Type of Resources

Dissertation/Thesis

Date Created

9-11-2019

Abstract

Big sagebrush ecosystems are widespread throughout the western United States and provide essential ecosystem services, including water and nutrient cycling, energy capture, and habitat for sagebrush obligate taxa. Notably, sagebrush ecosystems provide habitat for the greater sage grouse (Centrocercus urophasianus), which is a nearly threatened species of high concern. Sagebrush habitat has experienced a 45% reduction in range, and a large portion of intact habitat is at risk of loss from severe fire,cheatgrass (Bromus tectorum) invasion, encroachment of pinyon-juniper woodlands, fragmentation due to human development, and changes associated with anthropogenic climate change. Thus, it is of high conservation significance to manage intact ecosystems to prevent further loss and restore damaged ecosystems. One challenging factor of sagebrush habitat restoration is identifying and obtaining appropriate plant material for revegetation. Local adaptation and phenotypic plasticity are two factors that contribute to the successful establishment of plants in restoration and the resilience of the restored community. That is, selection pressure could result in plant populations with local evolutionary adaptations that increase fitness, or on the other hand, differences could result from plastic responses to environmental drivers. Therefore, the relative importance of local adaptation and phenotypic plasticity in a plant species has implications for restoration plant material sourcing protocols. Choosing local seeds may not be important to ensure successful restoration if plants express a large amount of plasticity. Therefore, I focused on phenotypic plasticity expressed by plant species with high restoration value using a germination study and by surveying plant functional traits at a local scale. A germination study consists of a growth chamber experiment to determine if germination rates are impacted by temperature preferences in seven sagebrush-associated species. I utilized seeds collected from three populations of each species to assess the impacts of temperature. There were consistently higher germination rates in colder temperatures. I also saw differences in seed traits among species and among populations of the same species. I attempted to tie this intraspecific diversity to climate traits, but did not find any strong correlations, suggesting that fine scale environmental variables contribute to intraspecific plasticity. A deeper understanding of these fine scale variables could elucidate patterns in germination behavior that can be used to improve seed restoration sourcing protocols. In my leaf traits survey, I measured six leaf traits related to drought tolerance in four sagebrush-associated species within one population on Bureau of Land Management land near Kremmling, Colorado. There were large interspecific differences in leaf area, specific leaf area, and light saturated photosynthetic rate. However, most of the variation observed was at a very small scale, probably due to differences in microhabitats within plots. Overall, these data suggest that sagebrush-associate species have a high degree of phenotypic plasticity and, therefore, locally adapted seeds may not provide a large advantage in increasing restoration success.

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