SFS Annual Meeting

5/24/2018  |   11:00 - 11:15   |  410 B

EFFECTS OF WARMING AND ELEVATED CO2 ON ORGANIC MATTER DECOMPOSITION IN A PEATLAND USING AN ECOSYSTEM-SCALE EXPERIMENT Globally, peatlands store a disproportionately large amount of carbon in peat relative to their surface area. Peat accumulates when primary production exceeds decomposition, therefore, it is important to understand how climate change may affect both production and decomposition rates in these saturated, carbon-rich environments. The Spruce and Peatland Responses Under Changing Environments (SPRUCE) experiment uses ten 12-m diameter enclosures to elevate air and peat temperatures (+0, +2.25, +4.5, +6.75, +9C) at ambient and elevated CO2 (eCO2) (+500 ppm) for 10 years in a northern Minnesota peatland. We measured decomposition rates of 6 litter types that vary in quality (spruce needles and fine roots, Labrador tea leaves and fine roots, and two Sphagnum species) for one year in the SPRUCE enclosures. There was little effect of temperature and eCO2 on aboveground litter decomposition; however, decomposition rates of fine roots increased with warming. A standardized cotton-strip assay deployed vertically into the peat found that tensile loss increased with temperature at all depths. Together, these results suggest that litter recalcitrance may be a stronger driver of aboveground litter decomposition than temperature in the first year of the SPRUCE experiment.

Natalie Griffiths (Primary Presenter/Author), Oak Ridge National Laboratory, griffithsna@ornl.gov;


Randy Kolka (Co-Presenter/Co-Author), USDA Forest Service Northern Research Station, rkolka@fs.fed.us;


Colleen Iversen (Co-Presenter/Co-Author), Oak Ridge National Laboratory, iversencm@ornl.gov;


Scott Tiegs (Co-Presenter/Co-Author), Oakland University, tiegs@oakland.edu;


Deanne Brice (Co-Presenter/Co-Author), Oak Ridge National Laboratory, bricedj@ornl.gov;


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5/24/2018  |   11:15 - 11:30   |  410 B

GLOBAL PATTERNS AND CONTROLS OF ORGANIC-MATTER DECOMPOSITION IN STREAMS AND RIPARIAN ZONES REVEALED THROUGH CROWDSOURCING Organic-matter decomposition is a central process in streams and riparian ecosystems, yet large-scale patterns and controls of this process are poorly known. Adopting a crowdsourcing approach, we deployed a standardized decomposition assay in over 500 streams and their riparian zones. Sites spanned 140 degrees of latitude, and were located on each continent and in each major biome. We observed global-scale patterns in decay rates, including stark differences among biomes, and negative relationships with latitude. Decay is particularly rapid in tropical forests (wet and dry) and slow in tundra and boreal forests; other biomes are bracketed by these extremes. Variability increases towards the equator, suggesting temperature limitation at high latitudes and greater scope for other environmental factors to influence decay at lower latitudes. The ratio of riparian to instream decomposition rates ranges widely among riparian-stream pairs and biomes. Activation energy is greater in streams than riparian zones, suggesting different factors govern decay. These findings are a step towards establishing baseline data to track global change, and providing a process-based tool for emerging international assessment programs (e.g., Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, Convention on Biological Diversity).

Scott Tiegs (Primary Presenter/Author), Oakland University, tiegs@oakland.edu;


David Costello (Co-Presenter/Co-Author), Kent State University, dcostel3@kent.edu;


Mark Isken (Co-Presenter/Co-Author), Dept. of Decision and Information Sciences, School of Business Administration, Oakland University, isken@oakland.edu;


Guy Woodward (Co-Presenter/Co-Author), Imperial College London, gu.woodward@imperial.ac.uk;


Peter B. McIntyre (Co-Presenter/Co-Author), Cornell University, pbm3@cornell.ecu;


Eric Chauvet (Co-Presenter/Co-Author), EcoLab, Université de Toulouse, CNRS, France, eric.chauvet@univ-tlse3.fr;


Alexander Flecker (Co-Presenter/Co-Author), Cornell University, Ithaca, NY, USA, asf3@cornell.edu;


Mark Gessner (Co-Presenter/Co-Author), Leibniz-Institute of Freshwater Ecology and Inland Fisheries / Berlin Institute of Technology , gessner@igb-berlin.de;


Natalie Griffiths (Co-Presenter/Co-Author), Oak Ridge National Laboratory, griffithsna@ornl.gov;


the CELLDEX Consortium (Co-Presenter/Co-Author), Multiple Institutions, CELLDEX.consortium@gmail.com;


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5/24/2018  |   11:30 - 11:45   |  410 B

DISSOLVED ORGANIC MATTER DYNAMICS IN GRASSLAND STREAMS Understanding the dynamics of dissolved organic matter (DOM) in streams is important for characterizing food webs and estimating global carbon budgets. However, not all DOM is the same and the composition of a given DOM molecule effects its eventual biogeochemical fate. The sheer quantity of different compounds that make up the DOM pool in streams makes it impractical to monitor all of them but some specific compounds can be detected relatively easily. We estimated the biological uptake of specific DOM compounds and classes in multiple grassland stream reaches across different seasons using glucose assays and fluorescence spectroscopy. From tracer experiments, we found that glucose and an amino acid-like component were consistently removed from the stream faster than two humic-like species. In addition, the humic-like species both remained elevated above background concentrations longer than the conservative tracer, indicating adsorption and re-release. Uptake calculations made using concentrations of specific compounds or components resulted in different parameters than those made using total dissolved organic carbon (TDOC) concentrations. This indicates that following the behavior of specific DOM components rather than TDOC could give more accurate results.

Sophie A. Higgs (Primary Presenter/Author), Kansas State University, sahiggs@ksu.edu;


Walter Dodds (Co-Presenter/Co-Author), Kansas State University, wkdodds@ksu.edu;


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5/24/2018  |   11:45 - 12:00   |  410 B

REVVING UP AND BURNING OUT? LEAF LITTER SPECIES IDENTITY AND DIVERSITY INFLUENCE WHOLE-STREAM NUTRIENT DYNAMICS Microbial decomposers supplement the low nutrient content of leaf litter with nutrients from the water column. At the same time, litter nutrient content and breakdown rates are strongly influenced by litter species identity. We tested the influence of litter identity and diversity on whole-stream nutrient dynamics by adding one of four different litter compositions (Cottonwood (Populus deltoides), Sycamore (Platanus occidentalis), Bur Oak (Quercus macrocarpa) and Mixed (three species mixture)) to 12 large (~20 m long) outdoor stream mesocosms. Nutrients were dosed once weekly to measure declines (removal) in water column NH4-N, NO3-N and PO4-P. Cottonwood (labile, low C:N) streams removed nutrients fastest at the beginning of the study, but slowed to where Oak (recalcitrant, high C:N) streams removed more nutrients. At the end of the study, Oak streams had higher cumulative NO3-N removal than Cottonwood streams, suggesting that slowly decomposing litter may be a longer-term nutrient sink than quickly decomposing species. Mixed litter removal was generally additive, although we observed some evidence of positive non-additivity in cumulative NO3-N removal that deserves future exploration. Litter identity could determine how and when leaf litter serves as a nutrient sink for stream ecosystems.

Caleb J. Robbins (Primary Presenter/Author), University of Alaska Fairbanks, Caleb_Robbins@baylor.edu;


Will Matthaeus (Co-Presenter/Co-Author), Baylor University, Will_Matthaeus@baylor.edu;


Stephen C. Cook (Co-Presenter/Co-Author), University of Oklahoma, stephencook@ou.edu;


Lauren Housley (Co-Presenter/Co-Author), Baylor University, Lauren_Housley@baylor.edu;


Sarah Hester (Co-Presenter/Co-Author), Baylor University, Sarah_Hester@baylor.edu;


Matt Garbarino (Co-Presenter/Co-Author), Baylor University, Matt_Garbarino@baylor.edu;


Erick LeBrun (Co-Presenter/Co-Author), Baylor University, Erick_LeBrun@baylor.edu;


Swastika Raut (Co-Presenter/Co-Author), Baylor University, Swastika_Raut@baylor.edu;


Chi-Yen Tseng (Co-Presenter/Co-Author), Baylor University, Chi-yen_Tseng@baylor.edu;


Ryan S. King (Co-Presenter/Co-Author), Baylor University, Ryan_S_King@baylor.edu;


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5/24/2018  |   12:00 - 12:15   |  410 B

(DE)-COUPLING OF DISSOLVED ORGANIC CARBON AND DISSOLVED ORGANIC NITROGEN ACROSS STREAM ECOSYSTEMS Dissolved organic matter (DOM) is both a major energy and nutrient source in stream ecosystems. DOM is comprised of both dissolved organic carbon (DOC) and dissolved organic nitrogen (DON); however, it is not well understood how variable the relationship is between DOC and DON across watersheds and if these fractions are under different biogeochemical controls. Here we use long-term observational data and experimental data from across a global array of watersheds to examine the coupled cycling of DOC and DON. While DOC and DON concentrations are correlated at the global scale, their power-law relationship indicates that DON concentrations scale at 80% of each unit increase in DOC concentration. Across watershed we found scaling properties to be highly variable indicating that some streams experience DON depletion while other streams maintain a near 1:1 isometric relationship with increases in DOC. DOC and DON also respond in unique ways to inputs of nitrate; however the direction of their response (i.e. increase/decrease in concentration) appears to vary primarily at the biome scale. We invoke hydrological, physical and biological controls to explain variability in the decoupling of DOC and DON across watersheds.

Adam Wymore (Primary Presenter/Author), University of New Hampshire, adam.wymore@unh.edu;
Dr. Adam Wymore is a Research Assistant Professor at University of New Hampshire.

Ashley Helton (Co-Presenter/Co-Author), University of Connecticut, ashley.helton@uconn.edu;


Rebecca Barnes (Co-Presenter/Co-Author), Colorado College, rbarnes@coloradocollege.edu;


Jack Brookshire (Co-Presenter/Co-Author), Montana State University, jbrookshire@montana.edu;


Sujay Kaushal (Co-Presenter/Co-Author), University of Maryland, skaushal@umd.edu;
Dr. Sujay Kaushal is currently a Professor in the Department of Geology & Earth System Science Center at the University of Maryland, College Park, and he has been in this position since 2010. Prior to that, Dr. Kaushal was an assistant professor at the University of Maryland Center for Environmental Science from 2005-2010. His research expertise deals with: investigating causes and consequences of freshwater salinization, understanding the impacts of stormwater management and stream restoration on water quality, elucidating fate and transport of urban pollutants; and tracking sources of nonpoint pollution using geochemical approaches and tracers. Dr. Kaushal has authored over approximately 100 peer-reviewed papers in journals such as Proceedings of the National Academy of Sciences, Nature Reviews Earth and Environment, and Nature Sustainability, and he has received awards such as the UMD College of Computer, Mathematical, and Natural Sciences Junior Faculty Award and the IRPE Prize in limnetic ecology (https://www.int-res.com/ecology-institute/eci-prize-awarding/eci-award-ceremony-2012/). From the perspective of education and training, he was a postdoctoral fellow at the Cary Institute from 2003-2005. He received his PhD from the University of Colorado, Boulder, and he received his bachelors degree from Cornell University.

Emily Bernhardt (Co-Presenter/Co-Author), Duke University, emily.bernhardt@duke.edu;


Walter Dodds (Co-Presenter/Co-Author), Kansas State University, wkdodds@ksu.edu;


Penny Johnes (Co-Presenter/Co-Author), University of Bristol, penny.johnes@bristol.ac.uk;


Sherri Johnson (Co-Presenter/Co-Author), U.S. Forest Service, Pacific Northwest Research Station, sherrijohnson@fs.fed.us;


Pirkko Kortelainen (Co-Presenter/Co-Author), Finnish Environment Institute, pirkko.kortelainen@ymparisto.fi;


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


Robert Spencer (Co-Presenter/Co-Author), Florida State University, rgspencer@fsu.edu;


Bianca Rodriguez-Cardona (Co-Presenter/Co-Author), University of New Hampshire, bianca.rodz.pr@gmail.com;


Alba Argerich (Co-Presenter/Co-Author), University of Missouri-Columbia, argericha@missouri.edu;
Assistant Professor Stream Ecology

Ashley Coble (Co-Presenter/Co-Author), National Council for Air and Stream Improvement, Inc., acoble@ncasi.org;


Carla López-Lloreda (Co-Presenter/Co-Author), Virginia Tech, carla.lpez09@gmail.com;


Pamela Sullivan (Co-Presenter/Co-Author), Oregon State University, Pamela.Sullivan@oregonstate.edu;


Shahan Haq (Co-Presenter/Co-Author), University of Maryland, shahan66@gmail.com;


Michelle Shattuck (Co-Presenter/Co-Author), University of New Hampshire, Michelle.Shattuck@unh.edu;


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5/24/2018  |   12:15 - 12:30   |  410 B

SUB-LETHAL SALT CONCENTRATIONS ALTER DETRITIVORE PERFORMANCE Mounting evidence supports that salts can alter detrital quality and riparian-stream linkages in agricultural, urban, and resource-extracted watersheds. Detritivore-specific responses to sub-lethal salt concentrations need to be quantified to understand ecosystem impacts. We quantified how sub-lethal ion concentrations affect detritivores with two experiments. First, sweetgum leaves were incubated in one of three sodium chloride (NaCl) and three sodium bicarbonate (NaHCO3) treatments (10 replicates per treatment): natural (from a local stream), low (16 mg/L Na), medium (32mg/L Na), and high (64 mg/L Na). In the first experiment, microbial respiration, leaf mass remaining, and fungal and algal biomasses were measured after 126 incubation days. In the second experiment, macro-detritivore growth and growth efficiencies were measured after 30 days. Overall, salt treatments had little effect on microbial-mediated decomposition and fungal and algal biomass; however, microbial respiration tended to be elevated in NaHCO3. In the second experiment, salt amendments tended to stimulate stonefly growth, but had varied effects on growth efficiencies compared to stream water. Ion-specific effects at multiple trophic levels may be from reduced energy expenditure for osmoregulation and altered detrital quality that together could have long-term effects on carbon cycling.

Sally Entrekin (Primary Presenter/Author), Virginia Tech, sallye@vt.edu;


Brooke Howard-Parker (Co-Presenter/Co-Author), University of Arkansas, bbhowardparker@gmail.com;


Natalie Clay (Co-Presenter/Co-Author), Louisiana Tech University, nclay@latech.edu;


Michelle Evans-White (Co-Presenter/Co-Author), University of Arkansas, mevanswh@uark.edu;


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