Faculty advisor University of California, Riverside Riverside, California, United States
Abstract: Restoration of fire-prone habitats, such as chaparral, have largely been unsuccessful due to drought, increasing fire frequency, and invasion. Moreover, the delayed arrival of management funds may impact when restoration can be done, creating a need to experimentally evaluate the timing and strategy of management efforts. In perennial woody systems, outplanting has emerged as the recommended strategy as sowing seeds has largely been unsuccessful, but outplanting can still result in relatively low survival rates, especially in dry systems. One method to improve outplanting success is to use a trait-based approach to select species mixes for different resource-use and growth strategies based on restoration goals (e.g. high diversity of traits to preempt invasive species establishment). This approach has often relied on adult traits, but recovery is mediated by seedling traits which may differ from adults for perennial species; thus, using traits at the regeneration stage to inform planting mixes may further improve restoration success. Here, we present a study investigating how to increase the efficacy of post fire chaparral restoration. We focus on two key factors that may influence restoration success – time since fire and regeneration trait strategy of planted species. We planted 960 native shrubs into two burn scars with different times since fire (two vs eight years after fire) in the Angeles National Forest, CA. To test differences in trait strategies, three communities were planted (resource-acquisitive, drought tolerant, and high diversity of both mixes combined) along with a control plot to compare natural recovery. Seedling establishment, survival, and cover was monitored at multiple timepoints during the first year after planting. We found a main effect of time since fire, where planting sooner after fire conferred higher establishment and survival. There was a main effect of trait strategy, where resource-acquisitive communities had the highest establishment and survival while the drought tolerant and high diversity plots had similarly low establishment and survival. We found no interaction between time since fire and trait strategy. Shrub cover was higher in treatment plots compared to control plots, indicating restoration can augment cover especially in low natural recovery areas. In summary, we show that regeneration trait strategies can increase restoration success and that while restoration sooner after a wildfire has the highest success, restoring even eight years post-fire can benefit community recovery.
