The Effect of Fire Frequency on the Presence of Native and Nonnative Species in the Santa Monica Mountains

We surveyed two sites in the Santa Monica Mountains of Southern California that experienced both high and low fire frequency (Figure 1). Our objective was to find out if increased fire frequency allowed for the invasion of non-native species. We collected data on herbaceous coverage and point to plant distance of woody chaparral species. A series of random points were used, and each area was divided up into four equal quadrants using two meter sticks. The individual nearest to the center in each quadrant was then identified and measured. To measure herbaceous coverage, percentages were took of cover of each species within a square area and assigned a number (1=0-25%, 2=25- 50%, 3=50-75%, 4=75-100%). We hypothesized that high fire frequency would increase the coverage of non-native species. We found that in the areas of high fire frequency, native chaparral shrubs were less frequent averaging about one shrub every 40m2, and in the low fire frequency, the native chaparral shrubs were more frequent averaging about one shrub every 1m2. For the herbaceous species, we found that in the high fire frequency sites there was 100% native species cover, and in the low fire frequency sites there was a 69% native species cover. This disproves our hypothesis and shows that high fire frequency does not necessarily allow for the invasion of non-native species