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Purpose Cheatgrass invasion of Intermountain sagebrush steppe in the western United States poses increasing challenges to the function and survival of this native ecosystem. The invasive success and persistence of cheatgrass has been attributed to the increasing soil total nitrogen, but mechanisms behind remain inconclusive. We hypothesized that soil microorganisms play a role in soil nitrogen associated with cheatgrass invasion. Methods We collected soil samples from the root zone of cheatgrass, native bunchgrass, and sagebrush at two depths and from two adjacent sites in April. We examined soil chemical properties (pH, moisture content, and NH 4 +  and NO 3 −  concentration) and soil microbial communities. Results We found that cheatgrass invasion was associated with different soil microbial community composition compared to native bunchgrass and sagebrush. In particular, we observed higher relative abundances of N2 fixers and ureolytic bacteria and lower relative abundance of denitrifiers providing a potential mechanistic belowground explanation of raising soil nitrogen. Conclusions Overall, our results indicate the importance of soil microorganisms in the dominance and persistence of invasive species. Targeted microbiome interventions should be considered to control cheatgrass invasion.

Altered climate, including weather extremes, can cause major shifts in vegetative recovery after disturbances. Predictive models that can identify the separate and combined temporal effects of disturbance and weather on plant communities and that are transferable among sites are needed to guide vulnerability assessments and management interventions. We asked how functional group abundance responded to time since fire and antecedent weather, if long‐term vegetation trajectories were better explained by initial post‐fire weather conditions or by general five‐year antecedent weather, and if weather effects helped predict post‐fire vegetation abundances at a new site. We parameterized models using a 30‐yr vegetation monitoring dataset from burned and unburned areas of the Orchard Training Area (OCTC) of southern Idaho, USA, and monthly PRISM data, and assessed model transferability on an independent dataset from the well‐sampled Soda wildfire area along the Idaho/Oregon border. Sagebrush density increased with lower mean air temperature of the coldest month and slightly increased with higher mean air temperature of the hottest month, and with higher maximum January–June precipitation. Perennial grass cover increased in relation to higher precipitation, measured annually in the first four years after fire and/or in September–November the year of fire. Annual grass increased in relation to higher March–May precipitation in the year after fire, but not with September–November precipitation in the year of fire. Initial post‐fire weather conditions explained 1% more variation in sagebrush density than recent antecedent 5‐yr weather did but did not explain additional variation in perennial or annual grass cover. Inclusion of weather variables increased transferability of models for predicting perennial and annual grass cover from the OCTC to the Soda wildfire regardless of the time period in which weather was considered. In contrast, inclusion of weather variables did not affect transferability of the forecasts of post‐fire sagebrush density from the OCTC to the Soda site. Although model transferability may be improved by including weather covariates when predicting post‐fire vegetation recovery, predictions may be surprisingly unaffected by the temporal windows in which coarse‐scale gridded weather data are considered.

Background Artemisia subg. Seriphidium , one of the most species-diverse groups within Artemisia , grows mainly in arid or semi-arid regions in temperate climates. Some members have considerable medicinal, ecological, and economic value. Previous studies on this subgenus have been limited by a dearth of genetic information and inadequate sampling, hampering our understanding of their phylogenetics and evolutionary history. We therefore sequenced and compared the chloroplast genomes of this subgenus, and evaluated their phylogenetic relationships. Results We newly sequenced 18 chloroplast genomes of 16 subg. Seriphidium species and compared them with one previously published taxon. The chloroplast genomes, at 150,586–151,256 bp in length, comprised 133 genes, including 87 protein-coding genes, 37 tRNA genes, 8 rRNA genes, and one pseudogene, with GC content of 37.40–37.46%. Comparative analysis showed that genomic structures and gene order were relatively conserved, with only some variation in IR borders. A total of 2203 repeats (1385 SSRs and 818 LDRs) and 8 highly variable loci ( trnK – rps16 , trnE – ropB , trnT , ndhC – trnV , ndhF , rpl32 – trnL , ndhG – ndhI and ycf1 ) were detected in subg. Seriphidium chloroplast genomes. Phylogenetic analysis of the whole chloroplast genomes based on maximum likelihood and Bayesian inference analyses resolved subg. Seriphidium as polyphyletic, and segregated into two main clades, with the monospecific sect. Minchunensa embedded within sect. Seriphidium , suggesting that the whole chloroplast genomes can be used as molecular markers to infer the interspecific relationship of subg. Seriphidium taxa. Conclusion Our findings reveal inconsistencies between the molecular phylogeny and traditional taxonomy of the subg. Seriphidium and provide new insights into the evolutionary development of this complex taxon. Meanwhile, the whole chloroplast genomes with sufficiently polymorphic can be used as superbarcodes to resolve interspecific relationships in subg. Seriphidium .

Declines in the spatial extent of the sagebrush ecosystem have prompted the consideration of conservation efforts that view the greater sage-grouse (Centrocercus urophasianus; sage-grouse) as an umbrella species at landscape scales. Conservation strategies that focus on an umbrella species, however, may have unintended negative consequences for co-occurring species at finer scales. In North America, grassland and shrubland songbird populations are declining faster than other avian groups. Conservation of sage-grouse habitats may protect songbird habitats where distributions overlap. To assess the umbrella species concept at fine scales, we quantified nest-site selection for a sagebrush-obligate songbird, the Brewer’s sparrow (Spizella breweri). We then compared the fine-scale habitat variables that influenced Brewer’s sparrow nest-site selection with fine-scale nest-site selection for sage-grouse in the Powder River Basin region of northeastern Wyoming, USA. We modeled nest-site selection using conditional logistic regression for Brewer’s sparrow (2016–2017) and logistic regression for sage-grouse (2004–2007). Both species selected nest sites with higher visual obstruction, shrub height, and branching density, although the selection for higher shrub height was stronger for sage-grouse. Brewer’s sparrows selected nest shrubs with higher percentage of living foliage (vigor), and the opposite was shown for sage-grouse. At the nest site, based on the variables we measured, our results suggest that Brewer’s sparrows and sage-grouse select for similar habitat attributes, with the exception of shrub vigor of the nest shrub. The stronger selection for more vigorous shrubs in Brewer’s sparrows may be because they nest in shrubs, rather than on the ground under shrubs (as in sage-grouse). Most of the conservation objectives for protection of sage-grouse habitats appear to be beneficial or inconsequential for Brewer’s sparrow. Local habitat management for sage-grouse as a proxy for conservation of other species may be justified if the microhabitat preferences of the species under the umbrella are understood to avoid unintentional negative effects.

The structure and composition of sagebrush‐dominated ecosystems have been altered by changes in fire regimes, land use, invasive species, and climate change. This often decreases resilience to disturbance and degrades critical habitat for species of conservation concern. Basin big sagebrush (Artemisia tridentata ssp. tridentata) ecosystems, in particular, are greatly reduced in distribution as land has been converted to agriculture and other land uses. The fire regime, relative proportions of shrub and grassland patches, and the effects of repeated burns in this ecosystem are poorly understood. We quantified postfire patterns of vegetation accumulation and modeled potential fire behavior on sites that were burned and first measured in the late 1980s at John Day Fossil Beds National Monument, Oregon, USA. The area partially reburned 11 yr after the initial fire, allowing a comparison of one vs. two fires. Repeated burns shifted composition from shrub‐dominated to prolonged native herbaceous dominance. Fifteen years following one fire, the native‐dominated herbaceous component was 44% and live shrubs were 39% of total aboveground biomass. Aboveground biomass of twice‐burned sites (2xB; burned 26 and 15 yr prior) was 71% herbaceous and 12% shrub. Twenty‐six years after fire, total aboveground biomass was 113–209% of preburn levels, suggesting a fire‐return interval of 15–25 yr. Frequency and density of Pseudoroegneria spicata and Festuca idahoensis were not modified by fire history, but Poa secunda was reduced by repeated fire, occurring in 84% of plots burned 26 yr prior, 72% of plots burned 15 yr prior, and 49% in 2xB plots. Nonnative annual Bromus tectorum occurred at a frequency of 74%, but at low density with no differences due to fire history. Altered vegetation structure modified fire behavior, with modeled rates of fire spread in 2xB sites double that of once‐burned sites. This suggests that these systems likely were historically composed of a mosaic of shrub and grassland. However, contemporary increases in fire frequency will likely create positive feedbacks of more intense fire behavior and prolonged periods of early‐successional vegetation in basin big sagebrush communities.

Genetic variation is a well-known indicator of population fitness yet is not typically included in monitoring programs for sensitive species. Additionally, most programs monitor populations at one scale, which can lead to potential mismatches with ecological processes critical to species’ conservation. Recently developed methods generating hierarchically nested population units (i.e., clusters of varying scales) for greater sage-grouse (Centrocercus urophasianus) have identified population trend declines across spatiotemporal scales to help managers target areas for conservation. The same clusters used as a proxy for spatial scale can alert managers to local units (i.e., neighborhoodscale) with low genetic diversity, further facilitating identification of management targets. We developed a genetic warning system utilizing previously developed hierarchical population units to identify management-relevant areas with low genetic diversity within the greater sage-grouse range. Within this warning system we characterized conservation concern thresholds based on values of genetic diversity and developed a statistical model for microsatellite data to robustly estimate these values for hierarchically nested populations. We found that 41 of 224 neighborhood-scale clusters had low genetic diversity, 23 of which were coupled with documented local population trend decline. We also found evidence of cross-scale low genetic diversity in the small and isolated Washington population, unlikely to be reversed through typical local management actions alone. The combination of low genetic diversity and a declining population suggests relatively high conservation concern. Our findings could further facilitate conservation action prioritization in combination with population trend assessments and (or) local information, and act as a base-line of genetic diversity for future comparison. Importantly, the approach we used is broadly applicable across taxa.

Selection of nest sites directly influences reproductive success for Greater Sage-Grouse (Centrocercus urophasianus); thus, regional evaluation of how this species selects nest sites is necessary for effective habitat management. We evaluated fine-scale nest site selection of Greater Sage-Grouse in the Centennial Valley of southwest Montana. We conducted vegetation surveys at nest sites (n = 90) of radio-tagged Greater Sage-Grouse and paired random locations across 2 breeding seasons (2014-2015). The majority of nests were located under mountain big sagebrush (Artemisia tridemata ssp. vaseyana), three-tip sagebrush (A. tripartita), and basin big sagebrush (A. tridentata ssp. tridenlata) shrubs. We used generalized linear models and information theory to evaluate competing hypotheses about nest site selection. Our top model indicated that nest site selection was primarily associated with nest shrub morphological characteristics and cover provided by the nest shrub. Mountain big sagebrush and three-tip sagebrush provided twice the amount of lateral cover that basin big sagebrush shrubs provided. Our results suggest that herbaceous cover was unimportant at fine scale nest site selection of Greater Sage-Grouse in our study area. Managers should focus on conserving large intact stands of mountain big sagebrush and three-tip sagebrush habitats because they provided the most lateral cover and supported the majority of nest sites. Received 2 June 2017. Accepted 30 January 2018. Key words: Artemisia spp., Centrocercus urophasianus. Greater Sage-Grouse, herbaceous cover, nest site selection, sagebrush, shrub morphology. La seleccion de sitios de anidacion influencia de manera directa el exito reproductivo del urogallo Cenfrocercus urophasianus. Por ello, necesitamos una evaluacion regional de como seleccionan sitios de anidacion para lograr un manejo efectivo de habitat. Evaluamos la seleccion de sitios de anidacion del urogallo a escala fina en el Centennial Valley en cl suroeste de Montana. Hicimos reconocimientos de la vegetacion en sitios de anidacion (n = 90) de urogallos marcados con transmisores de telemetria y en localidades aleatorias pareadas a lo largo de dos temporadas reproductivas (2014-2015). La mayoria de los nidos fueron encontrados debajo de los arbustos Artemisia tridentata ssp. vaseyana, A. tripartita y A. tridentata ssp. tridentata. Utilizamos modelos lineales generales y teoria de la informacion para evaluar la competencia entre hipotesis acerca de la seleccion de nidos. Nuestro modelo con mejor soporte se asocia principalmente con caracteristicas morfologicas y la cobertura provista por el arbusto de anidacion. Los arbustos de Artemisia tridentata vaseyana y A. tripartita proveen el doble de la cantidad de cobertura lateral que el provisto por A. tridentata tridentata. Nuestros resultados sugieren que la cobertura herbacea no es importante a escala fina en la seleccion de sitios nido de este urogallo en nuestra area de estudio. Quienes manejan estos habitats deben enfocarse en parcelas grandes e intactas de Artemisia tridentata vaseyana y A. tripartita porque proveen la mayor cobertura lateral y dan soporte a la mayoria de los sitios de anidacion. Palabras clave: Artemisia spp., Centroeercns urophasianus, cobertura herbacea, morfologia de arbustos, seleccion de sitios nido.

Microbial communities living on plant leaves can positively or negatively influence plant health and, by extension, can impact whole ecosystems. Most research into the leaf microbiome consists of snapshots, and little is known about how microbial communities change over time. Weather and host physiological characteristics change over time and are often collinear with other time‐varying factors, such as substrate availability, making it difficult to separate the factors driving microbial community change. We leveraged repeated measures over the course of an entire year to isolate the relative importance of environmental, host physiological, and substrate age‐related factors on the structure of leaf‐associated fungal communities. We applied both culturing and sequencing approaches to investigate these communities, focusing on a foundational, widely distributed plant of conservation concern: basin big sagebrush (Artemisia tridentata subsp. tridentata). We found that changes in alpha diversity were independently affected by the age of leaves and the air temperature. Total fungal abundance and species richness were not positively correlated and responded differently, sometimes oppositely, to weather. With regard to beta diversity, communities were more similar to each other across similar leaf ages, air temperatures, leaf types, and δ13C stable isotope ratios. Nine different genera were differentially abundant with air temperature, δ13C, leaf type, and leaf age, and a set of 20 genera were continuously present across the year. Our findings highlight the necessity for longer term, repeated sampling to parse drivers of temporal change in leaf microbial communities.

The sagebrush biome within the western United States has been reshaped by disturbances, management, and changing environmental conditions. As a result, sagebrush cover and configuration have varied over space and time, influencing processes and species that rely on contiguous, connected sagebrush. Previous studies have documented changes in sagebrush cover, but we know little about how the connectivity of sagebrush has changed over time and across the sagebrush biome. We investigated temporal connectivity patterns for sagebrush using a time series (1985–2020) of fractional sagebrush cover and used an omnidirectional circuit algorithm to assess the density of connections among areas with abundant sagebrush. By comparing connectivity patterns over time, we found that most of the biome experienced moderate change; the amount and type of change varied spatially, indicating that areas differ in the trend direction and magnitude of change. Two different types of designated areas of conservation and management interest had relatively high proportions of stable, high-connectivity patterns over time and stable connectivity trends on average. These results provide ecological information on sagebrush connectivity persistence across spatial and temporal scales that can support targeted actions to address changing structural connectivity and to maintain functioning, connected ecosystems.

Abstract World food supplies rely on pollination, making this plant–animal relationship a highly valued ecosystem service. Bees pollinate flowering plants in rangelands that constitute up to half of global terrestrial vegetation. Livestock grazing is the most widespread rangeland use and can affect insect pollinators through herbivory. We examined management effects on bee abundance and other insect pollinators on grazed and idle sagebrush rangelands in central Montana, USA. From 2016 to 2018, we sampled pollinators on lands enrolled in rest-rotation grazing, unenrolled grazing lands, and geographically separate idle lands without grazing for over a decade. Bare ground covered twice as much area (15% vs. 7) with half the litter (12% vs. 24) on grazed than idle regardless of enrollment. Bee pollinators were 2–3 times more prevalent in grazed than idle in 2016–2017. In 2018, bees were similar among grazed and idled during an unseasonably wet and cool summer that depressed pollinator catches; captures of secondary pollinators was similar among treatments 2 of 3 study years. Ground-nesting bees (94.6% of total bee abundance) were driven by periodic grazing that maintained bare ground and kept litter accumulations in check. In contrast, idle provided fewer nesting opportunities for bees that were mostly solitary, ground-nesting genera requiring unvegetated spaces for reproduction. Managed lands supported higher bee abundance that evolved with bison grazing on the eastern edge of the sagebrush ecosystem. Our findings suggest that periodic disturbance may enhance pollinator habitat, and that rangelands may benefit from periodic grazing by livestock.