Fog and the fire regime in coastal California

Background/Question/Methods

Fog is a significant force in shaping plant communities, particularly in coastal California where fog can ameliorate temperatures and reduce drought stress. The effect of fog on plant moisture content has not been well studied and the possibility that fog events may change in the future calls for research into the impact of fog on vegetation structure and functioning. Connecting fog events to changes in plant moisture content can inform our understanding of the relationship between fog and the fire regime. Understanding patterns of occurrence and effects of fire begins with exploration into the flammability of vegetation. Plant moisture content is one of the most important characteristics when evaluating plant flammability and is tied to water availability. In order to better manage and predict fires in California, we need to consider the influence of fog on plant moisture. This study conducted a field experiment monitoring fuel moisture and fog inputs in both chaparral and coastal sage scrub communities in Santa Barbara County, CA. Shrubs at field sites along the coast and in the interior were sampled throughout the summer of 2011. Plant water was also analyzed for stable isotopes of hydrogen and oxygen to determine potential fog water use.

Results/Conclusions

Although fog does not appear to directly increase fuel moisture, it buffers the effects of late summer drought and reduces the fuel moisture drydown for certain shrub species along the coast. I have also determined that water sources along the coast have different isotopic signatures which allows for the determination of fog use for both chaparral and coastal sage scrub species. Reducing fuel moisture loss late in the summer may prevent fire occurrence in areas of high fog frequency. Predictions of increasing fog along the coast and later Santa Ana wind events suggest that fire in coastal California could be reduced in the future.