Wildland Fire and Chaparral Succession Along the California Baja-California Boundary

Abstract

The United States-Mexico international boundary from ElPaso, Texas to the Pacific Coast shows clear differences in plant communities that were homogeneous prior to being split by a continuous fence at the turn of the century. This study evaluates how disparate fire regimes in California (fire suppression) and northern Baja California (little or no fire control) have influenced succession in the chamise (Adenostoma fasciculatum) chaparral communities spanning the international boundary between the border towns of Jacume and Tecate. Fire history was reconstructed using U.S. Forest Service fire maps and repeat aerial photography. Once plotted onto topographic maps and dated, the burns were divided into age-classes and sampled using 50 m point-quarter transects to develop successional chronosequences. Although fires are more frequent and smaller on the Mexican side of the border, our repeat photographs of the boundary monument markers together with field samples show that chaparral succession is similar across the international boundary in species composition, stem densities, and average mass shrub height. Chamise chaparral appears to be stable under disparate fire regimes because sprouting habits and latent seed pools permit efficient stand establishment under either short or long fire intervals. Chaparral recovery during the period examined here is unrelated to fire size because recolonization of burns by long-range seed dispersal is not a trait of the majority of the local shrub species and the shrubs either resprout. or germinate from soil seed reservoirs.