Location: Great Basin Rangelands Research2018 Annual Report
At more than 50 million hectares, the Great Basin is the largest North American desert but also the most threatened. Great Basin ecosystems have been significantly altered by invasive annual grasses and expanding native conifer populations. This has resulted in altered fire cycles, wildlife habitat loss, and massive expenditures on rehabilitation. Over the next five years, we will conduct research to further elucidate mechanisms of invasion and develop new and evaluate current control strategies for exotic grasses and encroaching woody species in Great Basin rangelands. Objective 1: Develop new strategies to improve the control of invasive annual grasses, especially cheatgrass and medusahead grass, in Great Basin ecosystems based on using an improved understanding of the ecology, biology, and genetic variation of these weeds and the native plant communities they are invading. Subobjective 1A: Describe and analyze the genetic structure of invasive annual grass populations. Subobjective 1B: Identify ecological associations relevant to the proliferation, impact, and control of invasive annual grasses. Subobjective 1C: Determine the effectiveness of seeding strategies on reducing invasive annual grasses and fire frequency. Subobjective 1D: Elucidate invasive-native plant associations across climatic gradients and determine native species mixes resistant to invasive annual grasses under future climate. Objective 2: Identify and quantify the effects of integrated weed control for invasive woody plants (including pinyon, juniper, and saltcedar) on ecosystem processes, such as water cycling and seed ecology, to improve restoration and management of Great Basin ecosystems under variable climatic conditions. Subobjective 2A: Quantify the long-term effects of Diorhabda carinulata (northern tamarisk beetle) on water and carbon cycling, tree mortality, and wildlife populations in areas affected by saltcedar biological control. Subobjective 2B: Investigate adapted foundational plant materials suitable for restoration strategies in woody plant invasions to prevent secondary weed invasions. Subobjective 2C: Investigate effects of post-invasion mechanical tree control in established pinyon and juniper stands on ecohydrology and sagebrush steppe community recovery and determine the effects of native seed eating insects in reducing juniper seed viability as a pre-establishment control strategy.
Over the next 5 years, we will embark on a research program that will enhance the ability to manage invasive weeds in riparian and rangeland environments. Sagebrush habitats are at risk due to downslope expansions of woody native trees and upslope expansion of invasive annual grasses. The studies will address factors that influence the resistance and resilience of sagebrush ecosystems, that allow them to either be resistant to invasion or to recover from disturbance. We will accomplish this by integrating innovative approaches to weed control, increasing our understanding of relevant ecological processes, and providing guidelines for rehabilitation of damaged ecosystems. Specifically, we will initiate new research to describe genetic variation and the population structure of invasive annual grass species, explore biological control strategies for these grasses, and evaluate how post-fire seeding treatments affect invasive annual grass populations and wildfire frequency and severity. We will build on existing saltcedar biological control studies to promote the return of key native species and prevent secondary weed invasion, expand our mechanistic studies of pinyon- and juniper-encroached sagebrush ecosystems and of the effects of tree control treatments on these systems, and begin investigating the role of climate change in weed invasion and native species survival. If data are not available, suitable field sites cannot be found, permissions to work are not granted, or if suitablie biological candidates cannot be found, then we will modify our plans and experimental procedures as necessary.
An ARS scientist from Reno, Nevada, worked for 27 weeks at the ARS European Biological Control Laboratory in Montpellier, France, as an invited researcher focusing on continued progress in Objective 1. In addition to the multiple cheatgrass and red brome populations that were sampled in the Great Basin and adjacent regions for genetic analysis, six new cheatgrass populations were collected from western and central Asia (in collaboration with European colleagues through 2060-22000-024-09S, "Discovery and Evaluation of Biological Control Agents of Invasive Annual Grasses”), four new medusahead populations were sampled in Europe and two new red brome populations were collected in Europe and northern Africa. DNA was extracted from all populations. Bioinformatic analyses on cheatgrass sequence data was obtained using DNASTAR Lasergene SeqNinja software to identify single-nucleotide polymorphism (SNP) markers found in cheatgrass populations collected throughout the Great Basin and Mojave regions of Nevada. The process of screening specific cheatgrass populations and a few red brome populations for SNPs was initiated, but it has not been completed due to loss of a genetics support scientist position, and an inability to refill this critical vacancy. Many of the SNPs isolated from cheatgrass could also be found in red brome populations. If the geneticist position is filled, completion of these analyses will allow a thorough characterization of cheatgrass and red brome genetic structure and diversity across Nevada for potential control applications, as well as to determine evolutionary relationships between these congeneric invasive annual grasses. Native-range collections of eriophyid mites on targeted annual grass species and collections of medusahead plants for endophyte studies are ongoing. On medusahead, the taxonomic description of Aculodes altamurgiensis, was completed and additional biological and taxonomic studies are underway to assess its suitability as a biological control agent. In addition to this new mite species, first discovered by an ARS scientist from Reno, Nevada, surveying in Italy in 2014, another new mite species was discovered on cheatgrass this year in Bulgaria (in collaboration with European colleagues through 2060-22000-024-09S, "Discovery and Evaluation of Biological Control Agents of Invasive Annual Grasses”). A taxonomic description has begun in collaboration with European colleagues, “Discovery, Description and Evaluation of Eriophyid Mites as Biological Control Agents of Invasive Annual Grasses”). Analyses of endophytes from medusahead are ongoing with the project evolving to focus on seed-borne endophytes, following preliminary results. Monitoring Trends in Burn Severity (MTBS) fire occurrence data was used to determine total area burned in the region from 1984-2016 and to identify areas with high frequency of fire occurrence (hot spots) in the Great Basin. MTBS burn severity data was used from within all identified hot spots to compare burn severity values across the region’s dominant vegetation types. These results were analyzed and presented at conferences. Additionally, long-term recovery after fire along burn severity gradients was examined in three different ecosystems. Manuscripts are in preparation for a special issue in the journal, Fire Ecology. Sixty-eight sites were sampled in the summer of 2014 and 2015 with four to six sites for each fire-rehabilitation treatment combination. The effects of fire number (0-6 fires) and rehabilitation treatment type (none, drilled, aerial, or drilled + aerial seeding) on 1) plant community composition, 2) cheatgrass invasion, and 3) fire regimes were tested. The effects of plant and climate variables on 1) plant species cover and density, 2) cheatgrass, crested wheatgrass, and native bunchgrass cover and density, and 3) the number of fires, fire frequency, and fire return interval over the past twenty years were tested. A combination of univariate (mixed model analysis of variance) and multivariate (non-parametric multiplicative regression, non-parametric multidimensional scaling, and multiple response permutation procedure) analyses were used. Three manuscripts are in preparation: 1) The effects of fire history, post-fire rehabilitation, and environmental factors on shrub steppe communities, 2) The effect of species, environment, and post-fire treatments on cheatgrass, and 3) Post-fire rehabilitation and climate effects on fire regimes in the sagebrush steppe. The rehabilitation-climate experiment was established on the Monroe fire near Winnemucca, Nevada. This experiment has 30 macroplots at the site with three replicates per treatment. Treatments in the macroplots include: 1) Herbicide/no herbicide and 2) Precipitation – ambient, spring addition, spring reduction, summer addition, and summer reduction. In each macroplot, nine subplots were established (three replicates per treatment) of the following forb treatments: 1) no forbs, 2) annual forbs, or 3) perennial forbs. Plots were raked, hand-broadcasted, and pressed with a mini imprinter. Percent cover and seedling counts were made on all subplots. A database of plant cover and climate information has been established. Elevation Gradients: Due to limited personnel and difficulties attaining suitable sites and permission, this experiment is discontinued. Work to measure ecosystem effects on wildlife of saltcedar biological control by the northern tamarisk beetle was conducted. Wildlife monitoring was mandated as part of the Animal and Plant Health Inspection Service (APHIS) permit for the release of Diorhabda. Annual monitoring of small mammal populations at saltcedar sites undergoing biological control was conducted at two sites, one of which has been monitored since before the beetles were released. Arthropods were collected from two saltcedar transects and two adjacent un-infested transects. Processing and identification of collected insects is currently underway. Water and carbon dioxide exchanges were measured with an eddy-covariance system over a stand of saltcedar to complete the last year of 10-year data set. In addition to the measurements of water and carbon dioxide, surveys were conducted every three weeks during the growing season to determine the abundance of northern tamarisk beetle and changes in leaf area index of saltcedar. This work is essential to continuation of the saltcedar biological control program, which has currently been discontinued by the United States Fish and Wildlife Service due to concerns about effects on the endangered southwestern willow flycatcher. Data collection in the Porter Canyon Experimental Watershed (PCEW) in the Desatoya Mountain Range is now in its seventh year. Results from work on rainfall interception were reanalyzed, expanded upon with new data and published. The project is also being expanded to look at more meadow systems within the Desatoya Mountain Range in collaboration with the Bureau of Land Managment (BLM), Nevada Department of Wildlife (NDOW) and the U.S. Geological Survey (USGS). This meadow project will look at greater sage grouse meadow habitat and restoration, plant phenology, and water availability. In November 2017, berries were collected from western juniper trees at each of two field sites in northeastern California, where this native tree species has been encroaching on sagebrush rangelands. Adult arthopods, 38 insect species and one mite species, have been found that occur in western juniper berries, at least 8 of which cause damage to seeds and render them inviable. Because it is not possible to identify larvae morphologically, larvae have been matched to adults using genetic analyses. This is essential to understanding impacts of these insect species on production of viable juniper seeds because it is in the larval form that they feed on and damage seeds. Quantifying local abundances of various species that limit seed production can inform management decisions regarding where to prioritize mechanical control or other control measures for western juniper. This work was completed for four common arthropods that we found associated with this juniper species, and this research was expanded into another juniper species, Utah juniper, that has also been undergoing range expansion within Great Basin piñon-juniper rangelands. Although Utah juniper hosts many of the same (or similar) arthropod taxa as western juniper, these species differ in the specific taxa that are most effective at reducing seed viability.
1. Insects and mites reduce western juniper seed production. Two ARS scientists in Reno, Nevada, have identified numerous insects and one mite species that inhabit the berries and seeds of western juniper, the most rapidly expanding native tree species on western rangelands. The mite and at least 7 of the insect species can cause damage that renders juniper seeds inviable. A paper was published describing the 4 most common species that damage seeds, levels of damage they cause, and yearly variation in their population sizes. This identified 2 of these 4 species as clearly having the greatest impacts on western juniper seed production. Recognizing outbreaks of these seed-damaging species can assist managers in prioritizing where to apply limited resources into juniper control measures. Mass rearing some insects that limit western juniper seed production for biological control applications in areas where juniper is expanding is also an option.
Clements, D.D., Jenkins, R. 2017. Managing cheatgrass in rangeland restoration efforts. The Progressive Rancher. 17(8):24-28.
Clements, D.D., Harmon, D.N., Blank, R.R., Weltz, M.A. 2017. Improving seeding success on cheatgrass-infested rangelands in Northern Nevada. Rangelands. 39(6):174-181.
Blank, R.R., Clements, D.D., Morgan, T.A., Harmon, D.N. 2017. Sagebrush wildfire effects on surface soil nutrient availability: A temporal and spatial study. Soil Science Society of America Journal. 81(5):1203-1210. https://doi.org/10.2136/SSSAJ2017.02.0039.
Rector, B.G., Czarnoleski, M., Skoracka, A., Lembicz, M. 2016. Change in abundance of three phytophagous mite species (Acari: Eriophyidae, Tetranychidae) on quackgrass in the presence of choke disease. Experimental and Applied Acarology. 90(1):35-43.
Laska, A., Rector, B.G., Kuczynski, L., Skoracka, A. 2017. Is body size important? Seasonal changes in morphology in two grass-feeding Abacarus mites. Experimental and Applied Acarology. 72:317-328.
Kiedrowicz, A., Rector, B.G., Lommen, S., Kuczynski, L., Szydlo, W., Skoracka, A. 2017. Population growth rate of dry bulb mite, Aceria tulipae (Keifer) (Acariformes: Eriophyidae) on agriculturally important plants and implications on taxonomic status. Experimental and Applied Acarology. 73(1):1-10.
Dimitri, L.A., Longland, W.S., Tonkel, K.C., Rector, B.G., Kirchoff, V.S. 2018. Impacts of granivorous and frugivorous arthropods on pre-dispersal seed production of western juniper (Juniperus occidentalis). Arthropod-Plant Interactions. 12(3):465-476. https://doi.org/10.1007/s11829-018-9603-3
McGwire, K.C., Weltz, M.A., Snyder, K.A., Huntington, J.L., Morton, C.G., McEvoy, D.J. 2017. Satellite assessment of early-season forecasts for vegetation conditions of grazing allotments in Nevada, United States. Rangeland Ecology and Management. 70(60):730-739. https://doi.org/10.1016/j.rama.2017.06.005.
Stringham, T.K., Snyder, K.A., Snyder, D.K., Lossing, S.S., Carr, C.A., Stringham, B.J. 2018. Rainfall interception by Singleleaf Piñon and Utah Juniper: implications for stand-level effective precipitation. Rangeland Ecology and Management. 71(3):327-335.
Clements, D.D., Harmon, D.N. 2017. Four-wing saltbush (Atriplex canescens) seed and seedling consumption by granivorous rodents. Rangelands. 39(6):182-186. https://doi.org/10.1016/j.rala.2017.10.002.
De Lillo, E., Vidovic, B., Petanovic, R., Cristofaro, M., Marini, F., Auge, M., Cyrkovic, T., Babic, E., Mattia, C., Lotfollahi, P., Rector, B.G. 2018. A new Aculodes species (Prostigmata: Eriophyoidea: Eriophyidae) associated with medusahead, Taeniatherum caput-medusae (L.) Nevski (Poaceae). Systematic and Applied Acarology. 23(7):1217-1226.