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Cumulative effects of land use, altered fire regime and climate change on persistence of Ceanothus verrucosus, a rare, fire-dependent plant species

Authors

  • DAWN M. LAWSON,

    1. Biology Department, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182, USA
    2. Naval Facilities Engineering Command Southwest, 1220 Pacific Hwy, San Diego, CA 92132
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  • HELEN M. REGAN,

    1. Biology Department, University of California, 900 University Ave, Riverside, CA 92521, USA
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  • PAUL H. ZEDLER,

    1. Nelson Institute for Environmental Studies and Arboretum, University of Wisconsin – Madison, 550 N. Park St, Madison, WI 53706, USA
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  • JANET FRANKLIN

    1. Biology Department, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182, USA
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    • 1Current Address: School of Geographical Sciences and Urban Planning, Arizona State University, P.O. Box 875302, Tempe, AZ 85287-5302, USA.

Errata

This article is corrected by:

  1. Errata: Cumulative effects of land use, altered fire regime and climate change on persistence of Ceanothus verrucosus, a rare, fire-dependent plant species Volume 18, Issue 9, 2980, Article first published online: 6 August 2012

Dawn M. Lawson, Biology Department, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182, USA, tel. +1 619 726 5684, fax +1 619 594 5676, e-mail: DMLawson@ucdavis.edu

Abstract

Mediterranean ecosystems are among the highest in species richness and endemism globally and are also among the most sensitive to climate and land-use change. Fire is an important driver of ecosystem processes in these systems; however, fire regimes have been substantially changed by human activities. Climate change is predicted to further alter fire regimes and species distributions, leading to habitat loss and threatening biodiversity. It is currently unknown what the population-level effects of these landscape-level changes will be. We linked a spatially explicit stochastic population model to dynamic bioclimate envelopes to investigate the effects of climate change, habitat loss and fragm entation and altered fire regime on population abundances of a long-lived obligate seeding shrub, Ceanothus verrucosus, a rare endemic species of southern California. We tested a range of fire return intervals under the present and two future climate scenarios. We also assessed the impact of potential anthropogenic land-use change by excluding land identified as developable by local governments. We found that the 35–50 year fire return interval resulted in the highest population abundances. Expected minimum population abundance (EMA) declined gradually as fire return interval increased, but declined dramatically for shorter fire intervals. Simulated future development resulted in a 33% decline in EMA, but relatively stable population trajectories over the time frame modeled. Relative changes in EMA for alternative fire intervals were similar for all climate and habitat loss scenarios, except under the more severe climate scenario which resulted in a change in the relative ranking of the fire scenarios. Our results show climate change to be the most serious threat facing obligate seeding shrubs embedded in urban landscapes, resulting in population decline and increased local extirpation, and that likely interactions with other threats increase risks to these species. Taking account of parameter uncertainty did not alter our conclusions.

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