COS 99-2
Chaparral immediate post-wildfire and wildfire re-burn response
Wildland fires are unpredictable in both place and time. Consequently, research normally lacks pre-burn vegetation measurements. While adjacent unburned sites may be used for comparison they are not ideal, particularly in diverse landscapes. Prescribed burns give insight into ecosystem fire dynamics but don't take place during extreme conditions when wildfires typically occur. Serendipitously, a wildfire burned pre-measured sites in southern California chaparral. Vegetation was measured after the 2006 Esperanza wildfire. During 2013 the Silver wildfire burned some previously sampled unburned and burned plots. Immediate post Silver data was collected to compare differences in species diversity, site recovery and fuels among three different burn scenarios. Soil seed bank samples, vegetation cover, plant diversity and fire intensity measurements were taken. Only species cover and diversity will be addressed here. The objective was to determine if initial post-fire chaparral differed between wildfires and after a close wildfire re-burn interval. Twenty-five (20x20m) plots were chosen for their involvement and proximity to the Silver wildfire and included 6 Silver, 8 Silver re-burn over Esperanza and 11 Esperanza. Plant species and cover were determined for each plot at 0.5m intervals using 5 (20m) point line transects and counts of all shrubs in corresponding belt transects (1x20m).
Results/Conclusions
Overall, 42 plant species were identified. Species varied among plots and burn scenarios. Species diversity was similar in Silver and Silver+Esperanza plots, but was several times geater in Esperanza only plots. Shrubs dominated live cover categories: average species per plot for Silver, Silver+Esperanza and Esperanza were 2.5, 2.9 and 6.6 respectively. Bare ground was similar in all plots burned in the Silver (72%) and re-burned Silver+Esperanza (72.1%) compared to 25% on Esperanza. Initial results show little difference in species diversity or bare ground among sites burned from the Silver and the re-burned Silver+Esperanza. Esperanza regeneration appears to have accumulated sufficient fuels for unburned and re-burned sites to have almost equal post-fire re-set points. These base line values will prove valuable for further interpretation of post-fire chaparral re-establishment.