Publications

@article{Finlay2011,

title = {Light-mediated thresholds in stream-water nutrient composition in a river network},

author = {J. C. Finlay and J. M. Hood and M. P. Limm and M. E. Power and J. D. Schade and J. R. Welter},

url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Finlay_2011_Ecology.pdf},

doi = {10.1890/09-2243.1},

year  = {2011},

date = {2011-01-01},

journal = {Ecology},

volume = {92},

number = {1},

pages = {140-150},

abstract = {The elemental composition of solutes transported by rivers reflects combined influences of surrounding watersheds and transformations within stream networks, yet comparatively little is known about downstream changes in effects of watershed loading vs. in-channel processes. In the forested watershed of a river under a mediterranean hydrologic regime, we examined the influence of longitudinal changes in environmental conditions on water-column nutrient composition during summer base flow across a network of sites ranging from strongly heterotrophic headwater streams to larger, more autotrophic sites downstream. Small streams (0.1–10 km2 watershed area) had longitudinally similar nutrient concentration and composition with low (∼2) dissolved nitrogen (N) to phosphorus (P) ratios. Abrupt deviations from this pattern were observed in larger streams with watershed areas >100 km2 where insolation and algal abundance and production rapidly increased. Downstream, phosphorus and silica concentrations decreased by >50% compared to headwater streams, and dissolved organic carbon and nitrogen increased by ∼3–6 times. Decreasing dissolved P and increasing dissolved N raised stream-water N:P to 46 at the most downstream sites, suggesting a transition from N limitation in headwaters to potential P limitation in larger channels. We hypothesize that these changes were mediated by increasing algal photosynthesis and N fixation by benthic algal assemblages, which, in response to increasing light availability, strongly altered stream-water nutrient concentration and stoichiometry in larger streams and rivers.},

keywords = {Angelo Coast Range Reserve, autotrophy, elemental stoichiometry, geomorphology, heterotrophy, N fixation, nitrogen, phosphorus, primary production, South Fork Eel Riverwatershed, stream network},

pubstate = {published},

tppubtype = {article}

}

@article{DOI:10.1002/esp.1689,

title = {Implications of the saltation-abrasion bedrock incision model for steady-state river longitudinal profile relief and concavity},

author = {L. S. Sklar and W. E. Dietrich},

url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Sklar_2008_EarthSurProc.pdf},

doi = {DOI:10.1002/esp.1689},

year  = {2008},

date = {2008-05-22},

journal = {Earth Surface Processes and Landforms},

volume = {33},

number = {7},

pages = {1129-1151},

abstract = {The saltation–abrasion model predicts rates of river incision into bedrock as an explicit 

function of sediment supply, grain size, boundary shear stress and rock strength. Here we 

use this experimentally calibrated model to explore the controls on river longitudinal profile 

concavity and relief for the simple but illustrative case of steady-state topography. Over a 

wide range of rock uplift rates we find a characteristic downstream trend, in which upstream 

reaches are close to the threshold of sediment motion with large extents of bedrock exposure 

in the channel bed, while downstream reaches have higher excess shear stresses and lesser 

extents of bedrock exposure. Profile concavity is most sensitive to spatial gradients in runoff 

and the rate of downstream sediment fining. Concavity is also sensitive to the supply rate 

of coarse sediment, which varies with rock uplift rate and with the fraction of the total 

sediment load in the bedload size class. Variations in rock strength have little influence on 

profile concavity. Profile relief is most sensitive to grain size and amount of runoff. Rock 

uplift rate and rock strength influence relief most strongly for high rates of rock uplift. 

Analysis of potential covariation of grain size with rock uplift rate and rock strength suggests 

that the influence of these variables on profile form could occur in large part through 

their influence on grain size. Similarly, covariation between grain size and the fraction of 

sediment load in the bedload size class provides another indirect avenue for rock uplift and 

strength to influence profile form.},

keywords = {bedrock channels, bedrock channels;erosion, erosion, geomorphology, laser altimetry},

pubstate = {published},

tppubtype = {article}

}

@article{Stock2005,

title = {Field measurements of incision rates following bedrock exposure: Implications for process controls on the long profiles of valleys cut by rivers and debris flows},

author = {J. D. Stock and D. R. Montgomery and B. D. Collins and W. E. Dietrich},

url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Stock_2005_GSABulletin.pdf},

doi = {10.1130/B25560.1},

year  = {2005},

date = {2005-01-01},

journal = {GSA Bulletin},

volume = {117},

number = {1-2},

pages = {174-194},

abstract = {Until recently, published rates of incision of bedrock valleys came from indirect dating of incised surfaces. A small but growing literature based on direct measurement reports short-term bedrock lowering at geologically unsustainable rates. We report observations of bedrock lowering from erosion pins monitored over 1–7 yr in 10 valleys that cut indurated volcanic and sedimentary rocks in Washington, Oregon, California, and Taiwan. Most of these channels have historically been stripped of sediment. Their bedrock is exposed to bed-load abrasion, plucking, and seasonal wetting and drying that comminutes hard, intact rock into plates or equant fragments that are removed by higher flows. Consequent incision rates are proportional to the square of rock tensile strength, in agreement with experimental results of others. Measured rates up to centimeters per year far exceed regional long-term erosion-rate estimates, even for apparently minor sediment-transport rates. Cultural artifacts on adjoining strath terraces in Washington and Taiwan indicate at least several decades of lowering at these extreme rates. Lacking sediment cover, lithologies at these sites lower at rates that far exceed long-term rock-uplift rates. This rate disparity makes it unlikely that the long profiles of these rivers are directly adjusted to either bedrock hardness or rock-uplift rate in the manner predicted by the stream power law, despite the observation that their profiles are well fit by power-law plots of drainage area vs. slope. We hypothesize that the threshold of motion of a thin sediment mantle, rather than bedrock hardness or rock-uplift rate, controls channel slope in weak bedrock lithologies with tensile strengths below ∼3–5 MPa. To illustrate this hypothesis and to provide an alternative interpretation for power-law plots of area vs. slope, we combine Shields' threshold transport concept with measured hydraulic relationships and downstream fining rates. In contrast to fluvial reaches, none of the hundreds of erosion pins we installed in steep valleys recently scoured to bedrock by debris flows indicate any postevent fluvial lowering. These results are consistent with episodic debris flows as the primary agent of bedrock lowering in the steepest parts of the channel network above ∼0.03–0.10 slope.},

keywords = {erosion, geomorphology, neotectonics, rivers, Weathering},

pubstate = {published},

tppubtype = {article}

}

@article{Howard2003,

title = {Freshwater mussels in a California North Coast Range river: occurrence, distribution, and controls},

author = {Jeanette K. Howard and Kurt M. Cuffey},

url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Howard_2003_JouNorthAmerBenthoSoc.pdf},

doi = {10.2307/1467978},

year  = {2003},

date = {2003-03-01},

journal = {Journal of the North American Benthological Society},

volume = {22},

number = {1},

pages = {63-77},

abstract = {We report the occurrence and habitat of mussel populations within a continuous 8-km section of the South Fork Eel River in the Northern Coast Range of California. The primary goals of our study were 1) to compile information on species composition and population density, and 2) to examine whether spatial distribution and variability were related to geomorphology and hydrology. High discharges almost certainly provide more of a constraint on the distribution and persistence of 

mussels in the South Fork Eel than do low summer flows, so we used the Hydrologic Engineering Center’s River Analysis System (HEC-RAS) hydraulic model to estimate physical conditions during high flows when in-channel investigations were not feasible. We found numerous individuals of 2 species (Margaritifera falcata and Anodonta californiensis), with the spatial distribution of both species 

characterized by high variability. Mussels in this system live almost exclusively in pools (with a few in runs), near the channel banks, and especially among sedge root-mat substrate. In all flow regimes (summer, winter, 5-y flood, and the largest floods on record), we found mussels in areas of lower boundary shear stresses and lower velocities. Our study suggests that, at various spatial scales, mussels appear to be distributed in a manner that protects them from the highest flow-induced stresses.},

keywords = {California, freshwater mussels, geomorphology, hydraulic model, hydrology, microhabitat, shear stress, South Fork Eel River},

pubstate = {published},

tppubtype = {article}

}

@article{111bp,

title = {Effect of stream flow regulation and absence of scouring floods on trophic transfer of biomass to fish in Northern California rivers},

author = {Michael S. Parker and Mary E. Power},

url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/parker-power-flow-regulation-food-webs-tech-report-1997-copy-1.pdf},

year  = {1997},

date = {1997-01-01},

urldate = {1997-01-01},

journal = {Technical Completion Report, University of California Water Resources Center},

volume = {UCAL-WRC-W-825},

number = {825},

abstract = {Scouring winter floods strongly influence the structure and dynamics of food webs in rivers with winter flood, summer drought hydrographs. Reduction or elimination of scouring floods, in addtition to altering physical conditions within rivers, may negatively affect salmonid populations by reducing energy flow to them from lower trophic levels. We compared food webs of two northern California rivers with drastically different flow regimes to assess the effects of differences in food web structure on the distribution and growth of juvenile steelhead trout. The upper Mad River has a highly regulated flow regime and rarely experiences scouring winter floods, while the upper Van Duzen River is free-flowing and experiences frequent scouring floods. Thrroughout spring and summer 1994 densities of the large, grazing caddisfly Dicosmoecus gilvipes exceeded 801m2 in the Mad River, but were < 21m2 in the Van Duzen. Consequently, filamentous green algae was nearly absent in the Mad from June through September, but was relatively abundant in the Van Duzen. Densities of other stream-dwelling insects (primarily Chironomids and mayflies, which are the preferred prey of juvenile salmonids) and juvenile steelhead were consistently mlich lower in the Mad than the Van Duzen. At the end of the summer, Dicosmoecus pupated, and thus became inactive, which resulted in a large bloom of filamentous green algae (primarily Oedogonium and Cladophora) and a several-fold increase in the densities of Chironomids and mayflies in the Mad but not the Van Duzen. River flows in 1995 were much higher than in 1994 and both rivers experienced a number of scouring floods. As a consequence, Dicosmoecus densities were reduced to < 21m2 in both rivers throughout the spring and summer. The Mad experienced a large Cladophora bloom, and densities of Chironomids and mayflies were several times higher in 1995 than 1994. These observations support our hypothesis that eliminating scouring floods favors large, slow-growing benthic insect taxa over smaller, faster-growing taxa whose populations build up rapidly after floods. Since the former are invulnerable to predation by juvenile salmonids, energy flow is reduced and juvenile salmonid populations decline. 

Experimental manipulation of juvenile steelhead in artificial channels with and without Dicosmoecus allowed us to test this hypothesis more directly and without potential influences from factors other than food web structure that may have varied between regulated and unregulated rivers. Experimental results revealed that Dicosmoecus significantly reduced the availability of small prey, which resulted in negative juvenile steelhead growth. Together, our surveys and experimental results show that elimination of scouring floods alters energy pathways in river food webs resulting in reduced biomass available to fish populations. Modifying flow regimes regulated by dams, so they more closely resemble natural hydrographs, may be an important step in restoring salmonid populations in some rivers.},

keywords = {algae, AQUATIC INSECTS, Benthos, Fish Ecology, Flood Control, geomorphology, River Beds, Water Diversion, Watershed Management},

pubstate = {published},

tppubtype = {article}

}

@article{Kupferberg1996,

title = {Hydrologic and geomorphic factors affecting conservation of a river-breeding frog (Rana boylii)},

author = {Sarah J. Kupferberg},

url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Kupferberg_EcolApp1996.pdf},

doi = {http://dx.doi.org/10.2307/2269611},

year  = {1996},

date = {1996-11-00},

journal = {Ecological Applications},

volume = {6},

number = {4},

pages = {1332-1344},

abstract = {Organisms that live in highly variable environments, such as rivers, rely on adaptations to withstand and recover from disturbance. These adaptations include behavioral traits, such as habitat preference and plasticity of reproductive timing, that minimize the effects of discharge fluctuation. Studies linking hydrologic regime, habitat preference, and population processes, however, are predominantly limited to fish. Information on other sensitive taxa is necessary to facilitate conservation of multispecies assemblages and restoration of biodiversity in degraded river channels. I studied the functional relationship between physical habitat and reproduction of the foothills yellow-legged frog (Rana boylii), a California State Species of Special Concern. From 1992 to 1994, I mapped breeding sites along 5.3 km of the South Fork Eel River in northern California and monitored egg survival to hatching. Frogs selected sites over a range of spatial scales and timed their egg-laying to avoid fluctuations in river stage and current velocity associated with changes in discharge. The main sources of mortality were desiccation and subsequent predation of eggs in a dry year and scour from substrate in wet years, both caused by changes in stage and velocity. At the finest spatial scale, frogs attached eggs to cobbles and boulders at lower than ambient flow velocities. At larger scales, breeding sites were near confluences of tributary drainages and were located in wide, shallow reaches. Clutches laid in relatively narrower and deeper channels had poor survival in rainy as well as dry springs. Most breeding sites were used repeatedly, despite between- and within-year variation in spring stage of the river. This pattern of site selection suggests that conservation of Rana boylii may be enhanced by maintaining or restoring channels with shapes that provide stable habitat over a range of river stages.},

keywords = {amphibians, Anura, frogs, geomorphology, hydrology, oviposition, physical habitat, Rana boylii, reproductive success, river, spatial scale},

pubstate = {published},

tppubtype = {article}

}