Subspecies Of Big Sagebrush Research Articles

A haploid pseudo-chromosome genome assembly for a keystone sagebrush species of western North American rangelands.

Increased ecological disturbances, species invasions, and climate change are creating severe conservation problems for several plant species that are widespread and foundational. Understanding the genetic diversity of these species and how it relates to adaptation to these stressors are necessary for guiding conservation and restoration efforts. This need is particularly acute for big sagebrush (Artemisia tridentata; Asteraceae), which was once the dominant shrub over 1,000,000 km2 in western North America but has since retracted by half and thus has become the target of one of the largest restoration seeding efforts globally. Here, we present the first reference-quality genome assembly for an ecologically important subspecies of big sagebrush (A. tridentata subsp. tridentata) based on short and long reads, as well as chromatin proximity ligation data analyzed using the HiRise pipeline. The final 4.2-Gb assembly consists of 5,492 scaffolds, with nine pseudo-chromosomal scaffolds (nine scaffolds comprising at least 90% of the assembled genome; n = 9). The assembly contains an estimated 43,377 genes based on ab initio gene discovery and transcriptional data analyzed using the MAKER pipeline, with 91.37% of BUSCOs being completely assembled. The final assembly was highly repetitive, with repeat elements comprising 77.99% of the genome, making the Artemisia tridentata subsp. tridentata genome one of the most highly repetitive plant genomes to be sequenced and assembled. This genome assembly advances studies on plant adaptation to drought and heat stress and provides a valuable tool for future genomic research.

Fundamental intra-specific differences in plant–water relations in a widespread desert shrub (Artemisia tridentata)

Big sagebrush (Artemisia tridentata) is a widespread and locally dominant shrub that is a key driver of water fluxes and storage in western North America. There are several recognized subspecies of big sagebrush that occupy different microsites across the landscape according to moisture availability, yet little is known about how these subspecies vary in drought tolerance or water management strategies. We measured diurnal and seasonal (i.e., early-, mid-, and late summer) variation in water status and transport efficiency, transpiration, and stomatal regulations in two subspecies of big sagebrush (A.t. wyomingensis and A.t. vaseyana) at the Reynolds Creek Critical Zone Observatory in southwestern Idaho. We hypothesized that water status, transport efficiency, and stomatal regulations would be greater in A.t. vaseyana compared to A.t. wyomingensis, because the first subspecies occupies wetter microsites. Predawn and midday water potentials were up to 2× more negative in A.t. wyomingensis compared to A.t. vaseyana, and transpiration was up to ~ 4× greater in A.t. vaseyana compared to A.t. wyomingensis. A.t. vaseyana was more isohydric with ~ 1.5× greater stomatal sensitivity to atmospheric vapor pressure deficit and a smaller hydroscape, compared to A.t. wyomingensis. Our data demonstrate that there are fundamental differences in plant–water relations among these subspecies that constitute the vast, but not homogeneous sagebrush landscapes. These important differences can have implications for modeling water fluxes in big sagebrush-dominated communities at shrub to ecosystem scales.

Effects of Mowing and Tebuthiuron on the Nutritional Quality of Wyoming Big Sagebrush

Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis Beetle & Young) is the most abundant and widely distributed subspecies of big sagebrush and has been treated through chemical application, mechanical treatments, and prescribed burning in efforts thought to improve habitat conditions for species such as greater sage-grouse (Centrocercus urophasianus) and mule deer (Odocoileus hemionus). Although the response of structural attributes of sagebrush communities to treatments is well understood, there is a need to identify how treatments influence the quality of sagebrush as winter food for wildlife. Our purpose was to identify how mowing and tebuthiuron treatments influenced dietary quality of Wyoming big sagebrush in central Wyoming. Two study areas were mowed in January and February 2014, and tebuthiuron was applied in two study areas in May 2014. We constructed 6 exclosures in each of these four study areas (24 total), which encompassed 30 × 30 m areas of treated and untreated sagebrush within each exclosure. Samples of current annual growth were collected from 18 sagebrush plants from treated and 12 plants from control portions of mowing exclosures during November 2013–2015 and tebuthiuron exclosures during November 2014–2015. Samples were analyzed for crude protein and plant secondary metabolites known to influence dietary selection of sagebrush by sage-grouse and other sagebrush-occurring herbivores. Our results suggest mowing and tebuthiuron treatments may slightly increase crude protein concentrations directly after treatments without immediate changes in plant secondary metabolites. Slight increases in dietary quality of sagebrush following treatments coupled with potential trade-offs with loss of biomass associated with treatments corroborates previous research that treating Wyoming big sagebrush may have little benefit for sage-grouse and other sagebrush-dependent wildlife. Future work should evaluate not only how treatments influence sage-grouse habitat use and reproductive success but also how treatments influence other wildlife species in fragile sagebrush ecosystems.

Restoring big sagebrush after controlling encroaching western juniper with fire: aspect and subspecies effects

AbstractThe 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.

Sagebrush Response to Conifer Cover

<p class="emsd">Sagebrush habitat is declining throughout the United States. This can have negative impacts for big game as well as other wildlife species. The purpose of our research was to analyze the relationship between several abiotic factors and the cover of two conifer species, Douglas-fir (<em>Pseudotsuga menziesii</em>) and Rocky Mountain juniper (<em>Juniperus scopulorum</em>), on the cover of Wyoming (<em>Artemisia tridentata spp. wyomingensis</em>) and mountain (<em>Artemisia tridentata spp. Vaseyana</em>) big sagebrush. Abiotic factors, percent cover of sagebrush and conifers, and individual conifer age and canopy area were recorded at 40 Wyoming and 40 mountain big sagebrush plots at each of three study sites in southwest Montana (n = 240). No correlation was found between any abiotic factor and live sagebrush cover over all sites (p>0.05). A model of the relationship between the combined cover of the two conifer species and the two subspecies of big sagebrush was developed. The best-fit model included the terms: study site, sagebrush subspecies, and the interaction, study site by sagebrush subspecies as the independent variables, with as the dependent variable ( = Intercept<sub>i</sub>– 0.401 ; R<sup>2</sup> = 0.61). There was a negative relationship between conifer cover and sagebrush cover and no difference in the effects of conifer cover on the two sagebrush subspecies. Validation trials were successful at one of three locations outside the study area and suggested that the model is better suited to lower elevation, less productive sites. Individual Douglas-fir have a 3 fold larger canopy area than Rocky Mountain juniper at comparable ages (p<0.001). Controlling conifers to increase Wyoming big sagebrush does not appear to be effective due to the low level of sagebrush cover. If conifer control is desired, Douglas-fir should be targeted over Rocky Mountain juniper on mountain big sagebrush sites, but not on Wyoming big sagebrush sites.</p>

Genetic and environmental effects on seed weight in subspecies of big sagebrush: applications for restoration

The sagebrush steppe is a patchwork of species and subspecies occupying distinct environmental niches across the intermountain regions of western North America. These ecosystems face degradation from disturbances and exotic weeds. Using sagebrush seed that is matched to its appropriate niche is a critical component to successful restoration, improving habitat for the threatened greater sage‐grouse and other species. The need for restoration is greatest in basin habitats composed of two subspecies: diploid basin big sagebrush (A. tridentata subsp. tridentata) and tetraploid Wyoming big sagebrush (subsp. wyomingensis). In this study we assess seed weights across five subspecies‐cytotype groups of big sagebrush and examine the genetic and environmental components. Our goal is to determine if seed weight can be used as a diagnostic test for subspecies and seed certification. Seed weight was measured from 55 wild collections and from progeny derived from these collections and grown in two common gardens. A linear mixed‐effect model showed 91% of the variation in seed weight is explained by genetic, genetic × environment and environmental effects (conditional R2 = 0.91). Moreover, genetic effects alone, subspecies‐cytotype groups, explained 39% of the variation (marginal R2 = 0.39). Of the five subspecies‐cytotype groups, most had overlapping weights using conservative 99% confidence intervals. However, diploid tridentata and wyomingensis had non‐overlapping 99% confidence intervals. To demonstrate the application of seed weighing to assess the subspecies purity of commercial seed lots, we compared confidence intervals of tridentata and wyomingensis developed from the experimental data to seed weights of commercial lots. The results showed that only 17% of the commercial seed lots certified as wyomingensis had mean seed weights that fell within the confidence intervals for this subspecies. The remaining lighter seed lots (83%) matched weights of tridentata. While restoring sagebrush ecosystems is a multifaceted problem, a fundamental component to restoration is ensuring the appropriate seed is used. We found seed weight is principally affected by genetic factors, with limited environmental effects. Seed weighing is an effective application to assess subspecies purity of wyomingensis and tridentata seed and could be used as a certification step for evaluating commercial collections used in restoration.

Transcriptome characterization and polymorphism detection between subspecies of big sagebrush (Artemisia tridentata)

BackgroundBig sagebrush (Artemisia tridentata) is one of the most widely distributed and ecologically important shrub species in western North America. This species serves as a critical habitat and food resource for many animals and invertebrates. Habitat loss due to a combination of disturbances followed by establishment of invasive plant species is a serious threat to big sagebrush ecosystem sustainability. Lack of genomic data has limited our understanding of the evolutionary history and ecological adaptation in this species. Here, we report on the sequencing of expressed sequence tags (ESTs) and detection of single nucleotide polymorphism (SNP) and simple sequence repeat (SSR) markers in subspecies of big sagebrush.ResultscDNA of A. tridentata sspp. tridentata and vaseyana were normalized and sequenced using the 454 GS FLX Titanium pyrosequencing technology. Assembly of the reads resulted in 20,357 contig consensus sequences in ssp. tridentata and 20,250 contigs in ssp. vaseyana. A BLASTx search against the non-redundant (NR) protein database using 29,541 consensus sequences obtained from a combined assembly resulted in 21,436 sequences with significant blast alignments (≤ 1e-15). A total of 20,952 SNPs and 119 polymorphic SSRs were detected between the two subspecies. SNPs were validated through various methods including sequence capture. Validation of SNPs in different individuals uncovered a high level of nucleotide variation in EST sequences. EST sequences of a third, tetraploid subspecies (ssp. wyomingensis) obtained by Illumina sequencing were mapped to the consensus sequences of the combined 454 EST assembly. Approximately one-third of the SNPs between sspp. tridentata and vaseyana identified in the combined assembly were also polymorphic within the two geographically distant ssp. wyomingensis samples.ConclusionWe have produced a large EST dataset for Artemisia tridentata, which contains a large sample of the big sagebrush leaf transcriptome. SNP mapping among the three subspecies suggest the origin of ssp. wyomingensis via mixed ancestry. A large number of SNP and SSR markers provide the foundation for future research to address questions in big sagebrush evolution, ecological genetics, and conservation using genomic approaches.

Plant Age and Growing Season Nutritional Content Relationships of Three Artemisia tridentata Subspecies

The effect of plant age on growing season chemical compositions and rumen fermentation characteristics was determined for three subspecies of big sagebrush: basin (Artemisia tridentata [Nutt.] subsp. tridentata), mountain (A. tridentata subsp. vaseyana [Rybd.] Beetle), and Wyoming (A. tridentata subsp. wyomingensis [Beetle and Young]). In vitro dry matter (IVDMD) and organic matter (IVOMD) disappearance, ammonia nitrogen (NH3N), and volatile fatty acid (VFA) content were determined at the end of two fermentation periods (24 h and 48 h) by combining rumen inocula with age-classified vegetative samples from each sagebrush subspecies. An additional one-way analysis of variance was performed to investigate potential differences among subspecies in IVDMD, IVOMD, total VFA, and NH3N following a 48-h fermentation period. Crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL) components were also compared among sagebrush subspecies. Age class responses were variable across the spectrum of sagebrush subspecies and response variables. Where plant age effects were indicated, the small numeric differences probably have little biological or ecological significance. Mountain sagebrush was lower in IVOMD and total VFA concentrations (P < 0.0001) than basin and Wyoming. NH3N concentration and CP were higher (P < 0.0001) in basin sagebrush than the other two subspecies, while Wyoming sagebrush was higher in NDF, ADF, and ADL than basin and mountain subspecies (P < 0.0001). NH3N concentration for all three subspecies was lower than the minimum level (20 mg · 100 mL−1) required for uninhibited rumen activity. Overall, this research questions the contention that older sagebrush plants offer less nutritional value than younger ones, at least for growing season conditions. The results also provide information that can be utilized in designing supplementation strategies for domestic animals on diets with characteristically high utilization of big sagebrush. El efecto de la edad de la planta sobre la composición química durante el crecimiento estacional, y las características de fermentación en el rumen se determinaron para tres subespecies de “big sagebrush”: basin (Artemisia tridentata [Nutt.] sbsp. tridentata), mountain (A. tridentata sbsp. vaseyana [Rybd.] Beetle), y Wyoming (A. tridentata sbsp. wyomingensis [Beetle and Young]). Digestibilidad in vitro de la materia seca (IVDMD) y digestibilidad in vitro de la materia orgánica (IVOMD), así como el contenido de nitrógeno amoniacal (NH3N) y ácidos grasos volátiles (VFA) se determinaron al final de dos periodos de fermentación (24 y 48 h) por medio de la combinación de fluido ruminal con muestras vegetativas clasificadas por edad de cada una de las subespecies de sagebrush. Se realizó un ANOVA adicional para investigar posibles diferencias entre subespecies en IVDMD, IVOMD, total VFA y NH3N después de un período de fermentación de 48 horas. Los componentes de proteína cruda (CP), fibra neutra detergente (FDN), fibra ácido detergente (ADF) y de lignina ácido detergente (ADL) se compararon también entre las subespecies de sagebrush. Las categorías basadas en edad fueron las respuestas de las variables en todos los rangos de las subespecies de tridentata y las variables de respuesta. En donde se especificó el efecto de la edad de planta, las pequeñas diferencias numéricas probablemente tuvieron poca importancia biológica o ecológica. La subespecie de “mountain sagebrush” presentó los valores más bajos de IVOMD y las concentraciones totales de VFA (P < 0.0001) que la subespecie basin y Wyoming. Las concentraciones de NH3N y contenidos de CP fueron mayores (P < 0.0001) en basin sagebrush que en las otras dos subespecies, mientras que Wyoming sagebrush fue mayor en NDF, ADF y ADL que las otras dos subespecies (P < 0.0001). Las concentraciones de NH3N para las tres subespecies fueron inferiores al nivel mínimo (20 mg · 100 mL−1) que son necesarios para la actividad de los microorganismos del rumen. En general, esta investigación pone en duda la afirmación de que las plantas más viejas de sagebrush proporcionan un valor nutricional menor que las más jóvenes, al menos durante la época de crecimiento. Estos resultados proporcionan información que también puede utilizarse en el diseño de programas de estrategias de suplementacion para los animales domésticos con dietas que se caracterizan en una gran utilización de “big sagebrush.”

Native Perennial Forb Variation Between Mountain Big Sagebrush and Wyoming Big Sagebrush Plant Communities

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.

Vegetation Characteristics of Mountain and Wyoming Big Sagebrush Plant Communities in the Northern Great Basin

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. Las especies de plantas dominantes se usan frecuentemente como indicadores de potencial en sitios de bosques y pastizales. Sin embargo, las subespecies de vegetación dominante a menudo indican diferentes características y entonces, pueden ser indicadores más útiles del potencial de una comunidad de plantas, ya que dan información más precisa para su manejo. Big sagebrush (Artemisia tridentata Nutt.) se encuentra presente en grandes extensiones a través del oeste de Estados Unidos. Especies comunes de big sagebrush tienen considerables variaciones en cuanto al tipo de lugares en las que están presentes, sin embargo, es escasa la información que cuantifique estas diferencias en cuanto a sus características vegetativas. En consecuencia, las directrices para el manejo de fauna y de la tierra no hacen diferencia entre subespecies de big sagebrush. Para cuantificar las características vegetativas entre dos subespecies comunes de big sagebrush, obtuvimos muestras de 106 plantas de comunidades intactas de big sagebrush. La mitad de las plantas muestreadas se obtuvieron de comunidades de Wyoming big sagebrush (A. tridentata subsp. wyomingensis [Beetle & A. Young] S. L. Welsh) y la otra mitad se seleccionó de una comunidad de mountain big sagebrush (A. tridentata subsp. vaseyana [Rydb.] Beetle). La cobertura de Sagebrush fue 2.4 veces mayor en promedio en las comunidades de mountain big sagebrush. La densidad y cobertura de herbáceas perennes fue 3.8 y 5.6 veces mayor en mountain sagebrush comparada con las comunidades de Wyoming big sagebrush. La biomasa total producida por las herbáceas fue aproximadamente 2 veces mayor en comunidades de plantas de mountain big sagebrush que en las comunidades de Wyoming big sagebrush. Los resultados de este estudio sugieren que las directrices para el manejo de pastoreo, fauna y otros usos deben reconocer la amplia variabilidad de subespecies como indicadores en sitios con diferentes potenciales.

Symbiotic regulation of plant growth, development and reproduction

The growth and development of rice (Oryzae sativa) seedlings was shown to be regulated epigenetically by a fungal endophyte. In contrast to un-inoculated (nonsymbiotic) plants, endophyte colonized (symbiotic) plants preferentially allocated resources into root growth until root hairs were well established. During that time symbiotic roots expanded at five times the rate observed in nonsymbiotic plants. Endophytes also influenced sexual reproduction of mature big sagebrush (Artemisia tridentata) plants. Two spatially distinct big sagebrush subspecies and their hybrids were symbiotic with unique fungal endophytes, despite being separated by only 380m distance and 60 m elevation. A double reciprocal transplant experiment of parental and hybrid plants, and soils across the hybrid zone showed that fungal endophytes interact with the soils and different plant genotypes to confer enhanced plant reproduction in soil native to the endophyte and reduced reproduction in soil alien to the endophyte. Moreover, the most prevalent endophyte of the hybrid zone reduced the fitness of both parental subspecies. Because these endophytes are passed to the next generation of plants on seed coats, this interaction provides a selective advantage, habitat specificity, and the means of restricting gene flow, thereby making the hybrid zone stable, narrow, and potentially leading to speciation.

Recovery of Big Sagebrush Following Fire in Southwest Montana

Fire plays a large role in structuring sagebrush ecosystems; however, we have little knowledge of how vegetation changes with time as succession proceeds from immediate postfire to mature stands. We sampled at 38 sites in southwest Montana dominated by 3 subspecies of big sagebrush (Artemisia tridentata Nutt.). At each site we subjectively located 1 sample plot representing the burned area and an unburned macroplot in similar, adjacent, unburned vegetation. Canopy cover of sagebrush was estimated, and plants were counted in 10 microplots. Age and height of randomly chosen sagebrush plants in each size class were determined from 5 microplots. Average postfire time to full recovery of mountain big sagebrush (ssp. vasseyana [Rydb.] Beetle) canopy cover was 32 years, shorter for basin (ssp. tridentata) and much longer for Wyoming (ssp. wyomingensis Beetle & Young) big sagebrush. Height recovered at similar rates. There was no difference in canopy cover or height recovery between prescribed fires and wildfires in stands of mountain big sagebrush. We found no relationship between mountain big sagebrush canopy cover recovery and annual precipitation, heat load, or soil texture. Nearly all unburned sagebrush macroplots were uneven-aged, indicating that recruitment was not limited to immediate postfire conditions in any of the subspecies. Average canopy cover of three-tip sagebrush (A. tripartita Rydb.) did not increase following fire, and many three-tip sagebrush plants established from seed instead of sprouting. Our results suggest that the majority of presettlement mountain big sagebrush stands would have been in early to midseral condition in southwest Montana assuming a mean fire interval of 25 years. Only long fire-return intervals will allow stands dominated by Wyoming big sagebrush to remain on the landscape in our study area. We speculate that effects of site-specific factors conducive to sagebrush recovery are small compared to stochastic effects such as fire.

Greater Sage-Grouse Response to Sagebrush Management in Utah

Greater sage-grouse (Centrocercus urophasianus) populations throughout much of their range have been declining. These declines have largely been attributed to the loss or deterioration of sagebrush (Artemisia spp.) habitat. In response government agencies such as the United States Department of Agriculture, Natural Resources Conservation Service are cost-sharing on management practices designed to improve habitat conditions for sage-grouse. Little is known regarding sage-grouse response to various sagebrush management techniques. We studied the effects of reducing sagebrush canopy cover using 2 mechanical (Dixie harrow and Lawson aerator) treatments and 1 chemical (Tebuthiuron) treatment on greater sage-grouse use of brood-rearing habitats on Parker Mountain, Utah, USA. To conduct this experiment, we identified 19 40.5-ha plots that exhibited >40% mountain big sagebrush (A. tridentata vaseyana) canopy cover and randomly assigned 16 as treatment or controls (4 replicates each). Tebuthiuron and Dixie-harrow-treated plots had more forb cover than did control plots (P = 0.01 and 0.02, respectively) in post-treatment periods. Greater sage-grouse brood use was higher in Tebuthiuron than control plots (P = 0.01). We believe this was attributed to increased herbaceous cover, particularly forb cover. However, in all plots, sage-grouse use was greatest within 10 m of the edge of the treatments where adjacent sagebrush cover was still available. Although the treatments we studied resulted in the plots achieving sage-grouse brooding-rearing habitat guidelines, caution should be exercised in applying these observations at lower elevations, on sites with less annual precipitation, or on a different subspecies of big sagebrush. Prior to using these techniques to implement large-scale sagebrush treatments, the specific rationale for conducting them should be clearly identified. Large-scale projects using the techniques we studied would not be appropriate within sage-grouse wintering or nesting habitat.

Browsing and Plant Age Relationships to Winter Protein and Fiber of Big Sagebrush Subspecies

Plants of 3 big sagebrush subspecies, mountain big sagebrush (Artemisia tridentata ssp. vaseyana [Rydb.] Beetle), Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis Beetle and Young), and basin big sagebrush (Artemisia tridentata Nutt. ssp. tridentata) were sampled for crude protein and acid detergent fiber (ADF) content. The ADF was determined as an indication of energy content and digestibility. Crude protein and ADF levels were compared among the 3 taxa and between lightly and heavily browsed plants and young and mature plants within each subspecies. Current year growth collected in mid-January was sampled to coincide with the season of greatest ungulate browsing on big sagebrush. Crude protein for mountain big sagebrush (8.34%) was less (P ≤ 0.05) than for Wyoming big sagebrush (11.25%) and basin big sagebrush (11.29%). All are well above the maintenance requirements of deer at 7.5% crude protein. The ADF levels between age and browse-use classes were not different (P ≤ 0.05) within any subspecies, although mountain big sagebrush generally had a lower ADF level than the other 2 subspecies. Wyoming big sagebrush was the only taxon with a crude protein difference (1.2%) (P ≤ 0.05) between age classes, although the difference is not biologically significant. Crude protein was not different between browse-use classes within any of the 3 taxa. Crude protein and digestibility do not indicate ungulate preference for these big sagebrush subspecies.

Browsing and Plant Age Relationships to Winter Protein and Fiber of Big Sagebrush Subspecies

Browsing and Plant Age Relationships to Winter Protein and Fiber of Big Sagebrush Subspecies

Browsing and Plant Age Relationships to Winter Protein and Fiber of Big Sagebrush Subspecies

Plants of 3 big sagebrush subspecies, mountain big sagebrush (Artemisia tridentata ssp. vaseyana [Rydb.] Beetle), Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis Beetle and Young), and basin big sagebrush (Artemisia tridentata Nutt. ssp. tridentata) were sampled for crude protein and acid detergent fiber (ADF) content. The ADF was determined as an indication of energy content and digestibility. Crude protein and ADF levels were compared among the 3 taxa and between lightly and heavily browsed plants and young and mature plants within each subspecies. Current year growth collected in mid-January was sampled to coincide with the season of greatest ungulate browsing on big sagebrush. Crude protein for mountain big sagebrush (8.34%) was less (P ≤ 0.05) than for Wyoming big sagebrush (11.25%) and basin big sagebrush (11.29%). All are well above the maintenance requirements of deer at 7.5% crude protein. The ADF levels between age and browse-use classes were not different (P ≤ 0.05) within any subspecies, although mountain big sagebrush generally had a lower ADF level than the other 2 subspecies. Wyoming big sagebrush was the only taxon with a crude protein difference (1.2%) (P ≤ 0.05) between age classes, although the difference is not biologically significant. Crude protein was not different between browse-use classes within any of the 3 taxa. Crude protein and digestibility do not indicate ungulate preference for these big sagebrush subspecies.

Climatic Influences on Recruitment of 3 Subspecies of Artemisia tridentata

Previous research suggested that big sagebrush (Artemisia tridentata Nutt.) recruitment occurs in pulses consistent with favorable climatic conditions. In 1997, 75 stem sections were collected from 9 stands of each of the 3 subspecies of big sagebrush in Wyoming along elevation and climatic gradients. Annual growth rings were used to identify the year plants were established. Large cohorts of Wyoming big sagebrush (A. tridentata ssp. wyomingensis Beetle and Young) appeared in 1982, 1981, 1964, 1961, and 1955. Basin big sagebrush (A. tridentata ssp. tridentata Beetle and Johnson) cohorts flourished in 1991, 1986, 1985, 1982, and 1977. Mountain big sagebrush (A. tridentata ssp. vaseyana [Rydb.] Beetle) cohorts prospered in 1985, 1982, 1981, 1979, and 1974. Mean monthly precipitation and temperature records were compared to years with high and low recruitment using logistic regression models at 3 geographic scales (single-stand, regional, statewide). Wyoming big sagebrush recruitment was greatest in years with above-average December and January precipitation occurring after the first growing season (r2 = 0.10, 0.04, P < 0.05). Basin big sagebrush recruitment was most successful in years with above-average March, May, and June precipitation during the first growing season (r2 = 0.06, 0.09, 0.18, P < 0.05). Mountain big sagebrush recruitment was greatest in years with below-average February, April, and May precipitation after the first growing season (r2 = 0.03, 0.04, 0.04, P < 0.05). While variable precipitation patterns appear to contribute significantly to recruitment of big sagebrush, responses among the 3 major subspecies were quite variable. More complex models need to be developed to foster our understanding of the mechanisms affecting big sagebrush establishment. DOI:10.2458/azu_jrm_v54i6_maier

Demographic Characteristics of 3 Artemisia tridentata Nutt. Subspecies

Previous research suggested that woody plant recruitment may occur in pulses in semi-arid areas. The overall objective of this study was to determine if this pulse phenomena was recorded in the demographic structures of big sagebrush (Artemisia tridentata Nutt.) stands in Wyoming. In 1997, approximately 75 stem cross sections were collected from 9 stands of each of 3 subspecies of big sagebrush in Wyoming along elevation and climatic gradients. Annual growth-rings were used to identify year of establishment and demographic characteristics were analyzed from age-class frequencies. Mean stand ages of the 3 subspecies were different (P = 0.002), and analyses revealed that Wyoming (A. tridentata ssp. wyomingensis) and mountain big sagebrush (A. tridentata ssp. vaseyana) stand ages (32 +/- 9 and 26 +/- 9 years, respectively) were significantly older than basin big sagebrush (A. tridentata ssp. tridentata) (17 +/- 3) stands (P < 0.05). Mean recruitment intervals (years) were shorter for basin (1.6) than for Wyoming (2.3) and mountain (2.2) sagebrush (P = 0.01). The number of cohorts did not differ among the subspecies (P = 0.11), but the percent of years with recruitment was significantly higher for basin (59%) compared to Wyoming (37%) and mountain (39%) subspecies (P < 0.0001). Age-class frequency distributions of each stand and regional stand combination were assessed for dispersion across each associated period of record. Chi-square goodness-of-fit tests were performed for the negative binomial distribution. All stands (with one exception) and all 3 regional stand combinations fit the negative binomial distribution. Age-class frequency patterns indicate that recruitment is clustered or aggregated across each period of record. Recruitment in big sagebrush stands occurs in pulses throughout Wyoming. DOI:10.2458/azu_jrm_v54i2_perryman

Demographic characteristics of 3 Artemisia tridentata Nutt. subspecies

Previous research suggested that woody plant recruitment may occur in pulses in semi-arid areas. The overall objective of this study was to determine if this pulse phenomena was recorded in the demographic structures of big sagebrush (Artemisia tridentata Nutt.) stands in Wyoming. In 1997, approximately 75 stem cross sections were collected from 9 stands of each of 3 subspecies of big sagebrush in Wyoming along elevation and climatic gradients. Annual growth-rings were used to identify year of establishment and demographic characteristics were analyzed from age-class frequencies. Mean stand ages of the 3 subspecies were different (P = 0.002), and analyses revealed that Wyoming (A. tridentata ssp. wyomingensis) and mountain big sagebrush (A. tridentata ssp. vaseyana) stand ages (32 +/- 9 and 26 +/- 9 years, respectively) were significantly older than basin big sagebrush (A. tridentata ssp. tridentata) (17 +/- 3) stands (P &lt; 0.05). Mean recruitment intervals (years) were shorter for basin (1.6) than for Wyoming (2.3) and mountain (2.2) sagebrush (P = &lt; 0.01). The number of cohorts did not differ among the subspecies (P = 0.11), but the percent of years with recruitment was significantly higher for basin (59%) compared to Wyoming (37%) and mountain (39%) subspecies (P 0.0001). Age-class frequency distributions of each stand and regional stand combination were assessed for dispersion across each associated period of record. Chi-square goodness-of-fit tests were performed for the negative binomial distribution. All stands (with one exception) and all 3 regional stand combinations fit the negative binomial distribution. Age-class frequency patterns indicate that recruitment is clustered or aggregated across each period of record. Recruitment in big sagebrush stands occurs in pulses throughout Wyoming.

Climatic influences on recruitment of 3 subspecies of Artemisia tridentata

Previous research suggested that big sagebrush (Artemisia tridentata Nutt.) recruitment occurs in pulses consistent with favorable climatic conditions. In 1997, 75 stem sections were collected from 9 stands of each of the 3 subspecies of big sagebrush in Wyoming along elevation and climatic gradients. Annual growth rings were used to identify the year plants were established. Large cohorts of Wyoming big sagebrush (A. tridentata ssp. wyomingensis Beetle and Young) appeared in 1982, 1981, 1964, 1961, and 1955. Basin big sagebrush (A. tridentata ssp. tridentata Beetle and Johnson) cohorts flourished in 1991, 1986, 1985, 1982, and 1977. Mountain big sagebrush (A. tridentata ssp. vaseyana [Rydb.] Beetle) cohorts prospered in 1985, 1982, 1981, 1979, and 1974. Mean monthly precipitation and temperature records were compared to years with high and low recruitment using logistic regression models at 3 geographic scales (single-stand, regional, statewide). Wyoming big sagebrush recruitment was greatest in years with above-average December and January precipitation occurring after the first growing season (r2 = 0.10, 0.04, P &lt; 0.05). Basin big sagebrush recruitment was most successful in years with above-average March, May, and June precipitation during the first growing season (r2 = 0.06, 0.09, 0.18, P &lt; 0.05). Mountain big sagebrush recruitment was greatest in years with below-average February, April, and May precipitation after the first growing season (r2 = 0.03, 0.04, 0.04, P &lt; 0.05). While variable precipitation patterns appear to contribute significantly to recruitment of big sagebrush, responses among the 3 major subspecies were quite variable. More complex models need to be developed to foster our understanding of the mechanisms affecting big sagebrush establishment.