Location: Great Basin Rangelands Research
2017 Annual Report
Objectives
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.
Approach
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.
Progress Report
An ARS scientist from Reno, Nevada, worked for 24 weeks at the ARS European Biological Control Laboratory in Montpellier, France, in order to build on the progress of Objective 1. In addition to the multiple cheatgrass and red brome populations that were sampled across the Great Basin for genetic analysis, seven cheatgrass and six medusahead populations were collected from Europe and Asia (Asian populations were collected in collaboration with European colleagues through 2060-22000-024-09S, "Discovery and Evaluation of Bioilogical Control Agents of Invasive Annual Grasses"). Ten red brome populations were collected in Europe. Numerous cheatgrass and red brome populations were collected throughout the Great Basin and Mojave regions of Nevada in 2016. DNA was extracted from all populations.
We acquired DNASTAR Lasergene SeqNinja software and initiated bioinformatic analyses to determine genetic variation using markers known as singles sequence repeats (SSRs) among these populations. The complexity of these analyses caused initial delays, but we have been making considerable progress recently. Completion of these analyses, which have been underway for several months, will allow us to identify hundreds of SSR markers. Using analyses conducted to date, we initiated comparisons of SSR and single nucleotide polymorphisms (SNP) variations in cheatgrass. Additional cheatgrass populations, as well as several red brome populations, were sampled in 2017. DNA was extracted to expand the geographic coverage of our genetic studies of invasive annual grasses.
Native-range collections of eriophyid mites on targeted annual grass species and of medusahead plants for endophyte studies are ongoing. On medusahead, the taxonomic description of Aculodes alta-murgiensis n. sp., continued. This is a new species of mite found on medusahead by an ARS scientist in Reno, Nevada, in earlier surveys. In addition, preliminary host-specificity bioassays for this biological control candidate were conducted with very promising results. It was discovered the mite only attacks medusahead and does not attack wheat, one of medusahead’s closest relatives, or any of four other economically important grasses. Progress was also made in rearing this new species under laboratory and greenhouse conditions. Analyses of endophytes from medusahead are ongoing, while collection of seedling plants from native-range sites for endophyte analysis is planned for the end of Fiscal Year 2017 in order to compare with endophytes from mature plants.
Sixty sites for plant community composition and fuel loads were sampled by measuring plant cover, density, and biomass. All vegetation data was compiled into a vegetation database. Multivariate analyses were used to examine the effect of environmental, fire, and rehabilitation on fuels composition, cover, density, and biomass. A site information database was created by compiling data on environmental (precipitation, temperature, soil), fire, and rehabilitation data. Using this database, 1,100 locations were randomly sampled and fire and treatment history was extracted. The effect of fire number and rehabilitation treatment on the fire return interval between subsequent fires was tested.
Rainout shelters are found to be effective at reducing precipitation and inducing drought. However, we discovered that the efficacy of previously used warming chambers is less than the desired increase in temperature. Thus, we have altered our design to replace the warming treatment with an increased precipitation treatment. The experiment will contain the following treatments: control, 50 percent rainfall reduction, and 50 percent rainfall increase. We have established site criteria, identified local fires with the the Bureau of Land Management (BLM) for site locations, and have coordinated with BLM to attain seed. Prototype shelters have been built and other shelters will be replicated this fall when the seed is planted. We have gathered information from the literature and ARS scientists from Boise, Idaho, scientists from the U.S. Forest Service, and universities, about existing elevation gradient studies and associated data. Using geographic informaton system data, we have selected 12 potential mountain ranges for site locations based on a broad range of elevation, vegetation types, and accessibility. Mountain ranges were also selected to geographically represent the variation in climate and flora of the Great Basin. One range has been selected for pilot measurements and sampling protocols have been designed.
Work continued to measure ecosystem effects on wildlife of saltcedar biological control by the northern tamarisk beetle. Wildlife monitoring was mandated as part of the Animal and Plant Health Inspection Service permit for the release of the northern tamarisk leaf beetle. 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. We continued to measure water and carbon dioxide exchanges with an eddy-covariance system over a stand of saltcedar where we have been measuring the ecosystem effects of biological control for a decade. In addition to the measurements of water and carbon dioxide, every three weeks during the growing season we conducted surveys of 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 sixth year. We have successfully implemented remote acquisition of data. PCEW was granted a conservation easement which will be managed by The Nature Conservancy and guarantee research in perpetuity in PCEW. We made tremendous headway in developing computer code to analyze plant phenology data from our ten land-based cameras. These results were published in the peer-reviewed journal “Sensors”. The project is also being expanded to look at more meadow systems within the Desatoya Mountain Range in collaboration with BLM, Nevada Department of Wildlife (NDOW) and the U.S. Geological Survey. This meadow project will look at greater sage grouse meadow habitat, plant phenology, and water availability.
In November 2016, we collected berries from western juniper trees at each of two field sites in Northeastern California, where this native tree species has been encroaching on sagebrush rangelands. Berries were frozen until they were analyzed for the presence of insect larvae and adults. Insects collected from berries are preserved in alcohol for subsequent identification. Using adult arthropods from these and previous collections, we have found thirty-eight insect species and one mite species that occur in western juniper berries, at least eight of which cause damage to seeds and render them inviable. Because we cannot identify larvae morphologically, we have matched larvae 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. During the past year we have also expanded this research into another juniper species, Utah juniper, which has also been undergoing range expansion within Great Basin piñon-juniper rangelands.
Accomplishments
1. Insects and mites associated with western juniper berries have been identified. Two ARS scientists from Reno, Nevada, have identified numerous insects and one mite species that inhabit the berries and seeds of western juniper. Western juniper is the most rapidly expanding native tree species on western rangelands. The mite and at least seven of the insect species can cause damage that renders juniper seeds inviable. Recognizing outbreaks of these seed-damaging species can assist managers in prioritizing where to apply limited resources for juniper control measures. It may also be possible to mass-rear some insects that limit western juniper seed production for biological control applications in areas where juniper is expanding. This will result in reduced loss of wildlife habitat, risks of wildfire, and provide increased forage availability for livestock.
2. Detecting phenology changes with land-based cameras. An ARS scientist from Reno, Nevada, determined that phenology curves and important windows of plant performance can be measured at fine spatial and temporal scales. This can be done with relatively inexpensive cameras and packaged code developed by the ARS scientist in conjunction with a scientist from the Environmental Protection Agency of Italy. The importance to land managers is the technology can identify periods of plant peak performance, forage availability, drought stress, or shifts in phenology due to weather variability. This allows managers to adapt to or develop strategies to mitigate adverse impacts of weather on the health of ecosystems and the sustainability of livestock production systems that depend on seasonal forage production.
Review Publications
Carroll, R.W., Huntington, J.L., Snyder, K.A., Niswonger, R., Morton, C., Stringham, T.K. 2016. Evaluating mountain meadow groundwater response to pinyon-juniper and temperature in a great basin watershed. Ecohydrology. doi: 10.1002/eco.1792.
Stringham, T.K., Novak-Echenique, P., Snyder, D.K., Peterson, S., Snyder, K.A. 2016. Fire rehabilitation decisions at landscape scales: utilizing state-and-transition models developed through disturbance response grouping of ecological sites. Rangelands. 38(6):371-378.
Snyder, K.A., Wehan, B., Filippa, G., Hungington, J.L., Stringham, T.K., Snyder, D.K. 2016. Extracting plant phenology metrics in a Great Basin watershed: methods and considerations for quantifying phenophases in a cold desert. Sensors. doi: 10.3390/s16111948.
Skoracka, A., Lewandowski, M., Rector, B.G., Szydlo, W., Kuczynski, L. 2017. Spatial and host-associated variation in prevalence and population density of wheat curl mite (Aceria tosichella) cryptic genotypes in agricultural landscapes. PLoS One. doi: 10.1371.journal.pone.0169874
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. PLoS One. 70(1):35-43.
