Document Type

Article

Publication Date

4-22-2015

Abstract

The Santa Monica Mountains represent one of the largest Mediterranean-type environments in the world. With sustained summer droughts, this ecosystem has become prone to frequent wildfires, a phenomenon that has affected the area with regularity (approximately 21 years apart). Naturally, this cycle of wildfires has had a great effect upon the mortality and survival of the diverse chaparral varieties that inhabit the Santa Monica Mountain region. This includes the Adenostoma fasciculatum (chamise), which is the most commonly-found form of chaparral shrub in California. (Redfeldt & Davis, 1996) This species of chaparral is particularly well-adapted to survival in a climate that experiences frequent wildfires, because it grows lignotubers which function to protect the plant stem from destructive flames even while the shoots of the chamise are consumed. A. fasciculatum lignotubers survive to regenerate and resprout in the years following a fire. (Wiens et al., 2011) In conjunction with possessing lignotubers, a second factor that contributes to the suitability of A. fasciculatum to a fire-frequented region is that the lignotubers are triggered to resprout by fire-related stimuli. These stimuli include heat, smoke, and charate, and it is the response of A. fasciculatum to these that increases its chances of survival and continued mortality after the fire of 1993. The purpose of this study was to answer the question: why are some chamise seedlings sprouting in one quadrat location, but not another? We hypothesized that chamise seedlings would more readily resprout in low-shade areas where there was more light exposure and higher soil temperature – as these factors mimic fire conditions and trigger lignotubers to resprout. We compared a data set taken from a series of quadrats put in place in 1994 in Stunt Canyon, (Stephen D. Davis, 1994), to a data collection that we made March 28, 2015, to see differences in the number of chamise resprouts from 1994 to 2015. We used an AccuPAR model LP-80 Ceptometer for radiation measurements and an Infrared Thermometer for ground temperature. Supporting our predictions, statistical analyses indicated that in low-shade conditions and higher ground temperatures, fire-like conditions triggered seedling resprouts of A. fasciculatum.

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