Magda Garbowski, Ecology, Colorado State University, Fort Collins, CO, Danielle B. Johnston, Colorado Division of Parks and Wildlife, Grand Junction, CO and Cynthia Brown, Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, CO
Background/Question/Methods: Dryland restoration success is often hindered by competition from exotic species and drought. When site conditions are predictable, cultivars with specific traits can be used to improve initial plant establishment. However, given the uncertainty of exotic species invasion and seasonal precipitation, selecting seeds from populations with high functional variability or using multi-variety (admixture) seed mixes may maximize initial establishment and adaptive potential of introduced plant populations. I conducted a series of greenhouse and common garden experiments to better understand how functional trait diversity (above and belowground) in the perennial grass Elymus trachycaulus influences establishment and growth under drought and competition from the annual grass, cheatgrass, Bromus tectorum. Specifically, I compared the performance of natural accessions to cultivated varieties, as well as the performance of multi-variety mixes to single variety mixes.
Results/Conclusions
When assessing individual plant responses to stress, cultivated varieties had higher performance aboveground (greater leaf biomass) than natural accessions. This trend was only apparent in unstressed conditions - under drought or competition, aboveground biomass was similar between natural accessions and cultivated varieties. In addition, the effects of drought on aboveground biomass were greater in cultivated varieties compared to natural accessions. Aside from biomass, leaf and root traits were largely unaffected by stress treatments in natural and cultivated varieties. When assessing mixture performance, the best performing mixtures in terms of aboveground biomass were those with specifically vigorous individuals regardless of their intraspecific diversity level (a selection effect). Differences in belowground traits (e.g. specific root length) were detected for some but not all of the mixtures.
