Biology ETDs

Publication Date

Summer 7-11-2021

Abstract

Species ranges are shifting due to anthropogenic climate change. However, it is unclear how climate variability affects species recruitment, an essential step in range expansion. Recruitment is challenging in drylands, where soil moisture is highly unpredictable. In Southwestern North America, creosotebush (Larrea tridentata) has expanded into Chihuahuan Desert grassland (CDG) dominated by black grama (Bouteloua eriopoda), and black grama is expanding into Great Plains grassland (GPG) dominated by blue grama (Bouteloua gracilis). To evaluate how precipitation variability affects germination and survivorship, we added blue and black grama seeds into a climate variability experiment in GPG in 2019 and 2020 and blue grama, black grama, and creosote seeds to a climate variability experiment in CDG in 2020. Seeds were monitored biweekly. Overall, 12.5% of seeds germinated. Soil moisture increases blue (p < 0.005) and black grama (p = 0.0463) germination probability and this effect is stronger in GPG. Temperature has a strong negative effect on creosote germination (p < 0.005). Climate variability did not affect survivorship (p = 0.5523), but ecosystem did (p < 0.005). Creosote had the highest survival with 44.8% of seedlings alive after 10 months. The germination and survival differences between ecosystems is likely due to vegetation and soil. At GPG, blue grama is a strong competitor for soil moisture and GPG contains higher amounts of clay, which retains moisture. Our results inform the impact of other climate change trends (e.g. increased temperature) on foundation species recruitment. Finally, we emphasize the importance of including germination in ecotone and climate variation studies.

Keywords

grasslands, seed ecology, recruitment, ecotone, seed addition, germination, seedling establishment

Document Type

Thesis

First Committee Member (Chair)

Scott Collins

Second Committee Member

Jennifer Rudgers

Third Committee Member

Nancy Emery

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