A Comparison of the Pattern of Herb and Shrub Growth in Comparable Sites in Chile and California

Abstract

Two physiognomically similar but floristically dissimilar brushland areas of central Chile and S California [USA] were compared to test the hypothesis that where the dominant overstory vegetations are structurally and functionally similar, the understory or herbaceous vegetations will also be similar. This hypothesis was tested in a relatively undisturbed site, a heavily disturbed site and a burned site within each study area. Values of percent ground surface covered and relative density were obtained using the line-intercept method. Two modifications of this method were used to determine the relationship between herb species location and canopy cover. In the Chilean site herbs were best developed beneath the shrub canopy, were predominantly perennial (75% of the most commonly found species) and were sparse following fire. In the California site few herbs were present in the mature chaparral, but in the 1st year following a fire an abundant herbaceous flora was observed; 75% of the most common species were annuals. The role of man-caused disturbance, climatic differences, floristic histories and the role of fire are discussed as possible explanations for the differences observed.