Resilient Plant Communities and Increasing Native Forbs After Wildfire in a Southwestern Oregon Oak Shrubland

Fire ecology in oak shrublands is among the least well understood for Pacific Northwest habitats. Following the 2018 Klamathon Fire, we examined the first three years of post-wildfire plant community change and measured soil properties in shrubland dominated by shrub-form Oregon white oak (Quercus garryana) in Cascade–Siskiyou National Monument, Oregon. Based on temporal change and comparison with unburned areas, burned oak shrubland communities displayed resiliency and at least transient increases in some native plants apparently benefiting from wildfire. Via oak resprouting and other native plants increasing, total native cover rapidly recovered in burned areas by the second post-fire year to not differ (P > 0.05) from unburned areas. Native species richness (number of species∙25 m-2) did not differ with burning any year while community evenness and diversity were usually highest in burned areas. Native plants associated with burned areas included the perennial grass blue wildrye (Elymus glaucus), the shrub Pacific serviceberry (Amelanchier alnifolia), and, most abundantly, forbs such as the perennial Scouler's hawkweed (Hieracium scouleri) and annuals such as slender clarkia (Clarkia gracilis). Cover of non-native plants on burned areas was not higher than on unburned areas within any year. After severe burning, the 0–5 cm mineral soil had the finest texture and highest bulk density. Overall, oak shrubland vegetation displayed rapid resilience to wildfire and native forbs at least transiently increased.