5/18/2015  |   10:30 - 10:45   |  101CD

ALIEN ECOGEOMORPHOLOGY: IMPACTS OF AN INVADING ECOSYSTEM ENGINEER ON RIVER SEDIMENT DYNAMICS AND TROPHIC INTERACTIONS Animals that dig burrows in river banks and beds are uncommon in the UK. The invasion of signal crayfish (Pacifastacus leniusculus), a prolific ecosystem engineer, has changed that, with implications for geomorphology, sediment dynamics and benthic ecology that benefit the invader. Burrowing directly introduces sediment to rivers and accelerates bank collapse, making substrates finer and increasing the quantity of sediment available for transport. In addition, energy expenditure by signals can mobilise sediment under incompetent hydraulic conditions. Field measurements in central England reveal suspended sediment fluxes that are partly driven by diel and seasonal variations in crayfish activity, with up to 50% of cumulative sediment load attributable to signals during summer low flows. These geomorphological impacts amplify the direct, ecological impacts of crayfish on benthic communities. For example, ex-situ experiments show that by limiting access to hyporheic refugia sedimentation constrains the avoidance (burrowing) behaviour of Gammarus pulex, increasing predation by signals. Alongside other ecogeomorphological interactions, crayfish-induced sedimentation may, therefore, extend the widely noted predatory effect of P. leniusculus on sessile taxa by rendering labile, burrowing macroinvertebrates relatively more vulnerable to predation.

Stephen Rice (Primary Presenter/Author), Manchester Metropolitan University, s.rice@lboro.ac.uk;


Kate Mathers (Co-Presenter/Co-Author), Loughborough University, k.mathers@lboro.ac.uk;


Matthew Johnson (Co-Presenter/Co-Author), University of Nottingham, m.johnson@nottingham.ac.uk;


Paul Wood (Co-Presenter/Co-Author), Loughborough University, UK, p.j.wood@lboro.ac.uk;


Jake Reeds (Co-Presenter/Co-Author), Environment Agency, jake.reeds@environment-agency.gov.uk;


Holly Longstaff (Co-Presenter/Co-Author), Environment Agency, holly.longstaff@environment-agency.gov.uk;


Chris Extence (Co-Presenter/Co-Author), Environment Agency, chris.extence@environment-agency.gov.uk;

5/18/2015  |   10:45 - 11:00   |  101CD

ARE ENGINEERING EFFECTS OF CRAYFISH ON GRAVEL BED MORPHOLOGY MEDIATED BY SPECIES IDENTITY, BEHAVIOR, AND BODY SIZE? Incorporating animal behavior and traits into biophysical frameworks is critical to quantitatively link ecological and physical processes. To investigate the impacts of ecosystem engineer behavior and size on gravel movement, we used a laboratory experiment to manipulate the presence/absence of spiny cheek crayfish (Orconectes limosus) of either 15 (young-of-the-year) or 25 mm (1+ year old) carapace length. Using videography, we found that crayfish frequently displayed territorial behaviors and 73% of interactions, on average, were aggressive regardless of size. Larger crayfish created significantly more pit structures and surface gravels were moved over 10% of the bed area compared to just 1.3% in smaller crayfish treatments and 0.003% in controls without crayfish, suggesting that young crayfish are less effective gravel engineers. We then manipulated the presence/absence of large, invasive rusty crayfish (Orconectes rusticus) in a field experiment and found that in treatments with rustys, 10% of the bed surface was moved, fine sediment accumulation was 2x lower, and macroinvertebrate density was 1.5x higher compared to controls without crayfish. We hypothesize that crayfish may indirectly increase macroinvertebrate abundance by reducing fine sediment accumulation.

Lindsey Albertson (Primary Presenter/Author), Montana State University, lalbertson@stroudcenter.org;


Melinda Daniels (Co-Presenter/Co-Author), Stroud Water Research Center, mdaniels@stroudcenter.org;

5/18/2015  |   11:00 - 11:15   |  101CD

TOPOGRAPHY ALTERS TREE GROWTH – CLIMATE RELATIONSHIPS IN A SEMI-ARID FORESTED CATCHMENT Topography and climate play an integral role in the spatial variability and annual dynamics of aboveground carbon sequestration. Despite knowledge of vegetation – climate – topography relationships on the landscape and hillslope scales, little is known about the influence of complex terrain coupled with hydrologic and topoclimatic variation on tree growth and physiology at the catchment scale. We determine how species-specific tree growth patterns and water use efficiency respond to interannual climate variability and how this response varies with topographic position. We found that lodgepole pine and ponderosa pine both show significant decreases in growth with water-limiting climate conditions, but complex terrain mediates this response by controlling moisture conditions in variable topoclimates. Foliar carbon isotope analyses show increased water use efficiency during drought for lodgepole pine, but indicate no significant difference in water use efficiency of ponderosa pine between a drought year and a non-drought year. The responses of the two pine species to climate indicate that semi-arid forests are especially susceptible to climate change and that topographic variability will play a significant role in determining their the future.

Holly Barnard (Primary Presenter/Author), University of Colorado - Boulder, holly.barnard@colorado.edu;


Hallie Adams (Co-Presenter/Co-Author), University of Colorado - Boulder, hallie.adams@colorado.edu;


Alexander Loomis (Co-Presenter/Co-Author), University of Colorado - Boulder, aloomis1918@gmail.com;

5/18/2015  |   11:15 - 11:30   |  101CD

GROUNDWATER DEPLETION IN WESTERN GREAT PLAINS PROJECTED TO DRY 250 STREAM-KM OF FISH HABITAT IN THE NEXT 45 YEARS Across the western Great Plains of North America, groundwater pumping for irrigated agriculture has depleted regional aquifers that sustain surface flow for native fishes. This loss of surface flow and subsequent fragmentation of fish habitat has contributed to population declines for 70% of endemic fishes. We used a network of observation wells distributed across portions of Colorado, Kansas, and Nebraska to measure changes in depth to water table (DTWT) over the High Plains Aquifer during 1950-2010. Based on DTWT values, we estimated the spatial distribution of stream segments that maintained connectivity to the aquifer and therefore surface flow to support fishes. We then used the relationship between time and DTWT to project future losses in aquifer-connected stream segments. Model results suggest >500 stream-km in the Republican River watershed disappeared during 1950-2010 as aquifer levels fell, and an additional 250 km will be lost by 2060 if withdrawal practices are not modified or reduced. We synthesize the ecological consequences of past and expected future changes in surface flow using existing fish assemblage data collected from across the region.

Josh Perkin (Primary Presenter/Author), Tennessee Tech University, jperkin@tntech.edu;


Keith Gido (Co-Presenter/Co-Author), Kansas State University, kgido@ksu.edu;


Jeffrey Falke (Co-Presenter/Co-Author), U.S. Geological Survey, Alaska Cooperative Fish and Wildlife Research Unit, jfalke4@alaska.edu;


Harry Crockett (Co-Presenter/Co-Author), Colorado Parks and Wildlife Department, harry.crockett@state.co.us;


John Sanderson (Co-Presenter/Co-Author), The Nature Conservancy, jsanderson@tnc.org;


Eric Johnson (Co-Presenter/Co-Author), Westar Energy, Eric.Johnson@westarenergy.com;


Kurt D. Fausch (Co-Presenter/Co-Author), Colorado State University, Department of Fish, Wildlife, and Conservation Biology, Fort Collins, CO 80523, Kurt.Fausch@colostate.edu;

5/18/2015  |   11:30 - 11:45   |  101CD

EFFECT OF STREAM HYDROLOGY AND RIPARIAN VEGETATION ON TERRESTRIAL ARTHROPOD COMMUNITY STRUCTURE AND WATER VS ENERGY LIMITATION IN DRYLAND FLOODPLAINS Intermittent rivers comprise over 30% of the Earth’s flowing water bodies, including 60% of total river length in the contiguous United States. Because stream and groundwater hydrology governs riparian vegetation composition in dryland ecosystems, we might expect different hydrologic regimes to generate microclimatic conditions that are either more arid or more mesic due to vegetation differences, where either water or energy could be more limiting to riparian food webs. Here I present the results of a replicated field experiment where I manipulated the availability of water and energy to 3 riparian floodplains on the San Pedro River in Arizona that varied in intermittence and riparian vegetation. Each site had significantly different terrestrial arthropod communities, differences that were largely driven by site differences in microclimate. Moreover, I found that the water effect size on cricket abundance increased with aridity, and that the the energy effect size on ant abundance decreased with aridity. These results suggest that riparian communities along perennial streams may function very differently than those along intermittent streams, and are subject to a different set of ecological controls.

Daniel Allen (Primary Presenter/Author), The Pennsylvania State University, dca5269@psu.edu;

5/18/2015  |   11:45 - 12:00   |  101CD

BIG FLOOD, SMALL FLOOD, SPRING FLOOD, FALL FLOOD: HOW CONTROLLED FLOOD TIMING AFFECTS FOOD WEB RESPONSE IN THE GLEN CANYON DAM TAILWATER Controlled floods are an important tool in river rehabilitation and restoration efforts worldwide. These floods have the potential to rehabilitate rivers by restoring geomorphic processes, disadvantaging non-native taxa, and returning a key component of the natural disturbance regime necessary for many aquatic organisms. Controlled floods have been released from Glen Canyon Dam on the Colorado River 6 times since 1996. Research conducted around the March 2008 flood demonstrated that this pulse disturbance reduced biomass and cover of aquatic macrophytes, and restructured invertebrate assemblages by favoring fast-growing insect taxa that prefer bare substrates and disadvantaging non-native and non-insect taxa that prefer macrophyte beds. In the years after this controlled flood (2009-2012), aquatic macrophytes returned, large bodied non-native taxa came to dominate, and fast-growing insect taxa declined. Controlled floods were again conducted in November 2012, 2013, and 2014, but these fall-timed floods did not restructure invertebrate assemblages, likely due to the seasonal scouring potential of aquatic macrophytes. Thus, the timing, rather than simply the magnitude, of controlled floods on the Colorado River affects food web response.

Ted Kennedy (Primary Presenter/Author), USGS Southwest Biological Science Center, Grand Canyon Monitoring and Research Center, tkennedy@usgs.gov;


Jeffrey Muehlbauer (Co-Presenter/Co-Author), University of Alaska Fairbanks, USGS Alaska Cooperative Fish and Wildlife Research Unit, jdmuehlbauer@alaska.edu;


Michael Dodrill (Co-Presenter/Co-Author), USGS, mdodrill@usgs.gov;


Adam Copp (Co-Presenter/Co-Author), USGS, acopp@usgs.gov;


Michael Yard (Co-Presenter/Co-Author), USGS, myard@usgs.gov;