Native grass seeding and forb planting establishment in a degraded oak savanna plant community in the Coast Range foothills of western Oregon

Abstract

After a dense stand of conifers encroaching on an oak savanna/meadow was removed, exotic forbs and grasses quickly populated the newly disturbed area. Establishing desirable native grasses and forbs that contribute to native plant diversity and compete with exotic species could aid in restoring this oak savanna plant community. Two experiments were conducted over time to test different native plant establishment approaches for increasing native plant diversity and abundance. The first evaluated effect of sown native grass species establishment on graminoid cover and composition. The second evaluated 3 outplanted native perennial forb species to determine their survival. Concurrent with the experimental work, we compared change in the plant community, including species richness and forb and graminoid cover. Graminoid cover changed over time, was significantly higher in sown than unsown plots, and significantly decreased cover of outplanted native forbs but not their survival. Species survival was high the first year after outplanting but declined in subsequent years; nevertheless, outplanted forbs produced flowers and fruits by the third year. Species richness and abundance increased, and composition of native and exotic forbs and grasses changed over the years, influencing establishment of native species. Efforts to improve native plant diversity and abundance within a dense population of native and exotic species may require varied and repeated treatments, as well as more time to assess plant interactions.