SFS Annual Meeting

5/22/2019  |   09:00 - 09:15   |  250 DE

CARBON EXPORT AND STORAGE ACROSS CHARRED COLORADO LANDSCAPES: FROM SOILS TO STREAMS Any shift in disturbance regime may disrupt an ecosystem’s carbon balance, resulting in C loss to the atmosphere, contributing to climate change. Warming climate will continue to increase the size and severity of fire, particularly in the Intermountain West. Predicting how fire alters the net ecosystem carbon balance requires us to understand how carbon is stored, processed, and transferred in both terrestrial and aquatic ecosystems. Results from paired watersheds and laboratory bioassays focused on five 2002 severe fires in Colorado provide insight as to how organic matter (OM) is processed from hillslopes to streams. Comparing results from intact soil column experiments to soil extractions and stream samples, suggests that the majority of this OM does not make it to the stream, potentially getting sorbed deeper in the mineral rich, organic poor, portion of the soil. Interestingly, stream dissolved OM (DOM) does not reflect the systematic shifts in quality within the terrestrial system. Further, burned and unburned watersheds export statistically similar amounts of DOM per unit area. This suggests that fire-affected landscapes are losing a greater fraction of the soil OM to the stream and atmosphere each year.

Rebecca Barnes (Primary Presenter/Author), Colorado College, rebecca.barnes@coloradocollege.edu;


Kyra Wolf (Co-Presenter/Co-Author), University of Montana, kyra.wolf@umconnect.umt.edu;


Asheton Gilbertson (Co-Presenter/Co-Author), Colorado College, agilby96@gmail.com;


Presentation:
This presentation has not yet been uploaded.

5/22/2019  |   09:30 - 09:45   |  250 DE

SEASONAL AND LONGITUDINAL NUTRIENT LIMITATION PATTERNS IN A WATERSHED INFLUENCE BY IRRIGATION DELIVERY AND RETURN FLOW Irrigation delivery of snowmelt from mountain reservoirs supports agriculture in the Yakima River Basin of Washington state. Yakima River water quality degrades longitudinally as irrigation return flows load nitrogen and phosphorus into the river. Moreover, stream water N:P ratios are low during irrigation season as low-nutrient snowmelt is delivered, and N:P ratios increase shortly after irrigation season ends as shallow ground water discharges nitrate-rich water back to streams. We hypothesized that longitudinal water quality degradation would relieve nutrient limitation in downstream ecosystems and that the seasonal change in N:P ratios would change nutrient limitation patterns during and after irrigation season. After deploying NDS arrays with N, P, and Si, the most common nutrient limitation response was nitrogen limitation of respiration (8 of 12 assays) and silica limitation of production (5 of 12 assays). We did not see downstream nutrient limitation relief, likely because biofilm nutrient demand never saturated. However, nutrient demand was more likely to differ between summer and fall in the sites most affected by agricultural return flow indicating that water management can change seasonal and longitudinal patterns of biofilm nutrient demand.

Clay Arango (Primary Presenter/Author), Central Washington University, arangoc@cwu.edu;


Sarah Roley (Co-Presenter/Co-Author), Washington State University, sarah.roley@wsu.edu ;


Alexander Alexiades (Co-Presenter/Co-Author), Heritage University, alexiades_a@heritage.edu;


Presentation:
This presentation has not yet been uploaded.

5/22/2019  |   09:45 - 10:00   |  250 DE

THE INFLUENCE OF IRRIGATION FLOWS ON MICROBIAL AND ALGAL NUTRIENT LIMITATION In watersheds with irrigated agriculture, water sources shift seasonally, from return flows during irrigation season to shallow groundwater during non-irrigation season. We investigated the effect of irrigation on stream algal and microbial communities in tributaries of the Yakima River in central Washington, USA. We deployed nutrient-diffusing substrates (NDS) in both irrigation and non-irrigation season across 5 tributary streams. The NDS were topped with either glass discs (autotrophs) or cellulose sponges (heterotrophs). We amended the NDS with nitrogen, phosphorus, and silica in a factorial design, and deployed in each stream for at least 1 week. After retrieval, we measured photosynthesis (GPP), respiration (ER), and chlorophyll-a concentration. During irrigation season, nutrient addition either increased GPP and ER or had no effect, suggesting that microbial communities had additional capacity for assimilation. During non-irrigation season, GPP and ER were much lower and nutrient additions either inhibited GPP and ER or were neutral. Microbes and algae may have been limited by sunlight and water temperature during the cooler and low-light non-irrigation season. Overall, our results suggest a high capacity for biological nutrient uptake during irrigation season, which is potentially important for maintaining water quality.

Sarah S. Roley (Primary Presenter/Author), Washington State University, sarah.roley@wsu.edu;


Clay Arango (Co-Presenter/Co-Author), Central Washington University, arangoc@cwu.edu;


Alexander Alexiades (Co-Presenter/Co-Author), Heritage University, alexiades_a@heritage.edu;


Presentation:
This presentation has not yet been uploaded.

5/22/2019  |   10:00 - 10:15   |  250 DE

KNOW YOUR WATER, KNOW YOUR SOIL, KNOW YOUR WORMS? – EARTHWORMS AND BIOGEOCHEMISTRY AT THE MARGINS OF NORTH AMERICAN FRESHWATER Both terrestrial and freshwater invertebrate macrofauna have long been recognized to have profound influences on processes like organic matter decomposition and nutrient dynamics. These organisms represent important reservoirs of biodiversity, and have utility as indicators of (soil or aquatic) ecosystem health. A few taxa exhibit considerable overlap between terrestrial and aquatic habitats, including several insect families, and some native North American earthworm families. Semi-aquatic earthworms are very poorly known relative to their terrestrial counterparts, perhaps because they occupy habitat that forms the boundary between wet and dry components of landscapes. Spatially, this habitat is narrow (10s of cm), but the linear extent of this habitat is prodigious (10,000s of km), and recent sampling revealed that earthworms in family Sparganophilidae are nearly ubiquitous along streams and lakes in eastern North America. This generality of distribution leads to obvious questions about what these earthworms do in terms of energy and nutrient processes, which have only recently begun to be addressed. We intend this presentation to introduce sparganophilid earthworms to the aquatic ecology community, with hopes that we may spark dialogue and collaboration in future ecological inquiries.

Mac Callaham (Primary Presenter/Author), USDA Forest Service, Southern Research Station, mac.a.callaham@usda.gov;


Roberto Carrera-Martinez (Co-Presenter/Co-Author), Warnell School of Forest Resources, University of Georgia, rcarrmart@gmail.com;


Melanie Taylor (Co-Presenter/Co-Author), USDA Forest Service, Southern Research Station, melanie.k.taylor@usda.gov;


Presentation:
This presentation has not yet been uploaded.