Sagebrush Plant Communities Research Articles

Differential seedling performance and environmental correlates in shrub canopy vs. interspace microsites

Shrubs in semi-arid ecosystems promote micro-environmental variation in a variety of soil properties and site characteristics. However, little is known regarding post-fire seedling performance and its association with environmental variation in former shrub canopy and interspace microsites. We compared post-fire seeding success and various soil properties important for seedling establishment between shrub canopy and interspace microsites in Wyoming big sagebrush (Artemisia tridentata) plant communities in southeast Oregon, U.S.A. We burned 5, 20 × 20 m sites and established paired canopy and interspace micro-transects seeded with bluebunch wheatgrass (Pseudoroegneria spicata, 193 seeds/m) or crested wheatgrass (Agropyron cristatum, 177 seeds/m). At one year post-fire, seedling density was 69% higher (p = 0.012) for crested wheatgrass (compared to bluebunch wheatgrass) and 75% higher (p = 0.019) for interspace microsites (compared to canopy). However, tiller and leaf area production were over twice as high (p < 0.05) in canopy microsites. Soil color and soil temperature, explained 19–32% of variation in seedling performance metrics. Shrub effects on seeding success are complex and interact with abiotic disturbances, but patterns of increased seedling performance in canopy microsites and their relationships to soil variables may suggest tactics for increasing success of restoration practices.

Comparing Burned and Mowed Treatments in Mountain Big Sagebrush Steppe

Fires in mountain big sagebrush [Artemisia tridentata spp. vaseyana (Rydb.) Beetle] plant communities historically shifted dominance from woody to herbaceous vegetation. However, fire return intervals have lengthened with European settlement, and sagebrush dominance has increased at the expense of herbaceous vegetation in some plant communities. Management actions may be needed to decrease sagebrush in dense sagebrush stands to increase herbaceous vegetation. Prescribed fire is often used to remove sagebrush; however, mechanical treatments, such as mowing, are increasingly used because they are more controllable and do not pose an inherent risk of escape compared with fire. However, information on the effects of burned and mowed treatments on herbaceous vegetation and whether fire and mowed applications elicit similar vegetation responses are limited. We evaluated the effects of prescribed burning and mowing for 3 years after treatment in mountain big sagebrush plant communities. The burned and mowed treatments generally increased herbaceous cover, density, and production compared with untreated controls (P < 0.05). However, neither treatment induced a response in native perennial forb cover, density, or biomass (P > 0.05). In contrast, annual forb (predominately natives) cover, density, and biomass increased with mowing and burning (P < 0.05). Vegetation generally responded similarly in burned and mowed treatments; however, the burned treatment had less sagebrush, greater herbaceous vegetation production, and more bare ground than the mowed treatment (P < 0.05). These differences should be considered when selecting treatments to decrease sagebrush.

Vegetation Response to Mowing Dense Mountain Big Sagebrush Stands

A decrease in fire frequency and past grazing practices has led to dense mountain big sagebrush (Artemisia tridentata Nutt. subsp. vaseyana [Rydb.] Beetle) stands with reduced herbaceous understories. To reverse this trend, sagebrush-reducing treatments often are applied with the goal of increasing herbaceous vegetation. Mechanical mowing is a sagebrush-reducing treatment that commonly is applied; however, information detailing vegetation responses to mowing treatments generally are lacking. Specifically, information is needed to determine whether projected increases in perennial grasses and forbs are realized and how exotic annual grasses respond to mowing treatments. To answer these questions, we evaluated vegetation responses to mowing treatments in mountain big sagebrush plant communities at eight sites. Mowing was implemented in the fall of 2007 and vegetation characteristics were measured for 3 yr post-treatment. In the first growing season post-treatment, there were few vegetation differences between the mowed treatment and untreated control (P > 0.05), other than sagebrush cover being reduced from 28% to 3% with mowing (P < 0.001). By the second growing season post-treatment, perennial grass, annual forb, and total herbaceous vegetation were generally greater in the mowed than control treatment (P < 0.05). Total herbaceous vegetation production was increased 1.7-fold and 1.5-fold with mowing in the second and third growing seasons, respectively (P < 0.001). However, not all plant functional groups increased with mowing. Perennial forbs and exotic annual grasses did not respond to the mowing treatment (P > 0.05). These results suggest that the abundance of sagebrush might not be the factor limiting some herbaceous plant functional groups, or they respond slowly to sagebrush-removing disturbances. However, this study suggests that mowing can be used to increase herbaceous vegetation and decrease sagebrush in some mountain big sagebrush plant communities without promoting exotic annual grass invasion. Una disminución en la frecuencia del fuego y anteriores practicas de pastoreo han llevado a la formación de montículos densos de artemisa de la montaña (Artemisia tridentata Nutt. subsp. vaseyana [Rydb.] Beetle) y la reducción del estrato herbáceo. Para revertir esta tendencia, con frecuencia se aplican tratamientos para reducir la artemisa y aumentar la vegetación herbácea. La remoción mecánica de la artemisa es el tratamiento comúnmente usado, sin embargo, no hay información detallada de la respuesta de la vegetación al chapoleo. Específicamente, se necesita información para determinar sí aumentos proyectados en pastos perennes y hierbas se posibles y como pastos exótico anuales responden al tratamiento de chapoleo. Para responder esta preguntas, evaluamos la respuesta de la vegetación al tratamiento de chapoleo in comunidades de plantas de gran artemisa de montaña en ocho sitios. El chapoleo fue implementado en el otoño de 2007 y las características de la vegetación fueron medida tres años post-tratamiento. En la primera época de crecimiento de post-tratamiento hubo pocas diferencias en la vegetación entre el tratamiento de chapoleo y el control (P > 0.05). La cobertura de artemisa se redujo de 28% a 3% con el chapoleo (P < 0.001). Para la segunda época de crecimiento post-tratamiento los pastos perennes, hierbas anuales y el total de la vegetación herbácea fueron generalmente mayores en el tratamiento de chapoleo que en el control (P < 0.05). El total de la producción de la vegetación herbácea aumento 1.7 a 1.5 veces con el tratamiento de chapoleo en la segunda y tercer época de crecimiento respectivamente (P < 0.001). Sin embargo, no todos los grupos funcionales de plantas aumentaron con el chapoleo. Las hierbas perennes y pastos exóticos anuales no respondieron al tratamiento de chapoleo (P > 0.05). Estos resultados sugieren que la abundancia de artemisa puede no ser el factor limitante de algunos grupos funcionales de plantas herbaceas o que ellas responden lentamente al disturbio de la remoción de la artemisa. Sin embargo, este estudio sugiere que el chapoleo puede ser usado para aumentar la vegetación herbácea y disminuir la artemisa en algunas comunidades de plantas de gran artemisa de montaña sin promover la invasión de pastos anuales exóticos.

Are There Benefits to Mowing Wyoming Big Sagebrush Plant Communities? An Evaluation in Southeastern Oregon

Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis Beetle & Young) communities frequently are mowed in an attempt to increase perennial herbaceous vegetation. However, there is limited information as to whether expected benefits of mowing are realized when applied to Wyoming big sagebrush communities with intact understory vegetation. We compared vegetation and soil nutrient concentrations in mowed and undisturbed reference plots in Wyoming big sagebrush plant communities at eight sites for three years post-treatment. Mowing generally did not increase perennial herbaceous vegetation cover, density, or biomass production (P > 0.05). Annual forbs and exotic annual grasses were generally greater in the mowed compared to the reference treatment (P < 0.05). By the third year post-treatment annual forb and annual grass biomass production was more than nine and sevenfold higher in the mowed than reference treatment, respectively. Our results imply that the application of mowing treatments in Wyoming big sagebrush plant communities does not increase perennial herbaceous vegetation, but may increase the risk that exotic annual grasses will dominate the herbaceous vegetation. We suggest that mowing Wyoming big sagebrush communities with intact understories does not produce the expected benefits. However, the applicability of our results to Wyoming big sagebrush communities with greater sagebrush cover and/or degraded understories needs to be evaluated.

The influence of plant removal on succession in Wyoming big sagebrush

Restoration treatments are based on the largely untested notion that desired recovery of plant communities following disturbance wouldn’t occur in the absence of active intervention. We identified rate of short-term (10 year) floristic changes following removal of plant functional groups in Wyoming big sagebrush plant communities in 1999–2005 and 2008. Treatments imposed on 6 × 6 m plots were: 1) removal of all plant functional groups, 2) perennial grass removal, 3) shrub removal and 4) control. Our data suggest recovery of the shrub component on shrub removal plots could take decades. Similarly, perennial grass cover and density on perennial grass removal plots was less than half that of unaltered plots 10 years after treatment. When all functional groups were removed, cover of annual forbs, annual grasses, and shrubs returned to unaltered levels within ten years or less. Perennial forbs were unaffected ( p > 0.05) by treatment. The fact that natural recovery of some components occurred within a relatively short post-disturbance time interval (i.e. <10 years) suggests that intervention may not be necessary for some functional groups. Restoring shrubs in areas dominated by perennial grasses may require targeted reductions of competing perennial grasses. Conversely, shrub dominance may limit perennial grass re-establishment.

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.

Cheatgrass: fire and forage on the range

This is a scientific and historical account of the cheatgrass invasion. (Bromus tectorum) is an exotic species that appeared in North America in the late nineteenth century and has since become a dominant plant in the arid and semiarid rangelands between the Sierra Nevada, Cascades, and Rocky Mountains. It is the first grass to appear after the region's long, cold winters and thus has become an important forage plant for livestock and wildlife. is also a major environmental hazard in the sagebrush plant communities where it has established itself, providing highly combustible fuel for the wildfires that have ravaged so much of the Great Basin since the mid-twentieth century. Cheatgrass is the first comprehensive study of this highly invasive plant that has changed the ecology of millions of acres of western rangeland. Authors Young and Clements have researched the biology and impact of cheatgrass for four decades. Their book addresses the subject from several perspectives: the history of the invasion; the origins and biology of cheatgrass; its genetic variations, breeding system, and patterns of distribution; its impact on grazing management; and the role it plays, both positive and negative, in the lives of high desert wildlife.

The Response of Thurber’s Needlegrass to Fall Prescribed Burning

Thurber’s needlegrass (Achnatherum thurberianum [Piper] Barkworth) is an important component of many sagebrush communities in the Intermountain West. Prescribed fall burning is often implemented in sagebrush plant communities to mimic historic wildfires, improve wildlife habitat, and increase livestock forage production. Burning is used because it shifts dominance from sagebrush to herbaceous vegetation. The effects of prescribed fall burning on Thurber’s needlegrass are largely unexplored. The purpose of this study was to determine the response of Thurber’s needlegrass to prescribed fall burning. A randomized block design was used, and each block consisted of a fall burned and unburned (control) Wyoming big sagebrush (Artemisia tridentata subsp. wyomingensis [Beetle & A. Young] S. L. Welsh)–bunchgrass communities. Response variables measured in the first and second years after burns were Thurber’s needlegrass community foliar cover and density, vegetative and reproductive biomass, photosynthetic rates, tissue carbon (C) and nitrogen (N) content, and N ( 15 N: 14 N) and C ( 13 C: 12 C) isotope ratios. Density of Thurber’s needlegrass in both postburn years and cover in the second postburn year were not different between treatments (P . 0.05), but cover was less in the burned than control treatment in the first postburn year (P 5 0.008). Carbon isotope ratios in Thurber’s needlegrass differed between the burn (225.9 6 0.1 SE) and control (226.3 6 0.1 SE) treatments in the first postburn year (P 5 0.019). Nitrogen isotope ratios indicated nitrogen was more available in the burned than control treatment in both years (P , 0.05). Photosynthetic rates of Thurber’s needlegrass were also generally greater in the burned than control treatment (P 5 0.045). Our results suggest burning altered the availability of resources to Thurber’s needlegrass plants. Our results also suggest that prescribed fall burning is not detrimental to Thurber’s needlegrass and, thus, can be used as a method to shift dominance from sagebrush to herbaceous vegetation.

Relationships Between Western Juniper (Juniperus occidentalis) and Understory Vegetation

AbstractWestern juniper has been actively invading sagebrush plant communities for about 130 yr. Western juniper canopy cover generally increases as western juniper invades sagebrush steppe communities and succession progresses toward a western juniper woodland. Our goal was to estimate the impact of juniper invasion and canopy increase on understory vegetation structure and productivity on 101 sites in northeastern California. The primary objectives of this study were to: (1) examine the influence of increasing western juniper canopy cover on the composition and productivity of understory vegetation; and (2) assess the effects of western juniper removal on understory vegetation. Sites in early, mid-, and late successional stages and sites on the same soils that had not been invaded were selected. Sites where western juniper had been removed by prescribed fire, mechanical, or chemical methods were compared to adjacent untreated sites. Western juniper canopy cover, understory cover and species composition, productivity, and bare ground were determined at each site during May through July 2005 and 2006. Regression analysis was used to evaluate the relationship between western juniper canopy cover and understory vegetation parameters. Logistic regression was used to detect understory differences between treated (juniper removed) and untreated (juniper not removed) sites. A significant relationship was found between western juniper canopy cover and understory species richness, shrub cover, forb cover, total grass cover, cheatgrass cover, herbaceous productivity, and bare ground. Removal of western juniper increased total grass cover, cheatgrass cover, and productivity, and reduced bare ground. The results of this study support findings by researchers in other states that western juniper influences plant community structure and productivity, and removal of western juniper might reverse these changes in structure, but also might increase opportunities for invasion of cheatgrass.

LONG-TERM VEGETATION DYNAMICS IN A CUT WESTERN JUNIPER WOODLAND

Abstract Western juniper (Juniperus occidentalis spp. occidentalis Hook.) expansion in the northern Great Basin has reduced shrubsteppe productivity and diversity. Chainsaw cutting of western juniper woodlands is commonly applied to remove tree interference and restore sagebrush plant communities. Studies assessing understory response following cutting have been limited to early successional stages and have not evaluated the effects of western juniper debris on plant succession. Cutting western juniper produces a large amount of debris which is commonly left on site, occupying a significant portion of treated areas. This study evaluated successional dynamics spanning 13 years after western juniper cutting. Four 0.45-ha blocks were selected on Steens Mountain in southeastern Oregon. Western juniper cover averaged 26% and mature tree density averaged 250 trees · ha−1. Blocks were cut in late summer 1991. Understory standing crop, cover, and density were compared among 3 locations: old canopy litter mats (ca...

Short-term Effects of Burning Wyoming Big Sagebrush Steppe in Southeast Oregon

Wyoming big sagebrush (Artemisia tridentata subsp. wyomingensis [Beetle & A. Young] S.L. Welsh) plant communities of the Intermountain West have been greatly reduced from their historic range as a result of wildfire, agronomic practices, brush control treatments, and weed invasions. The impact of prescribed fall burning Wyoming big sagebrush has not been well quantified. Treatments were sagebrush removed with burning (burned) and sagebrush present (control). Treatments were applied to 0.4-ha plots at 6 sites. Biomass production, vegetation cover, perennial herbaceous vegetation diversity, soil water content, soil inorganic nitrogen (NO { ,N H z ), total soil nitrogen (N), total soil carbon (C), and soil organic matter (OM) were compared between treatments in the first 2 years postburn. In 2003 and 2004, total (shrub and herbaceous) aboveground annual biomass production was 2.3 and 1.2 times greater, respectively, in the control compared to the burned treatment. In the upper 15 cm of the soil profile, inorganic N concentrations were greater in the burned than control treatment, while soil water, at least in the spring, was greater in the control than burned treatment. Regardless, greater herbaceous aboveground annual production and cover in the burned treatment indicated that resources were more available to herbaceous vegetation in the burned than the control treatment. Exotic annual grasses did not increase with the burn treatment. Our results suggest in some instances that late seral Wyoming big sagebrush plant communities can be prescribed fall burned to increase livestock forage or alter wildlife habitat without exotic annual grass invasion in the first 2 years postburn. However, long-term evaluation at multiple sites across a larger area is needed to better quantify the effects of prescribed fall burning on these communities. Thus, caution is advised because of the value of Wyoming big sagebrush plant communities to wildlife and the threat of invasive plants.

Vegetation Characteristics Across Part of the Wyoming Big Sagebrush Alliance

The Wyoming big sagebrush ( Artemisia tridentata ssp. wyomingensis [Beetle & A. Young] S.L. Welsh) alliance is the most extensive of the big sagebrush complex in the Intermountain West. This alliance provides critical habitat for many sagebrush obligate and facultative wildlife species and serves as a forage base for livestock production . There is a lack of information that describes vegetation cover values, characteristics, diversity, and heterogeneity of the Wyoming big sagebrush alliance. This study describes vegetation cover values and defines distinct associations for intact, late-seral Wyoming big sagebrush plant communities across part of its northwestern range. We sampled 107 Wyoming big sagebrush plant communities. Total herbaceous cover values were variable among sites with differences between sites exceeding 700%. Mean sagebrush cover was 12.3% with 90% of the sites producing 6% to 20% cover. Tall forb (> 18 cm) cover averaged 1.9% and 90% of the sites varied between 0.2% and 5.6% cover. Five associations delineated by dominant perennial bunchgrass species were identified: ARTRW8 (Wyoming big sagebrush)/PSSP6 ( Pseudoroegneria spicata [Pursh] A. Löve, bluebunch wheatgrass), ARTRW8/ACTH7 ( Achnatherum thurberianum [Piper] Barkworth, Thurber’s needlegrass), ARTRW8/FEID ( Festuca idahoensis Elmer, Idaho fescue), ARTRW8/HECO26 ( Hesperostipa comata [Trin. & Rupr.] Barkworth, needle-and-thread), and ARTRW8/PSSP6–ACTH7 (a codominance of bluebunch wheatgrass and Thurber’s needlegrass). Our results suggest when the vegetation cover values proposed for sage-grouse are applied as requirements at or above the stand level, they exceed the ecological potential of many of the sites sampled. La alianza de la artemisa grande de Wyoming ( Artemisia tridentata ssp. wyomingensis [Beetle & A. Young] S.L. Welsh) es el complejo de artemisa mas extenso del oeste intermontano. Esta alianza proporciona hábitat crítico para muchas especies específicas y generalistas de artemisa y sirve como forraje básico para la producción ganadera. Existe muy poca información que describe el valor de la cobertura vegetal, características, diversidad, y heterogeneidad de la alianza de la artemisa grande. El presente estudio describe valores de cobertura vegetal y define las diferentes asociaciones en comunidades intactas de plantas serales de artemisa grande en el rango noroeste. Muestreamos 107 comunidades de plantas de artemisa grande de Wyoming. El total de los valores de cobertura herbácea fueron variables entre sitios con diferencias que excedían el 700%. La cobertura promedio de artemisa fue de 12.3% con un 90% de los sitios con un rango de cobertura entre 6% y 20%. La cobertura de hierbas altas ( >18 cm) promedió 1.9% y el 90% de los sitios variaron en cobertura entre 0.2% y 5.6%. Se identificaron cinco asociaciones delineadas por especies perennes dominantes de pastos: ARTRW8 (Artemisa grande de Wyoming)/AGSP ( Agropyron spicatum [Pursh] Schibn. & Smith, bluebunch wheatgrass), ARTRW8/STTH ( Stipa thurberiana ajenjo, Thurber’s needlegrass), ARTRW8/FEID ( Festuca idahoensis Elmer, Idaho fescue), ARTRW8/STCO2 ( Stipa comata Trin. & Rupr., needle-and-thread), and ARTRW8/AGSP-STTH (una co-dominancia de bluebunch wheatgrass and Thurber’s needlegrass). Nuestros resultados sugieren que cuando los valores propuestos para sabio urogallo se aplican como requisitos promedio o por encima del mismo, estos exceden el potencial ecológico de muchos de los sitios muestreados.

Vegetation Characteristics Across Part of the Wyoming Big Sagebrush Alliance

The Wyoming big sagebrush (Artemisia tridentata ssp. Wyomingensis [Beetle A. Young] S.L. Welsh) alliance is the most extensive of the big sagebrush complex in the Intermountain West. This alliance provides critical habitat for many sagebrush obligate and facultative wildlife species and serves as a forage base for livestock production. There is a lack of information that describes vegetation cover values, characteristics, diversity, and heterogeneity of the Wyoming big sagebrush alliance. This study describes vegetation cover values and defines distinct associations for intact, late-seral Wyoming big sagebrush plant communities across part of its northwestern range. We sampled 107 Wyoming big sagebrush plant communities. Total herbaceous cover values were variable among sites with differences between sites exceeding 700%. Mean sagebrush cover was 12.3% with 90% of the sites producing 6% to 20% cover. Tall forb (.18 cm) cover averaged 1.9% and 90% of the sites varied between 0.2% and 5.6% cover. Five associations delineated by dominant perennial bunchgrass species were identified: ARTRW8 (Wyoming big sagebrush)/PSSP6 (Pseudoroegneria spicata [Pursh] A. Löve, bluebunch wheatgrass), ARTRW8/ACTH7 (Achnatherum thurberianum [Piper] Barkworth, Thurber’s needlegrass), ARTRW8/FEID (Festuca idahoensis Elmer, Idahofescue), ARTRW8/HECO26 (Hesperostipa comata [Trin. Rupr.] Barkworth, needle-and-thread), and ARTRW8/PSSP6-ACTH7 (a codominance of bluebunch wheatgrass and Thurber’s needlegrass). Our results suggest when the vegetation cover values proposed for sage-grouse are applied as requirements at or above the stand level, they exceed the ecological potentialof many of the sites sampled.

Economics and Optimal Frequency of Wyoming Big Sagebrush Control With Tebuthiuron

The optimal frequency of tebuthiuron (N-[5-(dimetylethyl)-1,3,4-thiadiazol-2yl]-N,N9-dimethylurea) treatments was investigated for Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis Beetle and Young) when added forage for livestock and wildlife are considered to be the economic benefit of the treatment. Data collected at 8 northwest New Mexico study sites were used to define key relationships for the economic analysis. This long-lived sagebrush control practice was found to be a viable investment for landowners who participate in available cost-share programs. At productive sites, where average herbaceous production increased to over 700 kg/ha following big sagebrush control, the economic value of added forage justified the total cost of the herbicide treatment. Tebuthiuron rates higher than 0.5 kg active ingredient/ha lengthened the expected life of the brush control treatment, but the extended life did not justify the added cost. The threshold abundance of sagebrush needed for economical control was found to be variable, depending on treatment cost, study site, and the economic value of forage. With a 50:50 cost-share arrangement and with forage valued at 7/AUM, the economic sagebrush canopy threshold from the livestock grazing perspective was estimated to range between 6% and 14%, depending on site productivity. A second brush control treatment would optimally be implemented before forage production was fully depleted by the recovering brush canopy. Because some native fauna are closely tied to big sagebrush plant communities and benefit from the shrubs’ presence, the trade-off in the desired abundance of big sagebrush must be weighed between economic considerations and other resource values of interest.

Economics and Optimal Frequency of Wyoming Big Sagebrush Control With Tebuthiuron

Abstract The optimal frequency of tebuthiuron ( N -[5-(dimetylethyl)-1,3,4-thiadiazol-2yl]- N,N ′-dimethylurea) treatments was investigated for Wyoming big sagebrush ( Artemisia tridentata Nutt. ssp. wyomingensis Beetle and Young) when added forage for livestock and wildlife are considered to be the economic benefit of the treatment. Data collected at 8 northwest New Mexico study sites were used to define key relationships for the economic analysis. This long-lived sagebrush control practice was found to be a viable investment for landowners who participate in available cost-share programs. At productive sites, where average herbaceous production increased to over 700 kg/ha following big sagebrush control, the economic value of added forage justified the total cost of the herbicide treatment. Tebuthiuron rates higher than 0.5 kg active ingredient/ha lengthened the expected life of the brush control treatment, but the extended life did not justify the added cost. The threshold abundance of sagebrush needed for economical control was found to be variable, depending on treatment cost, study site, and the economic value of forage. With a 50:50 cost-share arrangement and with forage valued at $7/AUM, the economic sagebrush canopy threshold from the livestock grazing perspective was estimated to range between 6% and 14%, depending on site productivity. A second brush control treatment would optimally be implemented before forage production was fully depleted by the recovering brush canopy. Because some native fauna are closely tied to big sagebrush plant communities and benefit from the shrubs’ presence, the trade-off in the desired abundance of big sagebrush must be weighed between economic considerations and other resource values of interest.

Ranching the View: Subdivisions versus Agriculture

Wuerthner ( 1994) recently contrasted the environmental effects of agriculture and rural subdivisions and concluded that Agriculture-both livestock production and farming-rather than being compatible with environmental protection has had a far greater impact on the western landscape than all the subdivisions, malls, highways, and urban centers combined. We suggest, however, that subdivisions can have profound impacts on the biodiversity of rural areas, particularly when they are adjacent to protected natural areas. In addition, we submit that much of the information required to evaluate the relationships between biodiversity and land-use patterns associated with agriculture and rural housing developments is still lacking. One of us recently completed a study of private landuse change in the Colorado mountains (Riebsame et al. 1994). The region's physical and political landscape limits private lands mostly to valley-bottom corridors that separate blocks of federal lands, including wilderness units. An assessment of the private-land corridors revealed repetitive patterns of land subdivision with negative ecological implications. Dense development (commercial strips, condominiums, and infrastructure) tended to encroach on riparian areas. Dispersed residential development occurred across valley bottoms and slopes, especially riparian areas, at forest edges (such as attractive building sites in aspen groves), and in the interior of coniferous forests (such as subdivisions carved from lodgepole pine [Pinus contorta] forests). Most of this dispersed development was not contiguous with existing town sites and other previous developments. A detailed mapping of subdivisions and roads in the East River Valley (from above Gunnison to Crested Butte, Colorado) showed that meadow, grassland, riparian, and sagebrush (Artemisia spp.) plant communities

PARTITIONING SMALL SCALE SPATIAL VARIABILITY OF RUNOFF AND EROSION ON SAGEBRUSH RANGELAND1

ABSTRACT: Most hydrologic models require input parameters which represent the variability found across an entire landscape. The estimation of such parameters is very difficult, particularly on rangeland. Improved model parameter estimation procedures are needed which incorporate the small‐scale and temporal variability found on rangeland. This study investigates the use of a surface soil classification scheme to partition the spatial variability in hydrologic and interrill erosion processes in a sagebrush plant community. Four distinct microsites were found to exist within the sagebrush coppice‐dune dune‐interspace complex. The microsites explained the majority of variation in hydrologic and interrill erosion response found on the site and were discernable based on readily available soil and vegetation information. The variability within each microsite was quite low and was not well correlated with soil and vegetation properties. The surface soil classification scheme defined in this study can be quite useful for defining sampling procedures, for understanding hydrologic and erosion processes, and for parameterizing hydrologic models for use on sagebrush range‐land.

Range Animal Diet Composition in Southcentral Wyoming

Because of the ongoing controversy about shrub forage value for different ungulates and significance of the shrub communities for spring-fall grazing in southcentral Wyoming, the relative importance of various forage classes was determined by fecal analyses in the spring, summer, and fall diets of pronghorn (Antilocarpa americana Ord), mule deer (Odocoileus hemionus hemionus), elk (Cervus elaphus), cattle (Bos taurus), and domestic sheep (Ovis aries) in the mountain brush and Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis Beetle and Young) plant communities. Mountain big sagebrush (A.t. ssp. vaseyana Rydb. Beetle) comprised 76% of pronghorn spring diets in the mountain brush plant community, and Wyoming big sagebrush comprised 91% of the pronghorn spring diets in the Wyoming big sagebrush plant community. Antelope bitterbrush (Purshia tridentata Pursh.) comprised about 80 to 90% of the pronghorn and deer summer and fill diets in the mountain brush plant community. Graminoids, primarily Bromus, Carex, Juncus, and Stipa spp., made up 80+% of elk, cattle, and sheep diets in either plant community. Forbs and shrubs other than sagebrush or bitterbrush were a minor component of either plant community and diets of any of the 5 kinds of animals. A shrub management program to maintain species diversity while increasing bitterbrush and graminoid production under common use grazing by both browsers and grazers is recommended for this area.

Spoil characteristics and vegetation development of an age series of mine spoils in a dry tropical environment: A. K. Jha & J. S. Singh, Vegetatio, 97(1), 1991, pp 63–76

Shrubs in semi-arid ecosystems promote micro-environmental variation in a variety of soil properties and site characteristics. However, little is known regarding post-fire seedling performance and its association with environmental variation in former shrub canopy and interspace microsites. We compared post-fire seeding success and various soil properties important for seedling establishment between shrub canopy and interspace microsites in Wyoming big sagebrush (Artemisia tridentata) plant communities in southeast Oregon, U.S.A. We burned 5, 20 × 20 m sites and established paired canopy and interspace micro-transects seeded with bluebunch wheatgrass (Pseudoroegneria spicata, 193 seeds/m) or crested wheatgrass (Agropyron cristatum, 177 seeds/m). At one year post-fire, seedling density was 69% higher (p = 0.012) for crested wheatgrass (compared to bluebunch wheatgrass) and 75% higher (p = 0.019) for interspace microsites (compared to canopy). However, tiller and leaf area production were over twice as high (p < 0.05) in canopy microsites. Soil color and soil temperature, explained 19–32% of variation in seedling performance metrics. Shrub effects on seeding success are complex and interact with abiotic disturbances, but patterns of increased seedling performance in canopy microsites and their relationships to soil variables may suggest tactics for increasing success of restoration practices.