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Dryland environments are experiencing shifting ecogeomorphic patterns due to climatic changes and anthropogenic activities, resulting in a shift from grasslands to shrub-dominated landscapes. This dissertation investigates the effects from increasingly variable monsoonal precipitation and ecogeomorphic connectivity on perennial grass growth, litter distribution, and soil organic matter in drylands, with a focus on grass-shrub ecotones. Field experiments were conducted in the Chihuahuan Desert at the Jornada Basin Long-Term Ecological Research (LTER) site using a precipitation manipulation system and connectivity modifiers (ConMods) to assess their effects on plant productivity, recruitment, and soil nutrient distribution. Results show that reducing connectivity, combined with increased monsoonal precipitation, can enhance perennial grass productivity and recruitment, and affect the distribution of soil organic matter and non-photosynthetic vegetation. These findings contribute to our understanding of how aeolian processes and shifting precipitation regimes will shape vegetation patterns and soil properties in dryland environments under future climate scenarios. This research provides insights into potential mitigation strategies for combating shrub encroachment and promoting the sustainability of dryland ecosystems.
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Microbial Communities in the Changing Vegetation of the Chihuahuan Desert
The encroachment of woody shrubs into grasslands is a phenomenon that has been occurring in the Chihuahuan Desert since the 1800s. Research shows that extensive livestock grazing and increased drought levels have acted as the main drivers of the grassland-to-shrubland transition. Very few studies have considered the impacts of such vegetation changes on microbial communities. Microbes play important ecosystem roles in nutrient cycling and carbon sequestration but also have the potential to act as pathogens. As the role of microbes in ecosystems is so important, it is crucial to understand the potential impacts of shrub encroachment on microbes and vice versa. Additionally, dryland microbes in general are understudied and as drylands cover over 40% of Earth’s land, understanding these microbes is of great ecological importance. The goal of this study was to assess microbial communities in shrub encroached systems in the Chihuahuan Desert to improve understanding of the ecological impacts of encroachment and increase general knowledge of dryland microbes. To conduct this study, soil samples were collected from sites dominated by black grama grass (Bouteloua eriopoda), sites dominated by honey mesquite shrubs (Prosopis glandulosa), and transition sites with both black grama and mesquite. DNA from soil samples was sequenced for bacteria (16S) and fungi (ITS2). Soil sampling was conducted through five sampling periods across a 10-month range to assess any potential seasonal variation in the microbial communities. In addition to DNA sequencing, microbial biomass and other environmental variables were collected. Statistical analyses were conducted to assess potential differences in microbial communities between vegetation types and seasons. Analyses included assessments of alpha and beta diversity, co-occurrence networks, and differential abundance analyses. Results show that there are significant changes in the microbial communities across vegetation types and seasons. Unique fungal and bacterial communities were identified in association with the different vegetation types, demonstrating that differences in vegetation influence microbial communities. Additionally, findings show that microbial communities are strongly impacted by seasons, showing decreases in biomass and changes to community composition in warm summer months compared to cooler months. Additionally, results show higher proportions of fungal pathogens in grass sites compared to other sites. Overall, this study demonstrates that microbial communities are influenced by shrub encroachment. As dryland microbial communities are often understudied, these findings can provide valuable insight into the ecology of dryland microbes and shrub-encroached systems.
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- Award ID(s):
- 2025166
- PAR ID:
- 10556945
- Publisher / Repository:
- ProQuest
- Date Published:
- Format(s):
- Medium: X
- Institution:
- New Mexico State University
- Sponsoring Org:
- National Science Foundation
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