Associate Professor University of California, Davis Davis, CA, United States
Background/Question/Methods
With increasingly frequent drought years, establishment of seedlings in semi-arid grasslands is essential to successful restoration projects. Cultivating seeds and seedlings with particularly desirable suites of traits can increase both the success of restoration efforts and the future resilience of grassland communities. The narrow window from germination to establishment is a perilous time for a seedling, potentially providing a strong selective force and influencing population growth rates. Yet differences in seedling traits and how these relate to performance remain understudied compared to adult traits. This project investigates how climate of origin and maternal environment influences seedling traits and performance in the face of drought. These factors were investigated by 1) determining differences between suites of seedling traits in a common garden from populations from three elevations and three experimentally manipulated maternal environments within each population and 2) determining which above and belowground traits drive seedling performance in the face of drought. These insights may translate into applications in other systems and inform patterns and processes occurring in water-limited grasslands across the West.
Results/Conclusions
Results demonstrate the importance of seed mass as a trait that impacts many other seedling traits. However, differences in patterns are not explained by seed mass alone. Population level differences in seedling traits shift with water availability. Where the site with the least water availability has the smallest seeds, the earliest emergence from the soil, and the highest early SLA compared to the other two populations. While the maternal environment has less pronounced effects on seedling traits than population, a droughted maternal plant results in a delay in emergence and growth for two of the three populations and lower SLA for seeds from the lowest elevation site. Additionally, the percentage of plants flowering within the first season is highly correlated with population and maternal treatment. The drier population had the highest reproductive rate ( >80%) and within this population the drought plants were the most likely to flower. Conversely at the high elevation site reproduction was very low in general (~10%). To restore grassland communities we need high quality seeds which are resilient to drought - this research suggests that per gram of seed production, seeds from dry environments have vastly higher productivity compared to seeds from more mesic sites.
