University of California, Riverside, California, United States
Background/Question/Methods
California’s coastal sage scrub (CSS) hosts high species diversity and endemism. CSS plant communities have adapted to periodic fire disturbances which benefit many fire-following forbs and fire-adapted shrubs. However, fire suppression, human ignitions, and climate change have drastically altered the natural CSS fire return interval of 30-40 years. This has resulted in fires of abnormal severity, frequency, seasonality, or extent. Changes in fire regimes have the potential to reshape plant communities by inhibiting woody plant recovery and enabling invasion by herbaceous species. As a result, the need to investigate how native plants are responding to changes in natural disturbance events is vital. While a majority of plant community recovery studies have occurred either immediately after a fire or at a period of time beyond a decade, there is a gap in our understanding of community dynamics during the critical mid-range years. In this study, we investigate how a low-to-moderate severity fire influenced plant invasions and the density of fire-following plant species at four- and five-years post-fire.
Results/Conclusions
At four and five years following a fire event, we found that increased native forb and shrub species richness was associated with burned plots while native foliar cover was associated with unburned plots. An investigation of how plant community composition differs at two elevations revealed that low elevation burned and unburned plots were more similar in plant cover than burned and unburned plots at high elevation sites. Additionally, unburned sites had an increased biotic resistance index with increasing native species richness while burned sites had increased biotic resistance at low diversity (< 5) and at high diversity (< 10). We also found average floral abundance for shrubs and forbs was influenced by burn treatment. Our study highlights the importance of including the mid-range period in investigations of post-fire changes. We also demonstrate that shifts in plant communities post-fire may be more complex than previously thought.
