An individual-based model of chaparral vegetation response to frequent wildfires

The Santa Monica Mountains are home to many species of chaparral shrubs that provide vegetative cover and whose deep roots contribute to the stability of the steep slopes. Recently, native chaparral have been threatened by an unprecedented drought and frequent wildfires in Southern California. Besid...

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Bibliographic Details
Published in:	Theoretical ecology Vol. 10; no. 2; pp. 217 - 233
Main Authors:	Lucas, Timothy A., Doña, Reanna A., Jiang, Wancen, Johns, Garrett C., Mann, Dayna J., Seubert, Cassandra, C. Webster, Noah B., Willens, Charlotte H., Davis, Stephen D.
Format:	Journal Article
Language:	English
Published:	Dordrecht Springer Netherlands 01-06-2017 Springer Nature B.V
Subjects:	Annual rainfall Biomedical and Life Sciences Chaparral Colleges & universities Community structure Competition Computer simulation Cues Drought Environmental impact Erosion Extreme drought Flammability Germination Landslides Life history Life Sciences Mathematical models Mountains Original Paper Plant communities Plant Sciences Plants (botany) Rain Rainfall Seed dispersal Seed germination Seedlings Seeds Shrubs Simulation Slope stability Species extinction Structural damage Survival Theoretical Ecology/Statistics Vegetation Wildfires Zoology Population ecology Chaparral Wildfire frequency Life history type
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Summary:	The Santa Monica Mountains are home to many species of chaparral shrubs that provide vegetative cover and whose deep roots contribute to the stability of the steep slopes. Recently, native chaparral have been threatened by an unprecedented drought and frequent wildfires in Southern California. Besides the damage from the wildfires themselves, there is the potential for subsequent structural losses due to erosion and landslides. In this paper, we develop a mathematical model that predicts the impact of drought and frequent wildfires on chaparral plant community structure. We begin by classifying chaparral into two life history types based on their response to wildfires. Nonsprouters are completely killed by a fire, but their seeds germinate in response to fire cues. Facultative sprouters survive by resprouting but also rely on seed germination for post-fire recovery. The individual-based model presented here simulates the growth, seed dispersal, and resprouting behavior of individual shrubs across two life history types as they compete for space and resources in a rectangular domain. The model also incorporates varying annual rainfall and fire frequency as well as the competition between plants for scarce resources. The parameters were fit using seedling and resprout survivorship data as well as point quarter sampling data from 1986 to 2014 at a biological preserve within the natural landscape of the Malibu campus of Pepperdine University. The simulations from our model reproduce the change in plant community structure at our study site which includes the local extinction of the nonsprouter Ceanothus megacarpus due to shortened fire return intervals. Our simulations predict that a combination of extreme drought and frequent wildfires will drastically reduce the overall density of chaparral, increasing the likelihood of invasion by highly flammable exotic grasses. The simulations further predict that the majority of surviving shrubs will be facultative sprouting species such as Malosma laurina .
ISSN:	1874-1738 1874-1746
DOI:	10.1007/s12080-016-0324-x