Graduate Thesis Or Dissertation
 

Experimental reintroduction of northern wormwood (Artemisia campestris var. wormskioldii), a rare species of dynamic cobble bar environments on the Columbia River

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/nc580p79b

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  • Rare plant reintroductions that result in additional or more viable wild populations are important conservation tools for maintaining biodiverse ecosystems. Ideally, such projects are best designed as experiments, to improve biological and ecological knowledge of the selected species and monitoring long-term results. Northern wormwood (Artemisia campestris var. wormskioldii: Asteraceae), a nearly extinct, early seral species restricted to Columbia River riparian habitat, is only known from two native populations in Washington, set 300 river kilometers apart. Both populations are declining and show minimal recruitment. In cooperation with the U.S. Fish and Wildlife Service and Army Corps of Engineers, we set up an experimental reintroduction project with the objectives of: (1) investigating the effect of environmental factors on survival of northern wormwood, to gain a better understanding of this species' habitat requirements; and (2) creating a second viable population to further recovery objectives. To achieve these goals, we obtained seeds from multiple sources in order to increase the diversity of the founding population and determine germination rates for each source. We then planted 2,100 greenhouse-grown plants on Rufus Island, Oregon, in October, 2011. We transplanted 1,450 of these in experimental plots to examine the impacts of three environmental factors: (1) substrate type; (2) distance from the water line; and (3) presence or absence of the invasive shrub false indigo (Amorpha fruticosa). The remaining plants were placed in four surplus populations in order to increase the founding population size and create a viable population. Results showed that seeds germinated at different rates across sources and years. Success of transplants was measured by survivorship and reproductive output. Transplants were most successful when planted in sand substrate and at least nine meters from the water line. The presence of false indigo, a listed invasive species, did not have a significant effect on survival of transplants. Reproductive output showed that this population produced viable seeds and recruitment was observed by way of eleven seedlings. The results from this project present new information on northern wormwood habitat requirements, as well as provide a protocol for future recovery efforts.
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