Bighorn River Research Articles

Influence of dams on sauger population structure and hybridization with introduced walleye.

Dams have negatively affected freshwater biodiversity throughout the world. These negative effects tend to be exacerbated for aquatic taxa with migratory life histories, and for taxa whose habitat is fundamentally altered by the formation of large reservoirs. Sauger (Sander candadensis; Percidae), large-bodied migratory fishes native to North America, have seen population declines over much of the species' range, and dams are often implicated for their role in blocking access to spawning habitat and otherwise negatively affecting river habitat. Furthermore, hybridization appears to be more frequent between sauger and walleye in the reservoirs formed by large dams. In this study, we examine the role of dams in altering sauger population connectivity and facilitating hybridization with introduced walleye in Wyoming's Wind River and Bighorn River systems. We collected genomic data from individuals sampled over a large spatial scale and replicated sampling throughout the spawning season, with the intent to capture potential variation in hybridization prevalence or genomic divergence between sauger with different life histories. The timing of sampling was not related to hybridization prevalence or population divergence, suggesting limited genetic differences between sauger spawning in different time and places. Overall, there was limited hybridization detected, however, hybridization was most prevalent in Boysen Reservoir (a large impounded section of the Wind River). Dams in the lower Wind River and upper Bighorn River were associated with population divergence between sauger upstream and downstream of the dams, and demographic models suggest that this divergence has occurred in concordance with the construction of the dam. Sauger upstream of the dams exhibited substantially lower estimates of genetic diversity, which implies that disrupted connectivity between Wind River and Bighorn River sauger populations may already be causing negative demographic effects. This research points towards the importance of considering the evolutionary consequences of dams on fish populations in addition to the threats they pose to population persistence.

Declining geomorphic diversity and potential adaptive management opportunities on a highly regulated reach of the Bighorn River, Montana

ABSTRACT Rivers downstream from dams often experience decreased flow variability and disrupted sediment transport. We investigated a highly regulated 35.5-kilometre reach of the Bighorn River, downstream from Yellowtail Dam, emplaced in 1965. This dam created a thriving trout fishery, but more recently, side channel networks and habitat diminished. We document how the Bighorn River's anabranching morphology responded to flow regulation and a near cessation of sediment supply. Geomorphic diversity drastically decreased since 1939 and the Bighorn River abandoned numerous side channels. By 1980, geomorphic loss slowed, and the river became laterally static. The 1980 river and side channel network could represent the maximum areal extent of a downscaled morphology, maintained through restoration and adaptive management. However, side channel restoration alone will not return natural alluvial processes to this river reach. The Bighorn River needs sediment to reinstate dynamic lateral movement, even within a downscaled morphology. Sediment augmentation is an option, but more complex to implement on rivers where potential downstream impacts and landowners must be considered. The decline of geomorphic diversity and potential adaptive management solutions on the Bighorn River has wide applicability to numerous dammed rivers, where similar changes to the flow and sediment transport regime are common.

Timing of sulfuric acid speleogenesis (SAS) as an indicator of canyon incision rates of the Shoshone and Bighorn rivers, Wyoming, USA

Two sulfuric acid speleogenesis (SAS) cave sites in northern Wyoming host speleogenetic byproducts that have been dated using the uranium-series method and thus provide the timing of the SAS events. Gypsum crusts that formed as byproducts of SAS in Lower Kane Cave, exposed by Bighorn River incision into the Little Sheep Mountain anticline, yield uranium-series dates of 20.5 ± 0.2 ka to 16.2 ± 0.2 ka that represent the timing of late stage speleogenesis of that cave. A calcite mammillary engulfed by elemental sulfur that formed during SAS of Shoshone Canyon Conduit Cave, exposed by Shoshone River incision of the homonymous canyon, yielded a uranium-series age of 174 ± 5 ka and represents late stage speleogenesis of that cave, although the process continued after the cave was elevated above the water table until at least 100 ± 5 ka. In addition to the timing of speleogenesis, the U-series results provide incision rates for these two canyons. The rate of canyon incision for the last 200 kyr by the Bighorn River in Little Sheep Mountain Canyon is measured as 190 ± 50 m/Ma, and for the Shoshone River in Shoshone Canyon as 400 ± 40 m/Ma. Using the Bighorn River incision rate, Upper Kane Cave located 33 m above Lower Kane Cave has a projected age of 170 ± 60 ka. We suggest that climatically driven hydrologic mechanisms rather than magmatic ones likely produced the pulses of SAS at these two cave sites.

Natural Recruitment Potential of a Reintroduced Shovelnose Sturgeon Population in the Bighorn River, Wyoming

AbstractShovelnose Sturgeon Scaphirhynchus platorynchus were extirpated from the Bighorn River, Wyoming during the 20th century after the construction of two main‐stem dams and the resulting modifications to fish passage and flow and thermal regimes. The species was reintroduced to the river between 1996 and 2020, but nothing was known about how these fish used the river and whether they could sustain themselves without consistent stocking. Radio telemetry during 2015–2018 identified at least two putative spawning locations 95.6 and 139.5 river kilometers upstream from a reservoir transition zone. Temperature and velocity data suggest that most of the drifting larvae will have insufficient fluvial habitat to complete their drift stage and are likely to enter the Bighorn Lake transition zone. Benthic dissolved oxygen concentrations in the reservoir transition zone were low enough to cause recruitment reduction or failure for drifting larvae that reach this habitat. Future monitoring will determine whether this population persists, but this study highlights the importance of understanding species life history and the causes of extirpations to better predict reintroduction success.

Reproduction on the Reservation: Pregnancy, Childbirth, and Colonialism in the Long Twentieth Century by Brianna Theobold

Reviewed by: Reproduction on the Reservation: Pregnancy, Childbirth, and Colonialism in the Long Twentieth Century by Brianna Theobold Abigail Markwyn Brianna Theobold. Reproduction on the Reservation: Pregnancy, Childbirth, and Colonialism in the Long Twentieth Century. Chapel Hill: University of North Carolina Press, 2019. 288 pp. Paper, $29.95. Brianna Theobold's excellent new book, Reproduction on the Reservation: Pregnancy, Childbirth, and Colonialism in the Long Twentieth Century, shows in vivid detail the effects of colonial policy on the reproductive lives of Indigenous women in the United States. The depth [End Page 302] and breadth of Theobold's research is extraordinary and is a significant contribution to both women's and Indigenous history. She deftly interweaves a comprehensive case study of reproductive health on the Crow reservation with the experiences of other Indigenous women across the United States to uncover the myriad ways that the long hand of the Office of Indian Affairs (OIA) extended across the nation to affect the reproductive practices of Indigenous women both on, and off, the reservation. Reproduction on the Reservation convincingly argues that the regulation of reproductive health and family structure was fundamental to assimilation policy and must be understood as a key part of US colonialism. The imposition of the reservation system in the late nineteenth century put the bodies of Native women under increased surveillance and regulation, which ranged from the coerced (birthing in a hospital and scheduled breast feedings) to the forced (unwanted sterilization). Theobold reveals that, despite this surveillance, Native women remained agents of their own lives. Some women willingly embraced the opportunity to birth in a OIA hospital, for instance, while others resisted. Some women sought sterilization procedures, but far more woke up from childbirth to find themselves subject to this invasive and unwanted procedure. And throughout the twentieth century, Indigenous women worked together to combat abuses and to gain access to the medical care they wanted and needed. This innovative and thoroughly researched narrative reveals the deeply intertwined relationship between federal Indian policy and women's reproductive lives and demonstrates the longterm effects of colonialism on Indigenous communities. The book consists of six chronologically organized chapters, which trace Crow women's lives from the late nineteenth century to the present. It focuses on the time period from roughly 1880 to 1980, but the epilogue does an excellent job of pulling the story together, recounting the decision of Zintkala Mahpiya Wi Blackowl (Lakota), a water protector, to birth her baby at Standing Rock in 2016, as well as that of Nicolle Gonzales, a Navajo nurse-midwife dedicated to founding a birthing center for Native women. Although the core of the narrative traces the histories of Crow women, particularly those of the Yellowtail family, Theobold expands her view to include the experiences of women from across the country. Her narrative reveals that Native women experienced many of the same historical changes as did their non-Native [End Page 303] contemporaries, such as the medicalization of childbirth, the flourishing of women's clubs, debates about birth control and eventually abortion, but these issues played out in sometimes radically different ways when set within the confines of colonial policies. After a brief introduction, the first chapter explores the reproductive lives of Crow women after their removal to the reservation along the Little Bighorn River. Here, the author lays out some of the themes that will recur throughout the book: the significance of "flexible childrearing," in Crow society and the ways in which government employees viewed, and intervened in, Native women's reproductive practices. Chapters 2 and 3 focus on the implementation of early-twentieth-century assimilation policy. Here, Theobold focuses on the significance of the OIA's "Save the Babies" campaign, and argues that it must be understood as "a cornerstone of early twentieth-century federal Indian policy" (45). Chapter 3 examines one goal of this policy, which was to transition Native women into giving birth in hospitals rather than at home. Theobold traces the uneven adoption of this policy through the life story of Susie Walking Bear Yellowtail, the first Crow registered nurse. Here we see the varieties of ways in which women navigated the OIA health system, at times acquiescing to...

Teleseismic P-Wave Coda Autocorrelation Imaging of Crustal and Basin Structure, Bighorn Mountains Region, Wyoming, U.S.A.

ABSTRACT We demonstrate successful crustal imaging via teleseismic P-wave coda autocorrelation, using data recorded on a 261 station array of vertical-component high-frequency geophones in the area of the Bighorn Mountains, Wyoming, U.S.A. We autocorrelate the P-wave coda of 30 teleseismic events and use phase-weighted stacking to yield seismic profiles comparable to low-passed versions of those produced via controlled-source vertical seismic reflection. Our process recovers reflections from the bottoms of the Bighorn and Powder River basins that flank the Bighorn Mountains. We also identify a mid-crustal reflector that aligns with a region of increased reflectivity, previously interpreted as a Precambrian province boundary. Our results demonstrate the utility of crustal imaging with teleseismic P-wave coda energy using modern large-array seismic data, and they corroborate previous interpretations of crustal structures in the study area.

Use of Wyoming Southern Bighorn Mountains Topographic Map Evidence to Test a Recently Proposed Regional Geomorphology Paradigm: USA

Detailed topographic maps covering a high elevation Bighorn-Powder River drainage divide segment in the southern Bighorn Mountains are used to test a recently proposed regional geomorphology paradigm. Fundamentally different from the commonly accepted paradigm the new paradigm predicts immense south-oriented continental ice sheet melt water floods once flowed across what is now the entire Missouri River drainage basin, in which the high Bighorn Mountains are located. Such a possibility is incompatible with commonly accepted paradigm expectations and previous investigators have interpreted Bighorn Mountains geomorphic history quite differently. The paradigm test began in the high glaciated Bighorn Mountains core area where numerous passes, or divide crossings, indicate multiple and sometimes closely spaced streams of water once flowed across what is now the Bighorn-Powder River drainage divide. To the south of the glaciated area, but still in a Precambrian bedrock region, the test found the roughly adjacent and parallel south-oriented North Fork Powder River and Canyon Creek headwaters located on opposite sides of the Bighorn-Powder River drainage divide with North Fork Powder River headwaters closely linked to a 300-meter deep pass through which south-oriented water had probably flowed. Shallower divide crossings located further to the south suggest diverging and converging streams of water once flowed not only across the Bighorn-Powder River drainage divide, but also across Powder River and Bighorn River tributary drainage divides. The paradigm test also found published geologic maps and reports showing the presence of possible flood transported and deposited alluvium. While unable to determine the water source, the new paradigm test did find evidence that large south-oriented floods had crossed what was probably a rising Bighorn Mountains mountain range.

Detrital zircon U-Pb geochronology of the Ordovician Lander Sandstone, Bighorn Mountains, Wyoming

The Ordovician Lander Sandstone, which occurs unconformably above the Cambrian Gallatin Limestone and beneath the Bighorn Dolomite, occurs in the Bighorn, Powder, and Wind River basins of Wyoming. The Lander ranges from 0-10 m in thickness and consists of texturally and compositional mature, cross bedded quartz arenite. This study uses detrital zircon U-Pb geochronology to elucidate its provenance. Samples were collected from two localities along the eastern flank of the Bighorn Mountains near Buffalo, Wyoming: a roadcut on US 16 just west of the Clear Creek thrust and from along Crazy Woman Canyon Road. The results showed a statistical similarity between the two samples, and that zircon ages are predominantly Proterozoic in age (~75%) while the minority ages were Archean (25%). Probability density plots of the two-source areas show that the peak ages for Crazy Woman Canyon (n=90) are ~1840, 2075 and 2695 Ma and the US 16 peak ages (n=141) are ~1825, 2075, and 2725 Ma. The detrital zircon age spectra for these samples indicate that the Lander was not derived from local Archean basement and was not recycled from the underlying Cambrian. The Lander has a provenance in either the Trans-Hudson Province and adjacent rocks in present day Saskatchewan and Manitoba more than 1000 km to the north or from the Peace River Arch, an early Paleozoic highlands in northwestern Alberta and northeastern British Columbia. The Lander zircons have a similar provenance to eolian zircons in the Bighorn Dolomite and to other Ordovician sandstones on the Cordilleran Continental margin and central Idaho. The Lander provenance is distinct from the Ordovician St. Peter Sandstone, which occurs extensively east of the Transcontinental Arch. We interpret that the Lander was derived on the late Ordovician shoreline, and then transported via prevailing winds across the Laurentian shelf from east to west during sea level low stand, and then distributed throughout the shelf by currents.

Detrital Zircon U-Pb geochronology of the Ordovician Lander Sandstone, Bighorn

The Ordovician Lander Sandstone, which occurs unconformably above the Cambrian Gallatin Limestone and beneath the Bighorn Dolomite, occurs in the Bighorn, Powder, and Wind River basins of Wyoming. The Lander ranges from 0-10 m in thickness and consists of texturally and compositional mature, cross bedded quartz arenite. This study uses detrital zircon U-Pb geochronology to elucidate its provenance. Samples were collected from two localities along the eastern flank of the Bighorn Mountains near Buffalo, Wyoming: a roadcut on US 16 just west of the Clear Creek thrust and from along Crazy Woman Canyon Road. The results showed a statistical similarity between the two samples, and that zircon ages are predominantly Proterozoic in age (~75%) while the minority ages were Archean (25%). Probability density plots of the two-source areas show that the peak ages for Crazy Woman Canyon (n=90) are ~1840, 2075 and 2695 Ma and the US 16 peak ages (n=141) are ~1825, 2075, and 2725 Ma. The detrital zircon age spectra for these samples indicate that the Lander was not derived from local Archean basement and was not recycled from the underlying Cambrian. The Lander has a provenance in either the Trans-Hudson Province and adjacent rocks in present day Saskatchewan and Manitoba more than 1000 km to the north or from the Peace River Arch, an early Paleozoic highlands in northwestern Alberta and northeastern British Columbia. The Lander zircons have a similar provenance to eolian zircons in the Bighorn Dolomite and to other Ordovician sandstones on the Cordilleran Continental margin and central Idaho. The Lander provenance is distinct from the Ordovician St. Peter Sandstone, which occurs extensively east of the Transcontinental Arch. We interpret that the Lander was derived on the late Ordovician shoreline, and then transported via prevailing winds across the Laurentian shelf from east to west during sea level low stand, and then distributed throughout the shelf by currents.

Topographic Map Interpretation of Bighorn River-Wind River Drainage Divide Located East of Wyoming's Wind River Canyon, USA

Detailed topographic map evidence is used to test the ability of two fundamentally different regional geomorphology paradigms to explain Bighorn-Wind River drainage divide evidence in the Copper and Lysite Mountain areas between Wind River Canyon and the Bighorn Mountains. Identified divide crossings were interpreted to be places where water had once flowed across what is now a major drainage divide. More than 20 such divide crossings were identified and ranged in elevation from 1924 to 2485 meters and could all be linked to north-oriented Bighorn River tributaries and also to south-oriented streams flowing to west-oriented Badwater Creek (a Wind River tributary). Lowest elevation divide crossings were located to the north of both Copper Mountain and Lysite Mountain. An attempt was first made to explain each identified divide crossing or group of divide crossings from the accepted paradigm's perspective, which requires drainage routes to have originated on the surface of a hypothesized Oligocene and Miocene sediment cover that buried the drainage divide area with the drainage routes eroding down through the sediment cover as the drainage divide was exhumed. Next the same evidence was interpreted from a recently proposed paradigm's perspective, which requires massive south- and southeast-oriented floods to have flowed across the Missouri River drainage basin as mountain ranges and plateau areas were being uplifted. The accepted paradigm could not easily explain the large number of observed divide crossings, many divide crossing details, and why geologic maps show few or no hypothesized sediment cover remnants. The new paradigm explained the large number of observed divide crossing and most observed divide crossing details and did not require an Oligocene and Miocene sedimentary cover.

Metagenomic Profiling of Microbial Pathogens in the Little Bighorn River, Montana.

The Little Bighorn River is the primary source of water for water treatment plants serving the local Crow Agency population, and has special significance in the spiritual and ceremonial life of the Crow tribe. Unfortunately, the watershed suffers from impaired water quality, with high counts of fecal coliform bacteria routinely measured during run-off events. A metagenomic analysis was carried out to identify potential pathogens in the river water. The Oxford Nanopore MinION platform was used to sequence DNA in near real time to identify both uncultured and a coliform-enriched culture of microbes collected from a popular summer swimming area of the Little Bighorn River. Sequences were analyzed using CosmosID bioinformatics and, in agreement with previous studies, enterohemorrhagic and enteropathogenic Escherichia coli and other E. coli pathotypes were identified. Noteworthy was detection and identification of enteroaggregative E. coli O104:H4 and Vibrio cholerae serotype O1 El Tor, however, cholera toxin genes were not identified. Other pathogenic microbes, as well as virulence genes and antimicrobial resistance markers, were also identified and characterized by metagenomic analyses. It is concluded that metagenomics provides a useful and potentially routine tool for identifying in an in-depth manner microbial contamination of waterways and, thereby, protecting public health.

Spatiotemporal distribution of river water stable isotope compositions and variability of lapse rate in the central Rocky Mountains: Controlling factors and implications for paleoelevation reconstruction

Stable isotope-based paleoaltimetry is the most widely used approach for paleoelevation reconstruction. Interpretations of stable isotope data in continental interiors, however, are undermined by surface water isotope compositions that are influenced by multiple factors. Here we present a stable isotope dataset of modern river water samples collected over two summers and one spring from the central Rocky Mountains (Rockies) and the adjacent Great Plains. By examining the spatial and temporal variations of river water δ18O, δD and d-excess values, and their relationships with climatic and geographic parameters, as well as through back trajectory analysis of moisture sources, we elucidate the influences of elevation and climatic parameters on the spatiotemporal variation of river water isotopic values. In the Bighorn River drainage, a typical intermontane drainage in the central Rockies, the isotopic difference between highland and lowland rivers is small, which we attribute to highland precipitation that dominates lowland river discharge. In the North Platte River drainage across the central Rockies and Great Plains, the river water δ18O values show poor correlation with elevation west of 105°W (central Rockies), but increase as elevation decrease east of 105°W (in the western Great Plains). This eastward increase across the western Great Plains leads to an average oxygen isotope lapse rate of −2.3‰/km, which we interpret as being caused primarily by condensation temperature-controlled isotopic fractionation at various elevations, and secondarily by evaporation in the upper reaches of streams that contribute to the North Platte River plus direct contribution of moisture from the Gulf of Mexico in the Great Plains. In this continental interior setting, multiple moisture sources, including recycled continental moisture, contribute to surface water, and evaporation influences river water isotope values to various degrees depending on the relative humidity within an individual river catchment. These results suggest that paleoclimate and atmospheric circulation pattern must be carefully evaluated when applying stable isotope-based paleoaltimetry in continental interiors. Our findings have implications for paleoelevation reconstruction in the study area, including that 1) within the central Rockies, the isotopic difference of river water and unevaporated basinal precipitation can be used to infer paleorelief of the Laramide ranges with respect to the basin floors; 2) along a regional transect crossing the central Rockies and Great Plains, the modern isotope lapse rate of the North Platte River drainage can be used to constrain the paleorelief between the two regions in semi-arid climate.

Palaeomagnetism, geochronology and geochemistry of the Palaeoproterozoic Rabbit Creek and Powder River dyke swarms: implications for Wyoming in supercraton Superia

Abstract It is likely that Archaean cratons of Laurentia had different palaeogeographic histories prior to their amalgamation. New palaeomagnetic, geochronological and geochemical evidence supports a reconstruction of the Wyoming craton adjacent to the southern margin of the Superior craton at 2.16 Ga, before rifting ( c. 2.1–2.0 Ga) and eventual reamalgamation after the Hudsonian Orogeny ( c. 1.8 Ga). U–Pb ages (TIMS on baddeleyite) from five dykes yield two groups of ages at c. 2164 and 2155 Ma. The younger group of ages defines the Rabbit Creek swarm at 2161–2152 Ma and precisely dates its palaeomagnetic pole. Two large and differentiated dykes (>100 m) in the Bighorn and Wind River uplifts are geographically related to the Rabbit Creek swarm but have slightly different orientations and yield slightly older ages at 2171–2157 Ma. These dykes may be parts of a single intrusion (the ‘Great Dyke of Wyoming’) that spans over 200 km between uplifts, possibly representing a different magmatic event. This older event does not have enough distinct intrusions to provide a correctly averaged palaeomagnetic pole, but correlates with magmatism in the Superior craton and has a palaeomagnetic remanence comparable to the Rabbit Creek dykes. With minor tilt corrections, the palaeomagnetic data from the Rabbit Creek swarm and Powder River–South Pass dykes support a reconstruction of the southeastern Wyoming craton against the southern Superior craton. This fit juxtaposes the Palaeoproterozoic Huronian and Snowy Pass Supergroups along two passive margins that experienced a prolonged period of mafic magmatism (>100 myr) and rift basin development. Although there are slight geochemical variations across the Rabbit Creek swarm, all dykes fit into two distinct groups that are independently dated and internally consistent. Supplementary material: Supporting figures and locality tables are available at www.geolsoc.org.uk/SUP18824

Reflections on Western General Stream Adjudications upon the Signing of Wyoming's Big Horn River Adjudication Final Decree

Reflections on Western General Stream Adjudications upon the Signing of Wyoming's Big Horn River Adjudication Final Decree

Model‐Based Nitrogen and Phosphorus (Nutrient) Criteria for Large Temperate Rivers: 2. Criteria Derivation

AbstractNitrogen and phosphorus criteria were developed for 233 km of the Yellowstone River, one of the first cases where a mechanistic model has been used to derive large river numeric nutrient criteria. A water quality model and a companion model which simulates lateral algal biomass across transects were used to simulate effects of increasing nutrients on five variables (dissolved oxygen, total organic carbon, total dissolved gas,pH, and benthic algal biomass in depths ≤1 m). Incremental increases in nutrients were evaluated relative to their impact on predefined thresholds for each variable; the first variable to exceed a threshold set the nutrient criteria. Simulations were made at a low flow, the 14Q5 (lowest average 14 consecutive day flow, July‐September, recurring one in five years), which was derived using benthic algae growth curves and EPA guidance on excursion frequency. An extant climate dataset with an annual recurrence was used, and tributary water quality and flows were coincident with the river's 10 lowest flow years. The river had different sensitivities to nutrients longitudinally,pHbeing the most sensitive variable in the upstream reach and algal biomass in the lower. Model‐based criteria for the Yellowstone River are as follows: between the Bighorn and Powder river confluences, 55 μg TP/l and 655 μg TN/l; from the Powder River confluence to Montana state line, 95 μg TP/l and 815 μg TN/l. Pros and cons of using steady‐state models to derive river nutrient criteria are discussed.

Detection and source tracking of Escherichia coli, harboring intimin and Shiga toxin genes, isolated from the Little Bighorn River, Montana

The Little Bighorn River flows through the Crow Indian Reservation in Montana. In 2008, Escherichia coli concentrations as high as 7179 MPN/100 ml were detected in the river at the Crow Agency Water Treatment Plant intake site. During 2008, 2009, and 2012, 10 different serotypes of E. coli, including O157:H7, harboring both intimin and Shiga toxin genes were isolated from a popular swim site of the Little Bighorn River in Crow Agency. As part of a microbial source tracking study, E. coli strains were isolated from river samples as well as from manure collected from a large cattle feeding operation in the upper Little Bighorn River watershed; 23% of 167 isolates of E. coli obtained from the manure tested positive for the intimin gene. Among these manure isolates, 19 were identified as O156:H8, matching the serotype of an isolate collected from a river sampling site close to the cattle feeding area.

Impacts of Tamarix‐mediated soil changes on restoration plant growth

AbstractQuestionDo soils impacted by Tamarix spp. affect the growth of plants used for restoration through altered soil chemistry and/or plant‐soil feedbacks?LocationThe Bighorn River, the Yellowstone River and the Fort Peck Reservoir, Montana, western USA.MethodsSoil was collected from paired subsites where Tamarix was either present or absent along three water bodies. To evaluate chemical and biological soil effects on plant growth, eight plant species (Achnatherum hymenoides, Astragalus cicer, Dalea candida, Elymus lanceolatus, Leymus cinereus, Pascopyrum smithii, Ratibida columnifera and Trifolium pratense) commonly used in restoration projects at Tamarix‐invaded sites were grown in the collected soil. Plant‐soil feedbacks were evaluated by growing two species (D. candida and P. smithii) in greenhouse soils inoculated with small amounts of the field soils. Germination, emergence and growth characteristics were compared between Tamarix‐invaded and un‐invaded subsites and across water bodies.ResultsSeedling emergence and plant relative growth rate, total biomass production and allocation of resources to roots and shoots were not negatively affected in field soils or in greenhouse soil inoculated with soil from areas where Tamarix was present. In fact, overall, plants emerged earlier and produced more biomass in soils affected by Tamarix than in soils from where Tamarix was not present. These results indicate that for sites in the northern range of Tamarix, restoration would not be inhibited by Tamarix‐induced soil changes.ConclusionsTamarix is a relatively new invader in the northern USA, and little is known about its impacts in this area or the potential implications for restoration. However, our results indicate that neither altered soil chemistry nor plant‐soil feedbacks negatively impact native plant growth, and restoration efforts would not be hindered by Tamarix‐induced changes to soil chemistry or microbiota.

Reduced Impacts or A Longer Lag Phase? Tamarix in the Northwestern U.S.A.

Tamarix spp. (tamarisk) have caused ecological impacts in the southwestern United States; however, such impacts have not been extensively studied in the Northwest where tamarisk is a relatively new invader. Here we present the results of soil, arbuscular mycorrhizal fungi, and vegetation studies from tamarisk-occupied and unoccupied areas on the dammed Bighorn River, Fort Peck Reservoir, and the free flowing Yellowstone River, in Montana. Soil sample results indicated that at Fort Peck Reservoir soil salinity was twice as high at occupied sites compared to unoccupied ones, and at the Bighorn River occupied sites nitrate, phosphorus and potassium were 2.2, 4, and 1.9 times higher, respectively, than at unoccupied sites. No soil differences were observed on the Yellowstone River. Mycorrhizal infectivity potential was high in both occupied and unoccupied soils, with a slight reduction (from 73% to 65% colonization) in tamarisk occupied soils. These impacts were statistically but not ecologically significant and did not extend to other metrics of impact such as richness, Simpson’s diversity or composition of plant communities. Our results indicate that either tamarisk has minimal impacts in the northwest, or it is still in a lag phase.

Low-temperature thermochronology of the northern Rocky Mountains, western U.S.A.

We dated 86 borehole and surface samples from basement-cored Laramide uplifts of the northern Rocky Mountain foreland (Wind River, Beartooth, Bighorn and Laramie Ranges) using the apatite (U-Th)/He system, and eleven samples using the apatite fission-track system (Wind River and Bighorn Ranges). Apatite (U-Th)/He ages generally decrease with increasing subsurface depth (decreasing elevation), and typically range from ∼100 to 50 Ma (Cretaceous to Eocene) within ∼1 km of the surface, to ∼20 Ma (Miocene) and younger ages at depths greater than ∼2 to 2.5 km. Most samples display (U-Th)/He age dispersion ranging from tens to hundreds of Ma, and for some samples we find ages that are older than corresponding fission-track ages. At least one sample per range shows a correlation between apatite (U-Th)/He age and effective U concentration (eU = \[U\] + 0.235\[Th\]) of the crystal, indicating that radiation damage has affected He diffusivity, and hence (U-Th)/He age. Forward modeling of simple Laramide-type thermal histories using a radiation damage diffusion model predicts: 1) fossil apatite fission-track partial annealing and apatite (U-Th)/He partial retention zones over similar elevation ranges, 2) (U-Th)/He age dispersion within a fossil partial retention zone up to hundreds of Ma, and 3) (U-Th)/He ages older than fission-track ages within a fossil partial retention zone if eU ≳ 20 ppm. We observe these features in our data from the Bighorn and Laramie Ranges. Most of our samples, however, do not show the correlation between (U-Th)/He age and eU predicted by radiation damage diffusion models. The age dispersion of these samples could be due to the influence of both grain size and eU content, or alternatively due to high U or Th secondary rims around the apatite crystals. (U-Th)/He ages that are older than fission-track ages from Gannett Peak and Fremont Peak in the Wind River Range, and some samples from the Beartooth Range, are most likely the result of He implantation from high eU secondary rims. Best-fit time-temperature paths from inverse modeling of (U-Th)/He age-eU pairs, when extrapolated to other elevations to create model age-elevation plots, reproduce the general distribution and dispersion of (U-Th)/He ages from the Bighorn, Beartooth and Wind River Ranges and suggest that rapid exhumation within the Laramide province likely began earlier in the Bighorn Range (before ∼71 Ma) than the Beartooth Range (before ∼58 Ma). Inverse modeling of borehole data at the northern end of the Laramie Range suggests that the well penetrated a fault sliver at depth. The amount and timing of post-Laramide burial and exhumation cannot be determined from these data.

Longitudinal variation and habitat associations of small fishes in the Bighorn River, Wyoming: influences of river regulation and introduced fishes

We assessed variation in longitudinal distributions of native and introduced fishes and their occurrences in different habitat types downstream from Boysen Dam in the Bighorn River, Wyoming. The closure of Boysen Dam in 1952 and construction of three downstream water diversion dams have led to channel changes in the Bighorn River causing reductions in the numbers and areas of side channels, backwaters, and riffles. Eleven native and five introduced fish species were collected by seining during 2005. Fish samples were dominated by sand shiner (Notropis stramineus), flathead chub (Platygobio gracilis), and longnose sucker (Catostomus catostomus). Introduced fish species included common carp (Cyprinus carpio), emerald shiner (Notropis atherinoides), plains killifish (Fundulus flavis), yellow perch (Perca flavescens), and sand shiner. Differences in relative abundances of fishes among habitat types were observed. Fathead minnow (Pimephales promelas), longnose sucker, white sucker (Catostomus commersoni), plains killifish, and sauger (Sander canadensis) were found almost exclusively in backwaters, and channel catfish (Ictalurus punctatus) was collected almost exclusively in side channels. Changes from the pre-European fish community are occurring in association with invasions of introduced fish species and losses of side channels, backwaters, and riffles.