River ecosystem conceptual models and non‐perennial rivers: A critical review

Conceptual models underpin river ecosystem research. However, current models focus on continuously flowing rivers and few explicitly address characteristics such as flow cessation and drying. The applicability of existing conceptual models to nonperennial rivers that cease to flow (intermittent rivers and ephemeral streams, IRES) has not been evaluated. We reviewed 18 models, finding that they collectively describe main drivers of biogeochemical and ecological patterns and processes longitudinally (upstream-downstream), laterally (channel-riparian-floodplain), vertically (surface water-groundwater), and temporally across local and landscape scales. However, perennial rivers are longitudinally continuous while IRES are longitudinally discontinuous. Whereas perennial rivers have bidirectional lateral connections between aquatic and terrestrial ecosystems, in IRES, this connection is unidirectional for much of the time, from terrestrial-to-aquatic only. Vertical connectivity between surface and subsurface water occurs bidirectionally and is temporally consistent in perennial rivers. However, in IRES, this exchange is temporally variable, and can become unidirectional during drying or rewetting phases. Finally, drying adds another dimension of flow variation to be considered across temporal and spatial scales in IRES, much as flooding is considered as a temporally and spatially dynamic process in perennial rivers. Here, we focus on ways in which existing models could be modified to accommodate drying as a fundamental process that can alter these patterns and processes across spatial and temporal dimensions in streams. This perspective is needed to support river science and management in our era of rapid global change, including increasing duration, frequency, and occurrence of drying.info:eu-repo/semantics/publishedVersio

Imidazol-1-ylethylindazole Voltage-Gated Sodium Channel Ligands Are Neuroprotective during Optic Neuritis in a Mouse Model of Multiple Sclerosis

[Image: see text] A series of imidazol-1-ylethylindazole sodium channel ligands were developed and optimized for sodium channel inhibition and in vitro neuroprotective activity. The molecules exhibited displacement of a radiolabeled sodium channel ligand and selectivity for blockade of the inactivated state of cloned neuronal Na(v) channels. Metabolically stable analogue 6 was able to protect retinal ganglion cells during optic neuritis in a mouse model of multiple sclerosis

Formation and Evolution of Concentrated Flowpaths on a Pinyon-Juniper Woodland

There has been a dramatic increase in the last thousand years in Pinyon-Juniper woodlands, which is primarily attributed to global climate change. The focus of this thesis is to describe the hydrologic impact of hand felling Pinyon and Juniper trees perpendicularly to the slope to provide physical barriers to overland flow, reduce velocity of flow, and minimize soil erosion. Experimental design consisted of two cover conditions (naturally occurring bare interspaces and slash piles from felled trees on naturally occurring bare interspaces) at two slope steepnesses (30% and 10%), and three concentrated flow water application rates. Water was applied from a specially designed flow initiator with pressure compensating flow regulators calibrated to rates of 15, 30 and 42 L min-1 for 12 minutes after runoff first occurred to quantify the ability of the treatment to reduce concentrated erosion rates. Each treatment-slope-water application rate combination was replicated three times. The research indicates that hand felling Pinyon and Juniper trees can be highly successful in reducing the size of concentrated flow paths, velocity and sediment load. Results from this research also indicate that soil detachment is a far more complex process that cannot be described in one function. There are processes such as soil armoring, detachment capacity of water, and litter dams that are created that contribute to the complexity of modeling soil detachment rates. This research is being used by the USDA to develop concentrated flow equations for use in the Rangeland Hydrology and Erosion Model (RHEM), which is being developed in support of the USDA‟s Conservation Effects Assessment Project (CEAP)

Abiotic controls and temporal variability of river metabolism: multiyear analyses of Mississippi and Chattahoochee River data

Whole-ecosystem metabolism is an important indicator of the role of organic matter, C cycling, and trophic structure in rivers. Ecosystem metabolism is well studied in small streams, but less is known about metabolism in large rivers. We estimated daily whole-ecosystem metabolism over 2 y for 1 site each at the Mississippi and Chattahoochee Rivers in the USA to understand factors influencing temporal patterns of ecosystem metabolism. We estimated rates of gross primary production (GPP), community respiration (CR), and net ecosystem production (NEP) with a curve-fitting approach with publicly available discharge (Q), dissolved O2, temperature, and photosynthetically active radiation (PAR) data. Models were run for week-long blocks, and power analyses suggested that rates should be established at least once for each 10-wk period throughout the year to characterize annual rates of metabolism accurately in these 2 rivers. We analyzed weekly rates averaged over 10-wk periods with Spearman rank correlation to identify potential drivers and with path analyses to identify interactions among variables driving GPP, CR, and NEP. Both rivers had an overall negative NEP, and the Mississippi River had stronger seasonal trends. In the Mississippi River, CR was strongly positively correlated with Q, which suggests variation in seasonal availability of allochthonous C. In the Chattahoochee, CR was most strongly positively correlated with GPP, whereas GPP was negatively correlated with Q, which suggests that autochthonous processes and water-column light attenuation played important roles in C dynamics. Our results suggest that these large rivers were net heterotrophic at annual time scales but autotrophy can be important seasonally

Substrate

Contains three excel sheet tabs: "indvar_substrate_select", "indvar_riffle_character", "substrate_profile". First, "indvar_substrate_select" corresponds to the evaluation of individual sampler bias in substrate selection at a point along a transect. Second, "indvar_riffle_character" corresponds to the evaluation of individual variation in Wolman pebble counts of a riffle. Third, "substrate_profile" refers to the Wolman pebble counts downstream of each dam

Wetted width and depth

Includes all field measurements of wetted width and depth

Dam size and river network context relative to other dams in the river network (number of upstream dams, distance to nearest upstream dam, height of 1^st upstream dam, and drainage area).

<p>Input variables for univariate regressions were standardized to multiples of mean width, except for drainage area, for the Upper Neosho and Lower Cottonwood rivers, respectively.</p

Channel widening, downstream, upstream, and total footprint for each dam.

<p>* footprint is estimated based on available data</p><p>Downstream footprints were determined by measuring the distribution of median substrate size (D₅₀) from riffles downstream of dam (see Figs <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0141210#pone.0141210.g006" target="_blank">6</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0141210#pone.0141210.g008" target="_blank">8</a>). Extent of channel widening, and upstream footprints were determined using aerial photography. Footprints are expressed in terms of multiples of mean wetted width, with kilometers in parentheses. The mean wetted width used in calculations was 0.022 km for the Neosho River and 0.035 km for the Cottonwood River.</p

Date of construction, primary purpose, and drainage area for dams on the Upper Neosho and Lower Cottonwood rivers.

<p>Drainage area is cumulative, including parts of the catchment upstream of Council Grove and Marion reservoirs (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0141210#pone.0141210.g002" target="_blank">Fig 2</a>).</p

Map of the Upper Neosho River network.

<p>Map of our study area in the Upper Neosho river network (A) located in Kansas. Also shown are (B) six dam sites and two undammed reference sites along the Upper Neosho River and Lower Cottonwood Rivers. Major U.S. Army Corps of Engineers (USACE) reservoirs in the study river network are labeled for reference.</p