Vegetation Change in Response to Extreme Events: The Effect of a Short Interval between Fires in California Chaparral and Coastal Scrub

This study describes changes in the abundance of shrub species after two fires in 1979 and 1980 on Otay Mountain in San Diego County, California. The 1979 fire burned a large area of dense chaparral and coastal sage scrub. The 1980 fire burned a portion of the 1979 fire area that had been seeded with annual ryegrass (Lolium multiflorum) as an erosion protection measure. Changes in the vegetation caused by the 1979 fire alone were similar to those commonly seen in chaparral wildfire, but the reburning of the vegetation in 1980 caused drastic changes in some areas. Ceanothus oliganthus was almost completely eliminated from the area of the 1980 burn. Adenostoma fascicu- latum, the most abundant shrub at the study site, was reduced in density by up to 97%. Even Xylococcuis bicolor, which normally resprouts with complete success after fire, suffered substantial mortality with reburning. It is concluded that the changes brought about by the 1980 fire will certainly persist for many decades. While sudden shifts in vegetation composition probably occurred without human intervention, we believe that human activity, especially after the introduction of aggressive annual grasses 200 yr ago, has caused an increase in the instances of abrupt change.

[1]  W. Cooper.  The broad-sclerophyll vegetation of California , 1922 .

[2]  C. R. Quick,et al.  GERMINATION OF CEANOTHUS SEEDS , 1961 .

[3]  P. Wells.  THE RELATION BETWEEN MODE OF REPRODUCTION AND EXTENT OF SPECIATION IN WOODY GENERA OF THE CALIFORNIA CHAPARRAL , 1969, Evolution; international journal of organic evolution.

[4]  J. S. Horton,et al.  Development of Vegetation after Fire in the Chamise Chaparral of Southern California , 1955 .

[5]  S. P. Mclaughlin,et al.  Effects of Wildfire on A Sonoran Desert Plant Community , 1982 .

[6]  N. Holmgren,et al.  A flora of southern California , 1974 .

[7]  P. Zedler.  Vegetation Change in Chaparral and Desert Communities in San Diego County, California , 1981 .

[8]  W. Westman,et al.  DIVERSITY RELATIONS AND SUCCESSION IN CALIFORNIAN COASTAL SAGE SCRUB , 1981 .

[9]  D. Hedrick.  Studies on the succession and manipulation of chamise brushlands in California , 1951 .

[10]  W. E. Jones,et al.  Annual Variability in Indicators of Sprouting Potential in Chamise. , 1961 .

[11]  D. Bradbury.  The Evolution and Persistence of a Local Sage/Chamise Community Pattern in Southern California , 2014 .

[12]  T. Cockerell,et al.  THE FLORA OF CALIFORNIA. , 1937, Science.

[13]  R. O. Slatyer,et al.  Vegetation succession after fire in sclerophyll woodland communities in south‐eastern Australia , 1976 .

[14]  Ted L. Hanes.  Succession after Fire in the Chaparral of Southern California , 1971 .

[15]  N. Christensen,et al.  Relative Importance of Factors Controlling Germination and Seedling Survival in Adenostoma Chaparral , 1975 .

[16]  H. Biswell.  10 – Effects of Fire on Chaparral , 1974 .

[17]  K. W. Parker.  Plant Succession on Burned Chaparral Lands , 1944 .

[18]  David J. Parsons,et al.  The Role of Fire in Natural Communities: An Example from the Southern Sierra Nevada, California , 1976, Environmental Conservation.