Climate change, urbanization, agricultural expansion – human activities are impacting ecosystems at an increasing rate and spatial scale. I am motivated to understand how watersheds are responding to these changes, and what the impacts are on how they transport, modify, and store nutrients and carbon. Across many different studies and field sites, a central theme is answering the question: How do hydrologic vs. ecological processes regulate nutrient export and carbon emissions at the watershed scale, and how does the balance of these biophysical controls respond to environmental change?
Research in our group addresses these questions using a combination of observational and experimental approaches in both the field and lab to better understand how watersheds function.
Research in our group addresses these questions using a combination of observational and experimental approaches in both the field and lab to better understand how watersheds function.
Dry streams at Youngmeyer Ranch, KS // Photo from Amy Burgin
Intermittent streams: Characterizing the hydrologic and biogeochemical regime of non-perennial stream ecosystems
How do intermittent streams transport and transform nutrients and organic matter? What are the spatial and temporal scales over which intermittent systems interact with and influence downstream perennial waters?
Intermittent streams make up over 50% of the global river network length, yet they remain understudied compared to their perennial counterparts. The vast majority of our understanding of how streams transport and transform nutrients and organic material has been based on studies of perennial streams, or systems in which surface water flow is present year-round. Climate change and anthropogenic pressure on water resources have the potential to increase stream intermittency in the future, making it increasingly important to understand the biogeochemical and hydrologic regimes of these dynamic systems.
Research on this theme has spanned several different funded projects and collaborative research networks:
How do intermittent streams transport and transform nutrients and organic matter? What are the spatial and temporal scales over which intermittent systems interact with and influence downstream perennial waters?
Intermittent streams make up over 50% of the global river network length, yet they remain understudied compared to their perennial counterparts. The vast majority of our understanding of how streams transport and transform nutrients and organic material has been based on studies of perennial streams, or systems in which surface water flow is present year-round. Climate change and anthropogenic pressure on water resources have the potential to increase stream intermittency in the future, making it increasingly important to understand the biogeochemical and hydrologic regimes of these dynamic systems.
Research on this theme has spanned several different funded projects and collaborative research networks:
- Aquatic Intermittency effects on Microbiomes in Streams (AIMS): The AIMS project is a multi-state EPSCoR grant that is focused on understanding the role of stream intermittency in controlling water quantity and quality across the Mountain West, Great Plains, and Southeastern Forest ecosystems. This field-oriented collaboration integrates datasets on hydrology, biogeochemistry, and microbial communities in three biomes to test the overarching hypothesis that physical drivers (e.g. climate, hydrology) interact with biological drivers (e.g. microbial communities, biogeochemistry) to control water quality in intermittent streams across the United States. Research in my lab group has explored how streamflow intermittency and patterns of drying impact dissolved oxygen regimes, ecosystem metabolism, and biophysical controls on surface water chemistry concentrations.
- Dry Rivers Research Coordination Network (DRRCN): is an NSF funded working group focused on advancing intermittent river ecology and hydrology. Research as part of this group led to numerous publications, and founding of the new Non-Perennial Ecosystems Chapter of the Society of Freshwater Science, which will serve as a hub for non-perennial stream/wetland researchers more broadly.
- USGS-EPA working group on Advancing Headwater Stream Modeling: is an active collaboration coordinated by the USGS Powell Center focused on understanding and modeling headwater stream function. Research as part of this group is exploring questions about how headwater streams, particularly those that are non-perennial, impact downstream water quality and quantity.
Kansas River // Photo by Lisa Grossman
Water resources, climate change, and agricultural adaptation in the Great Plains
How do disturbances like land use change, climate change, and reservoir management affect water quality and quantity in the Great Plains region, and how might agricultural adaptation create sustainable water resources in the future? What effect do nutrient legacies have on contemporary biogeochemical signals?
Land use change alters the supply of nutrients and carbon within landscapes, as well as the degree of aquatic-terrestrial connectivity. Climate change has been linked with increasing frequency of extreme precipitation events and droughts in the midwestern US, with cascading impacts on aquatic-terrestrial connectivity. These disturbances can interact with human management of reservoirs in complex, non-linear ways with the potential for diminished water quality and ecosystem function. Projects in my group that explore these themes include:
How do disturbances like land use change, climate change, and reservoir management affect water quality and quantity in the Great Plains region, and how might agricultural adaptation create sustainable water resources in the future? What effect do nutrient legacies have on contemporary biogeochemical signals?
Land use change alters the supply of nutrients and carbon within landscapes, as well as the degree of aquatic-terrestrial connectivity. Climate change has been linked with increasing frequency of extreme precipitation events and droughts in the midwestern US, with cascading impacts on aquatic-terrestrial connectivity. These disturbances can interact with human management of reservoirs in complex, non-linear ways with the potential for diminished water quality and ecosystem function. Projects in my group that explore these themes include:
- Sustainable Adaptations to the Future Environment of Kansas’s Agriculture and Water (SAFEKAW): As part of work funded by the SAFEKAW project, we are exploring numerous research avenues that, when taken together, will help us understand the historical controls on nitrate export from the Kansas River basin, future export under different climate scenarios, the impacts of changing extreme weather & weather whiplash on nitrate export, and the role of reservoir management in driving event-scale nitrate export.
- Aquifer Water Quality Assessment in Kansas (AWQuA-Kan): As the PI of the newly-funded state water quality program, we are establishing an ambitious statewide groundwater quality research and monitoring program to serve the needs of the state of Kansas and advance our understanding of agricultural nutrient legacies, groundwater sustainability, and rural health. This program integrates new data collection and data integration of historical datasets from across the state to generate a comprehensive groundwater quality database for the state of Kansas.
Wade Brook (VT) during a rain-on-snow event
Critical Zone Resiliency to Environmental Change
How does critical zone structure control the multidimensional response of ecosystems to disturbances, and thereby regulates ecosystem resilience and resistance?
The critical zone (CZ), Earth's near-surface layer that spans from bedrock to the tree canopy, is being increasingly affected by numerous types of anthropogenic change that have the potential to trigger ecosystem state changes. However the structure of the CZ may mediate how resilient or resistant ecosystems are to multiple, interacting disturbances. Research on this theme spans several different funded projects:
How does critical zone structure control the multidimensional response of ecosystems to disturbances, and thereby regulates ecosystem resilience and resistance?
The critical zone (CZ), Earth's near-surface layer that spans from bedrock to the tree canopy, is being increasingly affected by numerous types of anthropogenic change that have the potential to trigger ecosystem state changes. However the structure of the CZ may mediate how resilient or resistant ecosystems are to multiple, interacting disturbances. Research on this theme spans several different funded projects:
- CZNet Big Data: As co-PI of a Critical Zone Collaborative Network grant, our team is using complex systems tools (i.e. “Big Data” approaches) to understand what CZ properties and climate characteristics regulate water, carbon, and nutrient retention and how CZ properties, disturbance history, and land use affect resistance and resilience to more intense, large-scale disturbances under a changing climate and anthropogenic pressure. In particular, research in my group has focused on the northeastern US and how recovery from long-term acidification has impacted solute export and stoichiometry from watersheds.
- USGS Powell Center working group on Hydroclimatic-ecosystem asynchrony: As a co-PI of a newly funded synthesis group, we will explore how critical zone structure, including bedrock characteristics and vegetation, mediates the synchrony between hydroclimatic inputs and ecological, hydrologic, and biogeochemical processes. Specifically, we aim to determine how CZ characteristics influence the timing and coupling of these hydroclimatic inputs (e.g., precipitation) and hydrologic outputs (e.g., streamflow), and how these relationships may change under future climate scenarios. The findings will improve predictions of water availability and ecosystem responses, offering vital insights for water resource management and climate adaptation.
- Effects of winter climate change on catchment hydrology and biogeochemistry: Research on the broader topic of critical zone asynchrony emerged out of work focused specifically on understanding How changes in the distribution of precipitation as rain vs. snow impact the timing, magnitude and stoichiometry of nutrient export from watersheds? Winter is an often understudied season, but is increasingly vulnerable to our changing climate. Warmer temperatures and changes in the form of precipitation as rain or snow have the potential to greatly alter ecosystem function. In particular, the conversion of winter precipitation from snow (which accumulates in areas with seasonal snowpack) to rain will likely have important consequences for runoff generation and nutrient export, with cascading implications for soil nutrient dynamics, terrestrial vegetation responses, and lake primary productivity.
Elkhorn Slough, CA
Coastal hydro-biogeochemistry
How are terrestrially-derived solutes transformed along groundwater flowpaths in coastal ecosystems?
Coastal estuaries are the interface between uplands and the ocean and have the important role of intercepting, transforming, and transporting pollutants before entering the marine environment. While the importance of terrestrially-derived, nonpoint source nutrient pollution from rivers into coastal systems has been extensively characterized, the contribution and fate of pollutants from diffuse groundwater is less understood. Our team is focused on quantifying nitrogen fate and transport along shallow groundwater flowpaths at the aquatic-terrestrial interface in coastal watersheds draining into the Elkhorn Slough National Estuarine Reserve in Monterey, CA. Our research team combines empirical field data, ex-situ lab experiments, and reactive transport modeling to address these questions. This work is supported by grants from California SeaGrant and the Department of Energy Subsurface Biogeochemical Research Division (abstract).
How are terrestrially-derived solutes transformed along groundwater flowpaths in coastal ecosystems?
Coastal estuaries are the interface between uplands and the ocean and have the important role of intercepting, transforming, and transporting pollutants before entering the marine environment. While the importance of terrestrially-derived, nonpoint source nutrient pollution from rivers into coastal systems has been extensively characterized, the contribution and fate of pollutants from diffuse groundwater is less understood. Our team is focused on quantifying nitrogen fate and transport along shallow groundwater flowpaths at the aquatic-terrestrial interface in coastal watersheds draining into the Elkhorn Slough National Estuarine Reserve in Monterey, CA. Our research team combines empirical field data, ex-situ lab experiments, and reactive transport modeling to address these questions. This work is supported by grants from California SeaGrant and the Department of Energy Subsurface Biogeochemical Research Division (abstract).