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Bottlebrush squirreltail (Elymus elymoides)and big squirreltail (Elymus multisetus)are high-priority species for restoration of millions of hectares of rangeland in the western United States that have been degraded by accelerated wildfire and introduced annual grasses. Previous research has compared potential germination and seedling performance of these species in a common environment and noted significant genetic differentiation in characteristics that are associated with their environments of origin. In this experiment, we used wet-thermal germination models and long-term simulations of seedbed microclimate to conduct a virtual reciprocal-garden analysis of the potential germination response of these species. We confirmed significant species differentiation in germination rate that appears to confer site-specific advantages for initial seedling establishment in their respective habitats of origin. Our results specifically highlight the relative importance of late-fall seeding for the more rapidly germinating E. multisetusin order to avoid early-fall germination and post-germination seedling mortality from freezing conditions in the winter. In contrast, the slower-germinating E. elymoidesssp. brevifoliusA is less likely to germinate in the fall and likely avoids inherently harsher winter temperatures in the seedbed. Virtual simulations of this type might lead to identification of complex-trait genetic markers that are associated with intraspecific and interspecific adaptations to specific environments. Identification of these traits could also inform management of plant communities that are under threat from invasive weeds and climate change.

Seasonal precipitation and temperature directly affect total plant production in the California Annual Grassland (CAG). Technological advances have resulted in skillful seasonal climate forecasts (i.e., significant correlations between actual and forecasted climate), which could be input into plant production models to inform stocking and other rangeland management decisions. This study presents a procedure for forecasting plant production in the CAG ecosystem to predict annual plant production for grazing, restoration, or other rangeland management practices using a combination of historical gridMET climate data and seasonal hindcasts (i.e., retrospective forecasts, from the North American Multi-Model Ensemble program). The results of this study first confirmed high forecast skill, throughout the growing season at all sites. We also identified skillful plant production forecasts across most of the growing season at two sites and in three of the seven forecasting months at one study site. Forecasting climate and end-of-year plant production across the growing season at three CAG sites allowed us to identify the places and times in the growing season when forecasting might be most helpful in informing management decisions. Integrating plant production forecasting into rangeland management practices could significantly improve rangeland management outcomes. These procedures provide a user guide for creating plant production forecasts for any given area of interest and may be applicable across a wide range of other agricultural and rangeland management systems.

Invasive annual grasses now dominate millions of hectares of rangeland in the Intermountain Western United States. Local annual grass distribution, however, has been shown to follow landscape patterns of slope, aspect, and elevation that are correlated with ecological resilience to stress and disturbance and resistance to annual grass invasion. Although these patterns have previously been linked to soil-climate classes, several mechanistic factors in native-plant seedling establishment are also associated with both topography and seasonal weather patterns in the year following planting. In this study we used the Simultaneous Heat and Water (SHAW) model to estimate long-term weather effects on soil microclimate and hydrothermal-germination models to predict germination response of one fast- and one slow-germinating native grass as a function of planting date, slope, aspect, and elevation in the Boise Foothills in southwestern Idaho. Higher elevation and northerly aspect sites are more likely to defer germination of seeded species until late enough in the fall that they avoid postgermination/preemergence freezing mortality. These sites are also more favorable for survival of emerged seedlings through mid to late summer. Slope, aspect, and elevation effects on modeled restoration outcomes are consistent with previously modeled general patterns of ecological resilience and resistance as a function of soil hydrothermal class, but inclusion of slope and aspect effects may produce finer-scale metrics for mapping these patterns over space. The probabilistic nature of microclimatic variability as a function of elevation may yield useful insights into successful restoration approaches for reestablishment of native plant communities in lower-elevation ecosystems with inherently lower ecological resilience and resistance. The generally arid climate in this region, however, may limit successful restoration outcomes at lower elevation in most years even under conditions of long-term annual grass control.

Several recent studies have hypothesized that postgermination/preemergence soil freezing can have a major negative impact on spring emergence of seeded perennial grasses in the Intermountain western United States. In this experiment, we measured germination and emergence of 4 fall-seeded perennial grasses at 15 sites in southeastern Oregon, north-central Nevada, and southwestern Idaho in 2 different yr. We used hydrothermal germination and seedbed microclimatic models to estimate planting date effects on germination and preemergence mortality and evaluated these simulations relative to measured germination and seedling emergence in the field. There were clear indications that both germination and emergence were responsive to site-year effects, but premature fall germination before winter freezing events was not a factor in emergence rates. In all cases, planting was sufficiently late in the fall to avoid significant postgermination/preemergence freezing injury for the sites and years tested. Emergence was weakly correlated to seedbed favorability in the late winter and spring after the principal period of soil freezing. Our data show that for the 2 yr of this study, we can only account for a relatively small portion of any abiotic effects on spring emergence. General inferences about planting date effects, however, may have been limited by arid conditions during the 2-yr field study relative to long-term climate normals.

Precipitation pulses and interpulse dry periods are major drivers of dryland ecosystem function globally, yet how the patterning and timing of precipitation inputs and dry periods influence seedling recruitment in these systems is poorly understood. We conducted two experiments to understand how limited and variable patterns of precipitation inputs may influence recruitment of bluebunch wheatgrass (Pseudoroegneria spicata[Pursh] A. Löve). In the first experiment, we evaluated how precipitation magnitude and dry-d interval during spring influenced recruitment. Ambient precipitation was excluded during spring, and we experimentally applied 5 levels of water (25, 35, 45, 55, and 65 mm) and 5-dry-d durations (1, 2, 4, 6, or 8 dry d between waterings) to plots sown with P. spicata.In the second experiment, we evaluated how the seasonal timing and duration of dry d influenced recruitment. All ambient precipitation was excluded through late winter and spring, and we experimentally applied three levels of dry-d duration (10, 20, and 30 d) four times during the growing season (February, March, April, and May) to plots sown with P. spicata. We observed strong, nonlinear interactive effects of precipitation amount and dry-d interval on recruitment where the midpoint dry-d treatment (4 d) interacted with low water availability to drive a major decline in recruitment. We also found strong evidence that recruitment was limited by dry periods occurring in late winter as opposed to dry periods occurring through spring, with recruitment decreasing over 40% during February dry periods compared with dry periods in March, April, or May. By understanding how precipitation pulses and interpulse dry periods interact to drive recruitment, we can refine efforts to develop weather-centric restoration frameworks, as well as hone ongoing efforts to identify plant materials and seed enhancement technologies that may buffer effects of variable precipitation on recruitment.

Climate is the principal driver of plant production across all rangeland ecosystems. Monthly or seasonal forecasts of rangeland plant production could provide valuable management information pertaining to livestock stocking rates, restoration planning, wildfire fuel loads, and wildlife management. In the sagebrush steppe ecoregion, plant production is dependent upon climate but also varies by geographic location and the ecological state or dominant plant community. In this study, we used retrospective seasonal climate forecasts and plant production models to determine the utility of monthly or seasonal forecasting (with up to 7-month lead times) across both geographical sites and ecological states. This study was conducted in 45 intact late-seral sagebrush steppe sites over a 10-year period across a 50,000 km2area in southeastern Oregon. Research sites were sorted into five geographical sites and into five ecological states. The objectives of this study were to 1) model plant functional group responses to actual and forecasted climate across time and space; 2) Determine plant production forecast skill for lead times of up to 7 months; and 3) Differentiate plant production model and forecast skill among both geographical sites and ecological states. We found that plant production models and forecasts were able to identify key functional group responses to precipitation and temperature inputs. We also determined that climate and plant production forecasts could be used to produce significant monthly plant production forecasts for lead-times of up to 7-months for all site, state, and plant functional groupings. We also determined that forecasts of total plant production by ecological state were significantly better than forecasts based on geographical sites. Forecasting by ecological state could lead to better rangeland management decisions as it matches management inputs with inherent site conditions.

Precipitation and temperature inputs are the primary factors affecting net primary plant production across rangeland ecoregions. Skillful seasonal climate forecasts have the potential to directly aid in informing management for multiple agricultural and natural resource applications across the western United States. A key limitation in using these forecasts has been the availability of high-resolution climate forecasts across rangeland ecoregions given the high spatiotemporal heterogeneity in precipitation and temperature across these regions. This study examines the skill, or the correlation between of a climate forecast to actual data. Seasonal climate forecasts at lead times of up to 7 months lead times are statistically downscaled from models participating in the North American Multi-Model Ensemble (NMME). The skill of seasonal climate forecasts has typically been assessed at regional scales which may obscure forecast utility for site-specific management applications. Skill assessments are also typically only conducted on individual models, or the ensemble mean of all models which may overlook value-added skill by subsampling models. Here, we evaluated the skill of statistically downscaled monthly precipitation and temperature forecasts derived from seven NMME models for multiple rangeland ecoregions across the western United States. We found that multimodel aggregate forecasts often had synergistic skill when compared to both individual model forecasts as well as the ensemble mean. We also found that forecast skill was dependent on location, the month in which the forecast was made, and the forecast length. We suggest that a site and time-specific optimization of multimodel ensemble skill would increase the potential utility of these forecasts to inform rangeland management decision-making.

Rangelands in the western United States exhibit extremely high temporal variability in seedbed microclimate, and this variability contributes to poor establishment of revegetation species that are typically planted in the fall. We conducted long-term simulations of cumulative germination as a function of planting date and identified alternative germination syndromes based on population-level responses to environmental variability. These germination syndromes reveal ecologically significant differences but also noteworthy similarities in species and seed lot response that can inform rangeland restoration planning and management. Seed germination may occur much sooner than assumed under the traditional paradigm of fall-planting/spring-emergence in the intermountain western United States, and seed germination per se does not appear to be a bottleneck for successful establishment in most years. Instead, simulations of germination response support recent hypotheses that postgermination/preemergent mortality may be the larger contributor to poor seedling establishment. Our data support two general strategies to improve the likelihood of seedling survival into the spring: seeding as late as possible in the fall and active diversification of germination syndromes within a given seed mix. Consistent application of these strategies could increase the probability that some seeds are always available to take advantage of any pulse of seedbed favorability in the late fall, winter, or early spring.

Millions of hectares of sagebrush/bunchgrass rangeland in the western United States are undergoing type conversion to systems dominated by introduced annual grasses that proliferate after wildfire. Postfire rehabilitation and restoration are problematic in these complex systems, but restoration difficulties are exacerbated by high annual and seasonal variability in precipitation and persistent drought. Successful restoration of compositional, structural, and functional diversity in these weather-limited systems may require relatively long-term, iterative management that incorporates flexibility in the definition of the aspirational/goal state. Restoration planning should also explicitly accommodate a lack of predictability of individual-year management results and expectations of only partial success of individual-year management treatments. This planning environment may require rapid assessment and contingency planning in the short term but also long-term persistence to overcome expected failures and setbacks. New methodologies are needed to increase biodiversity without damaging previously established plants, and new metrics need to be developed to monitor successional trajectories between initial and multiple-potential goal states.

Restoring arid regions degraded by invasive annual grasses to native perennial grasses is a critical conservation goal. Targeting site availability, species availability, and species performance is a key strategy for reducing invasive annual grass cover while simultaneously increasing the abundance of seeded native perennial grasses. However, the potential for establishing successful seedings is still highly variable in rangeland ecosystems, likely because of variable year-to-year weather. In this study, we evaluated the independent and combined inputs of tilling, burning, applying imazapic herbicide, and varying seeding rates on existing species and seeded native perennial grass performance from 2008 to 2012 in a southwestern Idaho rangeland ecosystem. We found that combining tilling, fire, and herbicides produced the lowest annual grass cover. The combination of fire and herbicides yielded the highest seeded species density in the hydrologic year (HY) (October−September) 2010, especially at higher than minimum recommended seeding rates. Although the independent and combined effects of fire and herbicides directly affected the growth of resident species, they failed to affect seeded species cover except in HY 2010, when weather was favorable for seedling growth. Specifically, low winter temperature variability (few freeze-thaw cycles) followed by high growing season precipitation in HY 2010 yielded 14× more seeded perennial grasses than any other seeding year, even though total annual precipitation amounts did not greatly vary between 2009 and 2012. Collectively, these findings suggest that tilling, applying prescribed fire, and herbicides before seeding at least 5× the minimum recommended seeding rate should directly reduce resident annual grass abundance and likely yield high densities of seeded species in annual grass−dominated ecosystems, but only during years of stable winter conditions followed by wet springs.

Rangeland seeding practices in the Intermountain western United States are predominantly implemented in the year immediately following wildfire for the purposes of Emergency Stabilization and Rehabilitation (ESR). This necessarily links restoration and rehabilitation outcomes to the probability of a single year providing sufficiently favorable microclimatic conditions for desirable plant establishment. Field research studies in rangeland restoration are also typically of limited duration, and published results may not represent the full spectrum of conditions likely to be experienced at a given site. We propose that location-specific and temporal weather analysis may enhance the interpretation of historical planting data, support expanded inferences from short-term field studies, and facilitate meta-analysis of diverse field studies in rangeland restoration. We describe access and use of new databases and tools that can be used to characterize and rank weather and soil-microclimatic variables and suggest some standard graphs and weather metrics to establish a longer-term perspective for the interpretation of rangeland restoration outcomes. Tools of this type may also be useful in the interpretation of a wide range of agricultural and natural resource applications that are driven by similar weather inputs, particularly in arid and semiarid systems that exhibit high annual and seasonal variability in precipitation and temperature.

Our ability to restore rangelands is limited, and it is unknown if seedling herbivory on its own, or in interaction with other stressors, is a major contributor to restoration failure. To address this, we conducted two experiments: a No Defoliation (ND) experiment (n= 48), in which seedlings from three perennial grasses (crested wheatgrass [Agropyron cristatum{(L.} Gaertn.], bluebunch wheatgrass [Psuedoroegnaria spicata{Pursh} Á. Love], Sandberg bluegrass [Poa secundaJ Presl]) were subjected to wet and dry water regimes for 4 mo, and a concurrent Defoliation (D) experiment (n= 95), in which seedlings were factorially assigned to two defoliation treatments—frequency (LOW, HIGH) and intensity (30% vegetation removal, 70% vegetation removal). Indicators of seedling performance were aboveground and belowground biomass (AGB and BGB), root:shoot ratio, tillering, and mortality. The effect size statistic, Hedge’s g,allowed for comparisons between performance measures. Water stress induced reductions in most performance measures: BGB (g= ND: –1.3; D: –1.6), root:shoot ratio (g =ND: n.s.; D: –0.2), and tillering (g=ND: –1.7; D: –1.2), though not significantly for all species. For ABG, water stress interacted with defoliation, reducing performance less at an intensity of 70% (g= –2.0) as opposed to 30% (g= –3.0), but not always significantly in the former. Water stress also caused less reduction in AGB when no defoliation occurred (ND: –0.8; g= D: –2.5). Intensity and frequency of defoliation interacted; seedlings were generally resistant to reductions in performance except at high frequency, 70% defoliation. Agropyron cristatumand P. spicatadisplayed similar sensitivity to treatments, mostly in terms of changes in AGB and BGB, while P. secundaalso experienced increased mortality and reduced tillering. If these differences in sensitivity result in differential survival, herbivory could impact species postrestoration population demographics.

Weather drives plant community assembly and seasonal plant production in most rangeland ecosystems. Previous models in the California Annual Grassland have indicated that plant production is largely determined by the thermal accumulation, or degree days, between the start and end of the growing season. These models, however, were relatively limited in spatial and temporal scope and did not include seasonal parameters commonly used in more current production-system models. The purpose of this study is to develop models that account for the annual and seasonal effects of weather inputs on plant production. Weather variables for these models included seasonal effects of accumulated degree days, total precipitation, average temperature, season length, past year's precipitation, and past year's plant production. Our results indicated that sorting precipitation years into low, moderate, and high groupings resulted in better production-model fit compared to a full-suite analysis of all precipitation years. In addition, we found that precipitation, temperature, past year's precipitation, and past plant production significantly improved model fit over models that considered only accumulated degree days and season length. Linking these models to seasonal forecasting applications across western rangeland ecosystems could significantly enhance management of grazing production systems in this environment.

Compensatory increases in net photosynthetic assimilation rates (Anet) following herbivory are well documented in adult rangeland grasses but have not been quantified in bunchgrass seedlings, which may be more sensitive to tissue loss than established plants. To address this, we twice removed 30% and 70% leaf area of seedlings of crested wheatgrass (Agropyron cristatum[L.] Gaertn., var. Hycrest II) and the native bluebunch wheatgrass (Psuedoroegnaria spicata[Pursh] Á. Love, var Anatone) and compared Anetand aboveground and belowground growth of these to unclipped control plants. Compensatory Anetoccurred only after the second clipping, roughly 1 month after the first, and was similar in magnitude and duration between species and treatments, ca. 26% higher than control plant Anetfor 2 weeks following clipping. Despite similar compensatory Anetbetween species, increases in Anetwere more proportional with increased stomatal conductance to water vapor (gs) in crested wheatgrass. This resulted in higher intrinsic water use efficiency (WUEi= Anet/gs) integrated across the post-clipping recovery period compared with WUEiof bluebunch seedlings, which declined with clipping. Differences in WUEiwere attributable to differences in root-to-shoot ratios and root tissue quality (specific root mass; g dry mass · m−2root area), which were lower in crested wheatgrass. We concluded that compensatory photosynthesis is an important component of seedling herbivory tolerance, and that observed differences in post-herbivory WUEicould help improve management strategies by informing seedling selection criteria to help develop methods aimed at minimizing impacts of herbivory during the seedling stage.

Sagebrush steppe ecosystems in the western United States are characterized by harsh environmental conditions with high annual and seasonal variability in both precipitation and temperature. Environmental variability contributes to widespread failure in establishing stands of desired species on degraded and invaded landscapes. To characterize seasonal microclimatic patterns and planting date effects on restoration outcomes, we evaluated long-term simulations of seed germination response of cheatgrass (Bromus tectorumL.), bottlebrush squirreltail (Elymus elymoides[Raf] Swezey), and Idaho fescue (Festuca idahoensisElmer) to annual patterns of soil temperature and moisture. Extremely high annual variability in both the conditions favorable for germination and patterns of post-germination drought and thermal stress make it difficult to justify general inferences about seedbed treatment and planting date effects from individual, short-term field studies. We discuss the interpretation of individual-year and seasonal plant establishment factors and offer a mechanistic model for interpreting planting date and year effects on initial seedling establishment. Historical ranking and mechanistic descriptions of individual-year seedbed conditions may allow for expanded inferences through meta-analysis of limited-term field experiments.

Rangeland management is largely focused on managing vegetation change. Objectives may include managing against change if the desired vegetation is in place, or attempting to create a shift in vegetation if the desired plant community is not present. There is a rich body of research documenting influences of disturbance and management on rangeland vegetation. However, in many cases the information is largely observational and does not identify mechanisms driving change. We propose using the regeneration niche concept to more effectively predict when vegetation change is possible and to suggest successional direction. Simply stated, as plants die and leave gaps in the community, recruitment of new individuals will dictate successional direction. Recruitment requires that propagules are present, that the propagules find safe sites in which to establish, and that the seedlings and young plants are able to compete with existing vegetation and survive. In many rangeland communities, perennial bunchgrasses are a key to stability and invasion resistance. Existing literature shows that most rangeland bunchgrasses have average life spans of 10 yr or less, so periodic recruitment is necessary to maintain communities in which they are a major component. Disturbance can influence plant population dynamics, and we suggest classifying disturbances based on how they influence mortality and recruitment. We also suggest that more emphasis be placed on the concept of critical transitions and less on the degree of disturbance per se. In other words, a small disturbance at the wrong point in community composition (low plant density and high gap size for example) can cause a transition, whereas major disturbance in a high condition community may yield little risk of transition. We suggest that a focus on mortality and recruitment will provide a mechanistic approach for predicting vegetation change and making management decisions. We refer to this approach as recruitment-based management.

Advancing our ability to use invasive plants for producing commodities is central to the agricultural industry. Our objective was to evaluate Russian knapweed (Acroptilon repens[L.] DC.) as a winter feed supplement for ruminant livestock. In Experiment 1, we utilized three ruminally cannulated steers in a completely randomized design to compare the ruminal degradation characteristics of alfalfa and Russian knapweed. In the second experiment, Russian knapweed and alfalfa were compared as protein supplements using 48 midgestation, beef cows (530 ± 5 kg) offered ad libitum hard fescue (Festuca brevipilaTracey) straw in an 84-d study. Treatments included an unsupplemented control and alfalfa or Russian knapweed provided on an iso-nitrogenous basis. In Experiment 1, the rate and effective degradability of neutral detergent fiber was greater for alfalfa compared with Russian knapweed (P ≤ 0.02). Ruminal lag time for NDF (period before measurable disappearance began) was greater for knapweed (P = 0.03). Soluble nitrogen, rate of N degradation, rumen degradable N, and effective degradability of N were all greater for alfalfa compared with Russian knapweed (P &spilt; 0.01). In Experiment 2, supplementation increased (P &spilt; 0.01) cow weight gain and BCS compared to the unsupplemented control with no difference between alfalfa and Russian knapweed (P = 0.47). There was no difference (P = 0.60) in the quantity of straw offered between the unsupplemented cows and supplemented groups, but alfalfa fed cows were offered approximately 11% more (P = 0.03) than Russian knapweed-fed cows. Total DM offered to cows was greater (P &spilt; 0.01) for supplemented compared with unsupplemented cows with no difference noted between alfalfa and Russian knapweed (P = 0.79). Russian knapweed is comparable to alfalfa as a protein supplement for beef cows consuming low-quality forage. Using Russian knapweed as a nutritional supplement can help solve two major production problems; managing an invasive weed, and providing a feedstuff that reduces an impediment in livestock production systems.

Within the sagebrush steppe ecosystem, sagebrush plants influence a number of ecosystem properties, including nutrient distribution, plant species diversity, soil moisture, and temperature, and provide habitat for a wide variety of wildlife species. Recent increases in frequency and size of wildfires and associated annual grass expansion within the Wyoming big sagebrush alliance have increased the need for effective sagebrush restoration tools and protocols. Our objectives were to quay the success of Wyoming big sagebrush transplants relative to transplant stock (nursery seedlings vs. wildlings) across different ecological sites and vegetation types and to test the hypothesis that reduction of herbaceous vegetation would increase survival of transplanted sagebrush. We used a randomized block (reps=5) design at each of three sites—1) cheatgrass dominated, 2) native plant dominated, and 3) crested wheatgrass dominated—near Elko, Nevada. Treatments included plant stock (nursery stock or locally harvested wildlings) and herbicide (glyphosate) to reduce competition from herbaceous vegetation. Transplants were planted in the spring of 2009 and 2010 and monitored for survival. Data were analyzed for site and treatment effects using mixed-model ANOVA. Surviving plant density at and 2yr postplanting was generally highest (up to 3-fold) on the native site (P<0.05). Density of surviving transplants was almost 3-fold higher for nursery stock on most sites for the 2009 planting, but differences in survival by planting stock were minimal for the 2010 planting. Glyphosate application increased surviving plant density up to 300% (depending on site) for both years of planting. High labor and plant material investments (relative to traditional drilling or broadcasting) may limit the size of projects for which sagebrush transplants are practical, but these costs may be partially offset by high success relative to traditional methods. Our data indicate that sagebrush transplants can be effective for establishing sagebrush on depleted sites.

Our objective was to determine the short-term response of bluebunch wheatgrass and medusahead to defoliation of wheatgrass designed to stimulate regrowth through tillering. We hypothesized that defoliating bluebunch wheatgrass by 20% at the 3 to 3.5 leaf stage followed by a 50% defoliation at peak standing crop would increase its tillering and biomass production. Consequently, we expected a reduction of the density and biomass of medusahead over that of bluebunch wheatgrass defoliated 50% at peak standing crop. Treatments included four initial medusahead densities (200, 333, 444, 600 plants · m-2) created by hand-pulling and three defoliation regimes factorially arranged (12 treatment combinations) in a randomized complete-block design and replicated four times at two sites. In 2006 and 2007, defoliation was accomplished by hand-clipping bluebunch wheatgrass 1) by 50% once at peak standing crop (late June); 2) by 20% at the 3 to 3.5 leaf stage, then again to 50% at peak standing crop (mid May, late June); or 3) plants were not clipped. Density was sampled in 2006 and 2007, and biomass was harvested only at Star Mountain (near Riverside, Oregon) in 2007 because Warm Springs (near Drewsey, Oregon) was burned by a wildfire before final 2007 data could be collected. In 2006, no treatments applied at either site detectably altered the number of tillers produced by bluebunch wheatgrass nor did they affect bluebunch wheatgrass density or biomass in 2007 at Star Mountain. Changes in medusahead density were not detected in 2006, but this annual invasive grass increased in density and biomass in 2007 at Star Mountain in plots receiving two defoliations. The relatively short growing period caused by summer drought and the relative intolerance of bluebunch wheatgrass to grazing make the twice-over grazing an unlikely practice for arid rangelands in the western United States. In fact, it could possibly increase the risk of annual grass invasion.

The objective of this study was to determine the effects of crested wheatgrass (Agropyron cristatum[L.] Gaertn.) defoliation intensity and timing on medusahead density and biomass. We hypothesized that crested wheatgrass defoliation greater than 60% during the spring would provide maximum medusahead (Taeniatherum caput-medsae[L.] Nevski subsp. asperum[Simk.] Melderis; taxonomy from US Department of Agriculture) density and biomass. Eighteen treatments (six defoliation levels, three seasons of defoliation) were applied to 2-m2plots in a randomized complete block design on two sites with varying clay content. Blocks were replicated five times at each site. Plants were clipped in 2004 and 2005. Crested wheatgrass was hand clipped to defoliation levels of 0%, 20%, 40%, 60%, 80%, and 100% in the spring, summer, or fall. Density of crested wheatgrass and medusahead was sampled in June 2005 and 2006, but their biomass was harvested only in 2006. Data were analyzed with least square means analysis of variance. Over the two seasons, site had much more of an impact on medusahead invasion than either defoliation intensity or timing of defoliation. The results support previous suggestions that clayey soils favor medusahead and that perennial grasses with high biomass can resist this invasive species. On the clayey site where medusahead did persist, fall defoliation of crested wheatgrass reduced the density of this invasive species by 50% or more compared to spring defoliation. Given the developmental pattern of medusahead, the goal of any management program should be to maximize resource use by the desirable species during April to late July.

High plant functional group diversity has been hypothesized to reduce resource concentrations based on the assumption that species from one functional group acquire resources similarly to one another, while species from other functional groups acquire resources dissimilarly. To determine if functional groups use soil nutrients different from one another, we investigated the impact of removing individual functional groups on soil inorganic nitrogen (NO-3 and NH+4) concentrations in the Idaho fescue (Festuca idahoensisElmer)/bluebunch wheatgrass (Pseudoroegneria spicata[Pursh] A. Löve) habitat type in Montana. Treatments were imposed by removing 1) all plant species (total plant removal), 2) shallow-rooted (< 15 cm) forbs, 3) deep-rooted (> 15 cm) forbs, 4) all forbs (total forb removal), 5) grasses, and 6) spikemoss, compared to intact control plots. Inorganic nitrogen was measured at 2 soil depths (0–15 cm and 16–40 cm) in the spring, summer, and fall 1 year after treatment imposition. The removal of individual functional groups generally increased soil NO-3 and NH+4 concentrations. Total plant removal increased NO-3 concentrations more than removing individual functional groups. Grass removal generally increased soil NO-3 concentrations in the 0–15-cm depth more than other functional groups removal. Whether the grass or total forb removal treatment resulted in greater soil NH+4 concentrations in the 0–15-cm depth depended on season. These results suggest that functional groups vary in their soil nutrient acquisition patterns and that increased functional diversity decreases soil nutrient concentrations. Therefore, maintaining or improving functional diversity may be a method to more fully utilize soil nutrients because functional groups can differ in their spatial and temporal acquisition of resources.

Leafy spurge is an invasive Eurasian weed on pastures and rangeland in North America where it reduces grass forage production. Our objective was to determine the effects of multispecies grazing combined with Aphthonaflea beetles on leafy spurge-infested rangeland. On two western North Dakota sites divided into four 25- to 79-ha pastures, two grazing duration treatments were applied: season-long with 7 to 10 cow calf pairs and 20 to 25 sheep from late May through mid-September, and rotation with 18 to 21 cow calf pairs and 45 to 50 sheep for 3 weeks twice per year. Grazing treatments started in 1998 and continued through 2002. Aphthonaspp. were released beginning in 1991 and were widespread in both pastures by 1998. Four grazing exclosures were randomly located in each pasture in the spring of 1998. Cover of leafy spurge, grass, and forbs, as well as density of vegetative and flowering leafy spurge stems were measured in July 1998 through 2002. Aphthonadensities were counted July 1999 through 2002. Grazing initially increased leafy spurge vegetative stem density, but grazing decreased vegetative stem density from 104 in 1999 to 20 stems · m−2in 2002. Season-long grazing reduced vegetative stem density by over 30 stems · m−2compared to rotation grazing. Leafy spurge flowering stems decreased from 80 stems · m−2in 1998 to 4 stems · m−2in 2002 in all treatments. The decrease was more rapid when grazing was combined with Aphthona. Initially, Aphthonadensities were greater in the grazed areas than the exclosures, but by 2002 more Aphthonawere found in the exclosures than the grazed areas. Grazing reduced grass cover and increased forb cover. Results suggest combining multispecies grazing and Aphthonawhen restoring spurge-infested grasslands produces a synergistic effect.

Rangeland managers often must decide whether to suppress dicotyledonous weed populations with expensive and time-consuming management strategies. Often, the underlying goal of weed suppression efforts is to increase production of native forage plants. Many managers suppress weeds only when they feel the unwanted plants are substantially impacting their forage base. Currently, intuition and guesswork are used to determine whether weed impacts are severe enough to warrant action. We believe scientific impact assessments could be more effective than these casual approaches to decision making. Scientific approaches will necessitate data on weed abundances because the severity of a weed’s impact is highly correlated with its abundance. The need for weed abundance data poses major obstacles because gathering these data with readily available techniques is time consuming. Most managers cannot or will not spend a lot of time gathering vegetation data. In this paper, we explore a rapidly measured index (<2 minutes per sample location) that is highly correlated with weed (i.e., leafy spurge Euphorbia esulaL.) abundance per unit area. This index is based on the light attenuation leafy spurge causes. After measuring light attenuation in plots planted to leafy spurge and grasses, we developed a probabilistic model that predicts leafy spurge impacts on forage production. Data from experiments where herbicides suppressed leafy spurge provided an opportunity to evaluate prediction accuracy of the model. In each case herbicide experiment data fell within the range of values (i.e., credibility intervals) the model predicted, even though the model development experiments were separated from the herbicide experiments by several hundred kilometers in space and 4 years in time. Therefore, we conclude that the model successfully accounts for spatial and temporal variation. We believe light attenuation could help natural resource managers quickly quantify some kinds of weed impacts.

Adaptive management is a way for managers to do their jobs in the face of uncertainty and learn by doing. Managers gain greater knowledge of their systems by testing different strategies during the management process. The term “adaptive management” is used often, but there is confusion about exactly what adaptive management is, and managers are hard-pressed to find any clear guidelines for implementing it. As a result, they can find the process of moving from the concept of adaptive management to the actual practice intimidating; they need a clear understanding of adaptive management before they can begin to use it. Luckily, adaptive management is not as complicated as the literature sometimes makes it appear. The process of adaptive management involves formulating questions, selecting alternative techniques to test these questions, and testing these techniques on the landscape. Care is taken to measure those system responses that best tell whether the system is moving toward site objectives, and results are fed back into the decision process. We argue that there are 2 strategies that can be used to improve the success of adaptive management. The first is to start with a simple adaptive management plan and then add complexity over time. The second is to include researchers in all stages of the process to benefit from their expertise in ecology, experimental design, and data analysis. Although adaptive management takes time, rewards include increased understanding of the system, a management program that is scientifically valid, and a management strategy tailored to a particular site. In this paper we briefly explain adaptive management and then offer a step-by-step process for developing and implementing adaptive management in small reserves or on private lands. We believe increased understanding of adaptive management will lead to its widespread use and will ensure that more people benefit from its strengths.