SFS Annual Meeting

5/21/2019  |   11:00 - 11:15   |  151 ABC

PLANT SEX INFLUENCES LEAF LITTER CHEMISTRY, DECOMPOSITION, AND HERBIVORE-INDUCED SUMMER LITTER INPUTS TO STREAMS AT MOUNT ST. HELENS, WA, USA Research has shown that plant genetics can influence ecosystem processes, but one genetic difference that has received little study is sex in dioecious plants. Since headwater streams are reliant on carbon and nutrients from leaf litter fall, plant sex differences in litter chemistry may influence stream function. Sitka willow (Salix sitchensis) at Mount St. Helens are heavily infested with a stem-boring weevil that causes summer branch die-back and leaf drop. Willow is dioecious with female plants tending to grow closer to stream banks and showing higher weevil attack rates. In combination, these two factors lead to increased summer litter inputs from female willow trees. Female leaf litter is significantly elevated in condensed tannin concentrations which leads to slower decomposition rates. In all of these ways, female trees may provide more sustained carbon and nutrient resources to microbes and invertebrates in the early successional streams at Mount St. Helens. Dioecy is a relatively common trait in riparian habitats, and it is possible that plant sex plays a far more interesting role in structuring communities and ecosystem processes than we previously understood.

Carri LeRoy (Primary Presenter/Author), Evergreen State College, leroyc@evergreen.edu;


Shannon Claeson (Co-Presenter/Co-Author), USDA Forest Service, sclaeson@fs.fed.us;


Joy M. Ramstack Hobbs (Co-Presenter/Co-Author), The Evergreen State College, hobbsj@evergreen.edu;


Jordan Moffett (Co-Presenter/Co-Author), The Evergreen State College, jamandamoffett@gmail.com;


Logan Lancaster (Co-Presenter/Co-Author), The Evergreen State College, lanlog02@evergreen.edu;


Lauren Walker (Co-Presenter/Co-Author), Lewis and Clark College, walker.laurenjean@gmail.com;


Dylan Fischer (Co-Presenter/Co-Author), The Evergreen State College, fischerd@evergreen.edu;


Presentation:
This presentation has not yet been uploaded.

5/21/2019  |   11:15 - 11:30   |  151 ABC

SEASONAL PULSES OF DISSOLVED ORGANIC MATTER ARE DECOUPLED FROM ECOSYSTEM RESPIRATION IN A RESTORED TALLGRASS PRAIRIE STREAM Prairie restoration can increase soil organic matter, but the effects of watershed-scale upland soil restoration on stream functions remain unclear. Here, we assessed dissolved organic matter (DOM) pools and fluxes to a headwater tallgrass prairie stream within a watershed influenced by long-term prairie restoration and no-till agriculture. We measured soil porewater and streamwater DOM monthly during the growing season and stream fluorescent DOM and dissolved oxygen continuously for one year; these data were used to model whole-stream metabolism. We predicted that DOM fluxes from soils to stream would be related to whole-stream metabolism, especially ecosystem respiration. DOM was 1.5x higher, on average in prairie vs. agriculture soil porewater; prairie soils exhibited highest DOM at the onset of autumn. Streamwater fluorescent DOM concentrations peaked during early spring. Highest GPP (2.1 g O2 m-2 d-1) and ER (-4.45 g O2 m-2 d-1) occurred in late spring, and was preceded by peak concentrations of DOM, suggesting seasonal stream metabolism was driven by primary production, rather than flushing of terrestrial dissolved organic matter. Our findings imply prairie restoration can affect soil organic matter pools, but changes to stream functions may be less pronounced.

David Manning (Primary Presenter/Author), University of Nebraska at Omaha, davidmanning@unomaha.edu;


Ashlee Dere (Co-Presenter/Co-Author), University of Nebraska at Omaha, adere@unomaha.edu;


Andrew Miller (Co-Presenter/Co-Author), University of Nebraska at Omaha, andrewmiller@unomaha.edu;


Tracy Coleman (Co-Presenter/Co-Author), University of Nebraska at Omaha, tracycoleman@unomaha.edu;


Presentation:
This presentation has not yet been uploaded.

5/21/2019  |   11:30 - 11:45   |  151 ABC

AQUATIC ECOSYSTEM RESPONSES TO RIPARIAN CANOPY GAPS IN FORESTED HEADWATER STREAMS Across temperate North America, riparian zones are dominated by mid-succession forests. The dense and structurally uniform canopies that develop at the early/middle stages in forest succession limit light availability to streams, thereby limiting fundamental aquatic ecosystem processes such as primary production and biogeochemical cycling. In contrast to the light-limited streams with young uniform riparian forests, streams bordered by old-growth forests often have irregular canopy gaps that lead to patches of increased light availability. These patches of elevated light from canopy gaps are hypothesized to release benthic algae from light limitation, leading to increased primary production and greater nutrient cycling. To assess the influence of riparian forest structure on stream ecosystem processes, we conducted a field experiment with six replicate canopy gap treatments along streams bordered by dense mid-successional forests. We quantified changes in light availability, primary production, and nutrient demand. Creating canopy gaps resulted in localized increases in light, with subsequent increases in chlorophyll-a accrual and nutrient demand at the reach scale. This work will advance our understanding of how successional changes in terrestrial systems can impact processes in adjacent aquatic ecosystems.

Allison Swartz (Primary Presenter/Author), Oregon State University, allison.swartz@oregonstate.edu;


Dana Warren (Co-Presenter/Co-Author), Oregon State University, dana.warren@oregonstate.edu;


Presentation:
This presentation has not yet been uploaded.

5/21/2019  |   11:45 - 12:00   |  151 ABC

NUTRIENT DYNAMICS IN AN URBAN FOREST FRAGMENT. Abrupt transitions in riparian land use are a common feature of modern watersheds. In fragmented landscapes, forest remnants have the potential to ameliorate environmental conditions. Quantifying the temporal and spatial dynamics that modulate the biogeochemical reactivity in such transitions is key to estimate the potential of nutrient sequestration and retention of these remnants. In this study we examined the effects of flow regimes (hydrological opportunity) and temperature (biogeochemical reactivity) in the nutrient retention potential of a forest fragment within an urbanized catchment. The dataset is derived from a 3 year long weekly monitoring of nutrients in the Duke experimental forest. Along 1200 meters, NH4, NO3 and DOC were measured weekly in 7 sites along a 3-year period. We found higher input of nutrients summer days due to rainfall, as well as higher reactivity, with strong indication of nitrification. In general, the forested section was a net exporter export of both C and N. Export rates were lower in warmer temperatures for both total N and C. Export ratios of C and N were coupled in a 7.8 ratio and indicating strong biological modulation in nutrient export along the reach.

Rafael Feijó de Lima (Primary Presenter/Author), University of Montana, rfeijod@clemson.edu;


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


Steven Thomas (Co-Presenter/Co-Author), University of Alabama, sathomas16@ua.edu;


Presentation:
This presentation has not yet been uploaded.

5/21/2019  |   12:00 - 12:15   |  151 ABC

THE HIERARCHICAL EFFECTS OF RIPARIAN MANAGEMENT ON HEADWATER STREAM ECOSYSTEMS IN BRITISH COLUMBIA, CANADA Headwater streams are closely connected to the adjacent landscape but receive little protection from forest harvest activities. Riparian buffers are assumed to mitigate the effects of harvesting on stream ecosystem structure and function even though the efficacy of this approach for protecting streams is unclear. We compare the ecological effects of riparian buffers in two ecoregions located in southern British Columbia, Canada. We collected comprehensive data on channel geomorphology, riparian structure, water quality and a suite of ecological responses in 24 headwater streams that represent a gradient of riparian buffer interventions. The response variables capture an ecological hierarchy and include litter decomposition, ecosystem metabolism, algal biomass, and macroinvertebrate community composition. Ecological responses varied among buffer treatments and across the region. Generally, inland streams had faster rates of decomposition, greater accrual of algal biomass, more abundant macroinvertebrate communities, but lower organic matter standing stocks compared to coastal streams. Differences in canopy cover showed little effect on gross primary productivity and all sites were heterotrophic. Additionally, we integrate these findings with insights from the bioassessment literature and provide further context for future considerations of forestry related impairments on downstream freshwater ecosystems.

Claire Ruffing (Primary Presenter/Author), University of British Columbia, ruffing.cathcart@ubc.ca;


John Richardson (Co-Presenter/Co-Author), Department of Forest and Conservation Sciences, University of British Columbia, john.richardson@ubc.ca;


Presentation:
This presentation has not yet been uploaded.

5/21/2019  |   12:15 - 12:30   |  151 ABC

ANTIBIOTICS IN RURAL STREAMS AND GROUNDWATER IN THE PIEDMONT OF NORTH CAROLINA Antibiotics are a class of contaminants that is gaining more attention. A great deal of attention regarding antibiotic pollution focuses on streams receiving wastewater effluent. In rural areas, antibiotics can enter streams from application in the maintenance of livestock or improper disposal practices and leaking septic tanks. Due to the interaction between surface water and groundwater throughout the stream networks, there’s a potential for contamination in both systems. The present study investigated 16 residential rural well sites (groundwater) and streams in Guilford, Randolph, and Alamance County, North Carolina. We detected 14 antibiotics over three seasons. Sulfamethoxazole, sulfamerazine, danofloxacin, and erythromycin were commonly detected throughout the sampling period. Concentrations ranged from 0-1000 ng/L in surface and groundwater, while sediment samples ranged from 0-98 ng/g. Fall surface water had significantly higher concentrations compared to spring (p<0.05). Groundwater had higher concentrations in winter compared to spring (p<0.05). Correlation analysis showed that animal density was positively correlated with antibiotic concentration. Findings from this study demonstrate that antibiotic pollution is widespread in rural systems and provide a basis for future studies investigating the occurrence of antibiotics in rural areas.

Austin Gray (Primary Presenter/Author), Virginia Tech, austindg@vt.edu;
Assistant Professor, Department of Biological Sciences, Virginia Tech

Daniel Todd (Co-Presenter/Co-Author), University of North Carolina at Greensboro, datodd3@uncg.edu;


Anne Hershey (Co-Presenter/Co-Author), The University of North Carolina at Greensboro, aehershe@uncg.edu;


Presentation:
This presentation has not yet been uploaded.