Remote sensing analysis of vegetation recovery after the Green Meadows Fire (1993) and Springs Fire (2013) in the Santa Monica National Recreation Area

The Santa Monica National Recreation Area (SMNRA) is home to a rich and fragile Mediterranean chaparral ecosystem, divided by the National Park Service (NPS) into seven ecoregions with distinct microclimates and landscapes . We studied vegetation recovery after wildfire in the Santa Monica Mountains over roughly thirty years (1984-2019) using Landsat imagery. In particular, we focused our study on factors influencing vegetation regrowth after the Green Meadows (1993) and Springs (2013) fires, two events that largely burnt the same area, 20 years apart, spanning 4 of the 7 SMNRA ecoregions. Three vegetation recovery metrics (90% EVI, RdNBR and dNBR ) were used (and compared) as metrics for burn severity and recovery. These data were compared by ecoregion, as well as with local environmental and geographical data (e.g., slope, elevation, aspect, precipitation, ENSO, frequency of burns) to determine the major influences on vegetation recovery. Comparisons of distributions (using two-sample Kolmograv -Smirnov tests) of the topographical features of pixels of varying burn severity and regrowth status, used to determine if slope, elevation and/or aspect influenced vegetation regrowth, were inconclusive. Our results further indicate that the NPS ecoregions alone are not good predictors of vegetation recovery. Based on preliminary t-test analyses, however, aspect, elevation, precipitation and frequency of burns do seem to affect vegetation recovery in this region. Based on previous studies and our own, we know vegetation recovery after fires very likely is influenced by temperature, precipitation, local terrain influences, frequency of fires, and proximity to urban regions. Ongoing research by our group aims to analyze all of these factors , via ANOVA and other statistical measures, in order to better understand how the environmental and ecoregion scale variations in the SMNRA affect this particular ecosystem's response to a changing fire regime, information that is critically important for future management and protection of a n area that is ecologically rich, regionally varied, and highly accessible to a major metropolitan area.