2012
Yager, E. M.; Dietrich, W. E.; Kirchner, J. W.; McArdell, B. W.
Patch dynamics and stability in steep, rough streams Journal Article
In: Journal of Geophysical Research-Earth Surface, vol. 117, no. F2, 2012.
Abstract | Links | BibTeX | Tags: patch dynmics, stability, steep streams
@article{Yager2012,
title = {Patch dynamics and stability in steep, rough streams},
author = {E. M. Yager and W. E. Dietrich and J. W. Kirchner and B. W. McArdell},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Yager_2012_JournGeophysRes.pdf},
year = {2012},
date = {2012-04-18},
journal = {Journal of Geophysical Research-Earth Surface},
volume = {117},
number = {F2},
abstract = {The beds of steep streams are typically composed of relatively immobile boulders
and more mobile patches of gravel and cobbles. Little is known about how variability in
flow and sediment flux affect the area, thickness, composition, and grain mobility of
sediment patches. To better understand patch dynamics, we measured flow, sediment
transport, and bed properties in two steep channels. Patches close to the thalweg varied in
area, thickness, and grain size, whereas those outside the thalweg did not. Local variations
in transport of several orders of magnitude occurred, even on a patch with a spatially
homogeneous grain size distribution. During moderate flow events, partial to selective
transport dominated on the entire channel bed and all individual patches. Tracer particles
moved freely between different patch classes (e.g., fine and coarse patches exchanged
particles), and relatively fine sediment on all patch classes began motion at the same shear
stress. Therefore, the selective transport observed for the entire bed was not a result
of the preferential transport of only fine patches, but the high relative mobility of finer
sediment on all patches. Our results suggest that local flow and sediment supply,
and not spatial grain size variations, were the primary drivers of local bed load transport
variability. The use of reach-averaged flow properties to understand local patch dynamics
may not be applicable.},
keywords = {patch dynmics, stability, steep streams},
pubstate = {published},
tppubtype = {article}
}
The beds of steep streams are typically composed of relatively immobile boulders
and more mobile patches of gravel and cobbles. Little is known about how variability in
flow and sediment flux affect the area, thickness, composition, and grain mobility of
sediment patches. To better understand patch dynamics, we measured flow, sediment
transport, and bed properties in two steep channels. Patches close to the thalweg varied in
area, thickness, and grain size, whereas those outside the thalweg did not. Local variations
in transport of several orders of magnitude occurred, even on a patch with a spatially
homogeneous grain size distribution. During moderate flow events, partial to selective
transport dominated on the entire channel bed and all individual patches. Tracer particles
moved freely between different patch classes (e.g., fine and coarse patches exchanged
particles), and relatively fine sediment on all patch classes began motion at the same shear
stress. Therefore, the selective transport observed for the entire bed was not a result
of the preferential transport of only fine patches, but the high relative mobility of finer
sediment on all patches. Our results suggest that local flow and sediment supply,
and not spatial grain size variations, were the primary drivers of local bed load transport
variability. The use of reach-averaged flow properties to understand local patch dynamics
may not be applicable.
and more mobile patches of gravel and cobbles. Little is known about how variability in
flow and sediment flux affect the area, thickness, composition, and grain mobility of
sediment patches. To better understand patch dynamics, we measured flow, sediment
transport, and bed properties in two steep channels. Patches close to the thalweg varied in
area, thickness, and grain size, whereas those outside the thalweg did not. Local variations
in transport of several orders of magnitude occurred, even on a patch with a spatially
homogeneous grain size distribution. During moderate flow events, partial to selective
transport dominated on the entire channel bed and all individual patches. Tracer particles
moved freely between different patch classes (e.g., fine and coarse patches exchanged
particles), and relatively fine sediment on all patch classes began motion at the same shear
stress. Therefore, the selective transport observed for the entire bed was not a result
of the preferential transport of only fine patches, but the high relative mobility of finer
sediment on all patches. Our results suggest that local flow and sediment supply,
and not spatial grain size variations, were the primary drivers of local bed load transport
variability. The use of reach-averaged flow properties to understand local patch dynamics
may not be applicable.
2011
Limm, Michael P.; Power, Mary E.
The caddisfly Dicosmoecus gilvipes: making a case for a functional role Journal Article
In: Journal of the North American Benthological Society, vol. 30, no. 2, pp. 485-492, 2011.
Abstract | Links | BibTeX | Tags: camouflage, case, Dicosmoecus, drag, function, predation, stability, Trichoptera
@article{Limm2011b,
title = {The caddisfly Dicosmoecus gilvipes: making a case for a functional role},
author = {Michael P. Limm and Mary E. Power},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Limm_2011_JNAmBentholSoc.pdf},
doi = {10.1899/10-028.1},
year = {2011},
date = {2011-03-29},
journal = {Journal of the North American Benthological Society},
volume = {30},
number = {2},
pages = {485-492},
abstract = {Most caddisfly larvae build cases of silk and a variety of collected materials. Multiple functions,
including protection from predators, resistance to entrainment by high flows, and improved respiration,
have been suggested for caddisfly cases. We investigated the functional role of cases built by Dicosmoecus gilvipes, a limnephilid caddisfly. In this species, the 1st- through 4th-instar larvae build cases with plant material and attach Douglas-fir needles as lateral extensions that resemble vanes on an arrow. We tested whether the lateral extensions and entire case deterred predators by manipulating lateral extensions and case presence for larvae exposed to large steelhead trout. No larva with a case (with or without lateral extensions) was consumed during the experiment, whereas all larvae without a case were consumed. We tested whether lateral extensions provided stability against overturning and entrainment by manipulating presence of lateral extensions and subjecting larvae to turbulent flow conditions. Once dislodged, larvae with lateral extensions experienced fewer revolutions and regained their footing faster than those without extensions. Our results suggest lateral extensions provide stability against overturning in fast flow and may improve the ability of larvae to forage efficiently in turbulent flow conditions. Other caddisfly species build lateral extensions on their case, and the extensions may provide similar benefits for these taxa.},
keywords = {camouflage, case, Dicosmoecus, drag, function, predation, stability, Trichoptera},
pubstate = {published},
tppubtype = {article}
}
Most caddisfly larvae build cases of silk and a variety of collected materials. Multiple functions,
including protection from predators, resistance to entrainment by high flows, and improved respiration,
have been suggested for caddisfly cases. We investigated the functional role of cases built by Dicosmoecus gilvipes, a limnephilid caddisfly. In this species, the 1st- through 4th-instar larvae build cases with plant material and attach Douglas-fir needles as lateral extensions that resemble vanes on an arrow. We tested whether the lateral extensions and entire case deterred predators by manipulating lateral extensions and case presence for larvae exposed to large steelhead trout. No larva with a case (with or without lateral extensions) was consumed during the experiment, whereas all larvae without a case were consumed. We tested whether lateral extensions provided stability against overturning and entrainment by manipulating presence of lateral extensions and subjecting larvae to turbulent flow conditions. Once dislodged, larvae with lateral extensions experienced fewer revolutions and regained their footing faster than those without extensions. Our results suggest lateral extensions provide stability against overturning in fast flow and may improve the ability of larvae to forage efficiently in turbulent flow conditions. Other caddisfly species build lateral extensions on their case, and the extensions may provide similar benefits for these taxa.
including protection from predators, resistance to entrainment by high flows, and improved respiration,
have been suggested for caddisfly cases. We investigated the functional role of cases built by Dicosmoecus gilvipes, a limnephilid caddisfly. In this species, the 1st- through 4th-instar larvae build cases with plant material and attach Douglas-fir needles as lateral extensions that resemble vanes on an arrow. We tested whether the lateral extensions and entire case deterred predators by manipulating lateral extensions and case presence for larvae exposed to large steelhead trout. No larva with a case (with or without lateral extensions) was consumed during the experiment, whereas all larvae without a case were consumed. We tested whether lateral extensions provided stability against overturning and entrainment by manipulating presence of lateral extensions and subjecting larvae to turbulent flow conditions. Once dislodged, larvae with lateral extensions experienced fewer revolutions and regained their footing faster than those without extensions. Our results suggest lateral extensions provide stability against overturning in fast flow and may improve the ability of larvae to forage efficiently in turbulent flow conditions. Other caddisfly species build lateral extensions on their case, and the extensions may provide similar benefits for these taxa.
2000
Levine, Jonathan M.
Species diversity and biological invasions: relating local process to community pattern Journal Article
In: Science, vol. 288, no. 5467, pp. 852-854, 2000, ISSN: 0036-8075.
Abstract | Links | BibTeX | Tags: biodiversity, ecosystem, grasslands, invasibility, resistance, stability
@article{Levine2000b,
title = {Species diversity and biological invasions: relating local process to community pattern},
author = {Jonathan M. Levine},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Science-2000-Levine-852-4.pdf},
issn = {0036-8075},
year = {2000},
date = {2000-05-05},
journal = {Science},
volume = {288},
number = {5467},
pages = {852-854},
abstract = {In a California riparian system, the most diverse natural assemblages are the most invaded by exotic plants. A direct in situ manipulation of local diversity and a seed addition experiment showed that these patterns emerge despite the intrinsic negative effects of diversity on invasions. The results suggest that species loss at small scales may reduce invasion resistance. At community-wide scales, the overwhelming effects of ecological factors spatially covarying with diversity, such as propagule supply, make the most diverse communities most likely to be invaded.},
keywords = {biodiversity, ecosystem, grasslands, invasibility, resistance, stability},
pubstate = {published},
tppubtype = {article}
}
In a California riparian system, the most diverse natural assemblages are the most invaded by exotic plants. A direct in situ manipulation of local diversity and a seed addition experiment showed that these patterns emerge despite the intrinsic negative effects of diversity on invasions. The results suggest that species loss at small scales may reduce invasion resistance. At community-wide scales, the overwhelming effects of ecological factors spatially covarying with diversity, such as propagule supply, make the most diverse communities most likely to be invaded.