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Minneapolis, MN, United States

Walker R.E.D.,University of Minnesota | Walker R.E.D.,Barr Engineering Co. | Pastor J.,University of Minnesota | Dewey B.W.,University of Minnesota
Ecosystems | Year: 2010

Microbial immobilization of nitrogen (N) in litter from one year's production may cause oscillations in biomass production if it delays N availability the following year. We tested whether shoot and root litter and plant density affect biomass and seed production of populations of wild rice (Zizannia palustris L.) grown in 378 l stock tank mesocosms over four consecutive years. Half the tanks were thinned to a uniform seedling density whereas density in the remaining tanks was allowed to fluctuate ad libitum. Litter treatments included both shoot litter removal, leaving only root litter, and retaining shoot litter intact with root litter. A separate greenhouse fertilizer experiment tested whether N and/or phosphorus (P) limited productivity. Responses to N additions were much stronger than to P additions. Annual production and N availability in the tanks were correlated with each other and followed a concurrent cycle from 2004 to 2008. Furthermore, production in tanks with shoot + root litter did not fluctuate more than tanks with only root litter. Root litter immobilized more nitrogen and for a longer period than shoot litter. Neither litter immobilized P. Density did not affect mean seed weight, total seed production, or mean plant weight, but total seed production declined in years following productive years and was high only following years of low litter production. Root litter may therefore be primarily responsible for the delays in N availability that cause cycles in biomass and seed production. Consequently, both wild rice litter quantity and quality play central roles in production and population dynamics of wild rice stands. © 2010 Springer Science+Business Media, LLC. Source

Janetski D.J.,Grand Valley State University | Ruetz III C.R.,Grand Valley State University | Bhagat Y.,Grand Valley State University | Bhagat Y.,Barr Engineering Co. | Clapp D.F.,Charlevoix Fisheries Research Station
Transactions of the American Fisheries Society | Year: 2013

We assessed recruitment dynamics of juvenile Yellow Perch Perca flavescens in coastal habitats of eastern Lake Michigan. To investigate recruitment patterns and associations with environmental factors in a coastal drowned river mouth (DRM) lake, we sampled juvenile Yellow Perch seasonally in Muskegon Lake, Michigan, during 2003-2011. We also sampled three nearshore sites in Lake Michigan each fall to evaluate synchrony between the DRM lake and nearshore habitat. In Muskegon Lake, age-0 Yellow Perch CPUE during fall was high in 2005 and 2007; moderate in 2008, 2010, and 2011; and low in other years. Fall CPUE (age 0) was positively associated with CPUE in the next spring (age 1; slope = 0.98; R2 = 0.95), which we attribute to high overwinter survival. Fall CPUE of age-0 Yellow Perch showed a positive relationship with June air temperature (R2 = 0.76), suggesting that warm conditions at early larval stages positively influence recruitment of juveniles. Juvenile recruitment in Muskegon Lake was not synchronized with juvenile recruitment in nearshore Lake Michigan. The lack of synchrony may be an indication that (1) age-0 Yellow Perch recruitment in DRM lakes and Lake Michigan are influenced by different environmental controls and (2) dispersal between the two habitats does not strongly affect age-0 recruitment dynamics.Received August 6, 2012; accepted December 1, 2012. © 2013 Copyright Taylor and Francis Group, LLC. Source

Wickert A.D.,University of Colorado at Boulder | Martin J.M.,ExxonMobil | Tal M.,Aix - Marseille University | Kim W.,University of Texas at Austin | And 2 more authors.
Journal of Geophysical Research: Earth Surface | Year: 2013

Alluvial river channels are intrinsically mobile. We mapped channel planform extent in a series of experiments to measure instantaneous rates of channel motion, loss of planform overlap with the original positions of the channels, and reworking of the fluvial surface over which the channels moved. These experiments comprise two aggrading deltas, one subsiding delta that underwent cyclical base level changes, and one braided channel system that was seeded with vegetation. We find that the amounts of channel planform overlap and remaining unreworked fluvial surface area both decay exponentially with time, and that these metrics and the instantaneously-measured rates of channel motion scale predictably with one another in spite of the different time scales of the processes they record. Rates of channel planform change increase with increasing sediment flux and bed and planform irregularity, and decrease with the establishment of riparian vegetation. Aggradation does not noticeably affect channel mobility, but induces avulsions that allow the channels to more rapidly rework the fluvial surface. Additional findings include that: (1) sediment flux in the braided experiment equals its rate of bar migration, (2) channel widths are normally distributed with time, and (3) we can use our channel mobility metrics to connect surface processes with the resultant fluvial stratigraphy. Key Points We develop new analyses to quantify fluvial processes in a range of experiments River channel lateral mobility scales with sediment flux We link multiple time scales of fluvial processes, including stratigraphy ©2012. American Geophysical Union. All Rights Reserved. Source

Kowalsky N.,Barr Engineering Co.
American Fuel and Petrochemical Manufacturers, AFPM - Environmental Conference 2012 | Year: 2012

dP flow meters are most common in refinery fuel gas service, however at times, other instrumentation technologies, e.g., vortex or Corolis meters, are used in fuel flow applications. These alternative meter technologies are referred to as "all-in-one" meters due to the fact that a single instrument measures flow with an output reading for volumetric flow rate as compared to many additional measurements and calculations needed to obtain the same volumetric flow data for a dP meter. A discussion covers the variables that impact dP flow measurement accuracy and proper estimation of accuracy; a strategic approach to better understand installed accuracy and to provide a cradle-to-grave approach for improving the installed measurement accuracy using a refinery case study as an example; the cradle-to-grave approach for improving accuracy; and a case study, illustrating the cradle to grave approach. This is an abstract of a paper presented at the 2012 Environmental Conference (Denver, CO 10/14-16/2012). Source

Edmonds D.A.,Boston College | Paola C.,University of Minnesota | Hoyal D.C.J.D.,ExxonMobil | Sheets B.A.,Barr Engineering Co.
Journal of Geophysical Research: Earth Surface | Year: 2011

Densely populated river deltas are losing land at an alarming rate and to successfully restore these environments we must understand the details of their morphology. Toward this end we present a set of five metrics that describe delta morphology: (1) the fractal dimension, (2) the distribution of island sizes, (3) the nearest-edge distance, (4) a synthetic distribution of sediment fluxes at the shoreline, and (5) the nourishment area. The nearest-edge distance is the shortest distance to channelized or unchannelized water from a given location on the delta and is analogous to the inverse of drainage density in tributary networks. The nourishment area is the downstream delta area supplied by the sediment coming through a given channel cross section and is analogous to catchment area in tributary networks. As a first step, we apply these metrics to four relatively simple, fluvially dominated delta networks. For all these deltas, the average nearest-edge distances are remarkably constant moving down delta suggesting that the network organizes itself to maintain a consistent distance to the nearest channel. Nourishment area distributions can be predicted from a river mouth bar model of delta growth, and also scale with the width of the channel and with the length of the longest channel, analogous to Hack's law for drainage basins. The four delta channel networks are fractal, but power laws and scale invariance appear to be less pervasive than in tributary networks. Thus, deltas may occupy an advantageous middle ground between complete similarity and complete dissimilarity, where morphologic differences indicate different behavior. Copyright 2011 by the American Geophysical Union. Source

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