Middle Fork Research Articles

Upper Sun River Drainage Basin Origin Determined by Topographic Map Interpretation Techniques: Lewis and Clark and Teton Counties, Montana, USA

A new and fundamentally different regional geomorphology paradigm in which massive south- and southeast-oriented meltwater floods flowed across the entire Missouri River drainage basin is tested by interpreting detailed topographic maps of the Montana upper Sun River drainage basin region by trying to explain origins of previously unexplained or poorly explained erosional landforms located upstream from Sun River Canyon (which cuts across Montana’s north-to-south oriented Sawtooth Range). Mountain passes, through valleys, and other drainage divide low points along what are today high mountain ridges, including the North American east-west continental divide, are interpreted to be evidence of drainage routes that once crossed the region. These drainage divide crossings suggest that prior to erosion of present-day upper Sun River drainage basin valleys, massive floods moved in south directions across what are today the north-oriented Middle and South Fork Flathead River drainage basins into today’s upper Sun River drainage basin area and carved a complex of diverging and converging channels into what was probably a low relief surface now represented by the crests of the region’s highest mountain ridges. Further, the map evidence shows how a diverging complex of south- and southeast-oriented upstream Sun River drainage basin flood flow channels changed flow direction to cross the Sawtooth Range in a northeast direction before converging on the Montana plains at a location downstream from Sun River Canyon. The observed upper Sun River drainage basin area topographic map evidence is consistent with the new geomorphology paradigm predictions, in which massive south-oriented meltwater floods flowing across the rising rim of a continental ice sheet created deep “hole” (created by deep ice sheet erosion and ice sheet weight caused crustal warping) are diverted to flow in northeast and north directions into and across deep “hole” space being opened up by ice sheet melting.

What Matters Most: Are Future Stream Temperatures More Sensitive to Changing Air Temperatures, Discharge, or Riparian Vegetation?

AbstractSimulations of stream temperatures showed a wide range of future thermal regimes under a warming climate — from 2.9°C warmer to 7.6°C cooler than current conditions — depending primarily on shade from riparian vegetation. We used the stream temperature model, Heat Source, to analyze a 37‐km study segment of the upper Middle Fork John Day River, located in northeast Oregon, USA. We developed alternative future scenarios based on downscaled projections from climate change models and the composition and structure of native riparian forests. We examined 36 scenarios combining future changes in air temperature (ΔTair = 0°C, +2°C, and +4°C), stream discharge (ΔQ = −30%, 0%, and +30%), and riparian vegetation (post‐wildfire with 7% shade, current vegetation with 19% shade, a young‐open forest with 34% shade, and a mature riparian forest with 79% effective shade). Shade from riparian vegetation had the largest influence on stream temperatures, changing the seven‐day average daily maximum temperature (7DADM) from +1°C to −7°C. In comparison, the 7DADM increased by 1.4°C with a 4°C increase in air temperature and by 0.7°C with a 30% change in discharge. Many streams throughout the interior western United States have been altered in ways that have substantially reduced shade. The effect of restoring shade could result in future stream temperatures that are colder than today, even under a warmer climate with substantially lower late‐summer streamflow.

Geomorphic regulation of floodplain soil organic carbon concentration in watersheds of the Rocky and Cascade Mountains, USA

Abstract. Mountain rivers have the potential to retain OC-rich soil and store large quantities of organic carbon (OC) in floodplain soils. We characterize valley bottom morphology, floodplain soil, and vegetation in two disparate mountain river basins: the Middle Fork Snoqualmie in the Cascade Mountains and the Big Sandy in the Wind River Range of the Rocky Mountains. We use this dataset to examine variability in OC concentration between these basins as well as within them at multiple spatial scales. We find that although there are some differences between basins, much of the variability in OC concentration is due to local factors, such as soil moisture and valley bottom geometry. From this, we conclude that local factors likely play a dominant role in regulating OC concentration in valley bottoms and that interbasin differences in climate or vegetation characteristics may not translate directly into differences in OC storage. We also use an analysis of OC concentration and soil texture by depth to infer that OC is input to floodplain soils mainly by decaying vegetation, not overbank deposition of fine, OC-bearing sediment. Geomorphology and hydrology play strong roles in determining the spatial distribution of soil OC in mountain river corridors.

Mammalian Fauna of the Middle Eocene Kishenehn Formation, Middle Fork of the Flathead River, Montana

The Kishenehn Formation is a unit of sedimentary rocks exposed largely in the cutbanks of the Flathead River and its tributaries in and around Glacier National Park in northwestern Montana and adjacent British Columbia. From these rocks along the Flathead's Middle Fork, which range from very fine-grained oil shales to and including pebble-cobble conglomerates, vertebrate and molluscan faunas of middle Eocene age have been collected over nearly 40 years by a combination of prospecting, with access by raft, to screen washing sediment from the most fossiliferous exposures. The mammalian fauna from the formation includes at least twenty-six taxa, ranging in size from tiny rodents and insectivores to a very large brontothere. A radiometic date of ca. 46.2 Ma was obtained from below the fossiliferous deposits. The age of the fauna, presumably within one or two million years younger than the radiometric date, is reinforced by the presence of the Uintan index taxon Amynodon Marsh, 1877, as well as the co-occurrence of an eomyid rodent referred to Metanoiamys Chiment and Korth, 1996, and the sciuravid rodent Pauromys Troxell, 1923. The fauna has a scarcity of Carnivora, which may reflect the real faunal composition. It is striking for its total absence of selenodont artiodactyls. Whether the latter should be attributed to geologic age, which is presumably early after these animals developed in North America or Asia, or is environmentally significant, must remain conjectural. Somewhat widely distributed in the North American west, earlier Uintan and/or Shoshonean mammalian faunas remain difficult to correlate, due at least in part to distinctive endemism or environmental uniqueness. The fauna also has indications of interchange between North American and Asian components at that time.Of the twenty-six mammalian taxa recognized in the fauna, one is established as new, the rodent Microparamys solis, new species.

A physical framework for evaluating net effects of wet meadow restoration on late‐summer streamflow

AbstractRestoration of degraded wet meadows found on upland valley floors has been proposed to achieve a range of ecological benefits, including augmenting late‐season streamflow. There are, however, few field and modelling studies documenting hydrologic changes following restoration that can be used to validate this expectation, and published changes in groundwater levels and streamflow following restoration are inconclusive. Here, we assess the streamflow benefit that can be obtained by wet‐meadow restoration using a physically based quantitative analysis. This framework employs a 1‐dimensional linearized Boussinesq equation with a superimposed solution for changes in storage due to groundwater upwelling and evapotranspiration, calculated explicitly using the White method. The model and assumptions gave rise to predictions in good agreement with field data from the Middle Fork John Day watershed in Oregon, USA. While raising channel beds can increase total water storage via increases in water table elevation in upland valley bottoms, the contributions of both lateral and longitudinal drainage from restored floodplains to late‐summer streamflow were found to be undetectably small, while losses in streamflow due to greater transpiration, lower hydraulic gradients, and less laterally drainable pore volume were likely to be substantial. Although late‐summer streamflow increases should not be expected as a direct result of wet‐meadow restoration, these approaches offer benefits for improving the quality and health of riparian and meadow vegetation that would warrant considering such measures, even at the cost of increased water demand and reduced streamflow.

Using maximum entropy modeling to predict suitable habitat locations for the Cutshin Crayfish (Cambarus taylori)

The Cutshin Crayfish (Cambarus taylori) is a recently described species which is endemic to the Middle Fork of the Kentucky River basin. The Middle Fork of the Kentucky River lies within the anthracite coal fields of Eastern Kentucky, and thus a conservation assessment of C. taylori is warranted. The goal of this study was to predict suitable habitat locations for C. taylori through use of maximum entropy modeling (MaxEnt). The Middle Fork of the Kentucky River’s crayfish fauna was surveyed during the summer of 2014. The occurrence data from this study coupled with landscape scale environmental variables—such as stream order and land use data—was used to create the model. The mean area under the receiver operating characteristic curve (AUC) value was 0.898, showing the model had high predictive accuracy. The model indicated high probability of occurrence in streams at the southern end of the basin, and a low probability of occurrence at the northern end of the basin. Stream order and stream sinuosity had the highest contribution to the model showing that C. taylori prefers 3rd and 4th order streams with low sinuosity. Although the AUC value showed high predictive accuracy for the model, predicted sites will need to be ground validated to confirm the model’s predictive accuracy.

A network model for primary production highlights linkages between salmonid populations and autochthonous resources

AbstractSpatial variation in fish densities across river networks suggests that the influence of food and habitat resources on assemblages varies greatly throughout watersheds. Conceptual models predict that in situ primary production should vary with river characteristics, but the influence of autochthonous resource availability on the capacity for river reaches to support fish is poorly understood. We estimated primary production throughout the South Fork and Middle Fork of the John Day River, Oregon, by measuring diel cycles in dissolved oxygen (DO) during July 2013. Using these data, we (1) evaluated the extent to which juvenile salmonid abundance and resource limitation correlated with areas of high gross primary production (GPP), (2) developed models to predict GPP from both site‐level measurements and remotely sensed data, and (3) made predictions of GPP across the entirety of the Middle Fork John Day River (MFJD) network and assessed the utility of these spatially continuous predictions for describing variation fish densities at broad scales. We produced reliable estimates of GPP at sites where DO loggers were deployed using measurements of solar exposure, water temperature, and conductivity measured at each site, as well as surrogates for these data estimated from remote sensing data sources. Estimates of GPP across fish sampling sites explained, on average, 58–63% of the variation in juvenile salmonid densities during the summer sampling period, and 51–83% during the fall sampling period, while continuous network predictions of GPP explained 44% of the variation in fish densities across 29 km of the MFJD. Further, GPP explained nearly half of the variation in juvenile steelhead dietary resource limitation, as inferred from bioenergetics modeling results. These results comprise a first effort at quantifying variation in autochthonous production across an entire river network and, importantly, provide a much‐needed food‐web context for guiding more effective fish and habitat management.

Do River Drainage Boundaries Coincide with Phylogeographic Breaks in the Redband Darter?

The Redband Darter, Etheostoma luteovinctum, is a benthic headwater fish species found in the Caney Fork and Stones rivers (Cumberland River) and the Duck and Elk rivers (Tennessee River) of central Tennessee. Phylogenetic analyses of 2601 amplified fragment length polymorphisms (AFLPs) were used to assess the relationships among populations and identified two genetically distinct lineages of Redband Darter. One lineage is comprised of populations in the Duck R., Elk R., Middle Fork Stones R., West Fork Stones R., and Hickory Creek of the Caney Fork River, while the other lineage is confined to the remainder of the known localities in the Cumberland R. drainage. As clades were not restricted to drainage or system boundaries, patterns suggest system and drainage transfers. Additionally, morphological variation was examined among populations using standard meristic data and nuptial male color and pigmentation characteristics. Although some morphological traits varied between the two clades, members were not clearly diagnosable using morphology. Taxonomic recognition is not proposed for the two identified clades; however, each clade should be recognized as an evolutionarily significant unit and regarded as such in future conservation efforts. Furthermore, this study demonstrates the utility of AFLPs to assess genetic variation and phylogenetic relationships for species-level taxonomic or phylogeographic studies.

Survival of Translocated Clubshell and Northern Riffleshell in Illinois

Translocation of freshwater mussels is a conservation tool used to reintroduce extirpated populations or augment small populations. Few studies have evaluated the effectiveness of translocations, mainly because estimating survival is challenging and time-consuming. We used a mark-recapture approach to estimate survival of nearly 4,000 individually marked Clubshell (Pleurobema clava) and Northern Riffleshell (Epioblasma rangiana) translocated to eight sites over a five-year period into the Salt Fork and Middle Fork Vermilion rivers in central Illinois. Survival differed among sites and between species; Clubshell were approximately five times more likely to survive than Northern Riffleshell. Survival also increased in the fourth year following a release and decreased following high-flow events. Translocating numerous individuals into multiple sites over a period of years could spread the risk of catastrophic high-flow events and maximize the likelihood for establishing self-sustaining populations.

Integrated Metaheuristic Differential Evolution Optimization Algorithm and Pseudo Static Analysis of Concrete Gravity Dam

A differential evolution-algorithm-based optimum design method is presented for concrete gravity dams under stability, principal stress, and sliding constraints. A gravity dam is a large scale hydraulic structure providing its stability based on weight of concrete volume. Hence, optimization of dam cross-section leads to an economic and low cost structure. For this aim, a general dam section is reconstructed with seven proper horizontal and vertical geometric parameters which take into account all possible cross section shapes. Weight of dam is considered as goal function and the optimization problem of geometric parameters is solved using DE algorithm. The DE algorithm written as a MATLAB code are applied to Four benchmark gravity dams including Middle Fork, Richard, Pine Flat, and Friant. The comparison of DE optimum solutions with real dimension of dams and another optimization method in literature shows the performance of the DE algorithm. In mentioned benchmark dams, there are 26.82%, 30.11%, 25.31%, and 20.93% of weight reduction Compared to real values, respectively. Also, optimization results of DE algorithm are compared with literatures. The comparison shows 3.55%, 5.1%, 19.13% and 12.14% reduction of weight compared to GA and PSOD algorithms, respectively.

Spatial autocorrelation of microbial communities atop a debris-covered glacier is evidence of a supraglacial chronosequence.

Although microbial communities from many glacial environments have been analyzed, microbes living in the debris atop debris-covered glaciers represent an understudied frontier in the cryosphere. The few previous molecular studies of microbes in supraglacial debris have either had limited phylogenetic resolution, limited spatial resolution (e.g. only one sample site on the glacier) or both. Here, we present the microbiome of a debris-covered glacier across all three domains of life, using a spatially-explicit sampling scheme to characterize the Middle Fork Toklat Glacier's microbiome from its terminus to sites high on the glacier. Our results show that microbial communities differ across the supraglacial transect, but surprisingly these communities are strongly spatially autocorrelated, suggesting the presence of a supraglacial chronosequence. This pattern is dominated by phototrophic microbes (both bacteria and eukaryotes) which are less abundant near the terminus and more abundant higher on the glacier. We use these data to refute the hypothesis that the inhabitants of the glacier are randomly deposited atmospheric microbes, and to provide evidence that succession from a predominantly photosynthetic to a more heterotrophic community is occurring on the glacier.

A case of Appalachian endemism: Revision of the Cambarus robustus complex (Decapoda: Cambaridae) in the Kentucky and Licking River basins of Kentucky, USA, with the description of three new species.

The amazing levels of freshwater biodiversity found in the Appalachian Mountains of the eastern United States are among the highest recorded globally. Localized endemics make up much of this diversity, with numerous fish, freshwater mussels, salamanders and crayfish often being restricted to a single watershed, and in some instances, subwatersheds. Much of this diversity is the product of the processes of vicariance and historical stream drainage patterns. Herein, we describe three new crayfish species, all previously members of the Cambarus robustus complex, which occur in the Appalachian portion of the Kentucky and Licking river basins in Kentucky, USA. All three species differ from each other morphologically, genetically, and zoogeographically, fulfilling the requirements of the integrated species concept. Cambarus guenteri occurs in the southern tributaries of the Kentucky River mainstem as well as throughout the South Fork Kentucky River. Cambarus taylori is a narrow endemic, which only occurs in the Middle Fork Kentucky River. Cambarus hazardi, which has the widest distribution of the three new species, occurs in the North Fork Kentucky River, Red River, and upper reaches of the Licking River basin. Stream piracy events between the Cumberland and South Fork Kentucky River, as well as the Licking, Red and North Fork Kentucky rivers, are theorized to be important in the evolution of this complex. Cambarus guenteri is proposed as currently stable, though both C. taylori and C. hazardi are considered imperiled at this time due to habitat destruction throughout both of their respective ranges.

Organic geochemistry of funginite (Miocene, Eel River, Mendocino County, California, USA) and macrinite (Cretaceous, Inner Mongolia, China)

Funginite from the Miocene Sand Bank coal from outcrops along the Middle Fork Eel River in Mendocino County, California, and coprolitic macrinite from the Lower Cretaceous Shengli Formation No. 6 coal, Inner Mongolia, were investigated using optical microscopy, confocal scanning laser microscopy (CLSM), scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDS), Raman micro spectroscopy, and micro-Fourier transform infrared spectroscopy (FTIR). The examinations showed that the Sand Bank funginite has a higher reflectance than the surrounding vitrinite and that the Shengli macrinite has a 0.41–1.13% reflectance range, lower than the reflectance of the adjacent fusinite but higher than the 0.36–0.37% Rr of the vitrinite. CLSM revealed fine structure and morphology of multicellular fungal sclerotia with distinct smooth to granular margins, thick bands enveloping the entire fungal body, and thin- or thick hyphae and hyphae lumens. SEM-EDS indicated that the rootlet interior to the funginite contained Si, Al, S, and Ca; the funginite and macrinite contained S and Ca; and the surrounding matrix contained illite and, perhaps, the phosphates gorceixite-crandallite. The coprolitic macrinite contained quartz and clay. The funginite proved to be more aliphatic than the surrounding vitrinite. The coprolitic macrinite and the macrinite have shorter and more branched aliphatic chains than the associated vitrinite. The obtained results contribute to the assessment of funginite and macrinite in terms of morphology and maceral chemistry, indicating an interaction of plant hosts with mutualistic fungi and decomposers.

A geomorphic assessment to inform strategic stream restoration planning in the Middle Fork John Day Watershed, Oregon, USA

ABSTRACTA geomorphic assessment of the Middle Fork John Day Watershed, Oregon, USA, was used to generate a hierarchical, map-based understanding of watershed impairments and potential opportunities for improvements. Specifically, we (1) assessed river diversity (character and behavior) and patterns of reach types (and their controls); (2) evaluated the geomorphic condition of the streams; (3) interpreted their geomorphic recovery potential; and (4) synthesized the above into a hypothetical, strategic management plan. Collectively, these maps can set bounds and provide realistic guidance for river rehabilitation, design and implementation efforts. Fifteen distinct reach types were identified, two-thirds of which are found along perennial streams. On the basis of a variety of geo-indicators, approximately two-thirds of all perennial stream reaches were found to be in ‘good’ geomorphic condition, whereas one-third had departed to ‘moderate’ and ‘poor’ condition. Departures from ‘good’ condition were primarily related to riparian vegetation removal, conversion of floodplain to agricultural land uses (farming and grazing), logging, and channel bed dredge mining for gold. Encouragingly, the majority of reaches classified as being in moderate geomorphic condition were found to have high recovery potential. While our geomorphic assessment has practical utility for informing physically realistic expectation management for efforts like salmonid habitat restoration, the maps themselves are the key vehicle for communicating and visualizing among stakeholders.

Linking models across scales to assess the viability and restoration potential of a threatened population of steelhead (Oncorhynchus mykiss) in the Middle Fork John Day River, Oregon, USA

Species conservation is often informed by the use of models evaluating the effect of different management strategies on the status of at-risk populations. For Pacific salmon and steelhead (Oncorhynchus sp.), which have complex life cycles spanning diverse environments and jurisdictions, life-cycle models (LCMs) have proven particularly useful for this task. Yet, most salmonid LCM applications to date have not been able to tie projections of population performance to specific tributary habitat management actions, which is integral to many recovery plans. Here we describe a modelling framework that links reach-scale stream habitat models with a basin-scale LCM, bridged by statistical extrapolation models, to evaluate recovery opportunities for an imperiled population of steelhead (O. mykiss) in the Middle Fork John Day River, USA. We parameterized a LCM by leveraging results from (1) a large-scale environmental monitoring program that supports ecohydraulic modelling and characterizes habitat quality (with a salmonid emphasis) within individual stream reaches (ca. 100–600m segments), and (2) detailed demographic studies that provide estimates of survival, age structure, fecundity, etc. relevant to the model population. We then applied the model to quantify population performance under current/base (status quo) conditions and under two classes of restoration that aim to increase survival for juvenile steelhead: riparian revegetation, which reduces (otherwise limiting) stream temperatures during the warm summer months; and woody structure addition, which increases in-stream hydraulic complexity and thus juvenile rearing capacity. Status quo simulations produced abundance dynamics consistent with recent population monitoring data and the population’s current threatened status. Our evaluation of these basic restoration scenarios revealed that while both strategies have the potential to improve the conservation status of steelhead, the benefits of woody structure addition were relatively minor compared to those resulting from stream temperature reductions. Together, our findings suggest that in thermally stressed systems the benefits of wood addition will be optimized if (1) structures are added at a considerably higher rate than is often done, focusing on reaches that are not thermally limited initially, and (2) these efforts are paired with extensive riparian planting (i.e., in reaches that have the highest potential for effective shading), which will address thermal limitations (if relevant) and offer a natural source for future wood recruitment. In addition to shedding light on effective strategies for recovering steelhead, our study illustrates the power of coordinated monitoring programs that can parameterize the relationships needed to integrate modelling possibilities across scales.

Distribution and Status of the Freshwater Mussel Fauna of the Salt River Basin, Missouri

We qualitatively surveyed freshwater mussels in the Salt River basin, Missouri, during 1977–86 and 2005–7. A cumulative sample of 6,234 live individuals representing 31 species was recorded during both periods; six additional species were recorded only as shell material. Amblema plicata was the dominant species recorded, representing 31.3% of the total live animals. There were no significant differences in average species richness values, Brillouin's index values, or relative abundances of the tribes amblemini-pleurobemini-quadrulini between the two surveys. The most notable change was the complete loss of the mussel fauna in the South Fork Salt River. We also observed significantly higher probabilities of local extirpation in the mainstem Salt River, North Fork Salt River, Middle Fork Salt River, and South Fork Salt River. At the tribe level, the amblemini had a higher probability of local colonization and the lampsilini had a higher probability of local extirpation.

The Purple Hope Claims: Green Ridge, Middle Fork of the Snoqualmie River, King County, Washington

Few collectors outside the Pacific Northwest are aware of the exceptional quartz specimens found in King County, Washington. Only two King County quartz localities have ever been featured in nation...

Biogeochemical Stoichiometry Reveals P and N Limitation Across the Post-glacial Landscape of Denali National Park, Alaska

Global warming has accelerated glacial retreat in high-elevation and high-latitude ecosystems, exposing new terrain that can undergo predictable patterns of ecosystem succession, especially in coastal areas with relatively mild climates. However, little work has been done in harsher high-elevation and inland areas where the rate of plant and microbial succession may be greatly slowed by dryness and low temperatures. The present study is the first to address microbial succession at a major glacial foreland (the Middle Fork Toklat Glacier) in the interior of Alaska. We used a spatially nested sampling regime to reveal the landscape patterns in microbial activity and biogeochemical pools during the pre-plant stage of primary succession along this high-elevation and high-latitude chronosequence. Recently deglaciated soils (0–10 years) were colonized by a diverse microbial community that included many chemoautotrophs that likely subsist on high levels of un-weathered minerals (for example, pyrite) found at this site. Rates of N-fixation and extracellular enzyme activities were very low in the youngest soils sampled, but increased during the first 20 years of succession coinciding with a decrease in TOC and C:N levels. In older soils (20–54 years), TOC and TON increased and IN became undetectable perhaps indicating N limitation. Indicators of microbial activity stopped increasing 20 years post de-glaciation and remained at levels well below those seen at lower elevation and lower latitude sites, perhaps indicating severe nutrient limitations. Stoichiometric analyses also indicated phosphorus and nitrogen limitation across the entire chronosequence, with no indication of carbon limitation of microbial activity. These results indicate that nutrient limitation, rather than the constraints of a severe climate, may be the dominant factor slowing the rate of succession at high-latitude and high-altitude glacial forelands.

Topographic roughness as a signature of the emergence of bedrock in eroding landscapes

Abstract. Rock is exposed at the Earth surface when rates of erosion locally exceed rates of soil production. The thinning of soils and emergence of bedrock has implications spanning geomorphology, ecology and hydrology. Soil-mantled hillslopes are typically shaped by diffusion-like sediment transport processes that act to smooth topography through time, generating the familiar smooth, convex hillslope profiles that are common in low relief landscapes. Other processes, however, can roughen the landscape. Bedrock emergence can produce rough terrain; in this contribution we exploit the contrast between rough patches of bedrock outcrop and smooth, diffusion-dominated soil to detect bedrock outcrops. Specifically, we demonstrate that the local variability of surface normal vectors, measured from 1 m resolution airborne LiDAR data, can be used as a topographic signature to identify areas within landscapes where rock exposure is present. We then use this roughness metric to investigate the transition from soil-mantled to bedrock hillslopes as erosion rates increase in two transient landscapes, Bald Rock Basin, which drains into the Middle Fork Feather River, California, and Harrington Creek, a tributary of the Salmon River, Idaho. Rather than being abrupt, as predicted by traditional soil production models, in both cases the transition from fully soil-mantled to bedrock hillslopes is gradual and spatially heterogeneous, with rapidly eroding hillslopes supporting a patchwork of bedrock and soil that is well documented by changes in topographic roughness, highlighting the utility of this metric for testing hypotheses concerning the emergence of bedrock and adding to a growing body of evidence that indicates the persistence of partial soil mantles in steep, rapidly eroding landscapes.

Moyamoya in an infant with Down syndrome

In moyamoya disease, the anterior blood circulation in the brain is occluded and the characteristic appearance of the disease is seen in angiography. Moyamoya disease may be primary or secondary to diseases or syndromes such as Down syndrome. A 20-month-old girl with Down syndrome was admitted because of weakness and convulsions. She had left-sided hemiparesis. Cranial magnetic resonance imaging showed hyperintense lesions in both cerebral hemispheres in T2-fluid attenuated inversion recovery, and cranial angiography showed approximately 80-90% stenosis in the proximal region of the right middle cerebral artery fork, and left middle cerebral artery occlusion in the proximal region; left middle cerebral artery vascularization was provided by collateral arteries. These findings were consistent with those of moyamoya disease. Some proteins affecting arterial physiology are encoded on chromosome 21. These proteins are probably responsible for moyamoya disease in patients with Down syndrome. Our patient is one of the youngest with reported moyamoya syndrome and Down syndrome, and may point to the early onset of the disease.