Wyoming Big Sagebrush Density: Effects of Seeding Rates and Grass Competition

The mining industry commonly seeds shrubs and grasses concurrently on coal‐mined lands of northeastern Wyoming, but ecological interactions between seeded shrubs and grasses are not well documented. Artemisia tridentata Nutt. ssp. wyomingensis (Beetle and Young) (Wyoming big sagebrush) is the dominant pre‐mining shrub on many Wyoming mine sites. Despite past failures to establish Wyoming big sagebrush, the Wyoming Department of Environmental Quality, Land Quality Division's rules and regulations require establishment of 1 shrub per m² on 20% of post‐mined land in Wyoming. A study was established at the Belle Ayr Coal Mine south of Gillette, Wyoming to evaluate the effects of sagebrush seeding rates and grass competition on Wyoming big sagebrush seedling density. Three sagebrush seeding rates (1, 2, and 4 kg pure live seed [pls]/ha; 350, 700, and 1,400 pls/m², respectively) and seven cool‐season perennial grass mixture seeding rates (0, 2, 4, 6, 8, 10, and 14 kg pls/ha; 0, 187, 374, 561, 750, 935, and 1,309 pls/m², respectively) were applied during winter 1998–1999. Pascopyrum smithii (Rydb.) A. Love (western wheatgrass), Elymus lanceolatus (Scribner & J.G. Smith) Gould (thickspike wheatgrass), and Elymus trachycaulus (Link) Gould ex Shinners (slender wheatgrass) comprised the grass seed mix (equal seed numbers of each species). Sagebrush seedling density differed among sagebrush seeding rates but not among grass seeding rates. On all sampling dates in 1999 and 2000, sagebrush seedling density differed among sagebrush rates and was greatest at the 4 kg pls/ha sagebrush seeding rate. All sagebrush seeding rates provided densities of at least 1 shrub per m² after two growing seasons. Grass density and production in 2000 suggest that adequate grass production (75 g/m²) was achieved by seeding at 6 to 8 kg pls/ha. Within these grass seeding rates, four or more sagebrush seedlings per m² were attained when sagebrush was seeded at 2 to 4 kg pls/ha. Use of these seeding rate combinations in mine reclamation can achieve Wyoming big sagebrush standards and reduce reseeding costs.     

Attempting to restore mountain big sagebrush (Artemisia tridentata ssp. vaseyana) four years after fire

Restoration of shrubs is needed throughout the world because of altered fire regimes, anthropogenic disturbance, and overutilization. The native shrub mountain big sagebrush (Artemisia tridentata Nutt. ssp. vaseyana (Rydb.) Beetle) is a restoration priority because of its value to wildlife in western North America. One of the principal threats to mountain big sagebrush is encroachment by western juniper (Juniperus occidentalis ssp. occidentalis Hook) and other conifers. Fire is frequently applied to control juniper; however, sagebrush recovery after fire can be variable. Seeding sagebrush postfire can hasten sagebrush recovery; however, seeding is not always necessary. Therefore, it may be advantageous to monitor postfire recovery to determine if seeding is needed. The effect of seeding sagebrush several years after fire is unknown. We evaluated the efficiency of seeding mountain big sagebrush four years after fire‐controlled junipers at five sites. Sagebrush cover (<0.5%) and density (<0.07 plants/m²) was low in seeded plots and did not differ from unseeded controls in the three postseeding years. We conclude that seeding sagebrush four years after fire did not accelerate sagebrush recovery. We speculate that seeded sagebrush failed to establish because of competition from herbaceous vegetation that had four years to recover after fire. Although it would be beneficial to seed sagebrush only when needed, our results suggest postponing seeding until monitoring has determined that recovery is inadequate may not be advisable. We suggest researchers investigate methods to improve predicting sagebrush recovery to allow for seeding, when needed, before the first postfire growing season.     

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

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

Native seeds incorporated into activated carbon pods applied concurrently with indaziflam: a new strategy for restoring annual‐invaded communities?

Reestablishing native perennial vegetation in annual grass‐invaded rangelands is critical to restoring ecosystems. Control of exotics, often achieved with preemergent herbicides, is essential for successful restoration of invaded rangelands. Unfortunately, desirable species cannot be seeded simultaneously with preemergent herbicide application due to nontarget damage. To avoid this, seeding is commonly delayed at least 1 year. Delaying seeding increases the likelihood that annual grasses will begin reestablishing and compete with seeded species. Activated carbon (AC) can provide preemergent herbicide protection for seeded species because it adsorbs and deactivates herbicides. Previous studies suggest that a cylindrical herbicide protection pod (HPP), containing AC and seeds, allows desired species to be seeded simultaneously with the application of the preemergent herbicide imazapic. Unfortunately, imazapic is only effective at controlling annual grasses for 1–2 years. Indaziflam is a new preemergent herbicide which exhibits longer soil activity, with which HPPs may be useful. To assess this possibility, we evaluated seeding two native species (Wyoming big sagebrush [Artemisia tridentata Nutt ssp. wyomingensis] and bluebunch wheatgrass [Pseudoroegneria spicata (Pursh) Á. Löve]), both incorporated into HPPs and as bare seed, at four application rates of indaziflam in a grow room study. HPPs protected seeded species at low, mid, and high rates of indaziflam. The abundance and size of plants was greater in HPPs compared to bare seed treatments. These results suggest that HPPs can be used to seed native grasses and shrubs simultaneously with indaziflam application.     

Postwildfire seeding to restore native vegetation and limit exotic annuals: an evaluation in juniper‐dominated sagebrush steppe

Reestablishment of perennial vegetation is often needed after wildfires to limit exotic species and restore ecosystem services. However, there is a growing body of evidence that questions if seeding after wildfires increases perennial vegetation and reduces exotic plants. The concern that seeding may not meet restoration goals is even more prevalent when native perennial vegetation is seeded after fire. We evaluated vegetation cover and density responses to broadcast seeding native perennial grasses and mountain big sagebrush (Artemisia tridentata Nutt. spp. vaseyana [Rydb.] Beetle) after wildfires in the western United States in six juniper (Juniperus occidentalis ssp. occidentalis Hook)‐dominated mountain big sagebrush communities for 3 years postfire. Seeding native perennial species compared to not seeding increased perennial grass and sagebrush cover and density. Perennial grass cover was 4.3 times greater in seeded compared to nonseeded areas. Sagebrush cover averaged 24 and less than 0.1% in seeded and nonseeded areas at the conclusion of the study, respectively. Seeding perennial species reduced exotic annual grass and annual forb cover and density. Exotic annual grass cover was 8.6 times greater in nonseeded compared to seeded areas 3 years postfire. Exotic annual grass cover increased over time in nonseeded areas but decreased in seeded areas by the third‐year postfire. Seeded areas were perennial‐dominated and nonseeded areas were annual‐dominated at the end of the study. Establishing perennial vegetation may be critical after wildfires in juniper‐dominated sagebrush steppe to prevent the development of annual‐dominated communities. Postwildfire seeding increased perennial vegetation and reduced exotic plants and justifies its use.     

Fungal endophytes intrinsically associated with micropropagated plants regenerated from native <Emphasis Type="Italic">Bouteloua eriopoda</Emphasis> Torr. and <Emphasis Type="Italic">Atriplex canescens</Emphasis> (Pursh) Nutt.

Summary Black grama (Bouteloua eriopoda) and fourwing saltbush (Atriplex canescens) are important grass and shrub species in arid rangelands of the northern Chihuahuan Desert. They are naturally colonized by dark septate endophytic fungi that cannot be eliminated by seed disinfestation. Plants were regenerated from both species and appeared to be fungus-free in axenic cultures. Analysis of callus and regenerated plants of both species using dual staining with light and scanning electron microscopy revealed fungal endophytes intrinsically associated with cells, roots and leaves of regenerated plants that are also associated with native plants. Fungal layers and biofilms prevent direct exposure of callus, root or leaf tissues to the external environment. Micropropagation is a valuable tool for identifying key fungal endophytes that enhance drought tolerance in native desert plants.     

灌丛化对黄土高原草地植物群落结构和地上生物量的影响

中国北方草地普遍出现灌丛化现象,灌丛化改变植物群落结构、植物多样性和生产力,直接影响着草地生态保护与可持续利用.该研究以黄土高原灌丛化草地为研究对象,通过植被调查,分析比较不同坡向的灌丛斑块与禾草斑块植物群落结构(物种组成、优势种及物种多样性)和地上生物量的差异.结果发现:(1)灌丛化草地不同坡向对物种多样性及地上生物...     

Attempting to Restore Herbaceous Understories in Wyoming Big Sagebrush Communities with Mowing and Seeding

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

Ecological Factors Influencing Nest Survival of Greater Sage-Grouse in Mono County,California

ABSTRACT We studied nest survival of greater sage-grouse (Centrocercus urophasianus) in 5 subareas of Mono County, California, USA, from 2003 to 2005 to 1) evaluate the importance of key vegetation variables for nest success, and 2) to compare nest success in this population with other greater sage-grouse populations. We captured and radiotracked females (n = 72) to identify nest sites and monitor nest survival. We measured vegetation at nest sites and within a 10-m radius around each nest to evaluate possible vegetation factors influencing nest survival. We estimated daily nest survival and the effect of explanatory variables on daily nest survival using nest-survival models in Program MARK. We assessed effects on daily nest survival of total, sagebrush (Artemisia spp.), and nonsagebrush live shrub-cover, Robel visual obstruction, the mean of grass residual height and grass residual cover measurements within 10 m of the nest shrub, and area of the shrub, shrub height, and shrub type at the nest site itself. Assuming a 38-day exposure period, we estimated nest survival at 43.4%, with percent cover of shrubs other than sagebrush as the variable most related to nest survival. Nest survival increased with increasing cover of shrubs other than sagebrush. Also, daily nest survival decreased with nest age, and there was considerable variation in nest survival among the 5 subareas. Our results indicate that greater shrub cover and a diversity of shrub species within sagebrush habitats may be more important to sage-grouse nest success in Mono County than has been reported elsewhere.     

Canopy effects of the invasive shrub Pyracantha angustifolia on seed bank composition,richness and density in a montane shrubland (Córdoba,Argentina)

Abstract Invasive woody species frequently change the composition of the established vegetation and the properties of the soil under their canopies. Accordingly, invasion may well affect regenerative phases of the community, especially at the seed bank level, likely influencing community restoration. Pyracantha angustifolia (Rosaceae) is an invasive shrub in central Argentina that affects woody recruitment, particularly enhancing the recruitment of other exotic woody species. There is though no information regarding its effect on the soil seed bank within the invaded community. The present study was set up to gain further insight into the canopy effects of P. angustifolia. We aimed to assess whether the invasive shrub affects seed bank composition, richness and seed density as compared with the dominant native shrub Condalia montana (Rhamnaceae), and to relate the observed seed bank patterns with those of the established vegetation. We evaluated the composition of the germinable seed bank and the established vegetation under the canopy of 16 shrubs of P. angustifolia, 16 shrubs of C. montana, and in 16 control plots (10 m²) without shrub cover. The floristic composition of the seed bank differed among canopy treatments. However, seed bank richness did not differ significantly. There was an overall high seed density of exotic species throughout the study site, though exotic forbs showed significantly lower seed densities under the invasive shrub. Pyracantha angustifolia would not promote the incorporation of new species into the seed bank of the invaded community but rather favour the establishment of woody species that do not depend on seed banks. The absence of dominant woody species in the seed bank, the dominance of exotic forbs, and the high similarity between established exotic species and those present in the seed bank may surely affect community restoration following the main disturbances events observed in the region.     

Species‐specific influences of shrubs on the non‐dormant soil seed bank of native and exotic plant species in central‐northern Monte Desert

Deserts shrubs are well known to facilitate vegetation aggregation, mostly through seed trapping, and stress amelioration during and after plant establishment. Because vegetation aggregation effects are a by‐product of shrub presence, beneficiary species may not only be native, but also exotic. However, despite the high risk that exotic invasive species pose to ecosystem services, little is known of the role of desert shrubs on plant invasions. We assessed the influence of two shrub species on the non‐dormant soil seed bank (i.e. the number of seeds that readily germinate with sufficient water availability) of an invasive annual grass (Schismus barbatus) and of coexisting native species in a central‐northern Monte Desert (Argentina). Soil samples were collected beneath the canopies of two dominant shrub species (Bulnesia retama and Larrea divaricata) and in open spaces (i.e. intercanopies) in May 2001. Overall, the density of germinated seedlings of Schismus and that of the native species were negatively associated across microsite types. Schismus density was similar to that of all native species pooled together (mostly annuals), and was highest in Larrea samples (with no significant differences between Bulnesia and intercanopies). On the contrary, the density of all native species pooled together was highest in Bulnesia samples. Our results suggest that shrubs may contribute to plant invasions in our study system but, most importantly, they further illustrate that this influence can be species specific. Further research is needed to assess the relative importance of in situ seed production (and survival) and seed redistribution on soil seed bank spatial patterns.     

Grass-Shrub Associations over a Precipitation Gradient and Their Implications for Restoration in the Great Basin,USA

As environmental stress increases positive (facilitative) plant interactions often predominate. Plant-plant associations (or lack thereof) can indicate whether certain plant species favor particular types of microsites (e.g., shrub canopies or plant-free interspaces) and can provide valuable insights into whether “nurse plants” will contribute to seeding or planting success during ecological restoration. It can be difficult, however, to anticipate how relationships between nurse plants and plants used for restoration may change over large-ranging, regional stress gradients. We investigated associations between the shrub, Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis), and three common native grasses (Poa secunda, Elymus elymoides, and Pseudoroegneria spicata), representing short-, medium-, and deep-rooted growth forms, respectively, across an annual rainfall gradient (220–350 mm) in the Great Basin, USA. We hypothesized that positive shrub-grass relationships would become more frequent at lower rainfall levels, as indicated by greater cover of grasses in shrub canopies than vegetation-free interspaces. We sampled aerial cover, density, height, basal width, grazing status, and reproductive status of perennial grasses in canopies and interspaces of 25–33 sagebrush individuals at 32 sites along a rainfall gradient. We found that aerial cover of the shallow rooted grass, P. secunda, was higher in sagebrush canopy than interspace microsites at lower levels of rainfall. Cover and density of the medium-rooted grass, E. elymoides were higher in sagebrush canopies than interspaces at all but the highest rainfall levels. Neither annual rainfall nor sagebrush canopy microsite significantly affected P. spicata cover. E. elymoides and P. spicata plants were taller, narrower, and less likely to be grazed in shrub canopy microsites than interspaces. Our results suggest that exploring sagebrush canopy microsites for restoration of native perennial grasses might improve plant establishment, growth, or survival (or some combination thereof), particularly in drier areas. We suggest that land managers consider the nurse plant approach as a way to increase perennial grass abundance in the Great Basin. Controlled experimentation will provide further insights into the life stage-specific effectiveness and practicality of a nurse plant approach for ecological restoration in this region.     

Composition of soil seed banks in southern California coastal sage scrub and adjacent exotic grassland

Soil seed banks are important to many plant communities and are recognized as an important component of management plans. Understanding seed bank composition and density is especially important when communities have been invaded by exotic species and must be managed to promote desirable species. We examined germinable soil seed banks in southern California coastal sage scrub (CSS) that is heavily invaded by exotic grasses and in adjacent exotic grassland. Soils from both communities had similar seed banks, dominated by high densities of exotic grass and forb species. Up to 4,000 exotic grass seeds and at least 400 exotic forb seeds/m² were found in most soils, regardless of aboveground vegetation type. Native forbs averaged 400 seeds/m² in grass-dominated areas and about 800 in shrub-dominated soils. Shrub seed density was <1 and <10 seeds/m² in grass- and shrub-dominated areas, respectively, indicating that the shrub seed bank is not persistent compared to annuals. We also compared pre- and post-burn soil seed banks from one location that burned in October 2003. Late-season burning in both grass- and CSS-dominated areas disproportionately reduced exotic grass seed densities relative to native seed densities. The similarity of the seed banks in adjacent grass and shrub communities suggests that without intervention, areas currently dominated by CSS may become more similar to grass-dominated areas in terms of aboveground vegetation. In such areas, the first growing season following a wildfire is a window of opportunity for increasing native diversity at a time when density of exotic grass seeds is low. At time of research, Robert D. Cox was graduate student.     

Implications of Plant Density on the Resulting Community Structure of Mine Site Land

The relative abundances of Chenopodiaceae shrubs are different from the seed composition in the original seed mix when sown on mine waste material in semiarid regions of Western Australia. Experiments were therefore undertaken to determine what species interactions are responsible for shifts in relative abundance after seeding. The growth parameters of five members of the Chenopodiaceae were used to determine intra‐ and interspecific density‐dependent interactions. Dominant and subordinant species were paired and grown in pots at differing densities. The growth parameters measured were height, root, and shoot biomass. Of the five species chosen for this study, Maireana georgei (golden bluebush) and Enchylaena tomentosa (ruby saltbush) do not establish well on mine site areas. These were sensitive to density in monoculture, as well as in the presence of both Atriplex bunburyana (silver saltbush) and Atriplex codonocarpa (flat‐topped saltbush). Although Maireana brevifolia (small leaf bluebush) does establish successfully on mine sites when sown, it showed the same negative reaction when grown in monoculture and in a two‐species mixture. Atriplex bunburyana and A. codonocarpa, in contrast, are dominant species and reacted differently when grown with increasing numbers of the target species (M. georgei, M. brevifolia, and E. tomentosa). Atriplex bunburyana did not exhibit any decreases in growth when grown in competition with up to four plants of the target species. However, A. codonocarpa did react adversely to the presence of the target species. It is thought that the resulting plant community organization reflects the original seed mixture, which is usually sown at a high density. Yet, this study has shown that the differing intra‐ and interspecific density responses of these chenopod species provide an indication of the resulting community organization. To maximize diversity and to prevent dominance by highly competitive species, such as A. bunburyana, it is important to take density‐dependent effects into account during the restoration planning stage.     

Microsite and litter cover effects on seed banks vary with seed size and dispersal mechanisms: implications for revegetation of degraded saline land

Seed movements and fates are important for restoration as these determine spatial patterns of recruitment and ultimately shape plant communities. This article examines litter cover and microsite effects on seed availability at a saline site revegetated with Eucalyptus sargentii tree rows interplanted with 5?C6 rows of saltbush (Atriplex spp.). As litter accumulation decreases with increasing distance from tree rows, soil seed banks were compared between paired bare and litter-covered zones within three microsites; tree row, saltbush row closest to tree row and saltbush mid-row (middle row of saltbush between tree rows). Germinable seed banks of the four most abundant species with contrasting seed sizes and dispersal mechanisms were assessed to test the hypotheses that: (i) microsites with litter cover contain higher seed densities than bare areas, but that (ii) microsite and litter effects will vary depending on seed size and dispersal mechanisms. Overall, litter cover increased seed densities, however, litter effects varied with seed size, with no effect on small-seeded species and litter increasing densities of large-seeded species. Seed bank composition also differed between tree and shrub microsites due to differences in seed morphology and dispersal mechanisms. Water-dispersed species were unaffected by microsite but densities of wind-dispersed species, including Atriplex spp., were higher in saltbush microsites. Densities of wind-dispersed species also differed between the two saltbush microsites despite similar litter cover. Future plantings should consider row spacing and orientation, as well as the dimensions of seeding mounds and associated neighbouring depressions, to maximize litter and seed-trapping by microsites.     

Fire Effects on Cover and Dietary Resources of Sage-Grouse Habitat

Abstract: We evaluated 6 years of vegetation response following prescribed fire in Wyoming big sagebrush (Artemisia tridentata spp. wyomingensis) steppe on vegetation cover, productivity, and nutritional quality of forbs preferred by greater sage-grouse (Centrocercus urophasianus), and abundance of common arthropod orders. Habitat cover (shrubs and tall herbaceous cover [>18 cm ht]) was about 50% lower after burning compared to unburned controls because of the loss of sagebrush. Perennial grasses and an invasive annual forb, pale alyssum (Alyssum alyssoides), increased in cover or yield after fire. There were no increases in yield or nutritional quality of forb species important in diets of sage-grouse. Abundance of ants (Hymenoptera), a significant component in the diet of young sage-grouse, decreased after fire. These results suggest that prescribed fire will not improve habitat characteristics for sage-grouse in Wyoming big sagebrush steppe where the community consists of shrubs, native grasses, and native forbs.     

Exotic Grass Competition in Suppressing Native Shrubland Re-establishment

Disturbance of coastal sage scrub in southern California has led to extensive displacement of native shrubs by exotic annual grasses. The initial conversion from shrubland to exotic grassland is typically associated with disturbance caused by intense grazing, high fire frequency, or mechanical vegetation removal. While native shrubs have been shown to recolonize annual grasslands under some conditions, other annual grasslands are persistent and show no evidence of shrub recolonization. This study examined the mechanisms by which annual grasses may exclude native shrubs and persist after release from disturbance. Grass density was manipulated in experimental plots to achieve a series of prescribed densities. Artemisia californica, a dominant native shrub, was seeded or planted into the plots and responses to the grass density treatments were measured over two growing seasons. A. californica germination, first season growth, and survival were all negatively related to the density of neighboring annual grasses. The most probable mechanism underlying the reduction of first season growth and survival was depletion of soil water by the grasses. The effects of the grasses on A. californica were no longer significant in the second season. The results of this study indicate that Mediterranean annual grasses reduce recruitment and can persist by inhibiting post-disturbance establishment of A. californica from seed. Although succession alone may not return disturbed annual grasslands to their former shrubland composition, the results suggest that restoration can be achieved by using container plantings or grass removal followed by seeding.     

Evaluation of the Umbrella Species Concept at Fine Spatial Scales

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. © 2019 The Wildlife Society.     

桂北喀斯特石漠化地区不同植物群落土壤种子库特征及其与土壤养分关系

土壤种子库作为地上植被遗传信息库，对植被自然演替更新以及生态修复建设具有重要作用。为探明桂北喀斯特石漠化地区植被自然恢复潜力和恢复策略，该文选取恭城瑶族自治县喀斯特石漠化地区3种典型植物群落为研究对象，分析不同群落的土壤种子库结构、多样性及其对土壤养分特征的响应，以期为该地区石漠化治理和植被恢复提供理论依据。结果表明：(1)共计监测到幼苗3 648株，隶属于33科51属55种，其中1年生和2年生草本幼苗共20种，多年生草本幼苗21种，藤本幼苗5种、灌木幼苗3种、乔木幼苗6种；不同植物群落土壤种子库平均密度为三华李经济林(22 493 grain·m^-2)>青冈次生林(1 033 grain·m^-2)>金竹灌丛(793 grain·m^-2)。(2)土壤种子库植物生活型方面，三华李经济林主要分布1年生恶性杂草，青冈次生林和金竹灌丛则以多年生草本为主，木本植物占比较少；不同植被类型中土壤种子库物种多样性和相似性总体较低，同时与地上群落物种组成的相似性也较低。(3)研究区域的土壤元素存在高氮低磷的现象，其中磷元素为金...     

Evaluation of a positive conditioning technique for influencing big sagebrush (Artemisia tridentata subspp. wyomingensis) consumption by goats

Diets of angora goats (Capra hircus) positively conditioned to eat big sagebrush (Artemisia tridentata subspp. wyomingensis) were contrasted with control groups to assess the effects of positive conditioning. Goats were conditioned by including ever-increasing amounts of sagebrush in the daily ration, to a maximum of 25% by weight as fed. Conditioning effects were evaluated by comparing relative consumption of big sagebrush in a rangeland setting. Field trials were conducted at the Squaw Butte Experimental Range, a shrub steppe rangeland in eastern Oregon. Our results indicate that neither conditioned does nor kids had significantly different intake of sagebrush when compared with control animals. Young animals consumed shrub species sooner than adults and ate significantly more shrubs throughout all seasons until the second summer when diets did not differ between age groups.