SFS Annual Meeting

6/06/2024  |   15:30 - 15:45   |  Philadelphia Ballroom

THE WHOLE-ECOSYSTEM APPROACH APPLIED TO HIGHLY MODIFIED AND INTENSIVELY MANAGED WATERSHEDS The whole-ecosystem, watershed approach has a long history of advancing biogeochemistry in forested, headwater streams. The approach is less commonly applied in human-dominated landscapes, despite the global prevalence of managed ecosystems and the potential for gaining fundamental insights into human-ecosystem interactions. Since 2016 we have conducted watershed-scale studies on management practices in small watersheds in Indiana (USA) dominated by row-crop agriculture. Specifically, we paid farmers to plant winter cover crops as a watershed-scale manipulation to reduce nutrient loss and increase soil carbon. By monitoring fluxes at the watershed outlets, and from subsurface drainage within the watersheds, we documented substantial and consistent reductions in nitrate losses: lateral fluxes through subsurface drains were 50-80% lower with cover crops. Nitrate losses responded quickly to the cessation of cover cropping. Responses in dissolved phosphorus and carbon were less consistent than for nitrate, and all fluxes were strongly related to precipitation and discharge. Soil nitrate concentrations were a function of cover crop above-ground biomass, indicating plant uptake was the mechanism responsible for retaining nitrate in the terrestrial environment. Consistent cover cropping increased soil organic matter by about 0.1% per year and appeared to reduce DOC loss, though the mechanism is not fully resolved. We are now coupling terrestrial-aquatic fluxes to eddy covariance measurements of biosphere-atmosphere exchange to close the carbon budget using a true whole-ecosystem context. From our perspective, the watershed approach has proved valuable in an applied setting and offers a versatile platform for integrating natural and social sciences in human-dominated landscapes.

Todd V. Royer (Primary Presenter/Author), Indiana University Bloomington, troyer@iu.edu;

Jennifer L. Tank (Co-Presenter/Co-Author), University of Notre Dame, tank.1@nd.edu;

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6/06/2024  |   15:45 - 16:00   |  Philadelphia Ballroom

A long journey to recovery: exploring resilience trajectories of stream ecosystems six years after major disturbances The ability of ecosystems to withstand disturbance and maintain their crucial ecosystem functions has long intrigued ecologists, especially as rates of environmental change intensify due to the increasing magnitude and frequency of extreme climatic events associated with ongoing climate change. We evaluated the resilience trajectory of multiple ecosystem components in response to disturbances caused by two major hurricanes in Puerto Rico. We fit eight different models (linear positive, negative or flat curve, humped yield curve, quadratic function -upside down parabola curve, logistic curve, logarithmic curve, exponential curve, Gompertz asymmetric sigmoid model curve, goniometric curve) to determine the best fit explaining the resilience trajectory of ecosystem components six years after hurricanes. Our result showed that different components of the stream ecosystem exhibited varying response trajectories following the hurricanes. Canopy cover and leaflitter inputs showed a large change after the hurricanes, and the model that best explained the trajectory was the Humped yield curve type (i.e., Nelson-Siegel function, AIC>2). In contrast, the parabola curve (a quadratic regression model, AIC>2) was the best model that explained the resilience of stream algae, macroinvertebrates (inverted) and shrimp (up). These curve shapes suggest potential interactions among shrimp, macroinvertebrates, and algae influencing their respective responses. This study serves to underline the need for long-term data to understand ecosystem resilience and how streams respond to extreme events, which are expected to become more frequent due to climate change.

Pablo E. Gutierrez-Fonseca (Primary Presenter/Author), Rubenstein School of Environment and Natural Resources, University of Vermont, gutifp@gmail.com;

Alonso Ramirez (Co-Presenter/Co-Author), Department of Applied Ecology, North Carolina State University, alonso.ramirez@ncsu.edu;

Catherine Pringle (Co-Presenter/Co-Author), Odum School of Ecology, University of Georgia, cpringle@uga.edu;

Jesus Gomez (Co-Presenter/Co-Author), Department of Biology, University of Puerto Rico- Rio Piedras, jesuslobo06@gmail.com ;

Alan Covich (Co-Presenter/Co-Author), Odum School of Ecology, University of Georgia, a.covich@gmail.com;

Todd Crowl (Co-Presenter/Co-Author), Florida International University, facrowl@gmail.com;

William McDowell (Co-Presenter/Co-Author), Department of Natural Resources and the Environment, University of New Hampshire, 03824, Durham, New Hampshire, bill.mcdowell@unh.edu;

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6/06/2024  |   16:00 - 16:15   |  Philadelphia Ballroom

CROSSING DISCIPLINES, BUILDING BRIDGES, AND THINKING LONG-TERM: THE ROLE OF STREAM BIOGEOCHEMISTRY IN THE DEVELOPMENT OF ECOSYSTEM SCIENCE Ecosystem science has developed dramatically in the past 50 years. Many of its conceptual advances have been spurred by the study of aquatic systems, which are particularly amenable to using an ecosystem approach due to their relatively clear boundaries and opportunities for “replication” such as paired watersheds. Running waters have been particularly important in pushing ecosystem science forward, as they integrate land and water, and have spurred development of new approaches to understanding rapidly changing ecosystem dynamics. Three central questions have motivated my research. 1) How are land and water linked? Starting with the dictum of Hynes that the valley rules the stream, I have examined the many ways in which solutes such as dissolved organic carbon (DOC) are linked to soil and landscape attributes. 2) Gutters or reactors? “Rivers are the gutters down which flow the ruins of continents”; this is a testable hypothesis from Leopold et al. (1964) that I have been addressing since 1974 by examining in-stream controls on nitrate and DOC. 3) Leading indicators, or just noise? To what extent does spatial and temporal variability in stream chemistry reflect long-term changes in local or global conditions, or just short-term noise? How do we describe the short-term controls on stream chemistry and sort them out from longer-term drivers such as changing atmospheric deposition and increasing temperature? A combination of sensors and multi-decadal sampling records is necessary to address this question. It’s been a good ride, and I have worked with wonderful people.

William H McDowell (Primary Presenter/Author), University of New Hampshire, bill.mcdowell@unh.edu;

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6/06/2024  |   16:15 - 16:30   |  Philadelphia Ballroom

Closing Remarks and Discussion

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