Introduction Due to the prevalence of local adaptation in plants, the provenance of seed sources can impact plant community restoration outcomes. Yet programs developing commercial germplasm releases often overlook local adaptation as a development criterion, leading to the selection of traits that may not support restoration success. In many cases, commercial germplasms are more available than plant materials developed explicitly considering spatial adaptation patterns.Objectives This study aims to demonstrate how seed transfer models can calibrate restoration guidance for commercially available germplasms of bottlebrush squirreltail (Elymus elymoides) in the Western United States. The goal is to assess the alignment of these germplasms with spatial adaptation patterns predicted by seed transfer models.Methods We applied seed transfer models, derived from a common garden study of wildland seed sources, to evaluate six commercially available germplasms of bottlebrush squirreltail grown alongside the wildland sources. These models predicted trait expression in relation to the climate of origin. Predicted traits were compared with actual traits to find divergence that could be due to evolutionary shifts during germplasm development.Results Our analysis revealed that distances between actual and predicted trait values were generally greater for commercial germplasms than for wildland populations, indicating evolutionary changes during the germplasm collection and development processes.Conclusions Even when germplasm is developed under controlled standards, significant divergence from expected traits can occur. This emphasizes the need for assessing the degree to which seed transfer guidance frameworks developed for wildland populations can be used to guide seed transfer of commercial germplasms.

Background The risk of destructive wildfire on fire-prone landscapes with excessive fuel buildup has prompted the use of fuel reduction treatments to protect valued resources from wildfire damage. The question of how to maximize the effectiveness of fuel reduction treatments at landscape scales is important because treating an entire landscape may be undesirable or unfeasible. We reviewed 86 simulation studies that examined landscape-scale fuel reduction treatment effectiveness for landscapes of the USA or Canada. Each of these studies tested effects of fuel reduction treatments on wildfire through comparisons of landscape scenarios differing by treatment design or other attributes. Results from these studies were summarized to assess what they reveal about factors determining fuel treatment effectiveness at landscape scales. Results Qualifying studies focused primarily but not exclusively on forested landscapes of the western USA and ranged in size from 200 to 3,400,000 ha. Most studies showed that scenarios with fuel reduction treatments had lower levels of wildfire compared to untreated scenarios. Damaging wildfire types decreased while beneficial wildfire increased as a result of treatments in most cases where these were differentiated. Wildfire outcomes were influenced by five dimensions of treatment design (extent, placement, size, prescription, and timing) and other factors beyond the treatments (weather, climate, fire/fuel attributes, and other management inputs). Studies testing factorial combinations showed that the relative importance of these factors varied across landscapes and contexts. Conclusions Simulation studies have highlighted general principles of effective fuel treatment design at landscape scales, including the desirability of treating extensive areas with appropriate prescriptions at sufficient frequency to reduce wildfire impacts even under extreme conditions that may be more prevalent in the future. More specific, context-dependent strategies have also been provided, such as a variety of placement schemes prioritizing the protection of different resources. Optimization algorithms were shown to be helpful for determining treatment placement and timing to achieve desired objectives under given constraints. Additional work is needed to expand the geographical scope of these studies, further examine the importance and interactions of driving factors, and assess longer-term effects of fuel reduction treatments under projected climate change.

Questions Post-fire seeding has been widely implemented in the semiarid Great Basin because natural vegetation recovery may be compromised. Non-native species are often seeded to rapidly establish perennial cover and compete with invasive annuals. We asked whether seeding treatments with different amounts of native and non-native species followed different successional trajectories and whether they became more similar to reference communities over time. We considered restoration implications of seed mix choices and reference community options involving: (a) local unburned vegetation; and (b) reference states mapped by the USDA Natural Resources Conservation Service (NRCS) based on soil-vegetation associations. Location Tintic Valley, UT, USA. Methods Four post-fire seeding treatments differing by seed mix were installed alongside an unseeded control (USC) at two sites. Two seed mixes were comprised of native species and two were predominantly non-native. Vegetation was monitored 1-3 and 16-18 years after fire and seeding. Reference communities were characterized and compared using hierarchical clustering. Non-metric multidimensional scaling and permutation tests were used to determine successional trajectories of post-fire treatments in relation to reference communities. Results Local unburned reference communities had fewer herbaceous perennials and higher woody cover than NRCS reference communities, suggesting departure from conditions expected under minimal post-settlement disturbance. USCs became more similar to reference communities over time, though less so at a site with abundant invasive annuals. Trajectories of seeded treatments were driven by seed mix species, with native-only mixes approaching reference communities more closely than mixes with non-natives. Conclusions Gradual recovery of reference community composition is possible without seeding but the degree and rate of recovery can vary by site. Seeding can accelerate perennial vegetation recovery but may result in alternative successional trajectories, especially if non-native species are seeded. Carefully selected reference communities can serve as guides for formulating seed mixes when restoration of natural vegetation is desired.

Seed mixes used for postfire seeding in the Great Basin are often selected on the basis of short-term rehabilitation objectives, such as ability to rapidly establish and suppress invasive exotic annuals (e.g., cheatgrass, Bromus tectorum L.). Longer-term considerations are also important, including whether seeded plants persist, continue to suppress invasives, and promote recovery of desired vegetation. To better understand long-term effects of postfire seed mixes, we revisited study sites in Tintic Valley, Utah, where seeding experiments had been initiated after the 1999 Railroad wildfire. Four different mixes, including two comprised entirely of native species, had been applied using rangeland drills at a shrubland site and aerial seeding followed by one-way Ely chaining at a woodland site. New vegetation data collected 16 years post fire revealed changes relative to 3 years post fire. We found significant increases in total cover of seed-mix species in all treatments, including the unseeded control where these species were present as residual populations or had spread from seeded treatments. Significant increases of seed-mix species cover and density were observed in blocks where seeding treatments had previously been considered unsuccessful. Some seed-mix species, particularly rhizomatous grasses, increased while others declined. Exotic annual forb cover decreased in all treatments while cheatgrass increased in the unseeded control and to a lesser extent in the native-only seeded treatments. Recruitment of non-seed-mix native perennials was highest in the unseeded control. Results indicate that postfire seeding has lasting effects on vegetation composition and structure, implying that seed mixes should be carefully formulated to promote long-term management objectives. Seed mixes containing large amounts of competitive introduced species may be especially effective for long-term cheatgrass suppression, but native-only mixes can also serve this purpose to a lesser degree while avoiding drawbacks of non-native species introductions.

Variation in natural selection across heterogeneous landscapes often produces (a) among-population differences in phenotypic traits, (b) trait-by-environment associations, and (c) higher fitness of local populations. Using a broad literature review of common garden studies published between 1941 and 2017, we documented the commonness of these three signatures in plants native to North America's Great Basin, an area of extensive restoration and revegetation efforts, and asked which traits and environmental variables were involved. We also asked, independent of geographic distance, whether populations from more similar environments had more similar traits. From 327 experiments testing 121 taxa in 170 studies, we found 95.1% of 305 experiments reported among-population differences, and 81.4% of 161 experiments reported trait-by-environment associations. Locals showed greater survival in 67% of 24 reciprocal experiments that reported survival, and higher fitness in 90% of 10 reciprocal experiments that reported reproductive output. A meta-analysis on a subset of studies found that variation in eight commonly measured traits was associated with mean annual precipitation and mean annual temperature at the source location, with notably strong relationships for flowering phenology, leaf size, and survival, among others. Although the Great Basin is sometimes perceived as a region of homogeneous ecosystems, our results demonstrate widespread habitat-related population differentiation and local adaptation. Locally sourced plants likely harbor adaptations at rates and magnitudes that are immediately relevant to restoration success, and our results suggest that certain key traits and environmental variables should be prioritized in future assessments of plants in this region.

Wildfires in the Great Basin have resulted in widespread loss of Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis Beetle & Young), an ecologically important shrub that has proven difficult to establish from seed. We sought to identify optimal seeding practices for Wyoming big sagebrush in the context of postfire seeding operations involving rangeland drills. In an experiment replicated at three burned sites in the northern Great Basin, we compared Wyoming big sagebrush establishment across treatments differing by seed delivery technique, timing, and rate of seed application. A seed mix containing bunchgrasses was drill-seeded in alternate rows using one of two drill-types (conventional or minimum-till), and a mix containing sagebrush was either delivered by drill to the soil surface in remaining rows or broadcast by hand (simulating aerial seeding) following drilling in fall or winter. Drill-delivery of sagebrush seed was accompanied by drag chains (conventional drill) or imprinter wheels (minimum-till drill) to improve seed-soil contact and was carried out at multiple seeding rates (ca. 50, 250, and 500 pure live seed m−2). During 2 yr following seeding, sagebrush establishment was lower at two sites (yr 1: ≤ 1.2 plants m−2; yr 2: ≤ 0.8 plants m−2) compared with a third site (yr 1: ≤ 4.1 plants m−2; yr 2: ≤ 2.0 plants m−2) where treatment differences were more pronounced and significant. Wherever density differed between treatments, it was consistently higher in certain treatment levels (minimum-till > conventional drill, drill-delivery > broadcast-delivery, fall broadcast > winter broadcast, and higher rates > lower rates). Densities declined between years at two sites, but we did not find evidence that declines were due to density-dependent mortality. Results indicate that seeding success can likely be enhanced by using a minimum-till imprinter seeding method and using seeding rates higher than typical postfire seeding recommendations for Wyoming big sagebrush.

Purpose: To outline important considerations and options for post-fire seeding, including the selection of seed mixes and seeding equipment for restoring sagebrush communities following fire. The emphasis is on lower-elevation communities where restoration needs are greatest. References and resources are offered for greater detail and guidance on specific topics.

Objectives of postfire seeding in the Great Basin include reestablishment of perennial cover, suppression of exotic annual weeds, and restoration of diverse plant communities. Nonconventional seeding techniques may be required when seeding mixes of grasses, forbs, and shrubs containing seeds of different sizes. We conducted an operational-scale experiment to test the effectiveness of two rangeland drills (conventional and minimum-till) for seeding native plant mixes following wildfire in Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis Beetle & Young) communities. Both drills were configured to place small and large seeds in alternate rows. We hypothesized that the minimum-till drill’s advanced features would improve establishment compared with the conventional drill. We also hypothesized that the minimum-till drill would cause less damage to residual perennials, whereas the conventional drill would have a greater impact on annual weeds. The experiment was replicated at three burned sites and monitored for 2 yr at each site. Seeded plant establishment was lowest at a low-precipitation site that became dominated by exotic annuals. Another site had high perennial grass establishment, which effectively suppressed exotic annuals, while a third site attained high diversity of seeded species and life forms but became invaded by exotic annuals in plant interspaces. Small-seeded species generally established better with the minimum-till drill equipped with imprinter wheels than the conventional drill with drag-chains. However, large-seeded species frequently established better with the conventional drill despite its lack of depth bands and press wheels. Soil disturbance associated with the conventional drill had a negative effect on residual perennials and exotic annuals at some sites. Results indicate that different drill features are advantageous in different ways, but that either of the tested drills, if properly used, can be effective for seeding native plant mixes provided site conditions are otherwise favorable for seedling establishment.

Abstract. Vegetation surveys at Zion National Park (Zion), Utah, have contributed to our understanding of plant community patterns and their relationship to environmental factors. Previous authors used vegetation plot data to characterize vegetation types at Zion following conventional procedures that emphasize spatial discreteness and dominant species. We developed and applied an alternative approach for community characterization that emphasizes nondiscrete presence-absence patterns and is compatible with the individualistic concept. We reanalyzed existing plot data from Zion using coalition clustering, an algorithm that identifies groups of positively-associated species referred to as coalition groups. Each species and plot in the data set was linked to each coalition group via an “affinity” value obtained through weighted averaging. Affinity values were used to characterize environmental affinities of coalition groups through regression tree modeling and predictive mapping. We also identified species that frequently co-occurred with coalition groups (affiliate species) and those that frequently co-occurred with high cover (dominant-affiliates), viewing these as alternatives to conventional prevalent and dominant species. Following this approach, we identified 10 coalition groups at Zion that overlapped compositionally and spatially to differing degrees. Mesic environments on a gradient from low-elevation riparian zones through mid-elevation narrow canyons to high-elevation plateaus were represented by 3 overlapping groups. Two groups occupying slickrock and sand environments were detected on the Navajo Sandstone, as well as 2 on mesa tops above it. At lower elevations, 3 intergrading xeric coalition groups were distinguished. When previously classified associations of the National Vegetation Classification were clustered based on shared affinities to coalition groups, the arrangement differed from existing classification schemes but was environmentally interpretable. Although these patterns are contingent on conditions at the time of data collection, they provide a baseline that could be used for evaluating and predicting plant community change in the park. With proper attention to sampling and analysis issues, our community characterization approach could be applied in other settings as an alternative or supplement to conventional vegetation classification.

Positive and negative associations between species are a key outcome of community assembly from regional species pools. These associations are difficult to detect and can be caused by a range of processes such as species interactions, local environmental constraints and dispersal. We integrate new ideas around species distribution modeling, covariance matrix estimation, and network analysis to provide an approach to inferring non‐random species associations from local‐ and regional‐scale occurrence data. Specifically, we provide a novel framework for identifying species associations that overcomes three challenges: 1) correcting for indirect effects from other species, 2) avoiding spurious associations driven by regional‐scale distributions, and 3) describing these associations in a multi‐species context. We highlight a range of research questions and analyses that this framework is able to address. We show that the approach is statistically robust using simulated data. In addition, we present an empirical analysis of > 1000 North American tree communities that gives evidence for weak positive associations among small groups of species. Finally, we discuss several possible extensions for identifying drivers of associations, predicting community assembly, and better linking biogeography and community ecology.

Despite being a fundamental aspect of biodiversity, little is known about what controls species range sizes. This is especially the case for hyperdiverse organisms such as plants. We use the largest botanical data set assembled to date to quantify geographical variation in range size for similar to 85000 plant species across the New World. We assess prominent hypothesised range-size controls, finding that plant range sizes are codetermined by habitat area and long- and short-term climate stability. Strong short- and long-term climate instability in large parts of North America, including past glaciations, are associated with broad-ranged species. In contrast, small habitat areas and a stable climate characterise areas with high concentrations of small-ranged species in the Andes, Central America and the Brazilian Atlantic Rainforest region. The joint roles of area and climate stability strengthen concerns over the potential effects of future climate change and habitat loss on biodiversity.

The Twist Hollow restoration site on BLM land near St. George, Utah, had been badly disturbed by sand mining, rock quarrying, dumping, off-road vehicles and target shooting prior to its closure and treatment. In December 1992 the site was sculpted and drill seeded with Indian ricegrass (Stipa hymenoides), sand dropseed (Sporobolus cryptandrus), galleta (Hilaria jamesii), gooseberryleaf globemallow (Sphaeralcea grossulariifolia) Palmer penstemon (Penstemon palmeri), fourwing saltbush (Atriplex canescens) and winterfat (Krascheninnikovia lanata) in an effort restore natural vegetation and desert tortoise habitat. Vegetation was sampled before and after treatment and subsequently monitored over a period of 14 years. With the exception of winterfat, all the seeded species established and increased in density and/or cover during the period 1993-1998. Cheatgrass (Bromus tectorum) also increased and became dominant during this period. Seeding was most successful on a rockier substrate where fourwing saltbush became a dominant shrub. Drought conditions after 1998 corresponded with declines in most seeded species while broom snakeweed (Gutierrezia sarothrae), hairy goldenaster (Chrysopsis villosa), desert globemallow (Sphaeralcea ambigua) and sandsage (Artemisia filifolia) increased through recruitment from surrounding vegetation. Sandsage was the dominant shrub of nearby undisturbed sandy sites and grew rapidly following establishment in a sandier portion of the treated area. Cheatgrass and other annuals fluctuated from year to year in the treated area but had lower density and cover than nearby untreated areas throughout the monitoring period. We conclude that the restoration project's objectives have been met to varying degrees despite the limited persistence of the seeded species. Further research into management techniques aimed at reducing annual grasses and enhancing high-quality desert tortoise forage is recommended.

This paper presents a new clustering program named RCLUS that was developed for species (R-mode) analysis of plant community data. RCLUS identifies clusters of co-occurring species that meet a user-specified cutoff level of positive association with each other. The "strict affinity" clustering algorithm in RCLUS builds clusters of species whose pairwise associations all exceed the cutoff level, whereas the "coalition" clustering algorithm only requires that the mean pairwise association of the cluster exceeds the cutoff level. Both algorithms allow species to belong to multiple clusters, thus accommodating both generalist and specialist species. Using a 60-plot dataset of perennial plants occurring on the Beaver Dam Slope in southwestern Utah, we carried out RCLUS analyses and compared the results with 2 widely used clustering techniques: UPGMA and PAM. We found that many of the RCLUS clusters were subsets of the UPGMA and PAM clusters, although novel species combinations were also generated by RCLUS. An advantage of RCLUS over these methods is its ability to exclude species that are poorly represented in a dataset as well as species lacking strong association patterns. The RCLUS program also includes modules that assess the affinity of a given species, plot, or environmental variable to a given cluster. We found statistically significant correlations between some of the RCLUS species clusters and certain environmental variables of the study area (elevation and topographical position). We also noted differences in clustering behavior when different association coefficients were used in RCLUS and found that those incorporating joint absences (e.g., the phi coefficient) produced more clusters and more even numbers of species per cluster than those not incorporating joint absences (e.g., the Jaccard index). In addition to the species association application described in this paper, the RCLUS algorithms could be used for preliminary data stratification in sample (Q-mode) analysis. The indirect link between sample plots and RCLUS species clusters could also be exploited to yield a form of "fuzzy" classification of plots or to characterize species pools of plots.

After wildfires in 1996 in the sagebrush (Artemisia spp.) and pinyon-juniper (Pinus spp.–Juniperus spp.) zones of west-central Utah, the USDI-BLM attempted to reduce soil erosion and cheatgrass proliferation (Bromus tectorum L.) through rehabilitation treatments. We compared the vegetation of aerially seeded, chained treatments with aerially seeded but non-chained treatments for 3 years following seeding. Vegetation cover increased significantly in both treatments between the first and second year, concurrent with above-average precipitation. By the second year, seeded grasses, primarily crested wheatgrass [Agropyron cristatum (L.) Gaertn.] and intermediate wheatgrass [Elymus hispidus (Opiz) Meld. and Elymus elongatus (Host) Runem.], dominated the chained treatment while cheatgrass dominated the non-chained treatment. Seeded grass establishment in non-chained areas was highest beneath dead trees on steep northeast-facing slopes. The first year following the fires, frequency of most annual species and some native perennial species was higher in the non-chained than chained treatment. Native species richness and diversity declined in both treatments between the first and third year following the fires due to the loss of early-seral native annuals and probably because of climatic factors and competition from seeded grasses and cheatgrass. This study reaffirmed the utility of aerial seeding followed by chaining as a rehabilitation technique for rapid establishment of standard plant materials and suppression of cheatgrass, although the implications for soil protection were less clear. Maintenance of native biodiversity on public lands will require greater development and use of native plant materials for wildfire rehabilitation. Planning for future rehabilitation needs is important in light of continuing wildfire risks.

Fire ecology of sagebrush and pinyon-juniper vegetation in the Great Basin has been influenced by human disturbances and exotic plant introductions. Late-seral woody vegetation, which increased following Euro-American settlement, is now decreasing because of wildfire and exotic annuals. Multiple successional pathways following fire have been observed in these vegetation types. Following the 1996 wildfires in west-central Utah, burned and unburned vegetation were compared at four sites. Measures of frequency, cover, and density of vascular plant species were used to show fire effects and to follow population dynamics over a period of 3 years. Woody species characteristic of the unburned areas were generally absent from the burned areas. Native herbaceous species, particularly annual forbs, were abundant in the burned areas 1 year after the fires, but many of these declined by the second and third year, as exotic species, particularly cheatgrass (Bromus tectorum), increased. Cheatgrass became dominant in the interspaces among burned trees by the second year following the fires, a period of high precipitation. In the subcanopy zones of burned trees, cheatgrass did not become dominant until the third year following the fire, and was preceded by exotic annual forbs. Community composition and structure differed by site as well as by fire history. Cheatgrass cover was lowest at a site where perennial grasses and forbs had become established through aerial broadcast seeding.

Utilization of willow-leaf rubber rabbitbrush (Chrysothamnus nauseosus ssp. salicifolius) was determined by twig measurements in spring and fall at two populations in Duchesne County, Utah. These measurements indicted ungulates used between 38 and 59% of twig growth in 2 years at two sites. Use was mostly in winter when mule deer (Odocoileus hemionus) and elk (Cervus elaphus) were present. Cattle (Bos taurus) were also present in summer and fall. Most of the cattle use appeared to be in the fall. Use of two color morphs (white and green) was compared at one site. There was no significant (P > 0.05) difference between use of marked twigs of the color morhps. However, the percent branches browsed did show highly significant seasonal differences between the color morphs (P < 0.01 for three of the four dates but P > 0.2 for the fourth date).

Kuchler and Bailey constructed continental scale maps of the vegetation of the United States. These maps are compared for the 17 Western United States. The vegetation categories (vegetation types for Kuchler and ecoregions for Bailey) are quantified by category and by state with particular emphasis on shrub vegetation categories. The Kuchler map has 30 shrub vegetation types (including pinyon-juniper shrub mosaics) that account for about 40 percent (1.8 x 10(6) km(2)) of the area in the 17 states. In the Bailey map, 15 ecoregions account for about 34 percent (1.6 x 10(6) km(2)) of the area in shrublands.