be actively incorporated into restoration initiatives.

This data file contains the data described in Lewandrowski et al. ECE-2020-07-01165. The first worksheet containts the data from the petri-dish experiment that determined germination and the subsequent condition of seeds when they did not germinate (either being dead or alive) - the viable proportion is the sum of the germinated and ungermianted alive seeds. The data are stacked, and would need to be subsetted by the condition. The second worksheet contains the data from the climate chamber experiment that assessed seedling emergence and surival, and germination at the completion of the experiment. The data are also currently stacked and would need to be subsetted by process. The third worksheet contains data of the remaining ungerminated seeds after they were exposed to the different temperature and water stress combinations. The ungerminated seeds were tested for their viability in a petri dish experiment whereby dead and alive proportions were determined - the viable proportion is the sum of the germinated and alive seeds. The data are stacked, and would need to be subsetted by the condition. We also provide a detailed README file that contains definitions for the different columns. For detailed methodology please refer to our manuscript or contact wolfgang.lewandrowski@dbca.wa.gov.au for assistance.