Abstract
This paper presents the first record of fire in Pacific coast salt marshes; the 1993 Green Meadows Fire and the 2013 Camarillo Springs Fire burned an area of Salicornia-dominated salt marsh at Point Mugu, CA. These fires inspire concern about resiliency of ecosystems not adapted to fire, already threatened by sea-level rise (SLR), and under stress from extreme drought. We monitored vegetation percent cover, diversity, and soil organic carbon (SOC) in burned and unburned areas of the salt marsh following the 2013 Camarillo Springs Fire and used remotely sensed Normalized Vegetation Difference Index (NDVI) analysis to verify the in situ data. Two years following the fire, vegetation percent cover in burned areas was significantly lower than in unburned areas, with dominant-species change in recovered areas, and NDVI was lower than pre-fire conditions. Multi-year disturbance, such as fire, presents challenges for salt marsh resilience and dependent species, especially in sites facing multiple stressors. With anticipated higher temperatures, increased aridity, extreme drought, and higher frequency fires becoming a reality for much of the Pacific coast, this study indicates that fire in Salicornia-dominated marshes is a vulnerability that will need to be addressed differently from other grass- or reed-dominated marsh systems.
Highlights
In the past 200 years population growth and urbanization caused the destruction or conversion of an estimated 75% of the salt marsh habitat in California (Stein et al 2014)
The 20-years recurrence interval between the Green Meadows Fire and the Camarillo Springs Fire indicate that, while fire may not be a documented disturbance in Salicornia spp.-dominated salt marshes, Salicornia marshes are at risk from disturbance by fire, especially in climate change conditions
While more intensive soil or peat burns have been shown to result in damage to soil organic carbon (SOC) stock or increased soil organic matter (SOM) from increased productivity following biomass removal, we do not find any evidence to show that the Camarillo Springs Fire altered SOC content of burned and unburned soil, indicating a need for further research to understand post-fire wetland soil conditions
Summary
In the past 200 years population growth and urbanization caused the destruction or conversion of an estimated 75% of the salt marsh habitat in California (Stein et al 2014). According to recent ecosystem vulnerability models that use projected rates of sea-level rise (SLR) from the IPCC RCP 8.5 scenarios (Stocker et al 2013) up to 99% of vegetated salt marsh habitat may be converted to tidal flats by 2100. (Thorne et al 2018; Doughty et al 2019) These estimates do not include recent uncertainty surrounding continental ice sheet stability that could add an additional meter or more to sea-level rise projections in worst-case scenarios (Griggs et al 2017) and result in more rapid loss of salt marsh habitat; nor do they take into account some of the more dynamic, storm-, flooding-, and erosion- driven changes which will likely occur under anthropogenic climate change conditions (Barnard et al 2019). Fire is relatively common in reed- or grass-dominated salt marshes (Nyman and Chabreck 1995; Salvia et al 2012), to date we found no peer-reviewed
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