Plant Community Invasibility in Riparian Landscapes: Role of Disturbance, Geomorphology, and Life History Traits
AuthorMortenson, Susan G
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The majority of this dissertation focuses on the ecology of non-native, invasive riparian plants, river regulation, and the potential for restoration. For chapters one and two, I researched different aspects of the <italic>Tamarix</italic> invasion along the Colorado River through the Grand Canyon. Tree-ring analyses and surveys for <italic>Tamarix</italic> seedling establishment and adult density were used to understand the influences of hydrologic, climatic, and geomorphic factors on <italic>Tamarix</italic> establishment and persistence. The second chapter examines the spatial association of beavers, <italic>Tamarix</italic>, and <italic>Salix</italic> and the hypothesis that beavers may contribute to <italic>Tamarix</italic> dominance through selective foraging of <italic>Salix</italic>. The third chapter describes a regional survey of river segments in the southwestern US. Through this survey I addressed relationships between flow regime, climatic factors, and changes in flow regime with dominance of native and non-native woody species. Chapter four provides seven principles for riparian restoration for restoration practitioners. This chapter is based on a comprehensive literature review of riparian research. Important questions addressed by this study include: 1) How has the regulated flow regime along the Colorado River in the Grand Canyon influenced <italic>Tamarix</italic> establishment and persistence? 2) Do bi-trophic interactions contribute to <italic>Tamarix</italic> dominance? 3) How does the degree of flow alteration affect dominance of non-native, invasive woody plants?