A Fine-Scale Understanding of Sagebrush Islands to Improve Restoration Outcomes in the Intermountain West

In the Intermountain West, rapid expansion of non-native grasses, primarily cheatgrass, has created a repeating cycle where cheatgrass easily ignites and after a fire, more cheatgrass establishes in the burned area, leading to more fire, and more cheatgrass. The primary method to prevent further fires is to plant grass and shrub seeds after a fire because they can deter cheatgrass from establishing and reduce the chance of fire. However, this approach does not always work. There is a need and interest in alternative ways to establish native grasses and forbs. Sagebrush, the dominant shrub of lower-elevation regions of the Intermountain West, may act as a nurse plant: a plant that alters the environment around itself in a way that is beneficial to other plants. Capitalizing on the attributes that make sagebrush nurse plants, like shade and higher soil moisture, may help the establishment of grasses and forbs before a fire occurs, increasing the likelihood that cheatgrass will not dominate that system. While the area around nurse plants generally is thought of as a favorable place for grasses and forbs to grow, that may not always be the case. There may be minimal differences in the microenvironment between the canopy and interspace and there can be competition under the canopy between newly established plants and other vegetation that is already present. I found that the sagebrush canopy influenced the survival of two native wildflower species, Munro’s globemallow and common yarrow, when they were transplanted as seedlings, but survival of two native transplanted grass species, bluebunch wheatgrass and squirreltail, was unaffected by the sagebrush canopy. However, when those same grasses were planted as seeds, if the seeds emerged, their emergence was highest near the canopy. Some of the attributes that make the canopy a “good” place for grasses and wildflowers to grow extend into the interspace, making the interspace potentially similarly “good.” I found that bluebunch wheatgrass and globemallow were shade tolerant and grew in ways that may allow them to be competitive under the canopy and persist in the interspaces, outside of what is generally considered a “good” nurse shrub microenvironment

Restoring North America’s Sagebrush Steppe Ecosystem Using Seed Enhancement Technologies

Rangelands occupy over a third of global land area, and in many cases are in less than optimum condition as a result of past land use, catastrophic wildfire and other disturbance, invasive species, or climate change. Often the only means of restoring these lands involves seeding desirable species, yet there are few cost effective seeding technologies, especially for the more arid rangeland types. The inability to consistently establish desired plants from seed may indicate that the seeding technologies being used are not successful in addressing the primary sources of mortality in the progression from seed to established plant. Seed enhancement technologies allow for the physical manipulation and application of materials to the seed that can enhance germination, emergence, and/or early seedling growth. In this article we examine some of the major limiting factors impairing seedling establishment in North America’s native sagebrush steppe ecosystem, and demonstrate how seed enhancement technologies can be employed to overcome these restoration barriers. We discuss specific technologies for: (1) increasing soil water availability; (2) enhancing seedling emergence in crusting soil; (3) controlling the timing of seed germination; (4) improving plantability and emergence of small seeded species; (5) enhancing seed coverage of broadcasted seeds; and (6) improving selectivity of pre-emergent herbicide. Concepts and technologies in this paper for restoring the sagebrush steppe ecosystem may apply generally to semi-arid and arid rangelands around the globe

Problem Analysis for the Vegetation Diversity Project

Management of the majority of public rangeland in the Great Basin and Columbia-Snake River Plateau falls under the authority of the Bureau of Land Management. The flora of this land ranges from highly diverse native plant communities to deteriorated lands dominated by exotic annuals. Approximately nine percent of the BLM’s 78 million acres of public land in this region is degraded to such a degree that changes in land management alone will not result in significant improvement. The BLM intends to restore native plant communities on these deteriorated lands, but current revegetation techniques used to establish introduced perennial grasses are often unsuccessful in establishing native plants. On lands where native communities exist, the BLM desires to maintain and to enhance native plant diversity. Encroachment of highly competitive exotic forbs and annual grasses in native plant communities raises concern among managers over the appropriate management to maintain native communities. Coupled with these concerns are impacts on vegetation of the documented increase in CO, and of predicted global climate change. The BLM therefore recognizes the need for research to understand and solve these problems and for the results of this research to be transferred to land managers. The Great Basin and Columbia Plateau region consists of two major ecosystems: the sagebrush ecosystem, generally located in the northern half of the region; and the salt-desert shrub ecosystem, located in the southern half. These ecosystems differ greatly in their composition of plant species and in their climatic and soil conditions. Therefore, techniques developed in one ecosystem may not be directly transferred to the other ecosystem. We propose to initially concentrate studies in the Wyoming big sagebrush communities of the sagebrush ecosystem, because: (1) these communities represent a large amount of the BLM lands in Oregon, Idaho, northeastern California, Nevada and Utah; and (2) the low precipitation within these communities limits the success of standard revegetation methods. Shadscale communities of the salt-desert shrub ecosystem were given the next priority for study. These communities are a major component in four of the five participating states. Since the shadscale communities differ greatly from sagebrush communities, studies of shadscale communities will be initiated when the project reaches full funding. Similar studies to those proposed here for sagebrush communities would be conducted on this new suite of species and environmental conditions. Low sagebrush communities would be given the lowest priority and are unlikely to be initiated. Plant associations in low sagebrush and Wyoming sagebrush communities are similar and thus promising techniques for the Wyoming sagebrush communities may work well in low sagebrush communities and may be attempted later in the project

Use of Auto-Germ to Model Germination Timing in the Sagebrush-Steppe

Germination timing has a strong influence on direct seeding efforts, and therefore is a closely tracked demographic stage in a wide variety of wildland and agricultural settings. Predictive seed germination models, based on soil moisture and temperature data in the seed zone are an efficient method of estimating germination timing. We utilized Visual Basic for Applications (VBA) to create Auto‐Germ, which is an Excel workbook that allows a user to estimate field germination timing based on wet‐thermal accumulation models and field temperature and soil moisture data. To demonstrate the capabilities of Auto‐Germ, we calculated various germination indices and modeled germination timing for 11 different species, across 6 years, and 10 Artemisia‐steppe sites in the Great Basin of North America to identify the planting date required for 50% or more of the simulated population to germinate in spring (1 March or later), which is when conditions are predicted to be more conducive for plant establishment. Both between and within the species, germination models indicated that there was high temporal and spatial variability in the planting date required for spring germination to occur. However, some general trends were identified, with species falling roughly into three categories, where seeds could be planted on average in either fall (Artemisia tridentata ssp. wyomingensis and Leymus cinereus), early winter (Festuca idahoensis, Poa secunda, Elymus lanceolatus, Elymus elymoides, and Linum lewisii), or mid‐winter (Achillea millefolium, Elymus wawawaiensis, and Pseudoroegneria spicata) and still not run the risk of germination during winter. These predictions made through Auto‐Germ demonstrate that fall may not be an optimal time period for sowing seeds for most non‐dormant species if the desired goal is to have seeds germinate in spring

Downy brome (Bromus tectorum) and Japanese brome (Bromus japonicus) biology, ecology, and management: literature review

Date inferred from file name.Includes bibliographical references

Directing ecological succession : the role of competition in restoring semi-arid grasslands dominated by invasive plants

Successful ecosystem restoration requires an understanding of the ecological processes directing succession. One of the challenges in the semi-arid grasslands of western United States is replacement of native species by invasive annual grasses. Solutions to this problem require identifying and manipulating ecological processes that direct succession to favor desired vegetation. The overall objective of this research was to identify and understand processes or factors directing restoration of semi-arid grassland ecosystems dominated with invasive annual grasses. Two invasive annual (Bromus tectorum L. and Taeniatherum caput-medusae L. Nevski) and two native perennial (Pseudoroegneria spicata (Pursh) A) and Poa secunda J. Presl) grass species were used to provide a model system of semi-arid grasslands of western United States. Plant competition is considered to be the primary ecological process limiting the success of grassland restoration. Successful restoration requires knowing the relative strength and magnitude of competition during the early stages of plant growth and how this might be impacted by nitrogen (N) availability. My research involved three experiments designed to compare competition and growth rates of native and invasive species. First, in order to understand the degree to which intra- versus inter-specific competition controls invasive and native plant growth during the early phase of establishment, I performed a diallel competition experiment with species grown either alone or in 1:1 binary combinations in a greenhouse. I hypothesized that the type and intensity of competition for invasive and native species would vary among harvest times and competitive intensity for invasive species will be higher than native species with higher N availability. My results indicated that invasive and native species are subject to both intra- and inter-specific competition; however, the dominant type differed among harvests. Invasive species also became more competitive than native species with increasing N. I suggest that opportunities to improve restoration success exist by determining the optimum combination of density, species proportion, and their spatial arrangement in various ecosystems and environments. Second, I performed an addition series competition experiment in the field for two years to determine the intensity and importance of competition in an arid, resource poor production system. My results indicated that in resource poor environments, the intensity of competition did not significantly influence plant dominance during the first two years of plant establishment, and thus, competition was not important. I suggest that land managers may be most successful at restoration of resource poor ecosystems by overcoming the barriers associated with plant establishment other than plant-plant interactions, such as abiotic factors. Third, I studied growth rate and growth patterns of medusahead with bluebunch wheatgrass and cheatgrass in the field for two years. I hypothesized that medusahead would have a higher RGR, a longer period of growth, and as a consequence, more total biomass at the end of the growing season than bluebunch wheatgrass and cheatgrass. Medusahead had a longer period of growth, more total biomass and higher RGR than cheatgrass. However, bluebunch wheatgrass had more biomass and higher RGR than medusahead in 2008, but the relationship was reversed in 2009. Weather data identified that precipitation in 2008 was well below average, and this level of drought was very infrequent. Collectively, my results suggest that the continued invasion and dominance of medusahead onto native and cheatgrass dominated grasslands will continue to increase in severity because of its higher RGR and extended period of growth. The inability to identify key ecological processes important in directing invasion and succession has limited the adoption and implementation of ecologically based invasive plant management (EBIPM). A framework that allows ecologist to identify and prioritize ecological processes most in need of repair would help overcome this barrier. I developed an initial framework that allows ecologists to prioritize the ecological processes that appear to play a dominate role in vegetation dynamics. This was accomplished by using sensitivity analysis to identify the most important transitions in the life cycle of associated species and linking those transitions with key ecological processes and their modifying factors. This method could increase land manager's ability to implement EBIPM by allowing identification and prioritization of those ecological processes that appear to play a dominating role in vegetation dynamics

Restoration of Annual Grass-invaded Landscapes in the Sagebrush Steppe using Perennial Grass Seed Technologies and Wyoming Big Sagebrush Transplanting

Within the sagebrush steppe ecosystem, invasive annual grasses are of growing management concern as they outcompete native vegetation, change the fundamental nutrient cycling processes, decrease biodiversity, and increase frequency of wildfires. The most widely used and effective management tool to decrease invasive annual grass abundance, is the use of pre-emergent herbicides like imazapic. Although this herbicide is effective at annual grass control, it can have negative effects on native or desired seedlings. Thus, land managers often wait a year or more to seed native vegetation following herbicide treatment. In that time, cheatgrass and other invasive annual grasses have the opportunity to re-establish, making the herbicide treatment ineffective. By seeding and herbicide-treating annual grasses simultaneously (i.e., a single-entry approach), land managers can save a year or more in restoration costs. However, the native or desired seed needs to be protected in some sort of coating to prevent negative herbicide effects. An herbicide protection coating containing activated carbon has shown to successfully protect desired seeds in the form of pellets, and pods. This thesis outlines a new method of coating individual native grass seed in an herbicide protection formula containing activated carbon to test its effectiveness in both greenhouse and field settings. In the greenhouse study, we used a randomized block factorial design to test the efficacy of activated carbon-based herbicide protection coatings applied to individual bluebunch wheatgrass (Pseudoroegneria spicata (Pursh) A. Love) seeds for protecting seedlings from injury associated with low and high rates of pre-emergent herbicide (imazapic) application. The emergence of coated seed averaged 57% ± 5% (mean ± SE) compared to bare seed which had 14% ± 10% emergence with herbicide application. Seedling height for coated seed averaged 7.56 ± 0.6 cm compared to 2.26 ± 0.4 cm in uncoated bare seed in the presence of herbicide. Coated seeds produced 87% more plant biomass than uncoated seeds. The field study, a randomized block factorial design, repeated in two years, however, had two consecutive low precipitation and high temperature years resulting in low emergence and low survival of bare and coated seeds. Further field studies with either an added irrigation treatment or in more favorable climate conditions are suggested to determine effectiveness of carbon-based seed coatings in protecting desired seedlings from herbicide damage. This thesis also discusses a method of restoring Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis (Beetle & A. Young) S.L. Welsh) following wildfire. Sagebrush transplants have a higher establishment rate than seeding in low to mid elevation sagebrush steppe sites, however, their success is widely variable. Chapter four of this thesis outlines how 1) different ages of transplant at time of planting, 2) different seasons of planting (fall and spring planting), and 3) competition with invasive annual grasses, affect the survival and vigor (measured by transplant volume) of sagebrush transplants over two years. This completely randomized factorial design, repeated over two years, used ten age classes of transplants at time of planting (6, 8, 10, 12, 14, 16, 18, 20, 22, and 24 weeks of age). Age classes 10 weeks and older in the first planting year and 12 weeks and older in the second planting year had the highest survival. Spring-planted transplants had higher survival than fall-planted transplants in both years; however, fall-planted transplants had increased vigor (measured by transplant volume) in both years. Competition did not affect survival of transplants in either year but it did affect volume of transplants. Volume was 54-fold greater when not competing with annual grasses compared to transplants competing with annual grasses in the first year, and nine-fold greater in the second year. Overall, the second year of the study had much lower sagebrush survival compared to the first year. Transplants are typically grown in a greenhouse for 6 months to a year before being planted in the field. This study demonstrated that reducing greenhouse growing time to 12 weeks compared to the traditional 24+ weeks, would cut greenhouse growing costs in half making this method of restoration more cost effective and a more favorable alternative to traditional restoration methods

Competition from Bromus tectorum removes differences between perennial grasses in N capture and conservation strategies

Background and aims Competition from the annual grass Bromus tectorum threatens aridland perennial bunchgrass communities. Unlike annuals, perennials must allocate part of their first year nitrogen (N) budget to storage rather than growth, potentially placing them at a competitive disadvantage. Methods We evaluated N acquisition and conservation for two perennial bunchgrasses, Agropyron desertorum and Pseudoroegneria spicata, at the seedling stage to investigate potential trade-offs between storage and growth when grown with and without B. tectorum under two levels of soil N. Results Agropyron desertorum had higher growth rates, N uptake, and N productivity than P. spicata when grown without B. tectorum, but trait values were similarly low for both species under competition. Without competition, N resorption was poor under high soil N, but it was equally proficient among species under competition. Conclusions A. desertorum had higher growth rates and N productivity than P. spicata without competition, suggesting these traits may in part promote its greater success in restoration programs. However, B. tectorum neighbors reduced its trait advantage. As plant traits become more integral to restoration ecology, understanding how N capture and conservation traits vary across candidate species and under competition may improve our ability to select species with the highest likelihood of establishing in arid, nutrient-limited systems

Final Technical Report: Integrated Restoration Strategies Towards Weed Control on Western Rangelands

Invasive species are having severe ecological (Mack et al. 2000) and economic (Pimentel et al. 2005) impacts on ecosystems around the world. Invasive species can alter many ecosystem processes (Crooks 2002, Walker & Smith 1997) including: water and nutrient availability, such as form and amount of N if the soil (Evans et al. 2001, Sperry et al. 2006); primary productivity, through shifts in growth rates or efficiency of resource use; disturbance regimes, including the type, frequency, and severity of disturbances such as fire (D’Antonio 2002); and community dynamics, such as species replacements (Alvarez & Cushman 2002). The economic losses and damages by invasive plants are estimated to be ~$34 billion in the US and ~$95 billion worldwide (Pimental et al. 2005). Although trade and human migrations are among the most important vectors for introducing invasive plants (Mack et al. 2000), similar consensus on the causal mechanism for invasiveness is lacking (Dietz & Edwards 2006). Many different hypotheses have been proposed to explain why species are invasive. Some hypotheses, such as the vacant niche hypothesis, are conceptually appealing but lack concrete evidence to support them (Mack et al. 2000). Others, such as the allelopathy hypothesis (Callaway & Aschehoug 2000, Bais et al. 2003), have strong evidence to support them for some specific cases, but are unlikely to be important for most plants. Understanding why a species is invasive is important because it provides insight into how to control the invasion. Because a causal mechanism that is universally applicable to all plants has not been identified to date, careful attention must be made to biological and ecological characteristics of the plants and communities of interest if control strategies are to be implemented

Role of propagule pressure and priority effects on plant establishment during restoration of invaded shrub-steppe

Biological plant invasions are diminishing the ecological integrity and function of ecosystems worldwide. A primary example of this is in the Great Basin of the United States, where invasive annual grasses, like cheatgrass (Bromus tectorum L.) and medusahead (Taeniatherum caput-medusae L. Nevski), are dominating many sagebrush-steppe ecosystems. In these invaded areas, restoration is fundamental to recovering plant community structure and function of once productive and diverse systems. Seeding is a management practice that accelerates revegetation of perennial plants in annual grass invaded ecosystems. However, seeding generally produces poor establishment and patchy plant communities that are quickly replaced by invaders. Identifying and overcoming the processes limiting desirable plant recovery should increase restoration success in annual grass invaded ecosystems. Seed dispersal dynamics, including propagule pressure and priority effects, strongly influence plant establishment and community assembly, especially during invasion and restoration because they can control recruitment of newly arriving species by influencing safe site occupation. The overall objective of this research was to identify the role of propagule pressure and priority effects on seedling emergence, plant life history, and plant community assembly. My study involved three experiments that were evaluated on seeded annual grass invaded sagebrush-steppe ecosystems in eastern Oregon. First, in order to identify the role of propagule pressure, or number of viable seeds in the seed bank, and annual grass dispersal timing, I conducted a factorially arranged experiment that tested the priority effects of seeding annual grasses in autumn or spring, adding water, and varying annual and perennial grass propagule pressure by seeding 150, 1,500, 2,500, or 3,500 seeds m⁻². My results suggested that providing perennial grasses a priority seeding effect by delaying annual grass seeding until spring initially facilitated perennial grass density; however, this effect did not persist into the second-year following seeding. In addition, when annual grass propagule pressure exceeded 150 seeds m⁻², an ecological threshold was crossed which limited perennial grass recruitment regardless of perennial grass seeding rate. When water availability was high, perennial grass establishment was high because safe site availability increased, but perennial grass establishment depended on annual grass propagule pressure. These results demonstrated that restoring perennial grasses to annual grass invaded ecosystems may be possible when perennial grass seeding rates and water availability are high. However, if annual grass propagule pressure exceeds 150 seeds m⁻², an ecological threshold occurs, where, perennial grass recruitment will be limited regardless of seeding strategy. A second factorial experiment was designed to identify the priority effects of perennial grass seeding time and frequency, annual and perennial grass propagule pressure, and water availability on seedling emergence and annual and perennial grass density and biomass two-years following seeding. In this experiment, my results indicated that seeding perennial grasses seasonally split between the autumn and spring produced higher perennial grass density and biomass compared to seeding perennial grasses exclusively in either period. In addition, results supported my hypothesis that perennial grass density and biomass in seasonally split applications would be higher where perennial propagule pressure was high and annual grass propagule pressure was low. However, I found that there was a threshold between 150-1,500 annual grass seeds m⁻², where regardless of perennial grass seeding strategies, perennial grass density and biomass was low. When water was added, annual and perennial grass density was higher than in plots without additional water, suggesting that higher water availability facilitates the growth of all seeded species. Collectively, these results suggested that modifying perennial grass seeding times and frequency increased perennial grass recruitment to annual grass invaded ecosystems, but only if annual grass propagule pressure was below 1,500 annual grass seeds m⁻². Third, a life history approach was used to identify and quantify the effect of ecological processes on plant population demography when annual grass seeding times varied (autumn or spring), annual and perennial grass propagule pressure was modified by 150, 1,500, 2,500, or 3,500 seeds m⁻², and watering occurred (ambient or water added treatments). In this study, we found that all species had low emergence rates, even though seedling germination was relatively high. Based on prior research, this suggests that freeze-thaw cycles, pathogen attack, and soil crusts may strongly inhibit plant growth from the germination to emergence growth stages. Alternatively, my finding that perennial grass germination rates were higher when they were seeded with annual grasses in autumn compared to delaying annual grass seeding until spring suggests that perennial grass germination is facilitated by neighboring annual grasses during this life history stage. Following seedling emergence, my data indicated that adding water enhances the establishment and growth of all species and that providing perennial grasses a priority seeding effect by delaying annual grass seeding until spring yields higher perennial grass density. However, delaying annual grass seeding until spring only provided perennial grasses a priority effect when annual grass propagule pressure was high. When annual grass propagule pressure was low, seeding perennial grasses in autumn yielded the highest perennial grass density through their life history suggesting low numbers of neighboring annual grasses facilitates the density of perennial grasses. By the second growing season, annual grass density was two-times higher than initial annual grass seeding rates and over four-times higher than perennial grass density, suggesting that annual grass interference may increase during the second growing season. Plant community assembly of restored shrub-steppe ecosystems degraded by annual grasses will likely be determined by the establishment of seeded species in the first growing season. Because perennial grasses are facilitated by annual grasses in the germination stage, and by small numbers of neighboring annual grasses in later growth stages, if perennial grasses establish in areas with low annual grass propagule pressure in the first growing season, they will likely persist to become adults. Alternatively, high annual grass propagule pressure limits perennial grass recruitment regardless of seeding strategy because of their preemptive occupation of safe sites and soil resources and high density by the second growing season