5/21/2015  |   13:30 - 13:45   |  103C

EXTREME STREAM–ECOSYSTEM EFFECTS FROM RIPARIAN DISTURBANCE IN AN OTHERWISE INTACT WATERSHED Whole-watershed vegetation removal generally causes large alterations to stream hydrological and nutrient dynamics. Published experiments suggest riparian corridor preservation during watershed removals may mitigate impacts because the zones serve as a buffer between streams and terrestrial areas. Yet, the relative contribution of riparian zones to sediment and nutrient transport in an impacted watershed is largely unknown; ecosystem shifts could be only a response to riparian removal. We removed woody, riparian vegetation in a grassland stream watershed subject to streamside woody expansion. We measured stream physiochemical parameters (e.g., nutrients and sediments) before and after the removal in the impacted riparian watershed and a neighboring control watershed and used Before-After, Control-Impact analyses to test for treatment effects. Riparian wood removal led to ten-fold increases in mean stream water nitrate, total phosphorus and sediments for three years following disturbance. Our data suggested that riparian zones exert a disproportionate influence on streams relative to their small area in the watershed. Maintaining the native condition of riparian zones may be desirable over mechanical restoration to achieve native state given their extreme sensitivity to disturbance.

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


Danelle Larson (Co-Presenter/Co-Author), U.S. Geological Survey, dmlarson@usgs.gov ;


Allison Veach (Co-Presenter/Co-Author), Kansas State University, amveach@ksu.edu;

5/21/2015  |   13:45 - 14:00   |  103C

RESPONSE OF AUTOTROPHIC AND HETEROTROPHIC PATHWAYS TO NUTRIENTS ALONG STREAM NETWORKS Nutrient pollution stimulates algal carbon, but reduces retention/availability of terrestrially derived particulate organic carbon (POC). Algae and POC serve as food for animals and substrates for nutrient uptake throughout stream networks. We examined where carbon gain or loss may result across river networks due to nutrient pollution using the Little Tennessee River (LTR) network. We paired published relationships between stream network position and POC standing stocks and annual gross primary production with published POC loss and algal gain responses to nutrient enrichment to estimate potential for carbon loss or gain for each 10-m reach in the LTR. Net carbon losses were predicted in 1st-4th order streams, while net carbon gains were predicted in 5th-7th order streams. Human modification of landscapes is sometimes limited to higher-order streams, but can also impact headwaters. Our analysis is a first approximation of these dynamics and does not include serial processing and transport, but illustrates that terrestrially derived POC, essential for functions downstream of its source, can be reduced relative to algal gain in large parts of river networks

Ashley M. Helton (Co-Presenter/Co-Author), University of Connecticut, amhelton@gmail.com;


Phillip Bumpers (Co-Presenter/Co-Author), University of Georgia, bumpersp@gmail.com;


Jonathan P. Benstead (Co-Presenter/Co-Author), The University of Alabama, jbenstead@ua.edu;


Amy D. Rosemond (Primary Presenter/Author), University of Georgia, rosemond@uga.edu;

5/21/2015  |   14:00 - 14:15   |  103C

CONNECTING SEASONAL RIPARIAN BUFFER METRICS AND NITROGEN CONCENTRATIONS IN A PULSE-DRIVEN AGRICULTURAL SYSTEM Riparian buffers have been well studied as best management practices for nutrient reduction at field scales yet their effectiveness for bettering water quality at watershed scales has been difficult to determine. Seasonal dynamics of the stream network are often overlooked when evaluating the use of riparian buffers in water quality management. In the Willamette Valley, OR, seasonal precipitation results in surface flows within agricultural fields that carry pulses of nutrients past riparian buffers and into streams and rivers. We present seasonal spatially-explicit metrics and statistically relate them to seasonal nitrogen concentrations. Field data, LiDAR data and soils data are used to estimate seasonal stream extents for the Calapooia River Watershed, OR. Flow-weighted metrics of buffered agriculture are calculated and we attempt to use statistical models that use information theory and model averaging to provide seasonal watershed estimations of nitrogen removal and losses through riparian buffers in the watershed. Findings from the seasonal statistical analysis will be presented and their implications for water quality and buffer management will be discussed.

Jay Christensen (Primary Presenter/Author), US EPA, Watershed & Ecosystem Characterization Division, Cincinnati, OH , christensen.jay@epa.gov;


Maliha Nash (Co-Presenter/Co-Author), US EPA Office of Research and Development - Environmental Science Division, nash.maliha@epa.gov;


Jana Compton (Co-Presenter/Co-Author), US EPA, Pacific Ecological Systems Division, Corvallis, OR, compton.jana@epa.gov;


Parker J. Wigington, Jr. (Co-Presenter/Co-Author), US EPA Office of Research and Development - Western Ecology Division (retired), pjwigington@gmail.com;


Stephen Griffith (Co-Presenter/Co-Author), USDA Agricultural Research Service - Corvallis, OR, Steve.Griffith@ars.usda.gov ;

5/21/2015  |   14:15 - 14:30   |  103C

HOW DO CHANGES IN CONSERVATION ALTER HOT-SPOTS OF NUTRIENT EXPORT IN AGRICULTURAL WATERSHEDS? Our project is quantifying whether the watershed-scale planting of winter cover crops (e.g., ryegrass) after corn/soybean harvest reduces export of excess fertilizer nutrients from agricultural fields into subsurface tile drains. In the 3000-acre Shatto Ditch Watershed (Kosciusko Co, IN), we collected water samples every 14d from 25 tile drains and 10 longitudinally-distributed stream sites along 8km of the Shatto to quantify the effects of cover crops on tile drain and stream export of nitrate-N. High-frequency sampling revealed that tile drains are year-round sources of nitrate-N to streams, and ~60% of tiles flow even in dry seasons (e.g., Summer/Fall, mean=13.9 mgNO3-/L) while >85% of tiles flow in Winter/Spring when nitrate concentrations are higher (mean=17.1 mgNO3-N/L). Additionally, tile concentrations vary spatially highlighting the importance of field-specific management practices (e.g., fertilizer application). Planting cover crops decreased average tile nitrate-N concentrations by 36% in Winter/Spring, which represented a 45% reduction in N-flux from tiles compared to pre-cover crop planting. After one year of planting, cover crops significantly reduced nutrient export from agricultural fields, showing promise for improving water quality in freshwaters in agricultural landscapes.

Brittany Hanrahan (Primary Presenter/Author), USDA Agricultural Research Service, br.hanrahan@gmail.com;


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


Sheila Christopher (Co-Presenter/Co-Author), University of Notre Dame, sheila.christopher@nd.edu;

5/21/2015  |   14:30 - 14:45   |  103C

CAN WE CAN SOLVE COASTAL “DEAD ZONES” FROM A DISTANCE? WATERSHED-SCALE CONSERVATION REDUCES NUTRIENT EXPORT FROM AGRICULTURAL LANDSCAPES Excess fertilizer nutrients entering Midwestern agricultural streams degrade both local and downstream water quality, resulting in algal blooms and subsequent hypoxic “dead zones” far from the source. We are quantifying the benefits of watershed-scale conservation practices that may reduce nutrient runoff. Specifically, research is lacking on whether the watershed-scale planting of winter cover crops can reduce stream nutrient inputs. After a pre-treatment year of data collection, we planted cover crops on ~70% of croppable land (=1610 acres) in the Shatto Ditch Watershed (IN), quantifying nutrient loss from fields by sampling subsurface tile drains and the adjacent stream every 14d. Cover crops improved stream water quality by reducing excess nutrients exported downstream; dissolved N and P concentrations and fluxes were significantly lower in tiles draining fields with cover crops compared to those without. Annual watershed nitrate-N export decreased by 31%, from 91 to 67 kgN/day, translating to an additional 10,500kg of N retained annually on the landscape for crops. Finally, successful outcomes highlighted through watershed-scale demonstration projects can facilitate widespread adoption, making them powerful agents of change for advancing conservation success.

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


Brittany Hanrahan (Co-Presenter/Co-Author), USDA Agricultural Research Service, br.hanrahan@gmail.com;


Sheila Christopher (Co-Presenter/Co-Author), University of Notre Dame, sheila.christopher@nd.edu;

5/21/2015  |   14:45 - 15:00   |  103C

THE VALUE OF WATER QUALITY IMPROVEMENTS ACHIEVED WITH AGRICULTURAL BEST MANAGEMENT PRACTICES Excess nitrogen (N) is a concern for freshwaters, and it is particularly problematic in agricultural regions. One conservation strategy for removing excess N from agricultural run-off is the implementation of best management practices (BMPs). Despite their prevalence, cost information is lacking for many BMPs, which can be a barrier to implementation by farmers, and can also inhibit effective management planning by federal and state agencies that provide cost-share funds as incentives. In this analysis, we consider three N-removal BMPs: wetlands, two-stage ditches, and cover crops. For each, we estimate 1) direct costs of implementation; 2) costs to USDA conservation programs; and 3) cost-effectiveness, in $/kgN removed. Finally, we compare implementation cost with water quality benefits. Wetlands were generally the most cost-effective BMP. Over long time periods (50 years), two-stage ditches were the second-most cost-effective, and cover crops were the least cost-effective. In contrast, over 10 years, cover crops ranked second, and two-stage ditches were least cost-effective. Nevertheless, for all three BMPs, water quality benefits exceeded costs, suggesting that BMP implementation can be a cost-effective method for managing excess N.

Sarah S. Roley (Primary Presenter/Author), Michigan State University, roleysar@msu.edu;


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


John C. Tyndall (Co-Presenter/Co-Author), Iowa State University, jtyndall@iastate.edu;


Jonathan D. Witter (Co-Presenter/Co-Author), Ohio State University, witter.7@osu.edu;