Summer fog and plant flammability along the California coast
California, with a Mediterranean-type climate, experiences periodic fire disturbance with important consequences for plant communities. Fire in shrub-dominated ecosystems is typically high intensity and their size is thought to be heavily influenced by live fuel moisture (LFM), or the amount of water in plant tissue. Live fuel moisture patterns have generally been attributed to rainfall, but coastal regions of California also experience significant summertime fog events that inundate plant communities. This study investigated how fog affects live fuel moisture patterns in the Santa Barbara region of California and the consequences for the greater fire regime. To determine fog water use in shrub species, we used stable isotopes of hydrogen and oxygen to track fog water into plants. We also collected LFM of multiple shrub species from 2011-2013 to determine if fog influences their water content.
We found that although some species of shrubs use fog water in the late summer, the overall influence of fog on live fuel moisture appears to consist of reducing abiotic stress, not necessarily increasing water content. Fog appears to have a greater influence on LFM of lower elevation plant species than that of higher elevation chaparral species. Fog may be used opportunistically by some species, but there is minimal change to live fuel moisture except to reduce the dry down rate during the summer drought period.