Native Bunchgrass Research Articles

Improving seedling recruitment and dryland restoration using a targeted fungicide seed coating

The success of seeding projects in dryland systems is sporadic, with failure primarily driven by low seedling emergence and survival. This sporadic nature is influenced by a litany of biotic and abiotic factors that act in synergy to reduce recruitment success. These factors include erratic seasonal weather patterns, competition, predation, plant material selection, and restoration strategies. While some events are unpredictable and uncontrollable, others may be mitigated through thoughtful deliberation. Pathogenesis from soil‐ and seed‐borne fungi is one form of predation that can decrease restoration success. Fungicide seed coatings are technologies used in the agriculture industry to mitigate fungal pathogens, yet these technologies are novel to wildland seeding. We evaluated the ability of a fungicide seed coating to improve bluebunch wheatgrass (Pseudoroegneria spicata) recruitment across a broad range of sites and determined how soil and climate affected seed treatments across six sites over 650 linear kilometers of sagebrush‐steppe habitat in the Great Basin, United States. Treatment effects varied by site; however, on average, the fungicide treatment increased germination by 16%, emergence by 42%, and juvenile plant establishment by 60%. Fungicide seed treatments had a greater effect on seedling emergence in soils with lower pH, reduced wet‐thermal accumulation during the winter, lower bulk density, and higher organic matter content. Most notably, the fungicide seed treatment resulted in higher plant establishment when emerged seedlings were exposed to longer periods of available soil moisture. Fungicide seed treatments can improve the establishment of native bunchgrasses, when soil and climate regimes are considered.

Post-fire management decisions have consequences: Drill-seeding disturbance and effects of co-seeding introduced with native bunchgrasses

Wildfires and the demand for post-fire seeding are increasing in the sagebrush ecosystem threatened by invasive annual grasses. Drill-seeding bunchgrasses after wildfire is a common strategy for limiting annual grasses. However, there are concerns that the soil disturbance associated with drill-seeding may negatively impact the plant community, particularly if seeded species fail to establish. Similarly, there are worries that co-seeding introduced bunchgrasses with natives, to hedge against low native bunchgrass establishment, may limit native bunchgrass success. We investigated the effects of the disturbance of drill-seeding and the impacts of co-seeding introduced bunchgrasses after wildfire in sagebrush communities at four sites up to six years post-seeding. The disturbance of drill-seeding increased invasive annual grasses from ∼10 % to >15 % cover and increased its density by >200 plants∙m−2 by the end of the study. Bunchgrasses appeared to not be influenced by the disturbance of drill-seeding; however, drill-seeding slightly reduced perennial forb density. These results suggest that restoration practitioners need to consider potential negative consequences of drill-seeding, especially when and where selected plant materials may fail to establish in high abundance. Co-seeding introduced bunchgrasses with native bunchgrasses limited native bunchgrasses and also slightly decreased native perennial forbs. However, co-seeding introduced bunchgrasses reduced invasive annual grasses by ∼50 %, while seeding only native bunchgrasses did not reduce annual grasses. These findings suggest that co-seeding introduced and native bunchgrasses may not be advisable. We suggest: 1) If native bunchgrasses are unlikely to establish in high abundance, then introduced bunchgrasses should be used, and 2) If seeded native bunchgrasses are likely to meet management objectives, then introduced bunchgrasses should not be co-seeded. Additional investigations are needed in other areas to determine the applicability of the results of this study to the larger sagebrush ecosystem. Clearly, the potential consequences of post-fire management will need to be considered as restoration plans are developed, but additional research is needed to better inform management decisions.

Applied soft classes and fuzzy confusion in a patchwork semi-arid ecosystem: Stitching together classification techniques to preserve ecologically-meaningful information

Dryland ecosystems have complex vegetation communities, including subtle transitions between communities and heterogeneous coverage of key functional groups. This complexity challenges the capacity of remote sensing to represent land cover in a meaningful way. Many remote sensing methods to map vegetation in drylands simplify fractional cover into a small number of functional groups that may overlook key ecological communities. Here, we investigate a remote sensing process that further advances our understanding of the link between remote sensing and ecologic community types in drylands. We propose a method using k-means clustering to establish soft classes of vegetation cover communities from detailed field observations. A time-series of Sentinel-2 satellite imagery and a random forest classification leverages the mixing of different phenologies over time to impute such soft community classes over the landscape. Next, we discuss the advantages of using a fuzzy confusion approach for soft classes in cases such as understanding subtle transitions in ecotones, identifying areas for targeted remediation or treatment, and in ascertaining the spatial distribution of non-dominant covers such as biological soil crusts and small native bunchgrasses which have typically been difficult to map with traditional remote sensing classifications. Our pixel-level analysis is relevant to the scale of management decisions and represents the complexity of the landscape. The combination of cloud computing with the spatial, temporal, and spectral observations from Sentinel-2 allow us to develop these ecologically-meaningful observations at large spatial extents, including complete coverage at landscape scales. Re-interpretation of large extent maps of soft classes may be helpful to land managers who need community-level information for fuel breaks, restoration, invasive plant suppression, or habitat identification.

Sagebrush-Associated Bunchgrasses Drive Invasion Resistance in a Greenhouse Experiment

Invasion of non-native annual grasses is a significant threat to the sustainability of sagebrush steppe ecosystems. Ecological resilience, the ability to bounce back after a disturbance, and resistance, the ability to withstand invasion, are influenced by both abiotic factors, such as soil temperature, moisture, elevation, and aspect, and biotic factors, such as plant community composition. We quantified the effects of moss biocrusts, native shrubs, and native perennial grasses on invasion resistance in a greenhouse experiment containing dominant sagebrush ecosystem plants and invasive grasses. We saw greatest suppression of invasive annual grass biomass in treatment replicates containing native bunchgrass species (P < 0.01). Final invasive grass biomass was 4.79 g on average when perennial grasses were not present and was reduced to 1.59 g with perennial grass competition (P < 0.01). Presence of shrubs and moss biocrusts did not decrease annual grass biomass (P = 0.38 and P = 0.25, respectively). We saw complex interactions between native plants grown in these ideal greenhouse conditions such that native perennial grass seedlings grown with sagebrush seedlings had a mean of 4.50 g more biomass (P < 0.001) relative to pots grown with bitterbrush or without shrubs, but shrubs were an average of 7.9 cm (P < 0.001) shorter and had biomass 4.75 g lower (P < 0.001) in pots grown with perennial grasses compared with shrubs grown without perennial grasses. Our results demonstrate that with increased treatment complexity, we see greater invasion resistance, but that nuanced relationships between plant community members should also be considered in managing and restoring these imperiled ecosystems.

Fecal metabarcoding of the endangered Pacific pocket mouse (Perognathus longimembris pacificus) reveals a diverse and forb rich diet that reflects local habitat availability.

Information on diet breadth and preference can assist in understanding links between food resources and population growth and inform habitat restoration for rare herbivores. We assessed the diet of the endangered Pacific pocket mouse using metabarcoding of fecal samples and compared it to plant community composition in long-term study plots in two populations on Marine Corps Base Camp Pendleton, San Diego County, CA. Fecal samples (n = 221) were collected between spring 2016 and fall 2017 during monthly live-trap surveys. Concurrently, percent cover and plant phenology were measured in plots centered on trap locations. Fecal samples were sequenced with paired-end reads of the internal transcribed spacer 2 region of the nuclear ribosomal gene, and the resulting amplicons were matched to a regionally specific database. Seventy-three plant taxa were detected, which were mostly forbs and perennial herbs (70-90%). Diet composition differed between populations, years, seasons, and plots. Overall, diet and local habitat composition in plots were significantly correlated. However, we detected some differences in above-ground seed availability and proportion in fecal samples that indicate diet preferences for some forbs, perennial herbs, and native bunch grasses over perennial shrubs and non-native grasses. This is the first study of PPM to pair plant phenology surveys with diet metabarcoding to estimate resource selection, and results suggest that managing habitat for diverse native forb communities and reducing non-native grass cover may be beneficial for this critically endangered species.

P72 Native bunchgrasses for forage and bioenergy

P72 Native bunchgrasses for forage and bioenergy

Population Fluctuations of the Deer Mouse (Peromyscus maniculatus) in Old-Field and Bunchgrass–Sagebrush Habitats: The Role of Agricultural Setting and Optimum Habitat

In semiarid regions, the deer mouse (Peromyscus maniculatus) is a major small mammal species occupying perennial grassland habitats that include old-fields, native bunchgrass–sagebrush, and some agricultural settings. We investigated population changes in deer mouse populations in perennial grasslands, both natural and old-field, from 1982 to 2003 in southern British Columbia, Canada. Hypotheses (H) predicted that P. maniculatus populations will have (H1) multiannual fluctuations in abundance driven by population increases from extended breeding in summer and winter; (H2) relaxed spring reorganization events in some years leading to higher overall recruitment and survival; and (H3) interspecific competition with montane voles that causes deer mice to be lower in density when voles are higher. P. maniculatus populations in old-field and grass–sagebrush sites had clearly defined periods of high “peak” mean numbers (32–52/ha) and other times of low mean numbers (20–22/ha). Based on mean annual peak density in autumn, deer mouse populations exhibited fluctuations of 3–4 years in both habitats, but this pattern was not always present. The greater numbers of P. maniculatus in high than low years was directly related to population increases from extended breeding seasons and an increased number of lactating females, thereby supporting H1. Spring breeding season declines occurred but were similar or less in high than low years of mean abundance and were relaxed in comparison to forest populations of deer mice in other studies. Thus, H2 was supported for recruitment with high numbers of young-of-the-year breeding and total number of juvenile recruits but for survival was equivocal. Total summer survival was consistently higher in high than low population years but juvenile productivity in all years was poor. Mean abundance of P. maniculatus and M. montanus in old-field sites were highly correlated, and hence H3 was not supported. This latter result is the first, to our knowledge, of P. maniculatus coexisting in a similar pattern of population fluctuations with a Microtus species in a mainland grassland habitat. Higher than average precipitation in the year preceding a peak population of deer mice may have enhanced herbaceous vegetation and contributed to population increases in both habitats. We conclude that the old-field habitat associated with this agricultural setting provides optimum habitat for P. maniculatus and facilitates multiannual population fluctuations in this species.

A decade‐long study of repeated prescription burning in California native grassland restoration

Native bunchgrass communities dominated by Stipa pulchra are widely distributed in California but share dominance with non‐native annual grasses. Restoration of these grasslands focuses on altering the balance of native to non‐native grasses to favor the former. This study investigated the impact of burning on vegetation recovery. In the first postfire year burning showed a 70% reduction in cover of non‐native annual grasses (Bromus diandrus exhibited the greatest reduction) and minimal impact on S. pulchra recovery. In the following 3 years, S. pulchra recovered to levels comparable to controls, whereas the annual grasses remained below control levels until the fifth year. Also, in response to reduced annual grass cover on burned sites several species of non‐native Erodium increased from 10 to 30% relative cover, however, the low growth form of these forbs presented a less competitive threat to bunchgrasses than the non‐native annual grasses, and by the third postfire year returned to near control levels. The rare native geophyte Brodiaea kinkiensis was present throughout these grasslands and was not inhibited by burning treatments. To document the reliability of these patterns a second prescription burn was conducted on these sites 5 years after the first burn and vegetation recovery followed for the subsequent 4 years. Patterns observed after the first burn were duplicated following the second burn. The cover of S. pulchra varied in response to precipitation, with the 95% credible intervals of precipitation parameters overlapping zero, however, the cover of non‐native grasses varied greatly with precipitation and had similar trajectories in unburned and burned plots.

Fine‐scale spatial genetic structure in a locally abundant native bunchgrass (Achnatherum thurberianum) including distinct lineages revealed within seed transfer zones

AbstractAnalyses of the factors shaping genetic variation in widespread plant species are important for understanding the evolutionary history and local adaptation and have applied significance for guiding conservation and restoration decisions. Thurber's needlegrass (Achnatherum thurberianum) is a widespread, locally abundant grass that inhabits heterogeneous arid environments of western North America and is of restoration significance. It is a common component of shrubland steppe communities in the Great Basin Desert, where drought, fire, and invasive grasses have degraded natural communities. Using a reduced representation sequencing approach, we generated SNP data at 5677 loci across 246 individuals from 17 A. thurberianum populations spanning five previously delineated seed zones from the western Great Basin. Analyses revealed a pronounced population genetic structure, with individuals forming consistent geographical clusters across a variety of population genetic analyses and spatial scales. Low levels of genetic diversity within populations, as well as high population estimates of linkage disequilibrium and relatedness, were consistent with self‐fertilization as a contributor to population differentiation. Variance partitioning and partial redundancy analysis (pRDA) indicated local adaptation to environment as additionally influencing the spatial distribution of genetic variation. The environmental variables driving these results were similar to those implicated in recent genecological work which inferred local adaptation for seed zone delineation. Our analyses also revealed a complex evolutionary history of A. thurberianum in the Great Basin, where previously delineated seed zones contain distantly related populations. Our results indicate evolutionary history, mating system, and differentiation across distinct geographic and environmental scales have shaped genetic variation in A. thurberianum and illustrate how numerous aspects of population genetic variation might require consideration for restoration planning.

Blown Away: Extreme Wind Events Impact Grass Mortality

Understanding extremes in ecological change is critical given the anticipated increasing frequency of such events. This is especially true when extreme events trigger transitions to alternative stable states, as in drylands that have seen conversion from grass- to shrub-dominated states. We examined the responses of a Chihuahuan Desert community after record winds in 2019 killed grasses and reduced greenness. We argue that wind has two faces like Janus, aptly the Roman god of transitions, because it participates in change as both a forcing and a feedback and that, similarly, other types of extremes can alter the character of ecological interactions. Photo 1. Record-breaking wind in southern New Mexico in the spring of 2019 had major impacts on grass at the Jornada Long Term Ecological Research site in Las Cruces, New Mexico. The exposed roots of two Sporobolus spp. grasses are a result of these storms. Photo credit: G.S. Okin. Photo 2. In some cases, grasses, like the one on the left in this image, were able to green up following rain in the early summer. Other grasses appear to have been killed by the root exposure and sandblasting that occurred during the extreme wind events in the spring of 2019. Photo credit: G.S. Okin. Photo 3. UCLA undergraduate, Sarah Payne (shown here indicating the extent of root exposure on a native bunchgrass), conducted an NSF-supported summer research project that resulted in a publication of an article in Ecology. Photo credit: G.S. Okin. These photographs illustrate the article “The two faces of Janus: Processes can be both exogenous forcings and endogenous feedbacks with wind as a case study” by Sarah A. R. Payne, Gregory S. Okin, Abinash Bhattachan, and Michael R. Fischella published in Ecology. https://doi.org/10.1002/ecy.3998

Wildfire disturbance reveals evidence of ecosystem resilience and precariousness in a forest–grassland mosaic

AbstractForest and grassland ecosystems are sometimes located adjacently within the same climate. In Interior British Columbia, Canada, there are complex forest–grassland mosaics within the Interior Douglas‐fir biogeoclimatic zone. Historically, both grassland and forest ecosystems experienced high‐frequency, low‐severity fire regimes. Since European settlement and introduction of livestock grazing and fire exclusion, trees have encroached on grasslands, and tree densities in forests have increased. In this study, we characterize plant communities and near‐surface soil moisture in forest and grassland sites, and in historical grassland sites affected by tree encroachment. We hypothesized that spatial and temporal patterns of near‐surface soil moisture are reflected in aboveground plant community composition and structure. After initial sampling of soil moisture and plant communities, the study area was burned in a wildfire. Applying a multifactorial approach to comparing adjacent grassland and forest sites, we treated the wildfire event as a natural experiment, sampling post‐wildfire plant species composition and soil moisture, and measuring the severity and spatial heterogeneity of surface burn conditions. Evidence supports the concept of mutually exclusive fire‐reinforced bistable grassland and forest states, with greater spatial heterogeneity of soil moisture and burn severity in forests, and highly uniform patterns of soil moisture, vegetation, and burn severity in grasslands. Areas of forest encroachment on grasslands had understory plant communities dominated by exotic species, while restored grasslands had native bunchgrass cover like typical grasslands of the region. Additionally, there was post‐wildfire divergence of forest‐ and grassland‐associated plant communities. Viewed through a resilience theory conceptual framework, we suggest that ecosystem legacies are reinforcing post‐wildfire ecosystem identity and associated native plant communities. External factors—particularly past heavy livestock grazing and fire suppression—have caused ecosystem precariousness that can be addressed with management actions.

Reproductive compensatory photosynthesis in a semi-arid rangeland bunchgrass

While increased foliar photosynthesis is well documented across many plant species in response to diverse modes of herbivory, the compensatory ability of photosynthetically active reproductive structures is unknown. To address this, we partially defoliated basal florets in seed heads of crested wheatgrass (Agropyron cristatum (L.) Gaertn.), an exotic Eurasian perennial bunchgrass widely distributed across North American sagebrush steppe. We followed direct and indirect responses by tracking post-clipping photosynthesis in clipped basal and unclipped distal florets, respectively, and comparing these to similar florets on unclipped seed heads. Compensatory photosynthesis was apparent 24 h after clipping; over the pre-anthesis period, clipped basal floret photosynthesis was + 62%, stomatal conductance was + 82%, and PSII photochemical yield was − 39% of unclipped controls. After anthesis, intact florets distal to clipped florets had modestly higher photosynthetic rates compared to controls, while basal floret rates did not differ between treatments. Compensatory photosynthesis reduced intrinsic water use efficiency (iWUE; photosynthesis/stomatal conductance) 68–40% below controls over pre- and post-anthesis periods, respectively. Specific mass (dry mass/area) of clipped florets was − 15% of controls, while florets distal to these had specific mass 11% greater than distal or basal florets on unclipped seed heads. These results suggest damaged basal florets provided carbon to unaffected distal florets. This could explain crested wheatgrass’s ability to produce viable seeds under conditions limiting to native bunchgrasses, and presents a novel mechanism germane to the development of convergent drought- and grazing-tolerance traits important to arid and semi-arid rangeland plant community resilience to climate variability.

Native lagomorphs prolong legacy effects limiting restoration of imperiled shrub‐steppe communities

Over the last +150 years, increases in woody vegetation in drylands and associated declines in herbaceous vegetation have led to widespread interest in reversing this trend. However, the effects of native, noncharismatic herbivores, such as lagomorphs, on these efforts are largely unknown. For 11 years post‐treatment, we quantified the effects of native lagomorphs on restoration efforts in sagebrush (Artemisia L.) communities exhibiting legacy effects of past management, including depleted understories and overabundant sagebrush. Reducing sagebrush and seeding perennial grasses was necessary to attain substantial increases in large perennial grass cover and density, but this outcome was realized only with lagomorph exclusion. A small native bunchgrass and perennial forb cover and density increased in all treatments with lagomorph exclusion. This suggests that lagomorphs contribute to the persistence of a depleted understory in areas with increased woody vegetation. In areas where sagebrush was reduced, the cover and density of sagebrush was greater with lagomorph exclusion. This suggests that lagomorphs could hinder sagebrush recovery after disturbances that reduce or eliminate sagebrush. Lagomorph herbivory had a substantial effect on vegetation dynamics and affected the outcome of restoration efforts in these dryland systems. This could reduce livestock forage and alter habitat of wildlife species, potentially affecting their conservation. Lagomorphs and other noncharismatic, native herbivores may facilitate the persistence of depleted understories in areas where woody plants have increased. Results of this study suggests that the potential effects of lagomorph and other native herbivores should be considered and addressed in management, restoration, and conservation plans.

Postfire futures in southwestern forests: Climate and landscape influences on trajectories of recovery and conversion.

Southwestern ponderosa pine forests are vulnerable to fire-driven conversion in a warming and drying climate, yet little is known about what kinds of ecological communities may replace them. To characterize postfire vegetation trajectories and their environmental determinants, plant assemblages (361 sample plots including 229 vascular plant species, surveyed in 2017) were sampled within eight burns that occurred between 2000 and 2003. I used nonmetric multidimensional scaling, k-means clustering, principal component analysis, and random forest models to assess relationships between vegetation pattern, topographic and landscape factors, and gridded climate data. I describe seven postfire community types, including regenerating forests of ponderosa pine, aspen, and mixed conifers, shrub-dominated communities of Gambel oak and mixed species, and herb-dominated communities of native bunchgrasses and mixtures of ruderal, native, and nonnative species. Forest recovery was generally associated with cooler, mesic sites in proximity to forested refugia; shifts toward scrub and grassland types were most common in warmer, dryer locations distant from forested refugia. Under future climate scenarios, models project decreases in postfire forest recovery and increases in nonforest vegetation. However, forest to nonforest conversion was partially offset under a scenario of reduced burn severity and increased retention of forested refugia, highlighting important management opportunities. Burning trends in the southwestern United States suggest that postfire vegetation will occupy a growing landscape fraction, compelling renewed management focus on these areas and paradigm shifts that accommodate ecological change. I illustrate how management decisions around resisting, accepting, or directing change could be informed by an understanding of processes and patterns of postfire community variation and likely future trajectories.

Can delaying germination reduce barriers to successful emergence for early‐germinating, fall‐sown native bunchgrass seeds in cold deserts?

Efforts to restore semiarid wildlands in the western United States predominantly use fall seeding. Fall conditions are more amenable to seeding, and successfully over‐wintered seeds or plants are poised to take full advantage of spring moisture. However, over‐winter mortality can be a barrier to seeding success. One solution to avoid winter mortality without sacrificing the benefits of fall seeding is to delay germination of fall‐sown seeds. At six northern Great Basin field sites over three planting years (18 trials), we tested whether a hydrophobic seed coating reliably delayed germination and increased seedling establishment of a native bunchgrass. Despite considerable variation among sites and years, seed treatment successfully reduced pre‐winter germination by 84% compared to untreated, but also consistently reduced final germination by 23%. Still, treatment resulted in an average of 2.1‐fold higher emerged seedling density in seven trials, six of which were among the eight trials where more than 50% of untreated seeds germinated pre‐winter. Emergence was greater for untreated seed in five trials, all of them in the same year, and all but one of them with below‐average total germination. Our treatment consistently reduced pre‐winter germination, but only improved emergence when pre‐winter germination of untreated seeds was high. Continued research is merited with germination‐delaying treatments and to experimentally define—and develop models that predict—winter‐related mortality barriers. We also suggest future exploration of bet‐hedging strategies that mix treated and untreated seeds where fall seeding is required and significant but variable risk of over‐winter seedling mortality exists.

Invasive and native grasses exert negative plant-soil feedbacks on the woody shrub Artemisia tridentata.

Displacement of diverse native plant communities by low-diversity invasive communities is a global problem. In the western United States, the displacement of sagebrush-dominated communities by cheatgrass has increased since the 1920s. Restoration outcomes are poor, potentially due to soil alteration by cheatgrass. We explored the poorly understood role of plant-soil feedbacks in the dominance of cheatgrass in a greenhouse study where uninvaded sagebrush soils were conditioned with either cheatgrass, a native bunchgrass or sagebrush. Sagebrush seedlings were grown in the soils that remained following the removal of conditioning plants. We expected cheatgrass to strongly suppress sagebrush due to a change in belowground microbial communities, conspecifics to have neutral effects and the native bunchgrass to have intermediate effects as it coevolved with sagebrush but belongs to a different functional group. We assessed the effects of conditioning on sagebrush growth, tissue nutrients, and carbon allocation. We also characterized the abundance, diversity and community composition of root microbial associates. Cheatgrass strongly suppressed sagebrush growth at high and low conditioning densities, the native bunchgrass showed suppression at high conditioning densities only and conspecific effects were neutral. Tissue nutrients, amount of root colonization by soil fungi or root microbial community composition were not associated with these plant-soil feedbacks. Although we did not identify the precise mechanism, our results provide key evidence that rapid soil alteration by cheatgrass results in negative plant-soil feedbacks on sagebrush growth. These feedbacks likely contribute to cheatgrass dominance and the poor success of sagebrush restoration.

Using Genomic Selection to Develop Performance-Based Restoration Plant Materials

Effective native plant materials are critical to restoring the structure and function of extensively modified ecosystems, such as the sagebrush steppe of North America’s Intermountain West. The reestablishment of native bunchgrasses, e.g., bluebunch wheatgrass (Pseudoroegneria spicata [Pursh] À. Löve), is the first step for recovery from invasive species and frequent wildfire and towards greater ecosystem resiliency. Effective native plant material exhibits functional traits that confer ecological fitness, phenotypic plasticity that enables adaptation to the local environment, and genetic variation that facilitates rapid evolution to local conditions, i.e., local adaptation. Here we illustrate a multi-disciplinary approach based on genomic selection to develop plant materials that address environmental issues that constrain local populations in altered ecosystems. Based on DNA sequence, genomic selection allows rapid screening of large numbers of seedlings, even for traits expressed only in more mature plants. Plants are genotyped and phenotyped in a training population to develop a genome model for the desired phenotype. Populations with modified phenotypes can be used to identify plant syndromes and test basic hypotheses regarding relationships of traits to adaptation and to one another. The effectiveness of genomic selection in crop and livestock breeding suggests this approach has tremendous potential for improving restoration outcomes for species such as bluebunch wheatgrass.

Soil microbial communities and nitrogen associated with cheatgrass invasion in a sagebrush shrubland

Cheatgrass invasion of Intermountain sagebrush steppe in the western United States poses increasing challenges to the function and survival of this native ecosystem. The invasive success and persistence of cheatgrass has been attributed to the increasing soil total nitrogen, but mechanisms behind remain inconclusive. We hypothesized that soil microorganisms play a role in soil nitrogen associated with cheatgrass invasion. We collected soil samples from the root zone of cheatgrass, native bunchgrass, and sagebrush at two depths and from two adjacent sites in April. We examined soil chemical properties (pH, moisture content, and NH4+ and NO3− concentration) and soil microbial communities. We found that cheatgrass invasion was associated with different soil microbial community composition compared to native bunchgrass and sagebrush. In particular, we observed higher relative abundances of N2 fixers and ureolytic bacteria and lower relative abundance of denitrifiers providing a potential mechanistic belowground explanation of raising soil nitrogen. Overall, our results indicate the importance of soil microorganisms in the dominance and persistence of invasive species. Targeted microbiome interventions should be considered to control cheatgrass invasion.

Using Postfire Spatial Variability to Improve Restoration Success with Seeded Bitterbrush

Seed-based restoration of wildlife-important shrubs following wildfire is a management priority in many ecosystems. However, postfire restoration success is spatiotemporally variable and establishment from seed frequently fails in arid and semiarid rangelands. There may be opportunities to improve restoration success by taking advantage of small-scale spatial variability in environmental characteristics. Woody plants create distinct postfire microsites, which may influence establishment and growth of seeded species, under their canopies (canopies) compared with between their canopies (interspaces). Immediately after fire, former canopies generally have less vegetation and greater soil nutrient concentrations compared with interspaces. Thus, former canopy compared with interspace microsites may be more favorable for establishment and growth of seeded species, but rapid exotic plant invasion of former canopy microsites may hinder success. We evaluated seeding bitterbrush (Purshia tridentata Pursh DC) after wildfire in former western juniper (Juniperus occidentalis ssp. occidentalis Hook) canopy compared with interspace microsites at six locations for 3 yr post seeding. Bitterbrush abundance was 3.6-fold greater in former canopy compared with interspace microsites after 3 yr. Bitterbrush height was 1.5 to 2.5-fold greater in former canopy compared with interspace microsites. The first year after fire, exotic annual grass cover was 15.6-fold greater in interspace compared with canopy microsites. Abundance and cover of other herbaceous vegetation were generally also greater in the interspace. Exotic annual grass and native bunchgrass abundance increased substantially over time in former canopy microsites, suggesting abundant resource availability. Less herbaceous competition and presumably greater resource availability in former canopies probably resulted in greater success of seeded bitterbrush. These results suggest that capitalizing on spatial variability in environments can be used to increase restoration efficiency. After fire in western juniper−encroached rangelands, former juniper canopy microsites are a favorable environment for establishment and growth of seeded bitterbrush and could be targeted for restoration efforts to improve efficiency.

Moderate Grazing During the Off-Season (Fall-Winter) Reduces Exotic Annual Grasses in Sagebrush-Bunchgrass Steppe

Exotic annual grass invasion and dominance of sagebrush-bunchgrass steppe is a concern because it decreases biodiversity and promotes frequent wildfires. Management is needed to reduce exotic annual grasses to prevent sagebrush-bunchgrass communities from transitioning to annual grasslands. Grazing during the off season (fall-winter) has shown promise at reducing exotic annual grasses, but it has not been evaluated in plant communities dominated by sagebrush and native bunchgrasses. We compared moderate grazing during the off season with not grazing in five Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis [Beetle & A. Young] S.L. Welsh)−bunchgrass communities in the northern Great Basin. Treatments were applied annually for 10 yr (2009−2010 through 2018−2019). Plant community characteristics were measured after treatments had been applied from 6 to 10 yr. Off-season grazing reduced exotic annual grass density and cover. After a decade, annual grass cover was twofold greater in ungrazed areas. Sandberg bluegrass (Poa secunda J. Presl) density increased with off-season grazing, but large bunchgrass density was similar between off-season grazed and ungrazed areas. Perennial and annual forb density and cover were similar between off-season grazed and ungrazed treatments. Biological soil crust cover was also similar between off-season grazed and ungrazed areas. The results of this study provide strong evidence that off-season grazing has application for managing exotic annual grasses in sagebrush-bunchgrass steppe. Considering the vast scope of the exotic annual grass problem, properly applied grazing may be the most cost-efficient tool to mediate the impacts of annual grass invasion.