Introducing Young Researchers and High School Students to Native Plant Restoration on the Colorado Plateau
The fundamental motivations for this project were outreach and training: to introduce native plant restoration concepts and practices to a Native American college student at a minority serving institution (Navajo Technical University) and to students at a high school that enrolls at-risk youth. The secondary goals were to restore native plants to a small piece of private land that has been invaded by annual weeds (Kochia spp.) and to formally evaluate establishment of three different seed sources drawn from contrasting climate regimes.
The Plant Conservation Program, via Seeds of Success, provided the native plant materials used in the project and also provided partial research support for cultivation, out-planting, and field measurements. The NSF-REU program at Northern Arizona University also provided financial support via a student stipend (Vecenti) and research money. The U.S. Geological Survey provided infrastructural resources and Troy Wood of the USGS supervised the work. John Taylor and his students at Ponderosa High School germinated seeds of blue grama grass in their hoop house facility.
The REU student researcher and the high school students benefitted by gaining experience in plant cultivation and basic experimental design. In addition, the REU student was trained in data collection and analysis and studied the importance of local adaptation and seed sourcing in native plant restoration. His project, focused on blue grama grass (Bouteloua gracilis), addressed multiple hypotheses relevant to seed sourcing and other restoration themes. Three different seed sources were used to generate blue grama seedlings for out-planting at the weedy experimental study site. These sources were collected and processed by the Seeds of Success program. One of the sources, although X-ray tested to have an equivalent seed fill rate as the other two, had significantly lower germination rates. Relative to the grow out site, one of the remaining two seed sources represents a hot/dry source and the other a matching source (i.e., collected from a site with similar climatic conditions). At the final census near the end of the monsoon season (early September), 477 of 1000 out-planted seedlings of blue grama had survived. Those plants that died showed clear evidence of drought stress. Interestingly, the plants from the hotter/drier site had significantly higher survivorship than those from the matching site, 59 versus 45 %, respectively. A mowing treatment was also included: with sources pooled, mowing had a small but significantly positive effect on survivorship. In addition, blue grama seedlings in the unmowed plot incurred higher rates of herbivory.
The most basic lesson learned is that germination rates under controlled conditions across populations from a single species can be highly variable, even when results from seed quality tests are comparable. Thus, this factor should be taken into consideration when sowing for experiments using seedlings, and it is critical to include germination tests for evaluations of restoration effectiveness. We also learned that seed source does matter during the establishment phase of blue grama grass. The results of this study suggest that plants from hotter and drier environments are better able to establish under drought-stress conditions. Finally, the initial size of seedlings was a good predictor of survivorship, thus larger seedlings of blue grama should be used in out-planting applications. The next step is to assess survivorship of plants in the spring of 2015, after overwintering. We hypothesize that plants from the matching site will have an advantage during this life history phase, which may compensate for their lower survival during initial establishment.