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Restoring degraded plant communities is a global challenge and a major priority for land managers and conservationists. Degraded Wyoming big sagebrush communities (Artemisia tridentata ssp. wyomingensis [Beetle & A. Young] S.L. Welsh) have high sagebrush cover with a depleted perennial herbaceous understory. They are widespread in western North America and are a priority for restoration because they provide habitat for sagebrush-associated species and an important forage base for livestock production. Mechanically reducing sagebrush with mowing has been attempted to restore the understory in these communities but often fails because large native perennial bunchgrasses do not increase and exotic annual grasses proliferate. Seeding large native perennial bunchgrasses after mowing sagebrush may increase their density or cover and thereby limit exotic annual grasses. Native perennial bunchgrasses are slow growing; thus, long-term studies are needed to evaluate this treatment strategy. We evaluated mowing followed by drill-seeding large native perennial bunchgrasses in southeastern Oregon for 11 yr post treatment. Large bunchgrass cover and density were approximately 2 × greater with mowing followed by seeding compared with the untreated control. However, mowing, with and without seeding, increased exotic annual grasses and decreased biological soil crusts. Sagebrush cover was less in mowed treatments compared with the untreated control, but sagebrush cover increased over time. Mowing and seeding native bunchgrasses was less successful than desired, particularly since exotic annual grasses increased substantially. This treatment may be improved by reducing the disturbance associated with mowing and drill seeding, decreasing exotic annual grass competition, and increasing the establishment of native perennial bunchgrasses. The results of our study indicate that seeding native bunchgrasses into degraded Wyoming big sagebrush communities has potential as a restoration treatment but needs refinement to improve success.

Restoration of non-sprouting shrubs after wildfire is increasingly becoming a management priority. In the western U.S., Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis Beetle & Young) restoration is a high priority, but sagebrush establishment from seed is sporadic. In contrast, planting seedlings often successfully restores sagebrush, but is expensive and time consuming. After planting, hence, there is a need to protect the investment from disturbances such as fire that will erase gains in sagebrush recovery. Grazing is likely the only tool that can be applied feasibly across the landscape to decrease wildfire probability, but there are concerns that grazing and associated activities (e.g. trampling) may negatively impact sagebrush seedlings. We investigated effects of grazing by cattle, applied as a fine fuel management strategy, on planted sagebrush seedlings at five blocks for five years. Grazing substantial reduced exotic annual grasses, large perennial bunchgrasses, and total herbaceous cover, thus achieving fuel management goals. Sagebrush cover and reproductive efforts were almost 2-fold greater in grazed compared to non-grazed areas in the final year of the study. This suggests that grazing favored sagebrush, a generally unpalatable shrub, recovery, likely by reducing competition from highly palatable herbaceous vegetation. Density of sagebrush, however, was similar between grazed and non-grazed areas. This research demonstrates that grazing can be strategically applied to reduce the probability of wildfire in areas with planted sagebrush seedlings; thereby, protecting the investment in sagebrush recovery. With more refinement, it also appears that grazing can be utilized to accelerate the recovery of sagebrush and potentially other woody vegetation habitat by modifying the competitive relationship between herbaceous and woody vegetation.

Post‐fire restoration of foundation plant species, particularly non‐sprouting shrubs, is critically needed in arid and semi‐arid rangeland, but is hampered by low success. Expensive and labor‐intensive methods, including planting seedlings, can improve restoration success. Prioritizing where these more intensive methods are applied may improve restoration efficiency. Shrubs in arid and semi‐arid environments can create resource islands under their canopies that may remain after fire. Seedlings planted post‐fire in former canopy and between canopies (interspace) may have different survival and growth. We compared planting Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis Beetle & Young) seedlings post‐fire in former sagebrush canopy and interspace microsites at five locations. Four growing seasons after planting, seedling survival was 46 and 7% in canopy and interspace microsites, respectively. Sagebrush cover was 5.8 times greater in canopy compared to interspace microsites. Sagebrush survival and cover were likely greater because of less competition from herbaceous vegetation as well as benefiting from resource island effects in canopy microsites. Initially, post‐fire abundance of exotic annual grasses was less in canopy microsites, but by the third year post‐fire it was substantially greater in canopy microsites, indicating that resource availability to seedlings was greater, at least initially, in canopy microsites. These results suggest microsites with greater likelihood of success should be identified and then utilized to improve restoration success and efficiency. This is important as the need for restoration greatly exceeds resources available for restoration.

Crested wheatgrass (Agropyron cristatum [L] Gaertm. and Agropyron desertorum [Fisch.] Schult.), an introduced bunchgrass, has been seeded on millions of hectares of sagebrush steppe. It can establish near-monocultures; therefore, reestablishing native vegetation in these communities is often a restoration goal. Efforts to restore native vegetation assemblages by controlling crested wheatgrass and seeding diverse species mixes have largely failed. Restoring sagebrush, largely through planting seedlings, has shown promise in short-term studies but has not been evaluated over longer timeframes. We investigated the reestablishment of Wyoming big sagebrush (Artemisia tridentata spp. wyomingensis [Beetle & A. Young] S.L. Welsh) in crested wheatgrass communities, where it had been broadcast seeded (seeded) or planted as seedlings (planted) across varying levels of crested wheatgrass control with a herbicide (glyphosate) for up to 9 yr post seeding/planting. Planting sagebrush seedlings in crested wheatgrass stands resulted in full recovery of sagebrush density and increasing sagebrush cover over time. Broadcast seeding failed to establish any sagebrush, except at the highest levels of crested wheatgrass control. Reducing crested wheatgrass did not influence density, cover, or size of sagebrush in the planted treatment, and therefore, crested wheatgrass control is probably unnecessary when using sagebrush seedlings. Herbaceous cover and density were generally less in the planted treatment, probably as a result of increased competition from sagebrush. This trade-off between sagebrush and herbaceous vegetation should be considered when developing plans for restoring sagebrush steppe. Our results suggest that planting sagebrush seedlings can increase the compositional and structural diversity in near-monocultures of crested wheatgrass and thereby improve habitat for sagebrush-associated wildlife. Planting native shrub seedlings may be a method to increase diversity in other monotypic stands of introduced grasses.

Woody vegetation has increased on rangelands worldwide for the past 100–200 years, often because of reduced fire frequency. However, there is a general aversion to reintroducing fire, and therefore, fire surrogates are often used in its place to reverse woody plant encroachment. Determining the conservation effectiveness of reintroducing fire compared with fire surrogates over different time scales is needed to improve conservation efforts. We evaluated the conservation effectiveness of reintroducing fire with a fire surrogate (cutting) applied over the last ~30 years to control juniper (Juniperus occidentalis Hook.) encroachment on 77 sagebrush‐steppe sites. Critical to conservation of this imperiled ecosystem is to limit juniper, not encourage exotic annual grasses, and promote sagebrush dominance of the overstory. Reintroducing fire was more effective than cutting at reducing juniper abundance and extending the period of time that juniper was not dominating the plant community. Sagebrush was reduced more with burning than cutting. Sagebrush, however, was predicted to be a substantial component of the overstory longer in burned than cut areas because of more effective juniper control. Variation in exotic annual grass cover was explained by environmental variables and perennial grass abundance, but not treatment, with annual grasses being problematic on hotter and drier sites with less perennial grass. This suggests that ecological memory varies along an environmental gradient. Reintroducing fire was more effective than cutting at conserving sagebrush‐steppe encroached by juniper over extended time frames; however, cutting was more effective for short‐term conservation. This suggests fire and fire surrogates both have critical roles in conservation of imperiled ecosystems.

Degradation of shrublands around the world from altered fire regimes, overutilization, and anthropogenic disturbance has resulted in a widespread need for shrub restoration. In western North America, reestablishment of mountain big sagebrush (Artemisia tridentata Nutt. ssp. vaseyana [Rydb.] Beetle) is needed to restore ecosystem services and function. Western juniper (Juniperus occidentalis ssp. occidentalis Hook) encroachment is a serious threat to mountain big sagebrush communities in the northern Great Basin and Columbia Plateau. Juniper trees can be controlled with fire; however, sagebrush recovery may be slow, especially if encroachment largely eliminated sagebrush before juniper control. Short-term studies have suggested that seeding mountain big sagebrush after juniper control may accelerate sagebrush recovery. Longer-term information is lacking on how sagebrush recovery progresses and if there are trade-offs with herbaceous vegetation. We compared seeding and not seeding mountain big sagebrush after juniper control (partial cutting followed with burning) in fully developed juniper woodlands (i.e., sagebrush had been largely excluded) at five sites, 7 and 8 yr after seeding. Sagebrush cover averaged ~ 30% in sagebrush seeded plots compared with ~ 1% in unseeded plots 8 yr after seeding, thus suggesting that sagebrush recovery may be slow without seeding after juniper control. Total herbaceous vegetation, perennial grass, and annual forb cover was less where sagebrush was seeded. Thus, there is a trade-off with herbaceous vegetation with seeding sagebrush. Our results suggest that seeding sagebrush after juniper control can accelerate the recovery of sagebrush habitat characteristics, which is important for sagebrush-associated wildlife. We suggest land manager and restoration practitioners consider seeding sagebrush and possibly other shrubs after controlling encroaching trees where residual shrubs are lacking after control.

Grazing by cattle is ubiquitous across the sagebrush steppe; however, little is known about its effects on sagebrush and native bunchgrass structure. Understanding the effects of long-term grazing on sagebrush and bunchgrass structure is important because sagebrush is a keystone species and bunchgrasses are the dominant herbaceous functional group in these communities. To investigate the effects of long-term grazing on sagebrush and bunchgrass structure, we compared nine grazing exclosures with nine adjacent rangelands that were grazed by cattle in southeast Oregon. Grazing was moderate utilization (30 − 45%) with altering season of use and infrequent rest. Long-term grazing by cattle altered some structural aspects of bunchgrasses and sagebrush. Ungrazed bunchgrasses had larger dead centers in their crowns, as well as greater dead fuel depths below and above the crown level compared with grazed bunchgrasses. This accumulation of dry fuel near the meristematic tissue may increase the probability of fire-induced mortality during a wildfire. Bunchgrasses in the ungrazed treatment had more reproductive stems than those in the long-term grazed treatment. This suggests that seed production of bunchgrasses may be greater in ungrazed areas. Sagebrush height and longest canopy diameter were 15% and 20% greater in the ungrazed compared with the grazed treatment, respectively. However, the bottom of the sagebrush canopy was closer to the ground in the grazed compared with the ungrazed treatment, which may provide better hiding cover for ground-nesting avian species. Sagebrush basal stem diameter, number of stems, amount of dead material in the canopy, canopy gap size, and number of canopy gaps did not differ between ungrazed and grazed treatments. Moderate grazing does not appear to alter the competitive relationship between a generally unpalatable shrub and palatable bunchgrasses. Long-term, moderate grazing appears to have minimal effects to the structure of bunchgrasses and sagebrush, other than reducing the risk of bunchgrass mortality during a fire event.

The expansion of pinon-juniper woodlands over the past 100–150 yr in the western United States has resulted in large-scale efforts to kill trees and recover sagebrush steppe rangelands. Western juniper (Juniperus occidentalis spp. occidentalisHook.) expansion in the northern Great Basin has reduced sagebrush-steppe productivity and habitat. Chainsaw cutting of western juniper woodlands is a commonly applied practice to kill trees and restore shrub-understory composition. Studies reporting vegetation response following juniper cutting have been limited to early successional stages. This study assessed successional dynamics spanning 25 yr following tree cutting on Steens Mountain, southeast Oregon. Herbaceous standing crop and yield and plant densities were compared between chainsaw cut (Cut) and uncut woodland (Control) treatments. Cut plots were treated in 1991. In the Cut, total standing crop and yield have remained fairly consistent since 1996 and on average were 8 times greater than the Contro...

Restoration of shrubs in arid and semi-arid rangelands is hampered by low success rates. Planting shrub seedlings is a method used to improve success in these rangelands; however, it is expensive and labor intensive. The efficiency of shrub restoration could be improved by identifying microsites where shrub survival is greater. Bitterbrush (Purshia tridentata Pursh DC) is an important shrub to wildlife that has declined because of conifer encroachment, excessive defoliation, wildfires, and low recruitment. We investigated planting bitterbrush seedlings in western juniper (Juniperus occidentalis ssp. occidentalis Hook) encroached shrublands after prescribed fire was used to control trees. Bitterbrush seedlings were planted in under (canopy) and between (interspace) former juniper canopies at five blocks and evaluated for three growing seasons. Bitterbrush survival was greater than 50% in the former canopy, but only 5% in the interspace microsite by the third growing season. Growth of bitterbrush was also greater in the former canopy compared with the interspace, potentially due to markedly less perennial vegetation in this microsite. Exotic annual grasses and annual forbs became prevalent in the former canopy in the second and third growing season, suggesting that soil resource availability was greater in this microsite. These results suggest that restoration success will vary by specific locations within a burned landscape and that this variability can be used to improve restoration efficiency. In this situation, bitterbrush restoration can be improved by planting seedlings in former canopy compared with interspace microsites.

Restoration of shrubs is needed throughout the world because of altered fire regimes, anthropogenic disturbance, and overutilization. The native shrub mountain big sagebrush (Artemisia tridentata Nutt. ssp. vaseyana (Rydb.) Beetle) is a restoration priority because of its value to wildlife in western North America. One of the principal threats to mountain big sagebrush is encroachment by western juniper (Juniperus occidentalis ssp. occidentalis Hook) and other conifers. Fire is frequently applied to control juniper; however, sagebrush recovery after fire can be variable. Seeding sagebrush postfire can hasten sagebrush recovery; however, seeding is not always necessary. Therefore, it may be advantageous to monitor postfire recovery to determine if seeding is needed. The effect of seeding sagebrush several years after fire is unknown. We evaluated the efficiency of seeding mountain big sagebrush four years after fire-controlled junipers at five sites. Sagebrush cover (

The need for restoration of shrubs is increasingly recognized around the world. In the western United States, restoration of mountain big sagebrush (Artemisia tridentata Nutt. ssp. vaseyana [Rydb.] Beetle) after controlling encroaching conifers is a priority to improve sagebrush-associated wildlife habitat. Conifers can be cost effectively removed with prescribed burning when sagebrush is codominant; however, burning removes sagebrush and natural recovery may be slow. We evaluated seeding mountain and Wyoming big sagebrush (A. tridentata Nutt. ssp. wyomingensis Beetle & Young) on north and south aspects after western juniper (Juniperus occidentalis ssp. occidentalis Hook) control with prescribed burning. We included seeding Wyoming big sagebrush, a more drought tolerant subspecies of big sagebrush, because it might grow better than mountain big sagebrush on hot, dry south slopes, during drought, or after juniper encroachment. Seeding mountain big sagebrush increased sagebrush cover and density compared to unseeded controls. In mountain big sagebrush-seeded plots, sagebrush cover was 19 times greater on north compared to south aspects in the fourth year after seeding. At this time, sagebrush cover was also greater on mountain compared to Wyoming big sagebrush-seeded plots. Natural recovery (i.e. unseeded) of sagebrush was occurring on north aspects with sagebrush cover averaging 3% 4 years after fire. Sagebrush was not detected on unseeded south aspects at the end of the study. These results suggest that postfire sagebrush recovery, with and without seeding, will be variable across the landscape based on topography. This study suggests seeding sagebrush after controlling junipers with burning may accelerate sagebrush recovery.

More frequent wildfires and incidences of mega-fires have increased the pressure for fuel treatments in sagebrush (Artemisia) communities. Winter grazing has been one of many fuel treatments proposed for Wyoming big sagebrush (A. tridentata Nutt. subsp. wyomingensis Beetle and A. Young) communities. Though fire risk and severity can be reduced with winter grazing, its impact on vegetation characteristics of Wyoming big sagebrush plant communities is largely unknown. We evaluate the effect of winter grazing at utilization levels between 40% and 60% at five sites in southeastern Oregon. Winter grazing was applied for 5–6 yr before measurements. The winter-grazed and ungrazed treatments generally had similar vegetation characteristics; however, a few characteristics differed. The consumption of prior years' growth resulted in less large perennial bunchgrass, perennial forb, and total herbaceous cover and standing crop and litter biomass. Large perennial bunchgrass and perennial forb density and biom...

Fire, herbivory and their interaction influence plant community dynamics. However, little is known about the influence of prefire herbivory on postfire plant community response, particularly long‐term resistance to postfire exotic plant invasion in areas that historically experienced limited large herbivore pressure and infrequent, periodic fires. We investigated the long‐term postfire effects of prefire herbivory by cattle, an exotic herbivore, in Artemisia (sagebrush) plant communities in the northern Great Basin, USA. Study areas were moderately grazed or not grazed by cattle since 1936 and then were burned in 1993. Plant community response was measured the 19th through the 22nd year postfire. Prior to burning exotic annual grass presence was minimal (

Shrub steppe communities with depleted perennial herbaceous understories often need to be restored to increase resilience and resistance. Mowing has been applied to Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis Beetle & Young) steppe plant communities to reduce sagebrush dominance and restore native herbaceous vegetation, but success has been limited and hampered by increases in exotic annuals. Seeding native bunchgrasses after mowing may accelerate recovery and limit exotics. We compared mowing followed by drill-seeding native bunchgrasses to mowing and an untreated control at five sites in southeastern Oregon over a 4-year period. Mowing and seeding bunchgrasses increased bunchgrass density; however, bunchgrass cover did not differ among treatments. Exotic annuals increased with mowing whether or not post-mowing seeding occurred. Mowing, whether or not seeding occurred, also reduced biological soil crusts. Longer term evaluation is needed to determine if seeded bunchgrasses will increase enough to suppress exotic annuals. Seeded bunchgrasses may have been limited by increases in exotic annuals. Though restoration of sagebrush communities with degraded understories is needed, we do not recommend mowing and seeding native bunchgrasses because this treatment produced mixed results that may lower the resilience and resistance of these communities. Before this method is applied, research is needed to increase our understanding of how to improve establishment of seeded native bunchgrasses. Alternatively, restoration practitioners may need to apply treatments to control exotic annuals and repeatedly seed native bunchgrasses.

Vegetation change and anthropogenic development are altering ecosystems and decreasing biodiversity. Successful management of ecosystems threatened by multiple stressors requires development of ecosystem conservation plans rather than single species plans. We selected the big sagebrush (Artemisia tridentata Nutt.) ecosystem to demonstrate this approach. The area occupied by the sagebrush ecosystem is declining and becoming increasingly fragmented at an alarming rate because of conifer encroachment, exotic annual grass invasion, and anthropogenic development. This is causing rangewide declines and localized extirpations of sagebrush associated fauna and flora. To develop an ecosystem conservation plan, a synthesis of existing knowledge is needed to prioritize and direct management and research. Based on the synthesis, we concluded that efforts to restore higher elevation conifer-encroached, sagebrush communities were frequently successful, while restoration of exotic annual grass-invaded, lower elevation, sagebrush communities often failed. Overcoming exotic annual grass invasion is challenging and needs additional research to improve the probability of restoration and identify areas where success would be more probable. Management of fire regimes will be paramount to conserving sagebrush communities, as infrequent fires facilitate conifer encroachment and too frequent fires promote exotic annual grasses. Anthropogenic development needs to be mitigated and reduced to protect sagebrush communities and this probably includes more conservation easements and other incentives to landowners to not develop their properties. Threats to the sustainability of sagebrush ecosystem are daunting, but a coordinated ecosystem conservation plan that focuses on applying successful practices and research to overcome limitations to conservation is most likely to yield success.

Western juniper (Juniperus occidentalis subsp. occidentalis Hook.) woodlands are expanding from their historic range and causing significant declines of other plant communities. However, landscape-scale restoration projects are hindered by timeconsuming and expensive methods to inventory juniper cover and prioritize landscapes based on developmental phase of juniper encroachment. We investigated the ability of feature-extraction software to estimate western juniper cover from color aerial photographs obtained from the National Agriculture Imagery Program (NAIP) and explored the relationships between juniper cover at stand closure (potential juniper cover) and environmental/site indices (heat load, site exposure, and integrated moisture index) and characteristics measured from commonly available geospatial data layers. Estimates of juniper cover derived from NAIP imagery and ground measurements were similar (R 2 5 0.74; P , 0.01). Neither method consistently estimated juniper cover higher or lower than the other method (P 5 0.79). Environmental indices were either not correlated or weakly correlated with juniper cover at stand closure. However, the environmental/site characteristics (slope, aspect, and elevation) could be used to explain 40% of the variation in juniper cover at stand closure (R 2 5 0.40; P , 0.01). Thus, commonly available geospatial data layers can be used to assist in determining potential juniper cover. This information can then be compared to current juniper cover to determine juniper woodland developmental phase. Knowing the developmental phase is important because management strategies and effectiveness of restoration treatments differ among phases of juniper encroachment. Our results suggest that NAIP imagery can be a valuable tool to estimate juniper cover over large areas effectively to make landscape-scale restoration more feasible. The model of the relationship between environmental/site characteristics measured from commonly available geospatial data layers and potential juniper can be used to assist in restoration planning and prioritization, but could be improved with further refinement.

Big sagebrush (Artemisia tridentata Nutt.) occupies large portions of the western United States and provides valuable wildlife habitat. However, information is lacking quantifying differences in native perennial forb characteristics between mountain big sagebrush [A. tridentata spp. vaseyana (Rydb.) Beetle] and Wyoming big sagebrush [A. tridentata spp. wyomingensis (Beetle & A. Young) S.L. Welsh] plant communities. This information is critical to accurately evaluate the quality of habitat and forage that these communities can produce because many wildlife species consume large quantities of native perennial forbs and depend on them for hiding cover. To compare native perennial forb characteristics on sites dominated by these two subspecies of big sagebrush, we sampled 106 intact big sagebrush plant communities. Mountain big sagebrush plant communities produced almost 4.5-fold more native perennial forb biomass and had greater native perennial forb species richness and diversity compared to Wyoming big sagebrush plant communities (P < 0.001). Nonmetric multidimensional scaling (NMS) and the multiple-response permutation procedure (MRPP) demonstrated that native perennial forb composition varied between these plant communities (P < 0.001). Native perennial forb composition was more similar within plant communities grouped by big sagebrush subspecies than expected by chance (A = 0.112) and composition varied between community groups (P < 0.001). Indicator analysis did not identify any perennial forbs that were completely exclusive and faithful, but did identify several perennial forbs that were relatively good indicators of either mountain big sagebrush or Wyoming big sagebrush plant communities. Our results suggest that management plans and habitat guidelines should recognize differences in native perennial forb characteristics between mountain and Wyoming big sagebrush plant communities.

Dominant plant species are often used as indicators of site potential in forest and rangelands. However, subspecies of dominant vegetation often indicate different site characteristics and, therefore, may be more useful indicators of plant community potential and provide more precise information for management. Big sagebrush (Artemisia tridentata Nutt.) occurs across large expanses of the western United States. Common subspecies of big sagebrush have considerable variation in the types of sites they occupy, but information that quantifies differences in their vegetation characteristics is lacking. Consequently, wildlife and land management guidelines frequently do not differentiate between subspecies of big sagebrush. To quantify vegetation characteristics between two common subspecies of big sagebrush, we sampled 106 intact big sagebrush plant communities. Half of the sampled plant communities were Wyoming big sagebrush (A. tridentata subsp. wyomingensis [Beetle & A. Young] S. L. Welsh) plant communities, and the other half were mountain big sagebrush (A. tridentata subsp. vaseyana [Rydb.] Beetle) plant communities. In general, mountain big sagebrush plant communities were more diverse and had greater vegetation cover, density, and biomass production than Wyoming big sagebrush plant communities. Sagebrush cover was, on average, 2.4-fold higher in mountain big sagebrush plant communities. Perennial forb density and cover were 3.8- and 5.6-fold greater in mountain compared to Wyoming big sagebrush plant communities. Total herbaceous biomass production was approximately twofold greater in mountain than Wyoming big sagebrush plant communities. The results of this study suggest that management guidelines for grazing, wildlife habitat, and other uses should recognize widespread subspecies as indicators of differences in site potentials.

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. O...

Restoring range sites dominated by western juniper is central to maintaining healthy functioning shrub–steppe ecosystems. On sites without adequate species composition to respond favorably to juniper controlled by fire, revegetation is necessary. We tested the following two hypotheses related to restoration after juniper control: (1) higher seeding rates would translate into higher density of seeded species, and (2) a rich seeding mixture would provide higher density and biomass than monocultures. Western juniper control was done by cutting 25% of the trees in 2002, allowing cut trees to dry for one year, followed by a broadcast fire applied in October 2003 which killed the remaining live juniper trees. Seeding treatments were applied in 2003 and included seeding six native species in monocultures, seeding a mixture of all six species at four rates (16.8, 22.4, 28.0, or 33.6 kg ha−1of pure live seeds), and a nonseeded control. Treatments were applied on a Sagebrush/bunchgrass and Snowberry/fescue site. We found that bluebunch wheatgrass, Idaho fescue, big bluegrass, and western yarrow density ranged from 450 to 700 plants m−2, which was over six-fold that of the control in 2004 at both sites. Only arrowleaf balsamroot did not establish successfully. The density of big bluegrass nearly doubled from 2004 to 2005. The highest plant density resulted from the highest seeding rate. The highest biomass production was combination seeding at 22.4 kg ha−1on the Sagebrush/bunchgrass site and 33.6 kg ha−1on the Snowberry/fescue site. Seeding a combination of species resulted in a moderate to high density of plants and optimized plant diversity and richness over seeding monocultures.

The expansion of western juniper (Juniperus occidentalis ssp. occidentalis Hook.) in the northern Great Basin has resulted in management efforts to reduce juniper by prescribed fire or tree cutting to restore shrub-grassland plant communities. Herbaceous succession following juniper cutting or prescribed fire has been well documented, however, impacts of these disturbances to litter and nutrient cycling is limited in these invasive semi-arid woodlands. This study evaluated the effects of cutting juniper trees on leaf litter decomposition and nitrogen (N) dynamics over a 2-year period in eastern Oregon, USA. Litter bags were used to measure juniper leaf litter decomposition and track litter carbon (C) and N fluxes in cut and uncut juniper woodland treatments. Litter mass loss was 37% greater in the cut treatment compared to the uncut treatment after 2 years. Greater litter inputs, higher litter fall quality, and micro-environmental differences were suggested to have been the main causes for the higher litter decomposition rate in the cut treatment. In both treatments, litter N was released by the second year of decomposition, though N release was greater in the uncut treatment. Retention of juniper debris on site permits storage and release of nutrients through decomposition processes which is likely important in maintaining site productivity.

Western juniper (Juniperus occidentalis spp. occidentalis Hook.) has encroached on and now dominates millions of acres of sagebrush/bunchgrass rangeland in the Great Basin and interior Pacific Northwest. On many sites western juniper has significantly increased exposure of the soil surface by reducing density of understory species and surface litter. We used rainfall and rill simulation techniques to evaluate infiltration, runoff, and erosion on cut and uncut field treatments 10 years after juniper removal. Juniper-dominated hillslopes had significantly lower surface soil cover of herbaceous plants and litter and produced rapid runoff from low-intensity rainfall events of the type that would be expected to occur every 2 years. Direct exposure of the soil to rainfall impacts resulted in high levels of sheet erosion (295 kg ? ha 21 ) in juniper-dominated plots. Large interconnected patches of bare ground concentrated runoff into rills with much higher flow velocity and erosive force resulting in rill erosion rates that were over 15 times higher on juniper-dominated plots. Cutting juniper stimulated herbaceous plant recovery, improved infiltration capacity, and protected the soil surface from even large thunderstorms. Juniper-free plots could only be induced to produce runoff from high-intensity events that would be expected to occur once every 50 years. Runoff events from these higher-intensity simulations produced negligible levels of both sheet and rill erosion. While specific inferences drawn from the current study are limited to juniper-affected sites in the Intermountain sagebrush steppe, the scope of ecosystem impacts are consistent with woody-plant invasion in other ecosystems around the world.

Sagebrush cover is often estimated with the use of the line intercept method. However, a lack of standardized protocols may lead to variable estimates of sagebrush canopy cover. Our objectives were to determine the influence of gap size on 1) sagebrush canopy cover estimates, 2) time needed to read a transect, and 3) among-observer variability in sagebrush canopy cover estimates. We utilized 5-, 10-, and 15-cm gaps, and defined a gap as a lack of continuous live or dead shrub canopy. In instances where a segment of dead cover was less than the gap size and adjoined live cover, the dead cover was measured as live. We evaluated canopy cover at 6 Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. Wyomingensis Beetle & A. Young) sites in southeast Oregon. At each site, four 2-person teams measured sagebrush canopy intercept along 50-m transects. Each transect was read by multiple teams to allow for assessment of among-observer variability. Intercept values were converted to percent canopy cover and we used analysis of variance to determine the influence of site and gap size on measurement time and cover estimates. Observer variability was highest at the intermediate gap size (i.e., 10 cm). Transect measurement time was longest with the use of a 5-cm gap (P < 0.001). Total cover estimates were not related to gap size (P = 0.270). Live canopy cover estimates increased (P < 0.001) from 12.1% to 14.5% with increasing gap size, and cover of dead material decreased (P = 0.015) from 4.4% to 3.2%. These differences are small in magnitude and would not likely change a gross assessment of vegetation status. However, use of a standardized gap size will enhance comparability of canopy cover estimates among studies and will decrease between-year sampling error for repeat monitoring.

Western juniper ( Juniperus occidentalis spp. occidentalis Hook.) expansion into sagebrush steppe plant communities in the northern Great Basin has diminished shrub-steppe productivity and diversity. Chainsaw cutting of western juniper woodlands is a commonly applied practice for removing tree interference and restoring understory composition. Studies reporting understory response following juniper cutting have been limited to early successional stages. This study assessed successional dynamics spanning 13 years following tree cutting. Total herbaceous standing crop and cover increased significantly in the CUT. Total standing crop was 10 times greater in the CUT vs. WOODLAND. Herbaceous standing crop and cover, and densities of perennial grasses in the CUT did not change between 1996 and 2004 indicating that by the 5th year after cutting, remaining open areas had been occupied. In the early successional stages, perennial bunchgrasses and Sandberg’s bluegrass were dominant. By the 5th year after treatment, cheatgrass had supplanted Sandberg’s bluegrass and was codominant with perennial bunchgrasses. In 2003 and 2004, perennial bunchgrasses dominated herbaceous productivity in the CUT, representing nearly 90% of total herbaceous standing crop. A pretreatment density of 2–3 perennial bunchgrasses m −2 appeared to be sufficient to permit natural recovery after juniper control. Perennial bunchgrass density peaked in the 6th year after treatment and the results suggested that 10–12 plants m −2 were sufficient to fully occupy the site and dominate herbaceous composition in subsequent years. In the CUT, juniper rapidly reestablished from seed and from the presence of seedlings not controlled in the initial treatment. The shifts in herbaceous composition across years suggests that long term monitoring is important for evaluating plant community response to juniper control and to develop appropriate post treatment management to promote continued site improvement.

The rapid expansion of western juniper (Juniperus occidentalis spp. occidentalis Hook.) across the northern Great Basin has diminished shrub and understory plant composition and reduced forage production. Juniper removal has accelerated during the past decade in Oregon and California to restore shrub-steppe plant communities. Livestock grazing can affect posttreatment successional dynamics, but these impacts have not received adequate study. This study evaluated herbaceous plant recovery in a cut western juniper woodland subjected to grazed and ungrazed prescriptions over 4 growing seasons. The study consisted of 4 treatments: ungrazed cut, grazed cut, ungrazed woodland, and grazed woodland. Stocking rates were 0.78 cow-calf pairs per ha for 5 days in the first year following treatment and 0.94 cow-calf pairs per ha for 4 days in the second year after treatment. The grazing portion of the study lacked true replication because grazed plots were not independent of each other (cattle had access to all plots simultaneously). This limits the strength and interpretation of the grazing results. Juniper cutting removed overstory interference and resulted in significant increases in herbaceous cover, biomass, and seed production when compared to adjacent woodlands. Herbaceous cover, standing crop, perennial grass density, and seed production all increased in the ungrazed cut treatment compared to ungrazed woodland. A similar level of response was measured in the grazed pasture where herbaceous responses were greater in the grazed cut vs. the grazed woodland. Grazing in the cut treatment did not limit herbaceous recovery except that perennial grass seed production was lower in the grazed cut than in the ungrazed cut. Rest or deferment is required the first several growing seasons after juniper cutting to provide plants the opportunity to maximize seed crops. These results imply that juniper cutting had a greater effect on herbaceous dynamics than did the grazing application.

Western juniper ( Juniperus occidentalis spp. occidentalis Hook.) woodlands have rapidly spread into the sagebrush steppe of the northern Great Basin the past 100 years. The influence of juniper on soil N dynamics in cut and uncut woodlands was investigated. Eight 1-ha blocks were established in a juniper woodland. In half of each block all trees were cut with cut trees left on site. Sampling on cut plots was stratified to include intercanopy and debris zones. Debris zones were defined as sites under cut trees which had not previously received inputs of juniper litter. In the uncut treatment, intercanopy and canopy zones were sampled. Sampling was conducted for a 2 year period post-cutting. The first sample year was a moderately dry year and the second sample year was a very wet year. Measured parameters included KCl extractable N (NH 4 + -N and NO 3 − -N), nitrification, N mineralization (using buried bag technique), volumetric soil moisture, total soil C and N, and herbaceous biomass. In the dry year, soil moisture, KCl extractable N, and N mineralization were higher in the cut intercanopy zone vs. the other locations. In the wet year, KCl extractable N and N mineralization did not differ among the zones. The effect of year, dry vs. wet, overwhelmed the effect of juniper removal. The initial effect of juniper cutting was an increase in KCl extractable N, but by the second year post-treatment differences for the N variables measured were not apparent. In the dry year there was a higher potential for N loss from soils as a result of the buildup of KCl extractable N. The methods used to assess extractable N and N mineralization indicate that most of the extractable N in soils was taken up by soil micro-organisms and not lost via leaching or denitrification. Soils beneath downed trees had lower nitrification and N mineralization rates compared to the intercanopy. In the uncut woodland, N mineralization and nitrification rates and KCl-extractable NO 3 − levels in intercanopy soils were greater or equal to rates and levels in the canopy zone. There was not a fertility island effect in canopy influenced soils for available N in the uncut juniper woodland.

The interaction between grazing and fire influences ecosystems around the world. However, little is known about the influence of grazing on fire, in particular ignition and initial spread and how it varies by grazing management differences. We investigated effects of fall (autumn) grazing, spring grazing and not grazing on fuel characteristics, fire ignition and initial spread during the wildfire season (July and August) at five shrub steppe sites in Oregon, USA. Both grazing treatments decreased fine fuel biomass, cover and height, and increased fuel moisture, and thereby decreased ignition and initial spread compared with the ungrazed treatment. However, effects differed between fall and spring grazing. The probability of initial spread was 6-fold greater in the fall-grazed compared with the spring-grazed treatment in August. This suggests that spring grazing may have a greater effect on fires than fall grazing, likely because fall grazing does not influence the current year’s plant growth. Results of this study also highlight that the grazing–fire interaction will vary by grazing management. Grazing either the fall or spring before the wildfire season reduces the probability of fire propagation and, thus, grazing is a potential fuel management tool.

Measurement of carbon dioxide (CO 2 ) fluxes over sagebrush steppe ecosystems has received little attention, and seasonal dynamics of CO 2 uptake are not known for most portions of this expansive ecosystem. We utilized two techniques — Bowen ratio/energy balance (BREB) and closed chamber (CC) — to measure CO 2 fluxes during eight 24 h sampling periods throughout the 1997 growing season on ungrazed sagebrush steppe communities at the US Sheep Experiment Station near Dubois, ID and the Northern Great Basin Experimental Range near Burns, OR. Instantaneous CC measurements generally agreed with 20 min average CO 2 fluxes measured by BREB instrumentation, except later in the season at Burns when soil moisture was depleted. Maximum mid-day CO 2 assimilation occurred in June at both locations, with rates up to 0.4 and 0.5 mg CO 2 m −2 s −1 at Burns and Dubois, respectively. In August, mid-day assimilation was low, at about 0.1 mg m −2 s −1 at both locations. Slopes of CC fluxes as a function of BREB were not different between locations, so data were combined across locations. A significant, positive correlation was observed between CC and BREB ( R =0.82, n =190). These two independent measurements of CO 2 flux showed good agreement, except during extremely hot and dry periods in late summer. This suggests that both BREB and CC are valid techniques and can be used in concert to obtain reliable estimates of CO 2 flux on these shrub-dominated communities, although caution is advised for CC during periods when temperatures are high and soil moisture is low. The BREB technique is appropriate for large-scale, continuous measurements of CO 2 flux, and compares well with the CC technique, which can partition flux estimates between shrub canopy and interspace, thereby providing a measure of spatial variability.

An increase in mega-fires and wildfires is a global issue that is expected to become worse with climate change. Fuel treatments are often recommended to moderate behaviour and decrease severity of wildfires; however, the extensive nature of rangelands limits the use of many treatments. Dormant-season grazing has been suggested as a rangeland fuel treatment, but its effects on fire characteristics are generally unknown. We investigated the influence of dormant-season (winter) grazing by cattle (Bos taurus) on fuel characteristics, fire behaviour and area burned in Wyoming big sagebrush (Artemisia tridentata subsp. wyomingensis) shrub-grassland communities in south-eastern Oregon, USA. Winter grazing was applied for 5 years before burning and compared with ungrazed areas. Winter grazing decreased fine fuels and increased fine fuel moisture, which reduced flame height and depth, rate of spread and area burned. Winter-grazed areas also had lower maximum temperature and heat loading during fires than ungrazed areas, and thereby decreased risk of fire-induced mortality of important herbaceous functional groups. These results suggest that winter grazing may be a fuel management treatment that can be applied across vast shrub-grasslands to decrease wildfire risk and fire intensity to mediate climate change effects on wildfire activity.

A recent commentary by Smith et al. (2016) argues that our study (Davies et al. 2016) contained methodological errors and lacked data necessary to support our conclusions, in particular that winter grazing may reduce the probability of fire-induced mortality of bunchgrasses. Carefully reading Davies et al. (2016) and relevant literature provides strong evidence that the comments of Smith et al. are unfounded. Most notably, Smith et al. (2016) state that thermocouples placed in the air have no correlation to temperatures experienced by vegetation. However, in our study, thermocouples were placed inside the centre of meristematic crowns of bunchgrasses, as was clearly stated in the methods. Nowhere in the manuscript does it say that thermocouples were placed in the air. Duration of elevated temperatures has been repeatedly linked to an increased risk of fire-induced mortality of vegetation in the literature, contrary to claims by Smith et al. (2016) that no evidence of a relationship exists. The conclusion that winter grazing may decrease the likelihood of perennial bunchgrass mortality was not based solely on data collected in this experiment, but also Davies et al. (2009), where post-fire bunchgrass density and production in ungrazed areas were less than half those of grazed areas.

Mega-fires and unprecedented expenditures on fire suppression over the past decade have resulted in a renewed focus on presuppression management. Dormant season grazing may be a treatment to reduce fuels in rangeland, but its effects have not been evaluated. In the present study, we evaluated the effect of dormant season grazing (winter grazing in this ecosystem) by cattle on fuel characteristics in sagebrush (Artemisia L.) communities at five sites in south- eastern Oregon. Winter grazing reduced herbaceous fuel cover, continuity, height and biomass without increasing exotic annual grass biomass or reducing bunchgrass basal area or production. Fuel moisture in winter-grazed areas was high enough that burning was unlikely until late August; in contrast, fuels in ungrazed areas were dry enough to burn in late June. Fuel biomasson perennial bunchgrasses was decreased by 60% with winter grazing, whichmayreduce the potential for fire-induced mortality. The cumulative effect of winter grazing from altering multiple fuel characteristics may reduce the likelihood of fire and the potential severity in sagebrush communities with an understorey dominated by herbaceous perennials. Dormant season grazing has the potential to reduce wildfire suppression expenditures in many rangelands where herbaceous fuels are an issue; however, increasing woody vegetation and extreme fire weather may limit its influence. Additional keywords: fuel management, sagebrush, sage-grouse habitat, wildfire suppression, winter grazing.

Expansion of western juniper (Juniperus occidentalis spp. occidentalis Hook.) woodlands in the sagebrush steppe has the potential to change composition, structure, and productivity of understory vegetation. Cutting of western juniper woodland can potentially restore understory productivity and diversity. Understory responses were assessed after cutting a juniper woodland in southeastern Oregon in 1991. The experimental design was a randomized complete block with eight, 0.8 ha sized blocks and 2 treatments, cut and uncut woodland. Understory cover, density, diversity, biomass, and nitrogen (N) status were compared between treatments after cutting Plants were separated into S functional groups: bluegrass (Poa spp.), perennial bunchgrass, perennial forte, annual forte, and annual grass. Cutting of juniper reduced below ground interference for soil water and N. Leaf water potentials were less negative (p

Management of conservation-reliant species can be complicated by the need to manage ecosystem processes that operate at extended temporal horizons. One such process is the role of fire in regulating abundance of expanding conifers that disrupt sage-grouse habitat in the northern Great Basin of the United States. Removing conifers by cutting has a beneficial effect on sage-grouse habitat. However, effects may last only a few decades because conifer seedlings are not controlled and the seed bank is fully stocked. Fire treatment may be preferred because conifer control lasts longer than for mechanical treatments. The amount of conservation needed to control conifers at large temporal and spatial scales can be quantified by multiplying land area by the time needed for conifer abundance to progress to critical thresholds (i.e., “conservation volume”). The contribution of different treatments in arresting conifer succession can be calculated by dividing conservation volume by the duration of treatment effect. We estimate that fire has approximately twice the treatment life of cutting at time horizons approaching 100 yr, but, has high up-front conservation costs due to temporary loss of sagebrush. Cutting has less up-front conservation costs because sagebrush is unaffected, but it is more expensive over longer management time horizons because of decreased durability. Managing conifers within sage-grouse habitat is difficult because of the necessity to maintain the majority of the landscape in sagebrush habitat and because the threshold for negative conifer effects occurs fairly early in the successional process. The time needed for recovery of sagebrush creates limits to fire use in managing sage-grouse habitat. Utilizing a combination of fire and cutting treatments is most financially and ecologically sustainable over long time horizons involved in managing conifer-prone sage-grouse habitat.