Low native plant establishment is a common restoration challenge for land managers across many ecosystems. Determining the factors contributing to low establishment rates can lead to more efficient use of limited seed resources. This study considers seed predation as a potential factor for low establishment rates. Using exclusion cages, we tested whether small mammals and invertebrates prey on seed from five functionally important plants with less than 5% establishment rates in Pacific Northwest prairie restoration sites: Balsamorhiza deltoidea, Dichanthelium oligosanthes, Armeria maritima, Viola adunca, and Erigeron speciosus. Three other factors were tested to assess their influence on predation: seed size, edge effect, and timing. Five recently burned prairies were studied, each containing three 50 m transects with three plots along a gradient from the unburned edge to the burned interior. Each plot contained four subplots (treatments): insect entry, small mammal entry, complete exclusion (control), and no exclusion. Each treatment contained a seed dish with 20 seeds of each species. Seeds remaining were counted after 24 hr, 48 hr, and 1 wk. A preference by small mammals for larger-sized seeds (B. deltoidea, D. oligosanthes, and V. adunca) was found. No seed predation by insects was observed under the specific conditions of this study. Furthermore, no evidence of an edge effect influencing predation was found, and the majority of seed predation by small mammals was observed at the 1 wk count. These findings suggest that attempting to mitigate seed losses from small mammals could positively influence seedling establishment rates for species with larger seeds.
Cascadia Prairie-Oak Partnership
Providing coordination for the technical prairie community in the Willamette Valley, Puget Trough, Georgia Basin (WPG) ecoregion and beyond.