The Ecology and Genetics of \u3ci\u3eSchoenoplectus maritimus\u3c/i\u3e, an Important Emergent Macrophyte, Across Diverse Hydrologic Conditions—Implications for Restoration
AbstractWetlands in the Intermountain West are typically dominated by large monotypic stands of emergent wetland plants, are highly productive, and support millions of migratory birds as important stops along the Pacific Flyway. In systems with low species diversity, such as these, diversity within a species (intraspecific diversity) can play an important role in population fitness and ecosystem functioning and can impact restoration success. Our research was designed to inform future restoration and management activities by studying the pattern of diversity within and among natural plant populations, and by studying how hydrology and plant materials used in restoration (source and diversity of seeds) influenced plant success (establishment and productivity). We focused our research on Schoenoplectus maritimus L Lye. (alkali bulrush), a wide-spread wetland plant that is widely used in restoration projects in our study area due to its’ ecological importance.
In our second chapter we evaluate genetic diversity within and among stands of S. maritimus at six sites of southern Idaho and Utah (Bear Lake, Salt Creek, Bear River, Ogden Bay, Farmington Bay, and Fish Springs). We found that most genetic diversity was found within stands of S. maritimus and that all stands sampled are distinct populations. One population, Fish Springs, which was an isolated spring complex in the West desert of Utah, was very distinct from the other populations. We also found that the proportion of viable seeds produced was surprisingly high.
In our third chapter we discuss a field study and a greenhouse experiment that were conducted to look at the influence of hydrology, population of origin, and genetic diversity of seeds on S. maritimus. In the field study we measured environmental variables and productivity within established S. maritimus stands. In the greenhouse experiment we determined how source population identity and the genetic diversity of seeds impacted emergence and productivity under different hydrologic conditions. We found that stands of S. maritimus differed in proportion of time with water present, mean water level among sites, and soil conditions. Productivity also differed, with 3-fold differences in stem density and biomass among sites. In the greenhouse experiment, we found that productivity was reduced dramatically by drought and that seeds from some sources had greater seedling emergence and partitioned biomass to leaves or roots differently.
The results of the research presented here have important implications for the management and restoration of S. maritimus—dominated wetlands. First, populations of S. maritimus are sufficiently differentiated such that there should be limited translocation of plant materials between populations to conserve historic lineages. Second, if there are no remnant populations at a restoration site from which to obtain seeds, restoration practitioners should target source populations in close physical proximity to the proposed restoration area as no one seed source outperformed others in the greenhouse experiment. Third, genetic diversity is high within sites and genetic diversity may increase restoration success and reduce the risk of inbreeding, make sure to collect from many parent plants at any given site. Fourth, water level management is extremely important at all life stages of S. maritimus and should be an important consideration in wetland restoration and management in this water-limited region