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Role of seed mixes, biochar soil amendment, and the soil seed bank in improving Palouse Prairie restoration
Date of Award
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Date Available to Non-EWU Users
Thesis: EWU Only
Master of Science (MS) in Biology
The Palouse Prairie Ecoregion of Eastern Washington and Idaho is critically endangered. Eastern Washington University (EWU) has begun a ~120 acre campus prairie restoration; however, there is considerable uncertainty about the most effective restoration approach. Annual seeds and soil organic matter are important for succession and soil moisture, but their roles are unknown for Palouse prairie restoration. Additionally, the soil seedbank of the Palouse ecoregion is widely unknown but could provide insight into methods or species to use for restoration. My research aimed to determine the effects of seed mix diversity, annual seed addition, and soil organic matter (as biochar) addition on prairie restoration success accounting for the rolling topography of the Palouse. Additionally, I aimed to describe the species soil seed bank of prairie remnants to inform which species would be beneficial to use in future restoration projects, and compare species composition of aboveground vegetation and the soil seed bank, in remnants and at the EWU restoration site, across various topographic positions. This resulted in a two part thesis; Chapter 1 experimenting with the hand broadcast of seed mixes and biochar at the EWU restoration site, and Chapter 2 charactering the soil seedbank and aboveground vegetation of remnants and the EWU restoration site. First, I conducted a multifactorial experiment testing the interacting effects of perennial seed mix, annual seed mix, and biochar addition across north, southwest, ridge, and swale topographic positions. A mixed linear model was used to compare native and nonnative cover and richness across all treatments, and NMDS ordination was used to compare species composition. My results suggest that the addition of low diversity mixes, annual native species, and biochar increased native plant cover. In swale plots, native species richness was highest in low diversity perennial mix and annual seed addition treatments. However, neither treatment affected nonnative species cover. Species composition differed across topographic positions, with more native species in the swale plots. My study suggests that restoration practitioners selectively use annual native species and biochar with low diversity perennial seed mixes to improve restoration outcomes. I conducted a soil seedbank and aboveground characterization at three prairie remnants (Kamiak Butte, Medical Lake, and Steptoe Butte) and at the EWU restoration site. Soil seedbank and extant vegetation richness and composition were compared by remnant and restoration site using a general linear model and PERMANOVA. Then the aboveground and seedbank data was compared for correlation by site using a Mantel test. Results suggest that the soil seedbanks of Palouse remnants do not have more species than the restoration site, but their species composition differs. Aboveground and seedbank species correlated at Kamiak Butte, but at no other site. Lastly, the ratio between native and nonnative species was higher in aboveground vegetation, similar to the ratio of perennial to annual species. At the EWU restoration site, weed management should focus on the eight nonnative species in the soil seedbank. Additionally, the six native species found in the soil seed banks of remnants should be considered for use in the EWU restoration project
Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 4.0 International License.
Snyder, Kristine, "Role of seed mixes, biochar soil amendment, and the soil seed bank in improving Palouse Prairie restoration" (2022). EWU Masters Thesis Collection. 783.