Location: Great Basin Rangelands Research2016 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.
Subobjective 1A: We initiated new population genetic studies of two invasive annual grasses, cheatgrass, and red brome to expand on our previous research on cheatgrass genetics. During Spring and early Summer 2016, we collected samples of plants from cheatgrass populations at 44 sites throughout Nevada and at several additional sites outside Nevada. We also collected red brome samples at 27 Nevada sites, many of them the same as the cheatgrass collection sites. All samples were returned to the lab for DNA extraction, which has been completed for approximately half the collections to date. Extractions for remaining populations are ongoing. We conducted shotgun sequencing of DNA from several cheatgrass populations sampled over prior years, assembled contigs from the sequencing data, and have identified more than 20 new simple sequence repeat (SSR) markers for cheatgrass. Sequencing runs were being analyzed with GENIOUS software, however we found this to be too cumbersome and are currently switching to using DNASTAR Lasergene and Primer 3 software. Completion of these analyses, which have been underway for several months, will allow us to identify hundreds of single nucleotide polymorphisms (SNPs) and SSRs. One ARS scientist from Reno, Nevada, was selected by the Office of National Programs to work for 24 weeks at the ARS European Biological Control Laboratory in Montpellier, France, to accelerate progress of Objective 1 projects. As such, in addition to the Great Basin populations sampled, 14 cheatgrass populations and 17 medusahead populations were collected from Europe and Asia. Three populations of medusahead from the Great Basin, as well as five from Europe were sampled for the endophyte study and sent to ARS researchers in Peoria, Illinois, for metagenomic analysis (subobjective 1B). Medusahead and cheatgrass were surveyed in eight countries in Europe and Asia for eriophyid mites, which were identified from medusahead plants from three different countries and from cheatgrass plants in Serbia. Taxonomic and biological studies on these mites are underway in the laboratories of European collaborators. Subobjective 1C: We used a combination of fieldwork and geographical information systems (GIS) layers detailing fire and land treatment history in southern Idaho to assess the landscape-level impact of the number of fires and rehabilitation on vegetation and fire return intervals. We collected geospatial datasets spanning an area of 209,000 hectares (ha) of sagebrush steppe on Bureau of Land Management land in southern Idaho. Spatial data were compiled on rehabilitation treatment from various sources: Bureau of Land Management national data from Inside Idaho, Bureau of Land Management Field Offices, and the United States Geological Survey Land Treatment Data Library. Bureau of Land Management fire historical perimeters were obtained from Inside Idaho (for fire history). Two thousand random points were created throughout the study area (ArcGIS 10.1) and sites were eliminated that were in water bodies, agricultural fields, and on private property. Fire and rehabilitation history were extracted at the remaining 1000 points. Point extraction was used to identify the number of fires and the rehabilitation history at each point. We selected and established 68 sites within the study area and selected sites so all treatment combinations (fire x rehabilitation) would be distributed along the environmental gradients. Vegetation (density, cover, and biomass) and soil (texture) samples were collected at each site. Subobjective 1D: Rehabilitation Experiment: In a field experiment, we will examine the effects of increased temperature and altered precipitation on native and invasive plant growth, reproduction, and community dynamics. In field plots, we will establish plots with the following treatments: control, warming, drought, and warming plus drought. We found the rainout shelters to be effective at reducing precipitation and inducing drought. We discovered that the efficacy of previously used warming chambers is less than the desired increase in temperature. Thus, we have been testing new warming chamber designs. We have established site criteria and spoken with local landowners and the Bureau of Land Management about potential field sites although an experiment site has not been located to date. We have been communicating with the Bureau of Land Management and United States Forest Service on appropriate seed sources for the experiment. Elevation Gradients: Using elevation gradients along mountain ranges in the Great Basin, we will examine cheatgrass distributions in relation to climate and native plant communities. We have gathered information from scientists from ARS in Boise, Idaho, United States Forest Service, and universities about existing elevation gradient studies and associated data. Three potential gradient sites have been visited: Reynolds Creek Experimental Watershed, Snake Range, and the associated Nevada Climate-ecohydrological Assessment Network (NevCAN), as well as Peavine Mountain. Other mountain ranges are currently being investigated as potential sites. Subobjective 2A: We continued work to measure ecosystem effects on wildlife of saltcedar biological control by the northern tamarisk beetle, Diorhabda carinulata. We continued to measure water and carbon dioxide exchanges and eddy-covariance system. We conducted surveys of the abundance of northern tamarisk beetle and changes in leaf area index of saltcedar every three weeks during the growing season. Wildlife monitoring was mandated as part of the Animal and Plant Health Inpsection Service (APHIS) permit for the release of Diorhabda. Specifically, we monitored small mammal abundance and diversity in response to ongoing herbivory at sites where beetles have been established for multiple years leading to significant tree mortality. 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. One site that was previously monitored was lost as a research site, as biological control has progressed sufficiently that the landowner cleared the site of dead saltcedar trees and has put the area back into alfalfa production. 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. Two peer-reviewed journal articles were previously published reporting results of 11-12 years of wildlife monitoring in saltcedar and native riparian habitats, and a book article was published in a comprehensive volume regarding the saltcedar issue. Subobjective 2C: In October of 2015, we collected 100 berries from 20 western juniper trees at each of two field sites in North Eastern California, where this native tree species has been encroaching on sagebrush rangelands. We repeated sampling at these sites in March, 2016, but from only 10 trees per site. All berries were kept 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 37 insect species and one mite species that occur in western juniper berries, at least 8 of which cause damage to seeds and render them inviable. Because we cannot identify larvae morphologically, we are currently matching 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. It may also be possible to mass rear some insects that limit western juniper seed production for inundative biological control treatments in areas where juniper is expanding. Additionally under subobjective 2C, we refined the telemetry in the Porter Canyon Experimental Watershed (PCEW)(Agreements #2060-22000-024-01I and #2060-22000-024-02A). In collaboration with University Nevada, Reno, we obtained an outside grant that obtained Light Detection and Ranging (LIDAR) imagery for the entire watershed in July of 2015, this imagery will allow us to upscale transpiration from individual trees to the entire watershed. We have run algorithms on the point cluster data from the LIDAR imagery to spatially map the distribution of tree canopy coverage and shrubs and use these cover estimate to scale up tree transpiration to the landscape-scale. We are in the process of field ground truthing these estimates with sub-meter Global Positioning System (GPS) surveys of individual tree crowns. This will allow us to create a model of Effective Precipitation and Interception based Canopy Coverage (EPICC model). We completed an integrated groundwater and surface water model (GS-FLOW) for the entire watershed in collaboration with Desert Research Institute, and submitted a manuscript on this work. The Vice President of Research for the University of Nevada, Reno, identified Porter Canyon Experimental Watershed as a research site to put in a research pre-proposal for a National Science Foundation Long-Term Ecological Research program. In collaboration with University of Nevada, Reno, a Nevada scientist wrote a successful pre-proposal. The full proposal was submitted on August 2nd. This involved participation with nine other University and Desert Research Institute scientists.
1. Seed dispersal of two juniper species. An ARS scientist from Reno, Nevada, collaborated with a student studying for their Masters of Science degree at the University of Nevada, Reno, to study animal dispersal of seeds of two juniper species that are expanding on western rangelands. Despite being closely related, the dispersal systems of western and Utah juniper differ considerably. Western juniper berries are eaten by fruit-eating birds, and the seeds inside are defecated. Seed-eating rodents then harvest the seeds defecated by birds and cache them, where some seeds remain to germinate and establish new seedlings. Dispersal of Utah juniper seeds omits the first step in this strategy, as the berries are unattractive to fruit-eating birds. Instead, berries are harvested directly by rodents, which remove the hardened berry pulp and cache the seeds. Although the dispersal systems differ, they both ultimately end with seed-eating rodents caching them which has important implications for managing juniper in areas where it is encroaching on shrub-lands or grasslands.
2. Foreign exploration for biological control agents. An ARS scientist from Reno, Nevada, discovered one eriophyid mite from medusahead in Italy was subsequently found in Serbia. Bulgaria is currently under taxonomic description as a new species. Medusahead is an invasive annual grass that is a noxious weed on rangelands across the western United States. As a new species, this mite is a particularly promising candidate as a biological control agent, as it has been collected from areas where large acreages of wheat are grown. Wheat is among the closest relatives of medusahead. The fact that this species has never been described before indicates that it has never been collected from wheat and therefore does not potentially pose a risk to that important cereal crop. Host-range testing will determine the mite’s overall suitability as a biocontrol agent for medusahead.
3. Post-fire drill seeding effects on plants. Post-fire rehabilitation efforts in the Great Basin focus on reestablishing desirable vegetation and suppressing invasive annual grasses. Drill seeding is commonly used to seed native plants. Currently, most agency offices use the conventional rangeland drill although there is interest in using minimum-till drills, which may have lower impact on soils and greater effectiveness in establishing certain plants. ARS researchers in Reno, Nevada, found that the conventional drill was most successful in establishing large-seeded species and suppressing invasives, while the minimum-till drill was most successful in establishing small-seeded species. The results indicate that seeding techniques may vary in establishing native plant communities. Considering many forb and shrub species are small-seeded and important for sage-grouse habitat and forage, the results are informative on how to adjust current practices in post-fire rehabilitation.
ARS scientists in Reno, Nevada, continue to conduct research on tribal lands where saltcedar is a problematic invasive species. This research examined the effects of biological control on saltcedar mortality, rehabilitation of saltcedar infested ecosystems, and small mammal populations. This knowledge addresses tribal concerns regarding rehabilitation of degraded riparian ecosystems.
Huntington, J.L., Mcgwire, K., Morton, C., Snyder, K.A., Peterson, S., Erickson, T., Niswonger, R., Carroll, R., Smith, G., Allen, R. 2016. Assessing the role of climate and resource management on groundwater dependent ecosystem changes in arid environments with the landsat archive. Remote Sensing of Environment. doi: 10.1016/j.rse.2016.07.004.
Kuczynski, L., Rector, B.G., Kiedtowicz, A., Lewandowski, M., Szydio, W., Skoracka, A. 2016. Thermal niches of two invasive genotypes of the wheat curl mite Aceria tosichella (Acari: Eriophyidae): congruence between physiological and geographical distribution data. PLoS One. 11(4):e0154600.
Smith, A.M., Talhelm, A.F., Kolden, C.A., Newingham, B.A., Kremens, R.L., Adams, H.D., Cohen, J.D., Yedinak, K.M. 2016. The ability of winter grazing to reduce wildfire size, intensity, and fire-induced plant mortality was not demonstrated: a comment on Davies et al. (2015). International Journal of Wildland Fire. doi: 10.1071/WF15163
Longland, W.S., Dimitri, L.A. 2016. Are western juniper seeds dispersed through diplochory? Northwest Science. 90(2):235-244.
Kiedrowicz, A., Rector, B.G., Zawierucha, K., Szydlo, W., Skoracka, A. 2016. First plant-parasitic mites (acari: eriophyoidea) recorded from Svalbard, including the description of a new species. Polar Biology. 39(8):1359-1368. doi: 10.1007/s00300-015-1858-x.
Rector, B.G., Wang, S., Choi, Y., Thines, M. 2016. First report of albugo lepidi causing white rust on broadleaved pepperweed (lepidium latifolium) in Nevada and California. Plant Disease. 100:229.