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Fire is an important natural disturbance in the Mediterranean-climate coastal shrublands of southern California. However,
anthropogenic ignitions have increased fire frequency to the point that it threatens the persistence of some shrub species
and favors the expansion of exotic annual grasses. Because human settlement is a primary driver of increased ignitions, we
integrated a landscape model of disturbance and succession (LANDIS) with an urban growth model (UGM) to simulate the combined
effects of urban development and high fire frequency on the distribution of coastal shrublands. We tested whether urban development
would contribute to an expansion of the wildland-urban interface (WUI) and/or change in average fire return intervals and
compared the relative impacts of direct habitat loss and altered fire regimes on functional vegetation types. We also evaluated
two methods of integrating the simulation models. The development pattern predicted by the UGM was predominantly aggregated,
which minimized the expansion of the WUI and increase in fire frequency, suggesting that fire risk may be higher at intermediate
levels of urbanization due to the spatial arrangement of ignition sources and fuel. The comparison of model coupling methods
illustrated how cumulative effects of repeated fires may occur gradually as urban development expands across the landscape.
Coastal sage scrub species and resprouting chaparral were more susceptible to direct habitat loss, but increased fire frequency
was more of a concern to obligate seeder species that germinate from a persistent seed bank. Simulating different scenarios
of fire frequency and urban growth within one modeling framework can help managers locate areas of highest risk and determine
which vegetation types are most vulnerable to direct habitat loss, altered fire regimes, or both. 相似文献