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Introduction

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Spring-fed wetlands, embedded in the desert landscape, define Bitter Lake National Wildlife Refuge (BLNWR) in southeastern New Mexico. These wetlands, known regionally as ciénegas, create groundwater-dependent ecosystems that are of great value to people, wildlife, and native plants. 

Refuge managers must make wetland management decisions that guarantee long-term habitat conditions for multiple species of high conservation value, including rare and endangered plants and migratory birds. These wetland management decisions, such as flooding and drawdowns, affect soil moisture and salinity as well as depth to groundwater. Unfortunately, refuge managers lack data about the basic life histories of three rare plants on the refuge: the federally Threatened Pecos sunflower (Helianthus paradoxus) and Wright’s marsh thistle (Cirsium wrightii), and Leoncita false-foxglove (Agalinis calycina), an at-risk species that will be considered for federal listing in 2027. Lack of information challenges managers’ ability to develop conservation strategies for these species while also supporting migratory birds. 

Refuge managers are partnering with research scientists from Louisiana State University to learn more about the life history of these rare wetland plants. Researchers are investigating seed germination requirements and assessing effects of water management practices and associated abiotic conditions on plant abundance and distribution. This data will inform management decisions about rare plant species, migratory birds, and other wetland-dependent wildlife of BLNWR.

Key Issues Addressed

The lack of information about basic life-history characteristics, like germination requirements and responses to salinity, impedes land managers in making management decisions that benefit Pecos sunflower, Wright’s marsh thistle, and Leoncita false-foxglove.

Furthermore, these unique habitats are in jeopardy due to decreasing water availability and frequent drought. Detailed information about these species will help target appropriate locations for restoration and help ecologists restore habitat conditions for their conservation and recovery.

Current wetland management practices at BLNWR that provide habitat for migratory birds, such as seasonal flooding and drawdown of wetlands, change soil moisture and salinity conditions, which are often driving factors for establishment, growth, and survival of wetland-dependent plants. A better understanding of how these changes in soil moisture and salinity affect the presence and abundance of the three listed and at-risk plant species is needed to develop wetland management strategies that benefit these plants while still providing habitat for migratory birds and other wetland-dependent species. 

Project Goals

Water, Soil, Salt: Refuge managers need a thorough understanding of relationships among wetland management practices and abiotic processes to better support conservation and management of rare plants. 

• Inform land managers at BLNWR regarding key life-history characteristics of Pecos sunflower, Wright’s marsh thistle, and Leoncita false-foxglove that will facilitate wetland management decisions to enhance populations and/or guide conservation and restoration strategies for these species while also providing habitat for migratory birds and other wetland-dependent species of high conservation value
• Determine the seed germination requirements of Pecos sunflower, Wright’s marsh thistle, and Leoncita false-foxglove by examining seed dormancy break and evaluating germination responses to varied salinity levels
• Understand how current water management practices at BLNWR affect the presence and abundance of these three rare plant species

Project Highlights

Monitoring Variables and Processes: Researchers established monitoring stations throughout the study area consisting of groundwater wells equipped with water level recorders, soil moisture and soil salinity probes, and vegetation monitoring plots. These methods allowed for detailed investigation into how current wetland management affects processes like groundwater depth and groundwater salinity. These processes drive variables like soil moisture, soil salinity, vegetation structure structure
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Learn more about structure , and the presence and abundance of the three listed and at-risk plants.

Linking Lab and Field: Temperature, salinity, and moisture data from the field site were used to inform the seed germination and dormancy break (i.e., cold stratification treatments) experiments conducted in the lab. This allowed researchers to evaluate germination responses to different levels of salinity. 

Whole-System Thinking: Researchers used a systems approach to study the relationships among current wetland management practices, the resulting abiotic conditions and wetland processes, and the establishment and survival of the species of interest.

Strong Partnerships: Researchers developed close working relationships with refuge managers who assisted with data collection during furloughs and COVID-19 pandemic shutdowns.

Interdisciplinary Collaboration: Researchers collaborated with soil scientists and a hydrologist. This strengthened the knowledge base of the physical setting and key habitat features that support the habitats of the three rare plant species at BLNWR. It also enhanced the thinking process of the research project as a whole.

Lessons Learned

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Germination experiments revealed that seeds of Pecos sunflower, Wright’s marsh thistle, and Leoncita false-foxglove need exposure to cold and moist conditions to alleviate dormancy and promote germination. The three species tolerate soil and water salinity differently during germination, with Wright’s marsh thistle having the highest tolerance, followed by Pecos sunflower and Leoncita false-foxglove, respectively. However, germination for all species is enhanced in less-saline conditions. 

Researchers found that the three rare plants have different soil moisture preferences during the growing season that determine where they grow and how abundant they are. Wright’s marsh thistle and Leoncita false-foxglove need permanently saturated soils, while Pecos sunflower is better adapted to seasonally flooded areas with lower water tables. These moisture requirements have important implications for water management at BLNWR and for microsite selection for conservation of these species across their historical ranges. 

Soil salinity is a key factor that determines where vegetation establishes and what kind of plants can grow at BLNWR. Pecos sunflower, Wright’s marsh thistle, and Leoncita false-foxglove all have high tolerances for soil salinity during the growing season after germination. This might allow them to compete with other species that cannot survive in high salinity environments. 

Studies that aim to support the management of rare wetland plants may benefit from a systems approach to support management of rare wetland plants, as it facilitates an understanding of wetland functioning and processes that ultimately govern where, when, and how species establish and survive.

Spending longer periods of time at the refuge and maintaining close relationships with refuge managers and staff was key in helping researchers develop a nuanced understanding of the ciénegas.

Next Steps

• Integrate information about germination requirements and the effects of soil moisture and salinity on survival of the three rare wetland plants into current wetland management strategies to increase the abundance and distribution of the three rare wetland plants
• Expand seed germination experiments to other plant species of importance as waterbird foods
• Investigate the role of seed banks in restoration of these at-risk plants

Funding Partners

• USGS and bet365����ios partnership Science Support Partnership program

Contacts

Antonio Cantu, Louisiana State University: antoniocantu91@gmail.com

CART Lead Author

Ariel Léger, CART Research Specialist, University of Arizona: arielleger@arizona.edu

Suggested Citation

Léger, A., and Cantú, A. (2021) “Bitter Lake National Wildlife Refuge: Managing for Birds Benefits Rare Plants” CART. Retrieved from /project/managing-birds-benefits-rare-plants