Major reorganization of the Snake River modulated by passage of the Yellowstone Hotspot

The details and mechanisms for Neogene river reorganization in the U.S. Pacific Northwest and northern Rocky Mountains have been debated for over a century with key implications for how tectonic and volcanic systems modulate topographic development. To evaluate paleo-drainage networks, we produced an expansive data set and provenance analysis of detrital zircon U-Pb ages from Miocene to Pleistocene fluvial strata along proposed proto-Snake and Columbia River pathways. Statistical comparisons of Miocene-Pliocene detrital zircon spectra do not support previously hypothesized drainage routes of the Snake River. We use detrital zircon unmixing models to test prior Snake River routes against a newly hypothesized route, in which the Snake River circumnavigated the northern Rocky Mountains and entered the Columbia Basin from the northeast prior to incision of Hells Canyon. Our proposed ancestral Snake River route best matches detrital zircon age spectra throughout the region. Furthermore, this northerly Snake River route satisfies and provides context for shifts in the sedimentology and fish faunal assemblages of the western Snake River Plain and Columbia Basin through Miocene−Pliocene time. We posit that eastward migration of the Yellowstone Hotspot and its effect on thermally induced buoyancy and topographic uplift, coupled with volcanic densification of the eastern Snake River Plain lithosphere, are the primary mechanisms for drainage reorganization and that the eastern and western Snake River Plain were isolated from one another until the early Pliocene. Following this basin integration, the substantial increase in drainage area to the western Snake River Plain likely overtopped a bedrock threshold that previously contained Lake Idaho, which led to incision of Hells Canyon and establishment of the modern Snake and Columbia River drainage network.

First Report of Curly Top of Coriandrum sativum Caused by Beet curly top virus in the Columbia Basin of Washington State.

Two fields of coriander (Coriandrum sativum L.) seed crops of proprietary cultivars were observed in the Columbia Basin of Washington in July 2020 with 40 and 90% incidence of plants showing stunting and leaf and stem discoloration, sometimes with mild leaf curl. Foliar discoloration ranged from yellow to red and purple. Sweep-netting along the field edges collected one beet leafhopper (Circulifer tenellus Baker; BLH), the known vector of Beet curly top virus (BCTV), Beet leafhopper transmitted virescence agent (BLTVA) phytoplasma, and Spiroplasma citri, all of which affect Solanaceae and Apiaceae crops in Washington (Crosslin et al. 2006; Johnson and Martin 1998; Lee et al. 2006). Nucleic acids extracted from leaves and petioles of 12 coriander plants (8 from Field 1 and 4 from Field 2) using the Dellaporta method, and from the BLH using the CTAB method (Crosslin et al. 2006) were subjected to PCR assays to detect the BLH-transmitted pathogens which cause yellow and purple discoloration in potato (Solanum tuberosum L.) and carrot (Daucus carota subsp. sativus (Hoffm.) Arc.) in this region. BLTVA was targeted using a species-specific nested PCR assay with primers P1 and P7, followed by primers FU5 and BLTVA-int (Crosslin et al. 2006); S. citri was targeted using primers P89-F and P89-R (Yokomi et al. 2008); and BCTV was targeted using curtovirus primers BCTV2-F and BCTV2-R (Strausbaugh et al. 2008). BLTVA and S. citri were not detected in the plants, but curtovirus was detected in 10 of the 12 plants. All three pathogens were detected from the single BLH. A 519 bp region of the curtovirus capsid protein gene was amplified from seven plants (5 from Field 1 and 2 from Field 2) and the BLH, and cloned into TOP10 Escherichia coli cells using the pCR-2.1 TOPO vector (Invitrogen, Carlsbad, CA). Three clones were sequenced from each sample. For each of six plant samples and the BLH, the three clones were identical and consensus sequences were generated (GenBank Accessions MW234419 to MW234425). For the seventh plant, two clones were identical in sequence (MW234426) and the third contained 12 single nucleotide polymorphisms (MW234427). All sequences were subjected to an NCBI BLASTn analysis and showed 98.3 to 99.8% identity with BCTV sequences. Additional PCR assays with primers BMCTV-C1 2213F and BMCTV-C1 2609R (Strausbaugh et al. 2008), targeting the C1 gene of the Worland strain of BCTV, detected BCTV-Worland-like strains in all plants and the BLH, confirming that BCTV was present and indicating that the strain-specific primer pair was more sensitive than the universal curtovirus primers. Yield losses in the two fields were approximately 60%, with reduced seed size but not seed quality. BCTV infections in coriander crops have been observed in the Columbia Basin in 2002, 2005, 2008, and 2013, with yield losses ranging from 10 to 100% per field, though official reports were not made following the diagnoses (Crosslin, du Toit, and Frost, unpublished data). BCTV has caused millions of dollars of losses in the U.S. in crops such as sugar beet (Beta vulgaris subsp. vulgaris L.), tomato (S. lycopersicum L.), and pepper (S. annuum L.) (Johnson and Martin 1998). This is the first publication of BCTV affecting seed production of the specialty crop C. sativum. The observation of 90% incidence of symptoms in one field suggests that resistant cultivars and/or insect pest management practices are needed to prevent significant impacts of BCTV on coriander seed production in this semi-arid region.

Vertical Distribution of Insect Pests Using Insect Towers Placed Near Potato Fields in the Lower Columbia Basin

This study was conducted at the Oregon State University Hermiston Agricultural Research and Extension Center, Hermiston, Umatilla County, OR, during the 2016 and 2017 potato, Solanum tuberosum L. (Solanales: Solanaceae), growing seasons. The objective was to determine the vertical distribution of hemipteran (Bactericera cockerelli Šulc, Circulifer tenellus Baker, Myzus persicae Sulzer, Macrosiphum euphorbiae Thomas, and Lygus spp.) and thysanopteran (Frankliniella occidentalis Pergande and Thrips tabaci Lindeman) potato pests using insect towers placed near potato fields. Towers were 8 m tall and secured to the ground with metal cables. In each tower, yellow sticky cards were mounted at 1.5 m intervals up to 7.6 m aboveground. Data were collected at 7-d intervals from mid-April until mid or end of August. This study showed that B. cockerelli, C. tenellus, M. persicae, Lygus spp., and both species of thrips were captured on sticky cards placed closest to the ground; in both years, as sticky card height increased, abundances decreased. In contrast, trapped M. euphorbiae numbers were not affected by sticky card height. To our knowledge, this is the first study in the lower Columbia Basin of Oregon that evaluated the vertical distribution of major potato pests.

Soil Response to Fire Frequency in the Northern Columbia Basin Sagebrush Steppe

Fire is one of the most significant disturbances in an ecosystem, as it is capable of altering the physical, chemical, and biological properties of soil, and the fire frequency in semi-arid ecosystems is increasing. These changes can potentially alter plant-soil feedbacks that may affect post-fire recovery of the native plant and soil communities and lead to an ecosystem state change. However, there is much uncertainty about the magnitude of change as soils are exposed to more fires, because soil recovery and changes in fire severity following a first fire mediate the impact of successive fires on soil properties. To improve understanding of fire frequency effects on the soil ecology of the northern Columbia Basin sagebrush steppe ecosystem, this study assessed the physical, chemical and biological properties of soil that are critical to plant communities (e.g. soil pH, C and N, respiration and extracellular enzyme activity) from four different fire frequencies (unburned, burned once, twice, and thrice). Our study yielded three main results: 1) fire reduced the soil C concentration relative to unburned soil, but only when soil was exposed to fire once, 2) soil pH and NO3--N increased with fire frequency, whereas enzyme activity decreased, and 3) soil organic matter contents and microbial respiration were suppressed significantly in the once and thrice burned soils compared to the unburned and twice burned soils. Taken together, our findings suggest that a one-time fire in this region of the sagebrush steppe is capable of significantly changing soil properties that alter plant-soil feedbacks and hinder ecosystem resilience, thus contributing to ecosystem change particularly when fire frequency increases.

Development of inter-lava drainage systems in LIPs: The Columbia River Flood Basalt Province (U.S.A.) as a case study

ABSTRACT Volcanism in large igneous provinces (LIPs) is understood to have had the potential to affect global environments and ecosystems, triggering mass extinctions, climate change, and ocean acidification. However, basin-scale studies sediment distribution and sedimentary-system development in LIP lava fields are sparse and often limited to localized exposure. To gain a better understanding of the controls on inter-lava sedimentology across a continental LIP, a new sedimentological data set is presented from the Miocene Columbia River Flood Basalt Province (CRBP), situated in the Columbia Basin in south-central Washington State, northeast Oregon and eastern Idaho. Based on the qualification and quantification of sedimentary facies, petrography, paleoflow, channel dimensions, and catchment size from 96 sites across the Columbia Basin, a refined model of regional and local environmental change, integrating local volcanic and tectonic evolution, is presented. Here, CRBP stratigraphy is divided into six distinctive sedimentation intervals, which allows correlation of sedimentary interbeds formed in the western part and in the eastern part of the basin. The model describes and reviews drainage-system development and discusses the control of volcanic and tectonic activity on sediment distribution in the CRBP lava field at local to basin scale. The data presented here largely support findings of previous works suggesting a highly complex interplay between sedimentary, volcanic, and tectonic evolution of the area. In addition, it elaborates on the aspects of sediment–lava interaction and indicates that individual sub-basins in the CRBP formed separated depositional settings, emphasizing the lateral complexity of inter-lava sedimentation. Importantly, this work improves our understanding of sediment–lava relationships in continental LIPs and helps in building more generic models for sediment distribution in volcanic terranes where exposure is limited or absent.