Semester of Graduation

Summer 2021

Degree

Master of Science (MS)

Department

Renewable Natural Resources

Document Type

Thesis

Abstract

Spring-fed arid wetlands support high biological productivity and are hotspots for endemism and distribution of rare plants, making them areas of high conservation value. These systems are driven by complex interactions among groundwater discharge and the geomorphic and climatic features of the setting, which provide gradients of edaphic conditions, particularly soil moisture and salinity that influence the presence and abundance of rare plant communities. However, spring-fed arid wetlands are at particular risk of increases in salinity and drier hydrological regimes due to anthropogenic activities. Such alterations to abiotic conditions may jeopardize the distribution and abundance of rare plants by exceeding their tolerances during their life cycle. In this study, I evaluate how wetland management practices and associated abiotic factors affect three poorly known rare plants of spring-fed arid wetlands in Bitter Lake National Wildlife Refuge, New Mexico: the annual Pecos sunflower (Helianthus paradoxus, federally Threatened), the biennial Wright’s marsh thistle (Cirsium wrightii, proposed for listing as Threatened), and the annual Leoncita false-foxglove (Agalinis calycina, federal Species of Concern). In the lab, I used incubators to determine seed germination requirements and responses to field-derived salinities for the three species. Then, in the field, I established a series of monitoring plots equipped with groundwater wells to evaluate the hydrologic and soil factors influencing plant presence and abundance, with a particular focus on soil moisture and salinity. Pecos sunflower and Wright’s marsh thistle showed high seed germination percentages at all salinity treatments, while Leoncita false-foxglove exhibited negative responses to increasing salinities. In the field, Pecos sunflower was the most abundant and widespread of the three and was positively associated to moist-soil management. Wright’s marsh thistle and Leoncita false-foxglove occurred on permanently saturated soils associated to shallow groundwater. Reduced salinities during the spring were important for the three species. My results provide new plant life history information and insight on the abiotic processes needed to support their abundance. This information will guide management strategies to enhance their abundance and prevalence in the long term, as well as restoration efforts in areas where their populations are unstable or have been extirpated.

Committee Chair

King, Sammy L.

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