South-central Washington Research Articles

Physical and ecological evaluation of a fish-friendly surface spillway

Spillway passage is one of the commonly accepted dam passage alternatives for downstream-migrating salmonids and other species. Fish passing in spill near the water surface may have improved chances of survival over fish that pass deeper in the water column near spillway structures. In this study, an autonomous sensor device (Sensor Fish) was deployed in 2005 to evaluate fish passage conditions through the Removable Spillway Weir (RSW) at Ice Harbor Dam on the Snake River in south-central Washington State. The Sensor Fish deployment was undertaken concurrently with a separate live fish injury and survival study. Conditions at the RSW–Spillway Chute Transition and Deflector region were found to be potentially detrimental to fish. As a result, the spillway slope and deflector radius were modified, and the efficacy of the modifications was evaluated in 2015 using Sensor Fish and a concurrent live fish study. The frequency of severe acceleration events (acceleration≥95G) during passage decreased significantly (from 51% to 35%; p-value=0.049), and collisions with structures decreased from 47% to 27% (p-value=0.015). Pressures observed in the Spillway–Deflector region and pressure rates of change decreased as well. Overall, the modifications resulted in hydraulic conditions that contributed to improved fish passage conditions and increased fish survival.

Exploring the Distribution of Coccidioides immitis in South Central Washington State

ObjectiveOur objective is to describe the environmental conditions associatedwith confirmedCoccidioides immitisgrowth and accumulation sitesin south central Washington in an effort to understand the ecology andidentify additional potential sites across this emerging endemic zone.IntroductionCoccidioidomycosis, commonly referred to as Valley Fever, iscaused by the soil-borne saprophytic fungusC. immitisandposadasii.These species have historically been found in the desert southwest andMexico; however, in 2010 there were three coccidioidomycosis casesidentified in central Washington. Colonization of soils byC. immitishas been confirmed at exposure sites associated with these cases1.Multiple studies have identified a relationship between environmentalconditions andC. immitisgrowth areas2,3,4, but these relationshipshave not been evaluated in Washington. The Washington StateDepartment of Health has been conducting environmental surveillancein an effort to understand the geographic distribution ofC. immitisincentral Washington and the associated risk to humans and animals.Here we describe our environmental surveillance efforts and presentpreliminary findings related to environmental conditions ofC. immitisgrowth areas in central Washington.MethodsWe collected soil samples at potential human exposure sites incentral Washington, as identified through clinical surveillance andpatient interviews. Soil samples were also collected from areasnot associated with human cases by looking for similar soils inareas of interest Soil samples are analyzed by the U.S. Centers forDisease Control and Prevention using real-time PCR that detectsCoccidioides-specific targets. We employed data from the USDA SoilSurvey Geographic (SSURGO) database to describe environmentalconditions associated with positive samples. We used our findingsto identify un-sampled regions of central Washington that couldpotentially supportC. immitisgrowth.ResultsWe detectedCoccidioidesin 13 soil sampling sites at fivelocations withing the region. These detections included locations notpreviously described in central Washington. We identified a bandstretching across central Yakima and Benton counties with similarsoil characteristics to our positive sample sites, which suggests theseregions could potentially support the growth ofC. immitis.ConclusionsCoccidioidomycosis is emerging in south central Washington, andthe ecology and geographic distribution of the pathogen are poorlyunderstood. We found thatC. immitispresents a risk to humans andanimals across a larger region of central Washington than previouslydescribed and highlights a need for continued environmentalsurveillance. The potential growth sites we identified also providea valuable tool for human and veterinary health care providers andpublic health practitioners to understand and mitigate disease risk.

A Methodology to Evaluate Ecological Resources and Risk Using Two Case Studies at the Department of Energy's Hanford Site.

An assessment of the potential risks to ecological resources from remediation activities or other perturbations should involve a quantitative evaluation of resources on the remediation site and in the surrounding environment. We developed a risk methodology to rapidly evaluate potential impact on ecological resources for the U.S. Department of Energy's Hanford Site in southcentral Washington State. We describe the application of the risk evaluation for two case studies to illustrate its applicability. The ecological assessment involves examining previous sources of information for the site, defining different resource levels from 0 to 5. We also developed a risk rating scale from non-discernable to very high. Field assessment is the critical step to determine resource levels or to determine if current conditions are the same as previously evaluated. We provide a rapid assessment method for current ecological conditions that can be compared to previous site-specific data, or that can be used to assess resource value on other sites where ecological information is not generally available. The method is applicable to other Department of Energy's sites, where its development may involve a range of state regulators, resource trustees, Tribes and other stakeholders. Achieving consistency across Department of Energy's sites for valuation of ecological resources on remediation sites will assure Congress and the public that funds and personnel are being deployed appropriately.

Water Markets and Storage — Substitutes or Complements for Drought Risk Mitigation?

Are water storage and water markets complements or substitutes? This paper examines the conditions under which water storage for drought risk mitigation augments or attenuates water market gains from trade, and conversely, the conditions under which water markets augment or attenuate the value of additional water storage. The analysis is performed in the context of the Prior Appropriations doctrine in a fully appropriated basin. Two stylized examples based on water use at the intensive and extensive margin are provided, along with simulation results for proposed water storage projects and market development in the Yakima Basin in South-central Washington State.

Active faulting on the Wallula fault zone within the Olympic-Wallowa lineament, Washington State, USA

The Wallula fault zone is an integral feature of the Olympic-Wallowa lineament, an ∼500-km-long topographic lineament oblique to the Cascadia plate boundary, extending from Vancouver Island, British Columbia, to Walla Walla, Washington. The structure and past earthquake activity of the Wallula fault zone are important because of nearby infrastructure, and also because the fault zone defines part of the Olympic-Wallowa lineament in south-central Washington and suggests that the Olympic-Wallowa lineament may have a structural origin. We used aeromagnetic and ground magnetic data to locate the trace of the Wallula fault zone in the subsurface and map a quarry exposure of the Wallula fault zone near Finley, Washington, to investigate past earthquakes along the fault. We mapped three main packages of rocks and unconsolidated sediments in an ∼10-m-high quarry exposure. Our mapping suggests at least three late Pleistocene earthquakes with surface rupture, and an episode of liquefaction in the Holocene along the Wallula fault zone. Faint striae on the master fault surface are subhorizontal and suggest reverse dextral oblique motion for these earthquakes, consistent with dextral offset on the Wallula fault zone inferred from offset aeromagnetic anomalies associated with ca. 8.5 Ma basalt dikes. Magnetic surveys show that the Wallula fault actually lies 350 m to the southwest of the trace shown on published maps, passes directly through deformed late Pleistocene or younger deposits exposed at Finley quarry, and extends uninterrupted over 120 km.

Relative abundance and phenology ofDrosophilaFallén, 1815 (Diptera: Drosophilidae) species in south-central Washington State

Abstract. A monitoring program for a recently introduced vinegar fly, Drosophila suzukii Matsumura, 1931, was conducted in south-central Washington State, U.S.A. from March 2011 to November 2013. Along with D. suzukii, a complex of nine additional Drosophila Fallen, 1815 species were captured in baited traps and identified to species. The Drosophila were captured in Nalgene® and Haviland traps baited with apple cider vinegar or a sugar yeast mixture that were distributed among seven different horticultural crops or unmanaged habitats. All flies captured were identified to species and quantified for each sampling period. The species identified and quantified included D. busckii Coquillett, 1901, D. funebris Fabricius, 1787, D. hydei Sturtevant,1921, D. immigrans Sturtevant, 1921, D. melanogaster Meigen, 1830, D. simulans Sturtevant, 1919, D. obscura Fallen, 1823, D. subobscura Collin, 1936, D. subquinaria Spencer, 1942 and D. suzukii. The predominant species in 2011 were the obscura group and D. hydei. In ...

Effect of Powdery Scab Root Galls on Yield of Potato.

Powdery scab of potato, caused by Spongospora subterranea f. sp. subterranea, has increased in incidence since 1981 to become a major concern for potato production in the Columbia Basin of south-central Washington and north-central Oregon. Disease symptoms consist of pustules on the tuber surface and wart-like galls on roots, stolons, and tubers. In the current study, the effect of powdery scab root galls on potato yield was quantified by comparing yields of cultivars susceptible and resistant to root galling grown on soil naturally infested and noninfested with the powdery scab pathogen. Potato tuber yields for the three yield components of yield per plant, number of tubers, and weight of tubers were not negatively affected by powdery scab galls on roots of Umatilla Russet and Shepody, as indicated by yield ratios ≥1.0 in 3 of 4 years, and also by regression analyses in all 3 years. Regression lines with a nonsignificant slope or slopes that significantly increased with gall index also indicated that root galls did not negatively affect yield. Mean tuber weight increased as gall index increased for Umatilla Russet in 2 of 3 years. Consequently, control tactics directed solely at reducing powdery scab galls on roots are not justified economically under conditions encountered in the Columbia Basin of Washington and Oregon states. Effort has been made to develop resistant cultivars and search for soil applied chemicals to reduce root galls.

Establishment of Piper's daisy (Erigeron piperianus) in the shrub-steppe of south-central Washington

We studied protocols to enhance introduction of Erigeron piperianus Cronquist (Piper’s daisy [Asteraceae]) to a habitat similar to that of other existing populations in the shrub-steppe of south-central Washington. Seed from a population of E. piperianus growing within 4 km (2.5 mi) of the introduction site was used to propagate seedlings in a greenhouse. Germination was 50 ± 8%. We evaluated the effects of planting density and cover of existing vegetation on plant establishment and survival. Ultimately, seed production and recruitment were assessed. Density of outplanted E. piperianus seedlings had minimal effect on survival. Interference by perennial bunchgrasses reduced survival during the first year of growth. Interference by Salsola kali L. (Russian thistle [Chenopodiaceae]) significantly reduced populations in the second growing season. By spring of the second growing season, survivorship had dropped to 21% but summer seed production occurred on 99% of the remaining plants, resulting in 121 new plants in the summer of the third growing season. Two unplanned events allowed observation of natural impacts on seedling reintroduction. First, outplanting seedlings in late winter resulted in significant losses associated with a severe freeze. Establishment of plantings after the freeze was more successful. Second, severe insect herbivory was evident during the first growing season but appeared to have no impact on plant survival.

HUMAN DISTURBANCE AND THE PHYSIOLOGICAL RESPONSE OF ELK IN EASTERN WASHINGTON

Stress hormone measures have proven useful for assessing effects of human disturbance on wildlife populations. However, most studies are of short duration or limited geographic scope (i.e., without spatial replication), leading to concerns about confounding effects of biotic conditions. Previous research correlated fecal glucocorticoid metabolites (FGMs) of elk (Cervus elaphus) with human disturbance, but this factor also co-varied with seasonal climatic conditions, making it difficult to make broader inference regarding the role of human disturbance. In this study we attempted to simultaneously evaluate the effects of climatic conditions and human disturbance by comparing the year-round physiological stress response of elk to varying levels of human disturbance at three study sites in south-central Washington State. FGMs were consistently elevated throughout the year at the study site receiving the greatest amount of human disturbance. We observed support for a positive effect of precipitation and increasing temperature on FGMs at the low-disturbance site, but less support for importance of climatic variables in explaining FGMs at the high-disturbance sites - suggesting that climatic variables were likely of secondary importance compared to anthropogenic stressors in elk at those sites. Collectively, while we were unable to disentangle the effects of site- specific stressors, our findings suggest that in this environment, humans were a dominant stressor influencing FGM levels. Therefore, interpreting results of physiological studies requires that researchers account for a broad combination of biotic and abiotic stressors at a particular study location. We particularly encourage future investigators to account for the potential confounding effect of human disturbance that could override other stressors.

An autotrophic H2 -oxidizing, nitrate-respiring, Tc(VII)-reducing Acidovorax sp. isolated from a subsurface oxic-anoxic transition zone.

Increasing concentrations of H2 with depth were observed across a geologic unconformity and associated redox transition zone in the subsurface at the Hanford Site in south-central Washington, USA. An opposing gradient characterized by decreasing O2 and nitrate concentrations was consistent with microbial-catalysed biogeochemical processes. Sterile sand was incubated in situ within a multilevel sampler placed across the redox transition zone to evaluate the potential for Tc(VII) reduction and for enrichment of H2 -oxidizing denitrifiers capable of reducing Tc(VII). H2 -driven TcO4 (-) reduction was detected in sand incubated at all depths but was strongest in material from a depth of 17.1 m. Acidovorax spp. were isolated from H2 -nitrate enrichments from colonized sand from 15.1 m, with one representative, strain JHL-9, subsequently characterized. JHL-9 grew on acetate with either O2 or nitrate as electron acceptor (data not shown) and on medium with bicarbonate, H2 and nitrate. JHL-9 also reduced pertechnetate (TcO4 (-) ) under denitrifying conditions with H2 as the electron donor. H2 -oxidizing Acidovorax spp. in the subsurface at Hanford and other locations may contribute to the maintenance of subsurface redox gradients and offer the potential for Tc(VII) reduction.

Beauty with benefits: butterfly conservation in Washington State, USA, wine grape vineyards

The butterfly fauna of south central Washington State, USA is characterized by shrub-steppe specialists adapted to hot, dry summers and cold winters. However, the shrub-steppe ecosystem has diminished at an alarming rate due to extensive agricultural development fostered by access to an abundant water supply from the Cascade Mountains. This has resulted in loss and fragmentation of habitat for ~50 species of butterflies which are now in decline. Viticulture is a major agricultural industry in south central Washington and has transitioned in recent years to a sustainable, low pesticide-input enterprise. Current viticultural pest management research is focused on restoration of shrub-steppe habitat and native plants to enhance and sustain beneficial arthropod populations (predators and parasitoids) for pest control. Butterfly populations were surveyed during 2012–13 in a pair of vineyards (habitat-enhanced, conventional) in each of four viticultural regions [Columbia gorge (CG), Walla Walla valley (WWV), Yakima valley (YV), Wahluke slope (WS)] in south-central Washington. The habitat-enhanced sites supported a significantly greater number of flowering plant species (mostly native) than conventional vineyard sites. Twenty nine butterfly species were recorded from the habitat-enhanced vineyards with only nine of these recorded from the conventional vineyards. Overall, there were double the number of species in habitat-enhanced vineyards [mean (±SE) 5.62 ± 0.85] compared to conventional vineyards (2.75 ± 0.75) although this was not statistically significant. A significantly greater number of species occurred in the CG and WWV habitat-enhanced vineyards (10.5 ± 0.5) compared to the conventional vineyards (3.5 ± 0.0) in these regions. Smaller numbers of butterfly species occurred in YV and WS vineyards with no significant differences between habitat-enhanced and conventional sites. Butterfly abundance was significantly greater in habitat-enhanced vineyards (20.37 ± 5.34 individuals/visit) compared to conventional vineyards (5.5 ± 0.9) with greatest differences in the CG and WWV vineyards. The pest management strategy of restoring native plants and habitats in a low pesticide-input crop like wine grapes in central Washington may have substantial benefits for butterfly abundance, diversity and conservation. Many of the flowering native perennials important in attracting and sustaining endemic biological control agents, are also larval hosts and/or nectar sources for threatened shrub-steppe butterflies.

Solidification and stabilization of silver mordenite used to control radioiodine emissions from Hanford’s Waste Treatment Plant

The United States Department of Energy is building the Hanford Waste Treatment and Immobilization Plant (WTP) in south-central Washington State to immobilize a portion of the stored high-level radioactive wastes generated by decades of producing nuclear defense materials. To comply with United States Environmental Protection Agency (EPA) and Washington State air emission regulations, the WTP is planning to use reduced silver mordenite to control releases of any volatilized waste constituent radioiodine (129I t1/2=1.7×107a). Because the EPA and Washington State have designated silver as a hazardous or dangerous waste constituent, the disposal form for the waste reduced silver mordenite must comply with their land disposal regulations. We used the mandated EPA Toxic Characteristic Leach Procedure to evaluate and qualify a disposal form for the waste reduced-silver mordenite. Our development effort resulted in a regulation-compliant disposal form which used cast American Society for Testing and Materials (ASTM) Portland Type III cement modified to include calcium iodide to solidify and stabilize the reduced-silver mordenite and control silver release to regulatory levels.

Ground beetles (Coleoptera, Carabidae) of the Hanford Nuclear Site in south-central Washington State

In this paper we report on ground beetles (Coleoptera: Carabidae) collected from the Hanford Nuclear Reservation and Hanford National Monument (together the Hanford Site), which is located in south-central Washington State. The Site is a relatively undisturbed relict of the shrub-steppe habitat present throughout much of the western Columbia Basin before the westward expansion of the United States. Species, localities, months of capture, and capture method are reported for field work conducted between 1994 and 2002. Most species were collected using pitfall traps, although other capture methods were employed. Trapping results indicate the Hanford Site supports a diverse ground beetle community, with over 90% of the 92 species captured native to North America. Four species collected during the study period are newly recorded for Washington State: Bembidion diligens Casey, Calosoma obsoletum Say, Pseudaptinus rufulus (LeConte), and Stenolophus lineola (Fabricius). Based on these data, the Site maintains a diverse ground beetle fauna and, due to its size and diversity of habitats, is an important repository of shrub-steppe biodiversity.

Climate change and Yakama Nation tribal well-being

The Yakima River Basin (Basin) in south-central Washington is a prime example of a place where competing water uses, coupled with over-allocation of water resources, have presented water managers with the challenge of meeting current demand, anticipating future demand, and preparing for potential impacts of climate change. We took a decision analysis approach that gathered diverse stakeholders to discuss their concerns pertaining to climate change effects on the Basin and future goals that were collectively important. One main focus was centered on how climate change may influence future salmon populations. Salmon have played a prominent role in the cultures of Basin communities, especially for tribal communities that have social, cultural, spiritual, subsistence, and economic ties to them. Stakeholders identified the need for a better understanding on how the cultural, spiritual, subsistence, and economic aspects of the Confederated Tribes and Bands of the Yakama Nation could be affected by changes in salmon populations. In an attempt to understand the complexities of these potential effects, this paper proposes a conceptual model which 1) identifies cultural values and components and the interactions between those components that could influence tribal well-being, and 2) shows how federal natural resource managers could incorporate intangible tribal cultural components into decision-making processes by understanding important components of tribal well-being. Future work includes defining the parameterization of the cultural components in order for the conceptual model to be incorporated with biophysical resource models for scenario simulations.

Slow-Rusting Resistance in Native Spearmint to Puccinia menthae.

Rust, caused by Puccinia menthae, is often a serious yield-reducing problem on native and Scotch spearmint in south-central Washington State. Rust resistant mint cultivars would reduce a dependence on fungicides for disease management; however, conventional breeding practices are not possible because commercial mint plants are sterile. Mutant Scotch and native spearmint lines induced by irradiation were evaluated for partial resistance to rust. Latent period and number of uredinia per leaf from urediniospore inoculations in the greenhouse and aecial and uredinial development in the field were quantified. Length of latent period, number of uredinia per leaf, incidence of shoots with aecia, and area under the disease progress curve (AUDPC) for uredinia development all varied significantly among lines and standard cultivars. Length of latent period was significantly longer and number of uredinia per leaf was significantly lower for native spearmint line N87-1 than for most of the other mutant lines, native spearmint, and Scotch spearmint. Line N87-1 had the lowest AUDPC values of all lines and standard cultivars for 3 years in the field. However, line N87-1 had a relatively high incidence of shoots with aecia both of two years in the field. Length of latent period was significantly and negatively correlated with AUDPC 2 of 3 years. Mean incidence of shoots with aecia was not correlated with AUDPC or with length of latent period after urediniospore infection. Rust in native spearmint in south-central Washington State could be satisfactorily managed with slow-rusting resistance when coupled with good irrigation water management and sanitation tactics that limit aecia development on early spring mint foliage.

The Wallula fault and tectonic framework of south-central Washington, as interpreted from magnetic and gravity anomalies

Abstract The Yakima fold and thrust belt (YFTB) in central Washington has accommodated regional, mostly north-directed, deformation of the Cascadia backarc since prior to emplacement of Miocene flood basalt of the Columbia River Basalt Group (CRBG). The YFTB consists of two structural domains. Northern folds of the YFTB strike eastward and terminate at the western margin of a 20-mGal negative gravity anomaly, the Pasco gravity low, straddling the North American continental margin. Southern folds of the YFTB strike southeastward, form part of the Olympic–Wallowa lineament (OWL), and pass south of the Pasco gravity low as the Wallula fault zone. An upper crustal model based on gravity and magnetic anomalies suggests that the Pasco gravity low is caused in part by an 8-km-deep Tertiary basin, the Pasco sub-basin, abutting the continental margin and concealed beneath CRBG. The Pasco sub-basin is crossed by north-northwest-striking magnetic anomalies caused by dikes of the 8.5 Ma Ice Harbor Member of the CRBG. At their northern end, dikes connect with the eastern terminus of the Saddle Mountains thrust of the YFTB. At their southern end, dikes are disrupted by the Wallula fault zone. The episode of NE–SW extension that promoted Ice Harbor dike injection apparently involved strike-slip displacement on the Saddle Mountains and Wallula faults. The amount of lateral shear on the OWL impacts the level of seismic hazard in the Cascadia region. Ice Harbor dikes, as mapped with aeromagnetic data, are dextrally offset by the Wallula fault zone a total of 6.9 km. Assuming that dike offsets are tectonic in origin, the Wallula fault zone has experienced an average dextral shear of 0.8 mm/y since dike emplacement 8.5 Ma, consistent with right-lateral stream offsets observed at other locations along the OWL. Southeastward, the Wallula fault transfers strain to the north-striking Hite fault, the possible location of the M 5.7 Milton-Freewater earthquake in 1936.

Molecular Species Identification of Cryptic Apple and Snowberry Maggots (Diptera: Tephritidae) in Western and Central Washington

In Washington state, identification of the quarantine apple pest Rhagoletis pomonella (Walsh) is complicated by the presence of the cryptic species Rhagoletis zephyria Snow (Diptera: Tephritidae). Distinguishing the two flies is important because there is a zero tolerance policy for R. pomonella in apple production for export. Here, we attempt to distinguish the two species by scoring R. pomonella and R. zephyria populations from western and south-central Washington for a set of 11 nuclear markers, including four single nucleotide polymorphisms (SNPs) developed for rapid and inexpensive genotyping using Taqman real-time quantitative-polymerase chain reaction. We show that the four SNPs may be adequate in most cases for distinguishing whether a fly originated from apple or black hawthorn (the two major host plants for R. pomonella representing an economic risk) versus snowberry (the major host for R. zephyria, and not a commercial threat). However, directional introgression of R. zephyria alleles into R. pomonella can complicate the identification of flies of mixed ancestry based only on the four SNPs. Moreover, this problem is more acute in the sensitive apple-growing regions of central Washington where our results imply hybridization is common. Consequently, application of the four SNP quantitative-polymerase chain reaction assay can immediately assist ongoing apple maggot monitoring, while the development of additional genetic markers through next-generation sequencing would be valuable for increasing confidence in species identification and for assessing the threat posed by hybridization as R. pomonella further spreads into the more arid apple-growing regions of central Washington.

Survival and causes of mortality in a northern population of western gray squirrels

We studied survival of radio-marked western gray squirrels (Sciurus griseus) and quantified causes of mortality including incidence and severity of notoedric mange in south-central Washington, 1998–2005. We used known-fate models in Program MARK to explore alternative hypotheses on factors related to survival and correlation analysis to investigate parameters that might be related to incidence of mange. The best-supported models indicated that survival varied by year and by sex and that survival of males was lower during the breeding season compared to the non-breeding season. We found little support for differences in survival between juvenile (5–12 months old) and adult squirrels, or for winter severity or size of the acorn crop as significant influences on survival. We determined the likely proximate cause of death for 81 animals; 63% were killed by predators and 37% succumbed to disease, with most disease deaths attributed to mange. Mange was documented in the population during all years and occurred more frequently in animals captured in spring than in animals captured in fall. Counter to our predictions, occurrence of mange was not correlated with 2 measures of winter severity but was strongly correlated with mildness of the preceding winter (number of days with mean air temperature ≥0° C). Sequential use of nests by individual squirrels during mild winters with temperatures conducive to survival of ephemeral, free-living mites may partially explain the periodic epizootics of notoedric mange in this western gray squirrel population. Continued deterioration of squirrel habitat through fragmentation will place additional stressors on the population and may compound the effects of mange on this threatened species. © 2013 The Wildlife Society.

Wind erosion and PM10 emission affected by tillage systems in the world's driest rainfed wheat region

The Horse Heaven Hills of south-central Washington is the driest rainfed wheat growing region in the world. Low precipitation, high winds, poorly aggregated soils, sparse residue cover, and a tillage-based winter wheat (Triticum aestivum L.) – summer fallow (WW-SF) cropping system often combine to create soil surfaces which are susceptible to wind erosion. No-tillage summer fallow (NTF) and conservation tillage fallow (CTF) with an undercutter sweep implement were examined as alternative practices to traditional tillage fallow (TTF) with a tandem disk implement for reducing wind erosion and PM10 (particulate matter ≤10μm in aerodynamic diameter) emissions during the fallow phase of the WW-SF rotation. Wind erosion and PM10 emissions were assessed with a wind tunnel after primary spring tillage in mid-to-late April and after sowing winter wheat in August. Sediment loss and PM10 vertical flux and loss were generally less for NTF than with TTF, likely due to retention of surface residue and maintaining a soil crust in NTF. Sediment and PM10 loss increased after sowing wheat in both the TTF and CTF treatments. Although NTF abated the loss of sediment and PM0 compared with TTF, NTF is not yet an economical option for most growers in the region. Conservation tillage fallow using the undercutter sweep is an economically viable alternative to TTF for reducing windblown sediment and PM10 loss from agricultural soils in the Horse Heaven Hills.

Trajectories of change in sagebrush steppe vegetation communities in relation to multiple wildfires

Repeated perturbations, both biotic and abiotic, can lead to fundamental changes in the nature of ecosystems, including changes in state. Sagebrush steppe communities provide important habitat for wildlife and grazing for livestock. Fire is an integral part of these systems, but there is concern that increased ignition frequencies and invasive species are fundamentally altering them. Despite these issues, the majority of studies of fire effects in systems dominated by Artemisia tridentata wyomingensis have focused on the effects of single burns. The Arid Lands Ecology Reserve (ALE), in south-central Washington (USA), was one of the largest contiguous areas of sagebrush steppe habitat in the state until large wildfires burned the majority of it in 2000 and 2007. We analyzed data from permanent vegetation transects established in 1996 and resampled in 2002 and 2009. Our objective was to describe how the fires, and subsequent postfire restoration efforts, affected communities' successional pathways. Plant communities differed in response to repeated fire and restoration; these differences could largely be ascribed to the functional traits of the dominant species. Low-elevation communities, previously dominated by obligate seeders, moved furthest from their initial composition and were dominated by weedy, early-successional species in 2009. Higher-elevation sites with resprouting shrubs, native bunchgrasses, and few invasive species were generally more resilient to the effects of repeated disturbances. Shrub cover has been almost entirely removed from ALE, although there was some recovery where communities were dominated by resprouters. Bromus tectorum dominance was reduced by herbicide application in areas where it was previously abundant, but it increased significantly in untreated areas. Several resprouting species, notably Phlox longifolia and Poa secunda, expanded remarkably following competitive release from shrub canopies and/or abundant B. tectorum. Our results suggest that community dynamics can be understood through a state and transition model with two axes (shrub/grass and native/invasive abundance), although such models also need to account for differences in plant functional traits and disturbance regimes. We use our results to develop a conceptual model that will be validated with further research.