Grassland Restoration in Heterogeneous, Changing, and Human Dominated Systems
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Date
2022-10-04
Authors
Brambila, Alejandro
Journal Title
Journal ISSN
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Publisher
University of Oregon
Abstract
Ecological restoration is a powerful tool to promote biodiversity and ecosystem function. Understanding underlying system variability and directional change can help predict outcomes of restoration interventions. Spatial or temporal availability of resources, for example, can lead to a similarly applied intervention having different outcomes. Similarly, as climate change shifts underlying competitive dynamics management strategies that worked in the past may no longer work. Human influence has played a major role in determining patterns of heterogeneity and novelty across systems, and human-dominated systems can provide opportunities for extending restoration impacts beyond wildlands. Here, I examine how environmental variation, change, legacy and land use influence restoration outcomes in western U.S. grasslands. Specifically, I focus on semi-arid and Mediterranean grasslands of California, Oregon and Washington. These grasslands are invaded by introduced annual grasses, which threaten to displace native species and, especially in the perennial dominated north, transform ecosystem state and function. Each of the chapters presented in my dissertation ask a question that seeks to contextualize and improve grassland restoration across a variable landscape. In Chapter II, I examine how grazing herbivory enhances or dampens the effect of environmental variation on resource availability at different scales using data from a long-term cattle-herbivory exclusion study. In Chapter III, I ask how communities with variable starting conditions established by climate and management legacies respond to restoration burning across regional climate gradient. In Chapter IV, I consider how warming impacts competitive outcomes between species representative of two potentially dominant functional groups. Finally, in Chapter V, I test the feasibility of expanding restoration into a novel agricultural context potentially compatible with native grassland vegetation. Throughout, I consider what each of these outcomes mean in a management context, and how they can be applied more broadly to improve restoration success.
This dissertation includes previously published co-authored material.