Transcript Slide 1
Effects of Fire Suppression on Chaparral in Southern California Kathleen Patarak Look Familiar? Chaparral Biome A biome is a large, distinctive complex of plant communities created and maintained by climate Chaparral is a major biome on Earth Chaparral Shrub dominated community – Chaparral derived from Spanish word meaning dense, shrub thicket Mediterranean climate – Dry, hot summers and wet mild winters Found in Southern Europe, northern Africa, California, southern Australia, and Chile Green depicts chaparral Plants found in California Chaparral World wide Chaparral Biomes contain approximately 2,036 species of plants other than trees. Madrone - Arbutus Manzanita - Arctostaphylos Chamise - Adenostema Madrone menziesii patula fasciculatum Chamise Manzanita Adaptations Drought tolerant Sclerophyllous foliage - small, hard leaves which hold moisture i.e. poison oak, scrub oak, chamise Semidormant during summer Combination deep tap root and extensive lateral roots near surface Evergreen = photosynthesis during winter Fire Community Chaparral sp. have adapted to recurrent fire conditions Many plants depend on the fires for regeneration Scarification by fire i.e. Laurel Sumac seed coats need to be scorched to germinate Fire Community Space at premium Some chaparral sp. release allelopathic chemicals Fire – Opens space for reproduction and growth – Volatilizes growth inhibiting compounds Fire Community Many Chaparral sp. contain highly flammable chemicals Combustion of these chemicals may create temperatures above 500°C Only sp. highly adapted to fire survive Mature plants sprout Seeds germinate – Fire temp – Physical scaring – Chemical exposure i.e. charcoal & smoke – No allelochemicals – Massive nutrients released from dead plant material After the Fire 1-2 years – herbaceous plants 5+ years – herbaceous plants become 2° to shrubs that were not killed and are resprouting – Advantage of these shrubs – large intact root system to obtain water & nutrients Baja California vs. SoCal Frequency of fire is much higher in B.C. Acreage burned in southern California is much higher than B.C. Reason: heavy fuel load and Santa Ana winds in California Satalite imagery taken from Lan Sat shows fires in San Diego Co., San Bernadino Co., and Ventura Co, as well as fires near Rosarita and Encinada B.C. Paradise, Cedar, and Otay Fires Largest fire in California history Burned over 383,000 acres. Otay fire burned out shortly after crossing the border into Mexico because of scarcity of fuel Because of frequent fires used to clear grazing land, the chaparral stands in B.C. have a much lower fuel load than the stands in the U.S. B.C. shrublands are a mosaic of older stands and younger stands Factors Influencing Fire Wind Speed & Direction – Santa Ana’s Temperature Humidity Previous exposure to fire – Fuel load – Stand age Santa Ana driven dust storm after the Firestorm of 2003 Fire Suppression Suppression leads to buildup of fuel load resulting in large wilidfires in California chaparral USGS study Dr. Jon E. Keeley USGS Sequoia and Kings Canyon Field Station fire suppression does not cause large shrubland wildfires – fire suppression is not effective in halting shrubland wildfires Study focused on records for counties with high intensity wildfires from Monterey to San Diego Suppression failed due to Santa Ana wind conditions during wildfires Fires moved through all chaparral regardless of age class Conclusion: Prescribed burning to maintain young growth to act as firebreaks are ineffective Impacts of Shrubland Wildfires Increase in fire frequency caused by humans detrimentally impacts shrublands – Native shrubland is being replaced by non-native grasslands Unnaturally high fire frequency has been a leading cause of degradation of chaparral and coastal sage scrub ecosystems – loss of biodiversity – and increase in invasive species Shrubland ecosystems have a high number of rare and endangered plants Fire suppression does have a role in limiting the impacts of shrubland wildfires Fire Issues What kind of management of the wildland-urban interface will reduce fire movement into and out of the urban environment without converting native shrubland to nonnative grassland? What should be the role of prescription burning in shrublands? How can managers offset impacts of prescribed burning of chaparral stands (i.e., weed invasion, loss of native species, and conversion to nonnative grassland) at frequencies sufficient to stop Santa Ana driven fires? What are the benefits of fuel breaks relative to their visual impact and role in providing invasive weeds access to remote sites? Keeley USGS Report The End References http://www.signonsandiego.com/news/fires/images/031 028fire_satellite.html http://www.theshugars.com/blog/archives/000125.html www.werc.usgs.gov/fire/ Keeley, J. E., C. J. Fotheringham, and M. Morais. (2000) Reexamining fire suppression impacts on brushland fire regimes. Science 284: 1829-1831. Minnich, R. A. (1983) Fire mosaicx in Southern California and northern Baja California. Science 219:1287-1294. Moreno, J.M. and W.C. Oechel (1992) Factors controlling postfire seedling establishment in Southern California chaparral. Oecologia 90:50-60.