Cheatgrass Cover Research Articles

Crested Wheatgrass Control and Native Plant Establishment in Utah

Effective control methods need to be developed to reduce crested wheatgrass (Agropyron cristatum [L.] Gaertner) monocultures and promote the establishment of native species. This research was designed to determine effective ways to reduce crested wheatgrass and establish native species while minimizing weed invasion. We mechanically (single- or double-pass disking) and chemically (1.1 L · ha−1 or 3.2 L · ha−1 glyphosate–Roundup Original Max) treated two crested wheatgrass sites in northern Utah followed by seeding native species in 2005 and 2006. The study was conducted at each site as a randomized block split plot design with five blocks. Following wheatgrass-reduction treatments, plots were divided into 0.2-ha subplots that were either unseeded or seeded with native plant species using a Truax Rough Rider rangeland drill. Double-pass disking in 2005 best initially controlled wheatgrass and decreased cover from 14% to 6% at Lookout Pass and from 14% to 4% at Skull Valley in 2006. However, crested wheatgrass recovered to similar cover percentages as untreated plots 2–3 yr after wheatgrass-reduction treatments. At the Skull Valley site, cheatgrass cover decreased by 14% on herbicide-treated plots compared to an increase of 33% on mechanical-treated plots. Cheatgrass cover was also similar on undisturbed and treated plots 2 yr and 3 yr after wheatgrass-reduction treatments, indicating that wheatgrass recovery minimized any increases in weed dominance as a result of disturbance. Native grasses had high emergence after seeding, but lack of survival was associated with short periods of soil moisture availability in spring 2007. Effective wheatgrass control may require secondary treatments to reduce the seed bank and open stands to dominance by seeded native species. Manipulation of crested wheatgrass stands to restore native species carries the risk of weed invasion if secondary treatments effectively control the wheatgrass and native species have limited survival due to drought. Se necesitan desarrollar métodos eficaces de control para reducir los monocultivos del triguillo crestado (Agropyron cristatum [L.] Gaertner) y promover el establecimiento de especies nativas. Esta investigación se diseñó para determinar formas efectivas de reducir el triguillo crestado y establecer especies nativas y a la vez minimizar la invasión de malezas. Dos sitios de triguillo crestado al norte de Utah se trataron mecánicamente (pasando un disco un ves o dos veces) y químicamente (1.1 L · ha−1 o 3.2 L · ha−1 de glyphosate–Roundup Original Max) seguida por la siembra de especies nativas en 2005 y 2006. El estudio se hizo en cada sitio como un diseño de bloques al azar con parcelas divididas con cinco bloques. Después de los tratamientos de la reducción del triguillo crestado, las parcelas se dividieron en sub-parcelas de 0.2 ha que fueron sembradas o no sembradas con especies nativas utilizando una sembradora para pastizales Truax Rough Rider. El pasar dos veces los discos en 2005 controló el triguillo crestado mejor inicialmente y disminuyó la cubierta del 14% a 6% at Lookout Pass y de 14% a 4% at Skull Valley en 2006. Sin embargo, el triguillo crestado volvió a a los porcentajes de cobertura similar a las parcelas sin tratar 2 a 3 años después de los tratamientos de reducción del triguillo. En el sitio de Skull Valley, la cobertura del bromillo disminuyó de 14% en las parcelas tratadas con herbicidas comparadas con las parcelas tratadas mecánicamente que se incrementaron un 33%. La cobertura del bromillo fue también similar en las parcelas sin disturbio y las parcelas tratadas 2 años y 3 años después de los tratamientos de reducción indicando que la recuperación del triguillo crestado minimiza cualquier incremento en el dominio de las malezas como resultado del disturbio. Los pastos nativos presentaron una alta aparición después de la siembra, pero la falta de sobrevivencia fue asociada con los periodos cortos de humedad disponible en el suelo durante la primavera del 2007. El control efectivo del triguillo crestado quizá requiera de tratamientos secundarios para reducir el banco de semillas y favorecer el dominio de las especies nativas sembradas. La manipulación de las áreas para restaurar las especies nativas lleva el riesgo de la invasión de malezas si los tratamientos secundarios controlan efectivamente el triguillo crestado y las especies nativas tienen limitada sobrevivencia debido a la sequía.

Spatial Predictions of Cover Attributes of Rangeland Ecosystems Using Regression Kriging and Remote Sensing

Abstract Sound rangeland management requires accurate information on rangeland condition over large landscapes. A commonly applied approach to making spatial predictions of attributes related to rangeland condition (e.g., shrub or bare ground cover) from remote sensing is via regression between field and remotely sensed data. This has worked well in some situations but has limited utility when correlations between field and image data are low and it does not take advantage of all information contained in the field data. I compared spatial predictions from generalized least-squares (GLS) regression to a geostatistical interpolator, regression kriging (RK), for three rangeland attributes (percent cover of shrubs, bare ground, and cheatgrass [ Bromus tectorum L.]) in a southern Idaho study area. The RK technique combines GLS regression with spatial interpolation of the residuals to improve predictions of rangeland condition attributes over large landscapes. I employed a remote-sensing technique, object-based image analysis (OBIA), to segment Landsat 5 Thematic Mapper images into polygons (i.e., objects) because previous research has shown that OBIA yields higher image-to-field data correlations and can be used to select appropriate scales for analysis. Spatial dependence, the decrease in autocorrelation with increasing distance, was strongest for percent shrub cover (samples autocorrelated up to a distance [i.e., range] of 19 098 m) but present in all three variables (range of 12 646 m and 768 m for bare ground and cheatgrass cover, respectively). As a result, RK produced more accurate results than GLS regression alone for all three attributes when predicted versus observed values of each attribute were measured by leave-one-out cross validation. The results of RK could be used in assessments of rangeland conditions over large landscapes. The ability to create maps quantifying how prediction confidence changes with distance from field samples is a significant benefit of regression kriging and makes this approach suitable for landscape-level management planning.

Comparing Locally Derived and LANDFIRE Geo-Layers in the Great Basin, USA

Locally derived maps of pre-European settlement vegetation patterns (Biophysical Setting-BpS) and Fire Regime Condition Class (FRCC) were compared to concomitant products from LANDFIRE for the Wassuk Range in western Nevada, USA. While Biophysical Settings between the two sources matched approximately half of the time, only 2.5 % of the area matched both FRCC and BpS simultaneously. The poor FRCC performance is largely due to undetected and extensive cheatgrass (Bromus tectorum L.) cover, overestimation of perennial native grass in extensive shrublands, and mapping confusion between true pinyon-juniper woodlands and areas where trees have encroached into native shrublands. LANDFIRE National products should be useful to resource-limited managers where sufficient training plots were available to the project, but we include practical guidance for using LANDFIRE spatial products in areas where the LANDFIRE project had insufficient ground plot information.

Fuels Management at the Landscape Scale

important factor affecting burn severity. Grazing effects increased in grassland systems and decreased as shrub cover increased. While post-fi re determinations of grazing impacts were diffi cult at best, additional large-scale research on grazing/fi re behavior is needed. “Managing the Invasive Fine Fuels at the Landscape Scale” was presented by Ronald Clementsen, BLM, who reported on the Mojave Desert Initiative (MDI). The MDI was established as a forum for government agencies (BLM, National Park Service [NPS], US Fish and Wildlife Service [USFWS], Department of Defense, Nevada Department of Wildlife, Utah Department of Wildlife Resources, and Arizona Game and Fish Department) and other partners to collaboratively address wildfi re and invasive species issues within a defi ned eco-region of the northeastern Mojave Desert in Arizona, Nevada, and Utah. Their goals are to 1) protect remaining unburned Mojave Desert vegetation and reduce reburning; 2) restore strategically located islands, key habitat areas, and corridors; 3) improve communication, collaboration, and coordination; and 4) maximize leveraged funding. They developed regional priorities and guidance for incident commanders to minimize or avoid further habitat loss to fi re. They also completed regional assessment to identify priority work areas and to develop project selection criteria. High-density, unburned desert tortoise critical habitat is their fi rst priority for protection and restoration. It is followed by unburned critical habitat for all listed species (not included in priority one) within BLM National Conservation Areas, BLM and NPS monuments, NPS recreation areas, and USFWS refuges. They will identify, prioritize, and develop potential projects across the MDIdefi ned–eco-region, including fuel breaks, green-strips, seedings, plantings, applications of preemergent herbicide, etc. Robin Tausch, US Forest Service (USFS) Rocky Mountain Research Station, addressed “Fuels Management Strategies for Woody Natives to Avoid Promoting Invasive Species.” Using data from research projects in Nevada, Utah, Idaho, and Oregon, Robin showed the remarkable increase in the area, cover, size, and density of pinyon pine and juniper. These trees are changing plant communities in many areas of the western United States. Once established, Introductory Focus by Featured Speakers Workshop IV was moderated by Brad Washa, Bureau of Land Management (BLM). Jason Davison of the University of Nevada Cooperative Extension spoke about a “Case Study of the Murphy Complex Fire.” A team of scientists and managers1 had been charged to 1) provide preliminary observations and recommendations on how plant communities and livestock grazing affected fi re behavior, 2) recommend long-term research or studies needed to address issues regarding the use of livestock to reduce fuels while maintaining post-fi re resource values, and 3) discuss the potential application of the fi ndings from the Murphy Complex wildfi res in Idaho and Nevada to other locations. After identifying many areas with high discontinuity and contrast, the team evaluated each area using 10 factors: 1) actual use by livestock, 2) distance from water, 3) anomaly performance (related to pasture actual grazing pressures in grassland areas), 4) fi re history, 5) location of seedings, 6) vegetation type, 7) shrub cover, 8) cheatgrass cover, 9) prefi re plant biomass, and 10) fi re behavior/suppression. They ranked burn severity factors across all focus areas and across grass-dominated areas. Vegetation (fuel loads) was the most

Herbaceous Succession After Burning of Cut Western Juniper Trees

The expansion of western juniper (Juniperus occidentals spp. occidentalis Hook.) in the northern Great Basin has resulted in the wide-scale conversion of sagebrush-steppe communities to juniper woodlands. Prescribed fire and mechanical cutting are the 2 main methods used to remove juniper and restore sagebrush steppe. Mechanical treatments commonly leave cut juniper on site. Disadvantages of leaving cut juniper are the increased fuel hazard and the potential for increased establishment and growth of invasive species. This study evaluated the response of herbaceous plants to winter burning of cut western juniper. Vegetation response was compared among 2 burning treatments (burning trees the first winter after cutting and burning the second winter after cutting), a control (cut-unburned juniper), and the interspace between cut trees. To minimize fire impacts to herbaceous perennials, cut trees were burned in the winter when soils and ground litter were frozen and/or soils were at field capacity. Only felled trees were burned, as fire did not carry into interspaces or litter mats around western juniper stumps. We hypothesized that winter season burning would increase herbaceous perennials and would reduce cheatgrass establishment when compared to the cut-unburned control. After 10 years, total herbaceous and perennial grass cover was 1.5- to 2-fold greater, respectively, in burned treatments compared to cut-unburned controls. Perennial grass density was 60% greater in the burned treatments than in the cut-unburned treatment and the interspace. Cheatgrass cover was twice as great in the control than in the 2 burn treatments and the interspace. We concluded that burning cut western juniper when soils were wet and frozen in winter enhanced community recovery of native perennials compared to leaving cut juniper unburned.

Cheatgrass Encroachment on a Ponderosa Pine Forest Ecological Restoration Project in Northern Arizona

Land managers frequently thin small-diameter trees and apply prescribed fire to reduce fuel loads and restore ecosystem structure, function, and process in forested areas. There is increasing concern that disturbances associated with these management practices can facilitate non-native plant invasions. Cheatgrass (Bromus tectorum), an annual grass from the Mediterranean, has invaded large areas of the interior West and has become the dominant species in many of these areas. In 2003, a ponderosa pine (Pinus ponderosa) ecological restoration site on Mount Trumbull in the Uinkaret Mountains of northern Arizona experienced a large increase in cheatgrass. Thinning and burning projects had been conducted on this site since 1996. Cheatgrass cover increased 90-fold on the thinned and burned plots between 1996 and 2003. While cheatgrass also increased on thinned plots that were not burned and the untreated control plots, the cover of cheatgrass remained low. There were two additional factors that may have influenced the cheatgrass invasion. In 2002, the region experienced the most extreme drought recorded in the past 100 years. Substantial rainfall returned to the area in September 2002, coincident with the timing of cheatgrass germination. Additionally, cattle were reintroduced to the study area in August 2002 after a four-year hiatus in grazing. We present data suggesting that the interaction of prescribed fire and small-diameter tree thinning, potentially exacerbated by cattle grazing and drought, was the primary cause of the spread of cheatgrass. Furthermore, we offer management recommendations for reducing the risk of non-native plant invasion on ecological restoration projects.

Environmental and climatic variables as potential drivers of post-fire cover of cheatgrass (Bromus tectorum) in seeded and unseeded semiarid ecosystems

Cheatgrass, a non-native annual grass, dominates millions of hectares in semiarid ecosystems of the Intermountain West (USA). Post-fire invasions can reduce native species diversity and alter ecological processes. To curb cheatgrass invasion, land managers often seed recently burned areas with perennial competitor species. We sampled vegetation within burned (1–9 years post-fire) and nearby unburned (representing pre-fire) piñon–juniper (Pinus edulis–Juniperus osteosperma) woodland and sagebrush (Artemisia sp.) in western Colorado to analyze variables that might explain cheatgrass cover after fire. A multiple regression model suggests higher cheatgrass cover after fire with: (1) sagebrush v. piñon–juniper; (2) higher pre-fire cover of annual forbs; (3) increased time since fire; (4) lower pre-fire cover of biological soil crust; and (5) lower precipitation the year before fire. Time since fire, which coincided with higher precipitation, accounts for most of the variability in cheatgrass cover. No significant difference was found in mean cheatgrass cover between seeded and unseeded plots over time. However, negative relationships with pre-fire biological soil crust cover and native species richness suggest livestock-degraded areas are more susceptible to post-fire invasion. Proactive strategies for combating cheatgrass should include finding effective native competitors and restoring livestock-degraded areas.

Initial Invasion of Cheatgrass (Bromus tectorum) into Burned Piñon-Juniper Woodlands in Western Colorado

We studied initial invasion of cheatgrass (Bromus tectorum) into burned pinon-juniper woodlands to determine: (1) if particular features enhance invasion and (2) if particular grasses promote or retard invasion. We compared cheatgrass cover among roads, burn edges, seeded interiors, unseeded interiors and unburned woodlands and quantified grasses present or absent near cheatgrass. Invasion was favored by burn edges, roads and seeded interiors, but not unseeded interiors. Odds of finding cheatgrass were seven times higher near prairie junegrass (Koeleria macrantha), but six times lower near James' galleta (Hilaria jamesii) and two times lower near intermediate wheatgrass (Agropyron intermedium). Invasion may be favored: (1) in burn edges because of higher seed-bank survival, (2) along roads because of moisture, disturbance and dispersal and (3) in seeded interiors because of seed-mix contamination or seeded species that enhance invasion.

Relationships Between Western Juniper (Juniperus occidentalis) and Understory Vegetation

AbstractWestern juniper has been actively invading sagebrush plant communities for about 130 yr. Western juniper canopy cover generally increases as western juniper invades sagebrush steppe communities and succession progresses toward a western juniper woodland. Our goal was to estimate the impact of juniper invasion and canopy increase on understory vegetation structure and productivity on 101 sites in northeastern California. The primary objectives of this study were to: (1) examine the influence of increasing western juniper canopy cover on the composition and productivity of understory vegetation; and (2) assess the effects of western juniper removal on understory vegetation. Sites in early, mid-, and late successional stages and sites on the same soils that had not been invaded were selected. Sites where western juniper had been removed by prescribed fire, mechanical, or chemical methods were compared to adjacent untreated sites. Western juniper canopy cover, understory cover and species composition, productivity, and bare ground were determined at each site during May through July 2005 and 2006. Regression analysis was used to evaluate the relationship between western juniper canopy cover and understory vegetation parameters. Logistic regression was used to detect understory differences between treated (juniper removed) and untreated (juniper not removed) sites. A significant relationship was found between western juniper canopy cover and understory species richness, shrub cover, forb cover, total grass cover, cheatgrass cover, herbaceous productivity, and bare ground. Removal of western juniper increased total grass cover, cheatgrass cover, and productivity, and reduced bare ground. The results of this study support findings by researchers in other states that western juniper influences plant community structure and productivity, and removal of western juniper might reverse these changes in structure, but also might increase opportunities for invasion of cheatgrass.

DESERT HORNED LIZARD (PHRYNOSOMA PLATYRHINOS) LOCOMOTOR PERFORMANCE: THE INFLUENCE OF CHEATGRASS (BROMUS TECTORUM)

Abstract Vegetation plays a critical role in lizard activities such as thermoregulation. Less understood is the influence of vegetation structure on lizard mobility. This study examined the influence of cheatgrass (Bromus tectorum) patches on: 1) distribution patterns of the desert horned lizard (Phrynosoma platyrhinos) using transect surveys along an elevational gradient, and 2) sprint performance of adult and juvenile P. platyrhinos using raceways established under field conditions. There was a significant negative association between cheatgrass cover and lizard scat abundance across the study gradient, suggesting horned lizards might avoid areas with higher cheatgrass cover. Adult and juvenile sprint performance were reduced on grass raceways by 50 to 70% of their bare-substrate speeds; adult speeds decreased from 0.93 m/s on bare substrate to 0.26 m/s on grass, and juvenile speeds decreased from 0.41 to 0.11 m/s. The findings were consistent based on 2 independent measures of velocity (burst and susta...

Iterative Model Development for Natural Resource Managers: A Case Example in Utah's Grand Staircase-Escalante National Monument

Non-native plant species, which threaten native plant diversity, are a major concern to managers of Grand Staircase-Escalante National Monument in Utah. Predictive spatial maps with Inverse Distance Weighting provided an effective way to identify “hot spots” of occurrence for three cover types of interest: native species richness, cryptobiotic soil crust cover (lichen, moss, algae, and bacteria), and cover of non-native cheatgrass (Bromus tectorum). Maps based on regression tree analysis showed that B. tectorum was found throughout the Monument with cover usually <0.1%, but has heavily invaded mesic sites and areas of disturbance, (cover ranging from 3.4 to 17.8 %). The analysis also showed that B. tectorum cover could be predicted by positive correlations with percent soil nitrogen and phosphorous (ppm). We also found a significant inverse relationship between high native plant species cover and cryptobiotic soil crust cover. These methods provide managers with an effective way to concentrate mitigation and conservation programs.