Trait and community-based approaches to restoring degraded sagebrush steppe communities
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Authors
Agneray, Alison
Issue Date
2022
Type
Dissertation
Language
Keywords
community evolution , functional traits , local adaptation , native plants , restoration , species interactions
Alternative Title
Abstract
Restoring and maintaining sagebrush steppe ecosystems is crucial for halting the spread of invasive species and biodiversity loss in the Great Basin Desert. New seeding strategies are needed to improve establishment success in restoration. We sought to understand how evolutionary history, local adaptation, and trait composition impact establishment and community function within restored plant communities. We first asked whether community outcomes differed between communities established with species sharing a history of co-occurrence (sympatric) or with associations of species from different locations (allopatric), with a fully factorial experiment growing communities of six species from six locations in either sympatric or allopatric mixes (Chapter 1). Then, we quantified and described seedling traits for seven different native plant taxa, asking which characteristics increase establishment from seed in invaded settings and determining the patterns of trait-environment variation across plant populations and co-occurring species (Chapter 2). Finally, we asked how functional traits, source environments, and shared history impact community responses for 12 different community mixtures (Chapter 3). We collected wild seeds of multiple co-occurring species and used these seeds to establish experimental communities that differed in coevolutionary history. Then, we measured seed and seedling traits in the greenhouse, conducted a series of competitive restoration experiments, and asked which traits most strongly predicted establishment. Lastly, we installed another set of experimental communities that differed not only in coevolutionary history but also in field performance and traits. In Chapter 1, we found no consistent differences between allopatric or sympatric communities, but rather there was evidence of a complex interaction with species and population. While most species did not differ in performance in allopatric or sympatric mixes, when they did, this difference in performance had large effects on community function. In Chapter 2, we found numerous trait-environment associations consistent with local adaptation, and both environments of origin and phenotypic traits predicted survival in competitive restoration settings. There were similarities in some characteristics that promoted establishment for multiple species (e.g., germination timing and seed size), but also species-specific predictors of establishment success. Finally, after creating additional seed mixtures with varying trait compositions, we found that the experimental communities founded with allopatric mixtures consistently outperformed communities built with plants sharing a sympatric association. Further, every community-level performance response was predicted by either provenance climate measurements (i.e., local adaptation) or seedling traits to some degree. Our results conclusively demonstrate that plant populations differ in important characteristics that affect field survival and plant interactions, and that while community composition does affect plant performance, simply assembling sympatric communities does not ensure high ecosystem services. Instead, choosing native plant sources with the most adaptive traits and matching climates will likely improve seedling establishment in invaded communities, and practitioners should continue to test the community-level outcomes of mixes that vary in propagule origin. This community-level result, with allopatric communities better resisting invasion, challenges what we expected from past findings of resource partitioning in sympatric plant communities but suggests that the identity of seed sources in restoration mixes can be optimized to achieve desired results.
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Creative Commons Attribution-NonCommercial-ShareAlike 4.0 United States