Date of Award

2003

Document Type

Research Paper

First Advisor

Cheryl Swift

Abstract

The table of contents include Mediterranean Ecosystems Worldwide, Characteristics of the Local Flora, Reasons and Effects of Invasive Species, the Spread of Invasives in Southern California, Theories of Disturbances and Succession and the Past and Future of Landscape Ecology. Additionally there is a scientific paper included. Landscape and plant community structure is complex, explained by factors such as climate, topography, soil biota, successional stage, disturbance regime, species competitive ability, and land use history. Dispersal, seedling recruitment and (shade tolerance) also maintain patchy vegetation communities. I will examine the characteristics of the ecotone between non-native and native plants in a Southern California highly invaded, anthropogenic Coastal Sage Scrub habitat. My goals were to determine (1) the vegetation structure in different ecotones; (2) the seedling recruitment in small-scale gaps in vegetation; (3) the resilience of different communities to invasion; and (4) the invasive power of native shrubs versus non-native grasses and herbs. The cover of invasive annuals, native grasses and native shrub along six belt transects was surveyed twice over a growing season. Gaps with bare ground were found to be concentrated in the ecotone. Invasive seedlings were found to have higher rates of seed dispersal over longer distances, compared to natives. Invasive non-grass annuals were most invasive, as there was no interaction between distance and seedling density. Invasive grasses were limited by native shrub cover. Coastal Sage Shrub as a community was less resilient to invasions compared to invasive grassland. Both these factors help explain the large-scale conversion of Coastal Sage Scrub to annual invasive grasslands that has taken place in California. The project includes pictures and maps as well as references.

Comments

WSP Major: Biology

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