California grasslands are well known for the exotic species invasions they have undergone and the resulting decrease in native flora. Issues with restoring these lands lie in determining the pre-invasion vegetation composition and the mechanisms of invasion. This study compares data from three surveys of a set of permanent quadrats in La Jolla Valley in order to determine changes over time. Each iteration included data on vegetation cover, frequency, and shrub density. It was found that native grass cover has decreased, and exotic grass cover has fluctuated widely. Also, both native and exotic forb cover increased greatly. This supports Minnich’s forb-field theory over Clements’ bunchgrass theory. The natural enemies and disturbance hypotheses did not accurately predict these results. When the quadrats were divided in valley floor and valley edge categories the post-disturbance hypothesis accurately predicted the result that edge quadrats have greater native grass cover than their floor counterparts.
|Commitee:||Langdon, Spencer, Rodrigue, Christine M.|
|School:||California State University, Long Beach|
|School Location:||United States -- California|
|Source:||MAI 56/05M(E), Masters Abstracts International|
|Keywords:||Bio-geography, California grasslands, Forbs, Grasses, La jolla valley, Native versus exotic species|
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