Environmental Effects during Early Life-History Stages and Seed Development on Seed Functional Traits of an Australian Native Legume Species

Simple Summary Seed-based restoration is likely to become less successful with climate change due to reduced seed germination and seedling emergence. Studying how native plant species respond to environmental stress using a whole life cycle approach can help predict climate change impacts on successful plant establishment. Therefore, the aim of this study was to understand how temperature and moisture stress affect seed germination and seedling emergence together with determining how soil moisture stress can impact the reproductive biology of plants. A native Australian legume species, Desmodium brachypodum A. Gray, was selected as a model species. The seed germination and seeding emergence were reduced by more than half when exposed to elevated temperatures and moisture stress. When the plants produced seeds under moisture stress, the duration of seed production and the number of produced seeds decreased. On the other hand, no differences were observed in the seed traits of those produced seeds. In conclusion, the reproductive output of D. brachypodum had low seed variability under moisture stress, which might be useful when sourcing seeds from climates with high variability. Even so, a reduction in the seed quantity under maternal moisture stress can impact the long-term survival of restored plant populations. Abstract Understanding how seed functional traits interact with environmental factors to determine seedling recruitment is critical to assess the impact of climate change on ecosystem restoration. This study focused on the effects of environmental factors on the mother plant during early plant life history stages and during seed development. Desmodium brachypodum A. Gray (large tick trefoil, Fabaceae) was used as a model species. Firstly, this study analyzed seed germination traits in response to temperature and moisture stress. Secondly, it investigated how seed burial depth interacts with temperature and soil moisture to influence seedling emergence traits. Finally, it determined if contrasting levels of post-anthesis soil moisture could result in changes in D. brachypodum reproductive biology and seed and seedling functional traits. The results showed that elevated temperature and moisture stress interacted to significantly reduce the seed germination and seedling emergence (each by >50%), while the seed burial improved the seedling emergence. Post-anthesis soil moisture stress negatively impacted the plant traits, reducing the duration of the reproductive phenology stage (by 9 days) and seed production (by almost 50%). Unexpectedly, soil moisture stress did not affect most seed or seedling traits. In conclusion, elevated temperatures combined with low soil moisture caused significant declines in seed germination and seedling emergence. On the other hand, the reproductive output of D. brachypodum had low seed variability under soil moisture stress, which might be useful when sourcing seeds from climates with high variability. Even so, a reduction in seed quantity under maternal moisture stress can impact the long-term survival of restored plant populations.