Spatial Simulation of Chaparral Vegetation Response to Frequent Wildfire
Authors:Wancen Jiang, Noah Webster
Mentor:Timothy Lucas, Assistant Professor of Mathematics, Pepperdine University
The recent increase in fire frequency in the Santa Monica Mountains (SMM) has drastically impacted the surrounding vegetation. Chaparral shrubs represent the dominant vegetation type in the SMM. Chaparral can be divided into three life history types that characterize their response to wildfires. Nonsprouters are completely killed by fire and reproduce by seeds that germinate in response to fire cues. Obligate sprouters survive by resprouting because their seeds are destroyed by fire. Facultative sprouters can both resprout and reproduce by seeds postfire. We have created a spatial simulation that models the growth, reproduction and resprouting behavior of individual plants that interact in an environment similar to our study site adjacent to Pepperdine University. The parameters associated with the simulation have been estimated using over 27 years of data on species density, plant growth, rainfall and recorded fires from that study site. Our simulations show that short fire return intervals can eliminate nonsprouting species such as Ceanothus megacarpus; this reflects the change in plant community structure of our study site. If the average fire return interval of 6.5 years continues, we project that the vegetation cover would shrink from 74.5% to 8.74% over 60 years. This would lead to an increased risk of mudslides near our site.