Establishment Of Perennial Grasses Research Articles

STRUCTURAL-AGGREGATE COMPOSITION AND SOIL WATER RESISTANCE BASED ON TILLAGE REGIMES IN SOUTHEAST KAZAKHSTAN

The promotion and rational development of drylands employed two tillage regimes (plowing to 20–22 cm and no-till) during the spring wheat and barley cultivation in Southeast Kazakhstan. The results established that the no-till scheme contributed to forming an excellent aggregate state of the arable soil layer for spring wheat and barley (65%–69%). The water-resistant aggregates were the highest with no-tillage (19.3%–21.8%), indicating the unsatisfactory water resistance of the soil structure. Enhancing the water-resistant aggregates requires using organic fertilizers to improve the establishment of perennial grasses, green manuring, and cover crops. No-till system inclined to boost the optimal soil density from a loose and slightly compact state of 1.19–1.23 g/cm3 to a dense 1.32–1.39 g/cm3. According to crop cultivar and tillage methods, the spring wheat and barley grain yield varied between 2.84 and 3.89 t/ha. High grain yield came from the spring barley cultivar Symbat. Spring showed promising performance when the plowing level was 20–22 cm and inferior only by 0.25 and 0.15 t/ha with no-till. Based on the two-factor analysis of variance, the cultivar contribution to the spring wheat and barley grain yield buildup depended on the shares of crop season of the research (year – environment) (40.9%–62.2%) and the tillage regimes (22.4%–32.2%). The grain yield formation was more dependent on the studied crops and their cultivars, and the dependence increased over the crop seasons due to weather conditions during the crop period.

Establishment of sand bluestem with the aid of pre‐emergence‐applied herbicides

AbstractControlling competition with weeds is critical to successful native perennial grass establishment. Our objective was to determine the potential of several pre‐emergence‐applied herbicides to control annual weeds and aid sand bluestem (Andropogon hallii Hack.) establishment. Sand bluestem was seeded at one site in two adjacent areas during the end of March 2002 and 2003 in Woodward, OK, and at one site during the end of March 2004 near Fort Supply, OK, at 14.4 lb pure live seed acre−1 each year. Herbicides were applied within a few days of seeding and were watered in with ∼0.75 inch irrigation water within 1 wk of application at the Woodward sites whereas no irrigation water was supplied at the site near Fort Supply. Response variables measured were sand bluestem stand frequency 13 mo after seeding and forage production 16 mo after seeding. Thiazopyr prevented germination of sand bluestem in all plots, and atrazine + acetochlor produced stands significantly lower than the untreated controls in both locations. Imazapic produced stands of sand bluestem that were significantly greater than the untreated plots in both locations. Forage production of sand bluestem was significantly greater when imazapic was applied within 7 d after seeding than in untreated plots at both locations. Over all three sites, sand bluestem forage production averaged 3,202 lb acre−1 where imazapic was applied compared with only 1,663 lb acre−1 in plots not treated with herbicide. Sand bluestem forage production was consistently increased where imazapic was applied shortly after planting.

Pelleted manure compost improves mine spoil properties enhancing plant growth and phyto-stabilization of potentially toxic metals

Feedlot manure is rich in plant nutrients and can immobilize potentially toxic metals. However, pelleted manure compost as an amendment material in mine spoils (chat) is not well studied. This study was conducted to investigate the impact of pelleted cattle manure on improving chat properties facilitating phyto-stabilization and the establishment of grasses. A greenhouse pot experiment was conducted with unamended and amended chat (lime treated) with pelleted manure at three rates (60, 120, and 180 Mg ha−1) with and without bentonite (B), using two native grasses, switchgrass ( Panicum virgatum L.) and wheatgrass ( Pascopyrum smithii (Rydb.) A. Löve). Leachates from pots were collected periodically until harvest. Nutrients and metal concentrations were measured in chat treatments, and metal concentrations were measured in plant tissues and leachates. Manure-amended chat reduced leachate Cd and Zn on average by >75% and >80%, respectively. Above-ground dry matter yield increased by >2.5-fold and >4-fold, respectively, in switchgrass and wheatgrass with the increase of 3-fold manure rate. The manure rate at 180 Mg ha−1 reduced plant Cd and Zn by 50% and 20%, respectively, in wheatgrass, and 30% and no reduction, respectively, in switchgrass, compared to the 60 Mg ha−1 manure rate. Overall, pelleted manure compost significantly increased available nutrients and decreased available metals in amended chat, with no significant effect of B. This study indicated that pelleted manure, preferably at 180 Mg ha−1 rate with lime, can be used in acidic metal-contaminated chat to facilitate the establishment of perennial native grasses and reduce the potentially toxic metal availability.

Field-Deployed Extruded Seed Pellets Show Promise for Perennial Grass Establishment in Arid Zone Mine Rehabilitation

Current methods of mine rehabilitation in the arid zone have a high failure rate at seedling emergence largely due to limited availability of topsoil and low water-holding capacity of alternative growth substrates such as mining overburden and tailings. Further, seedlings have consistently failed to emerge from seeds sown on the soil surface using traditional broadcasting methods. Seed pellets, formed by extruding soil mixtures and seeds into pellets, can potentially increase soil water uptake through enhanced soil-seed contact and thereby improve seedling emergence. We tested an extruded seed pelleting method in a three-factor field experiment (i.e., different pellet-soil mixtures, organic amendments, and simulated rainfall regimes) in north-western Australia. Given the observed lack of seedling emergence from broadcast seeds, the aims of the experiment were to assess: (i) the use of pellets to promote native seedling emergence and establishment and; (ii) the soil physico-chemical and microbiological changes that occur with this method of rehabilitation. The effects of pellet-soil mixtures, organic amendment, and rainfall regime on seedling emergence and survival of three native plant species suggest trade-offs among responses. Pellets made with a 1:1 blend of topsoil and a loamy-sand waste material had the highest seedling emergence, while 100% topsoil pellets had lower emergence probably because of hardsetting. Triodia pungens (a native grass) survived to the end of the experiment while Indigofera monophylla and Acacia inaequilatera (native shrubs) emerged but did not survive. Adding an organic amendment in the extruded pellet inhibited Triodia seedling emergence but increased soil microbial activity. Overall, extruded pellets made from a 1:1 blend showed promise for the establishment of Triodia seeds and beneficially, incorporates mine waste overburden and lesser amounts of topsoil. Further research is needed to improve pelleting production and to test the applicability of the method at scale, for different species and other ecosystem types.

Suppression of Cheatgrass by Perennial Bunchgrasses

Long-term control of the invasive annual grass cheatgrass is predicated on its biological suppression. Perennial grasses vary in their suppressive ability. We compared the ability of a non-native grass (“Hycrest” crested wheatgrass) and two native grasses (Snake River wheatgrass and bluebunch wheatgrass) to suppress cheatgrass. In a greenhouse in separate tubs, 5 replicates of each perennial grass were established for 96 d, on which two seeds of cheatgrass, 15 cm apart, were then sown in a semicircular pattern at distances of 10 cm, 30 cm, and 80 cm from the established perennial bunchgrasses. Water was not limiting. After 60 d growth, cheatgrass plants were harvested, dried, weight recorded, and tissue C and N quantified. Soil N availability was quantified at each location where cheatgrass was sown, both before sowing and after harvest. Relative to cheatgrass grown at 80 cm, all perennial grasses significantly reduced aboveground biomass at 30 cm (68% average reduction) and at 10 cm (98% average reduction). Sown at 10 cm from established perennial grasses, cheatgrass aboveground biomass was inversely related with perennial grass root mass per unit volume of soil. All cheatgrass sown at 10 cm from “Hycrest” crested wheatgrass died within 38 d. Before sowing of cheatgrass, soil 10 cm from established perennial grasses had significantly less mineral N than soil taken at 30 cm and 80 cm. Relative to cheatgrass tissue N for plants grown at 80 cm, cheatgrass nearest to the established perennial grasses contained significantly less tissue N. All perennial grasses inhibited the NO2− to NO3− nitrification step; for “Hycrest” crested wheatgrass, soil taken at 10 cm from the plant had a molar proportion of NO2− in the NO2− + NO3− pool of > 90%. In summary, a combination of reduced nitrogen availability, occupation of soil space by perennial roots, and attenuation of the nitrogen cycle all contributed to suppression of cheatgrass.

Differential regulatory pathways associated with drought-inhibition and post-drought recuperation of rhizome development in perennial grass.

Rhizomes are key organs for the establishment of perennial grass stands and adaptation to environmental stress. However, mechanisms regulating rhizome initiation and elongation under drought stress and during post-drought recovery remain unclear. The objective of this study is to investigate molecular factors and metabolic processes involved in drought effects and post-drought recovery in rhizome growth in perennial grass species by comparative transcriptomic and proteomic profiling. Tall fescue (Festuca arundinacea) (B-type rhizome genotype, 'BR') plants were exposed to drought stress and re-watering in growth chambers. The number and length of rhizomes were measured following drought stress and re-watering. Hormone and sugar contents were analysed, and transcriptomic and proteomic analyses were performed to identify metabolic factors, genes and proteins associated with rhizome development. Rhizome initiation and elongation were inhibited by drought stress, and were associated with increases in the contents of abscisic acid (ABA) and soluble sugars, but declines in the contents of indoleacetic acid (IAA), zeatin riboside (ZR) and gibberellin (GA4). Genes involved in multiple metabolic processes and stress defence systems related to rhizome initiation exhibited different responses to drought stress, including ABA signalling, energy metabolism and stress protection. Drought-inhibition of rhizome elongation could be mainly associated with the alteration of GA4 and antioxidants contents, energy metabolism and stress response proteins. Upon re-watering, new rhizomes were regenerated from rhizome nodes previously exposed to drought stress, which was accompanied by the decline in ABA content and increases in IAA, ZR and GA4, as well as genes and proteins for auxin, lipids, lignin and nitrogen metabolism. Drought-inhibition of rhizome initiation and elongation in tall fescue was mainly associated with adjustments in hormone metabolism, carbohydrate metabolism and stress-defence systems. Rhizome regeneration in response to re-watering involved reactivation of hormone and lipid metabolism, secondary cell-wall development, and nitrogen remobilization and cycling.

Indaziflam effects on seed production for established perennial grasses

Indaziflam effects on seed production for established perennial grasses

Responses of Native Plants and Downy Brome to a Water-Conserving Soil Amendment

Restoring native plants in rangelands threatened by downy brome (Bromus tectorum L.) presents a serious challenge to land managers. Higher, more consistent soil moisture, as well as slightly compacted soils, may reduce the competitive abilities of downy brome. We manipulated these factors with three treatments: superabsorbent polymer (SAP), a soil-binding agent, and roller compaction at two restoration sites, Wagon Road Ridge (WRR) and Sagebrush (SGE), in northwestern Colorado. SAPs absorb water when soils are wet and then gradually release it, often reducing plant water stress. The binding agent we used is purported to increase water infiltration while reducing soil movement. In Experiment 1, we crossed an SAP, a binding agent, and rolling and found that SAP benefitted perennial grass establishment at the WRR site only. SAP also decreased downy brome cover and biomass at WRR. The binding agent increased soil moisture at both sites, and the highest level of binding agent reduced downy brome cover in the absence of SAP at the SGE site. In Experiment 2, we examined only SAP, with larger plots and a more complex seed mix. Again, SAP benefitted perennial grass establishment at WRR only. SAP reduced initial perennial forb density at both sites but did not affect forb cover in subsequent years. SAP effects on downy brome were site-specific. There was a trend for reduced downy brome cover with SAP at WRR, but SAP caused a large increase in downy brome cover in yr 3 at SGE. Granulated SAP can be applied easily along with drill seeding, making it potentially applicable for dryland restoration. However, site specific factors may influence whether perennial grasses or downy brome most benefit from SAP application.

Seeding, Herbicide, and Fungicide Impact on Perennial Grass Establishment in Cheatgrass Infested Habitats

Seeding, Herbicide, and Fungicide Impact on Perennial Grass Establishment in Cheatgrass Infested Habitats

Soluble phenolics extracted from Larrea divaricata leaves modulate soil microbial activity and perennial grass establishment in arid ecosystems of the Patagonian Monte, Argentina

Sheep grazing induces the reduction of perennial grass cover and the increase of shrub cover with high concentration of chemical defences. We analysed the effects of secondary metabolites released from green and senesced leaves of the shrub Larrea divaricata on soil microbial activity and the establishment of perennial grasses in arid ecosystems of the Patagonian Monte. We carried out microcosm experiments with soil from plant patches without and with L. divaricata and inert substrate seeded with the perennial grasses Poa ligularis and Nassella tenuis, which are characteristic of the Patagonian Monte. Microcosms were subjected to three watering treatments: distilled water and aqueous extracts of green and senesced leaves of L. divaricata with high concentration of soluble phenolics. We assessed the microbial N-flush and net-N mineralization in soil, and seed germination, survival, and biomass of both perennial grass species. Aqueous leaf extracts led to a 29% increase in microbial N-flush and a 20% reduction in the net-N mineralization. Seed germination was less negatively affected by aqueous leaf extracts in P. ligularis ( < 18% reduction) than in N. tenuis (2–69% reduction). Survival of P. ligularis was not affected by aqueous leaf extracts while that of N. tenuis was 21–45% reduced only in the soil from plant patches without L. divaricata. Biomass accumulation of both perennial grass species was negatively affected by aqueous extracts of senesced leaves. We concluded that soluble metabolites extracted from L. divaricata may have positive or negative effects on microbial activity and potential allelopathic effects on perennial grass regeneration depending on species.

Effects of initial functional‐group composition on assembly trajectory in savanna restoration

AbstractAimsIndicators that can provide information during the early stages of restoration are very useful for predicting restoration outcomes. We posed the following questions: Can savanna restoration outcomes be affected by the initial functional‐group composition? Are there functional groups that, when established early, can prevent colonization by invasive grasses, trigger a successful restoration trajectory, and be used as early indicators of restoration success?LocationBrazilian savanna (cerrado) in Central Brazil (14°07′2.54″ S, 47°38′30.36″ W).MethodsWe established 110 plots spanning a naturally occurring range of species composition in savanna areas that had been restored through direct seeding. We looked for different initial compositions of the following functional groups: perennial grasses, annual grasses, short‐lived shrubs, and invasive grasses. We measured vegetation cover over two years and evaluated the effects of the initial functional composition on the successional trajectory of the plots.ResultsThe initial dominant functional group determined the assembly trajectory. Short‐lived and fast‐growing species were replaced by perennial species, indicating a fast species turnover. Invasive grass cover remained stable over time, demonstrating that once they establish and dominate an area, an alternative stable state is achieved.ConclusionsOur results demonstrate the importance of introducing a mixture of functional groups when restoring savannas in severely disturbed areas. Fast‐growing and short‐lived species are important for quickly covering the ground, creating the conditions for the establishment of perennial grasses that naturally dominate the herbaceous layer of savannas. Trees are also characteristic of the savanna structure and must be introduced. Our results indicate that invasive grasses must be eliminated and/or constantly controlled before native species are introduced.

Improving Seeding Success on Cheatgrass-Infested Rangelands in Northern Nevada

On the Ground Cheatgrass has transformed secondary succession in arid sagebrush plant communities in the Great Basin by providing a fine-textured, early maturing fuel that increases the chance, rate, spread, and season of wildfires. The best known method to suppress cheatgrass densities and associated fuels is through the establishment of perennial grasses. Crested wheatgrass plots seeded the first fall following the wildfire (2006) averaged an establishment of 9.6 plants/m2 compared with plots seeded the second fall at 3.9 plants/m2. Native perennial species bluegrass and squirreltail experienced high failure rates. Over the 2-year study, un-disced cheatgrass plots averaged more than 1,350 cheatgrass seeds/m2, while plots receiving our April/May discing application averaged fewer than 250 cheatgrass seeds/m2, an 82% reduction in cheatgrass seed bank densities, which significantly improved seeded species establishment. The use of soil-active herbicides, Imazapic (Plateau) and Sulfometuron methyl (Landmark...

Soils Determine Early Revegetation Establishment with and without Cover Crops in Northern Mixed Grass Prairie after Energy Development

Cover crops have been used to build soil health and improve ecosystem services in agricultural fields and pastures, but they have not been tested in restoration contexts. We conducted two experiments in interim oilfield reclamations at Ft. Berthold Indian Reservation in North Dakota: in 2014 two different perennial grass mixes, with and without an oat cover crop and, in 2015, a single grass mix with and without a cover crop cocktail. To determine whether cover crops speeded site recovery or whether they competed with perennial grasses, all sites were assessed for plant establishment and rangeland health in August 2015. Sites planted in 2014 ranged from 20 (± 10 SD) to 38 (± 0.5) perennial grass plants/m2. Sites planted in 2015 ranged from 6 (± 1.8) to 29 (± 11) plants/m2. Cover crop treatment and grass mix treatments were not significant determinants of perennial grass establishment ( p 0.05). Soil nutrients appeared to drive early revegetation establishment: sites with poor perennial grass establishment had lower levels of phosphorous and higher levels of calcium, iron and manganese. Rangeland health trended towards being greater when a cover crop was planted, but the effect was very small. We will eventually test whether the long-term benefits of cover crops in agricultural systems transfer to restoration, but when cover crops establish at low densities, as we observed in these studies, they may only have small effects in reclamations.

Downy Brome Control and Impacts on Perennial Grass Abundance: A Systematic Review Spanning 64 Years

Given the high cost of restoration and the underlying assumption that reducing annual grass abundance is a necessary precursor to rangeland restoration in the Intermountain West, United States, we sought to identify limitations and strengths of annual grass control methods and refine future management strategies. We systematically reviewed all published journal articles spanning a 64-yr period (1948−2012; n = 119) reporting data on research efforts to either directly or indirectly reduce the abundance of the most common invasive annual grass, downy brome (Bromus tectorum L.). The seven most common control methods studied were herbicide, burning, revegetation, woody removal, defoliation or grazing, soil disturbance, and soil amendment. In addition, the majority of control methods were 1) applied at scales of 10−100 m2, 2) sampled within small plots (i.e., 0.1−1.0 m2), 3) implemented only once, and 4) monitored at time scales that rarely exceeded 5 yr. We also performed summary analyses to assess how these control methods affect downy brome and perennial grass abundance (i.e., cover, density, biomass). We found conflicting evidence regarding the assumption that reducing downy brome abundance is necessary to enhance the growth and establishment of perennial grasses. All methods, with the exception of woody plant removal, significantly reduced downy brome in the short term, but downy brome abundance generally increased over time and only herbicide and revegetation remained reduced in the long term. Only burning, herbicide, and soil disturbance led to long-term increases in perennial grass abundance. We suggest that future research should prioritize a broader array of ecological processes to improve control efficacy and promote the reestablishment of desirable rangeland plant communities.

Establishment‐Year Native Perennial Bunchgrass Biomass Yields

Weak seedling vigor of native North American perennial bunchgrasses may result in poor establishment‐season herbage dry matter (DM) yields (HY). Interseeding North American annual legumes as an N source during grassland restoration, pasture establishment, or bioenergy crop seeding might compound this limitation. Our first objective was to evaluate yellow Indiangrass [Sorghastrum nutans (L.) Nash], switchgrass (Panicum virgatum L.), and little bluestem [Schizachyrium scoparium (Michx.) Nash] first‐season HY in the southern Great Plains of North America. This took place in north–central Texas on a Windthorst fine sandy loam soil with no irrigation or soil amendments. Our second objective was to measure the effects of cross‐drilling native North American annual legumes smooth‐seeded wild bean [Strophostyles leiosperma (Torr. &amp; Gray) Piper], trailing wild bean [Strophostyles helvula (L.) Elliott], and showy partridge pea [Chamaecrista fasciculata (Michx.) Greene] on bunchgrass first‐season HY. In the drier (340 mm) year, legumes failed to establish, while switchgrass produced 2410 and Indiangrass yielded 1980 kg HY ha−1 y−1. In the year with 687 mm rainfall, legumes had no negative effects (P &gt; 0.05) on grass HY (5490 kg HY ha−1 y−1 for switchgrass) despite providing up to 49 through 1800 kg HY ha−1 y−1 (showy partridge‐pea with little bluestem; P ≤ 0.05 for year by grass × legume interactions). Our results indicate that these bunchgrasses produced harvestable HY during their establishment year and that simultaneously seeding annual legumes did not impair native perennial grass establishment while, in 1 yr, making potential N contributions for subsequent stand productivity.

Postfire Drill-Seeding of Great Basin Plants: Effects of Contrasting Drills on Seeded and Nonseeded Species

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.

Small‐scale barriers mitigate desertification processes and enhance plant recruitment in a degraded semiarid grassland

AbstractAnthropogenic desertification is a problem that plagues drylands globally; however, the factors which maintain degraded states are often unclear. In Canyonlands National Park on the Colorado Plateau of southeastern Utah, many degraded grasslands have not recovered structure and function &gt;40 yr after release from livestock grazing pressure, necessitating active restoration. We hypothesized that multiple factors contribute to the persistent degraded state, including lack of seed availability, surficial soil‐hydrological properties, and high levels of spatial connectivity (lack of perennial vegetation and other surface structure to retain water, litter, seed, and sediment). In combination with seeding and surface raking treatments, we tested the effect of small barrier structures (“ConMods”) designed to disrupt the loss of litter, seed and sediment in degraded soil patches within the park. Grass establishment was highest when all treatments (structures, seed addition, and soil disturbance) were combined, but only in the second year after installation, following favorable climatic conditions. We suggest that multiple limiting factors were ameliorated by treatments, including seed limitation and microsite availability, seed removal by harvester ants, and stressful abiotic conditions. Higher densities of grass seedlings on the north and east sides of barrier structures following the summer months suggest that structures may have functioned as artificial “nurse‐plants”, sheltering seedlings from wind and radiation as well as accumulating wind‐blown resources. Barrier structures increased the establishment of both native perennial grasses and exotic annuals, although there were species‐specific differences in mortality related to spatial distribution of seedlings within barrier structures. The unique success of all treatments combined, and even then only under favorable climatic conditions and in certain soil patches, highlights that restoration success (and potentially, natural regeneration) often is contingent on many interacting factors.

Role of Dispersal Timing and Frequency in Annual Grass—Invaded Great Basin Ecosystems: How Modifying Seeding Strategies Increases Restoration Success

Abstract. Seed dispersal dynamics strongly affect plant community assembly in restored annual grass—infested ecosystems. Modifying perennial grass seeding rates and frequency may increase perennial grass establishment, yet these impacts have not yet been quantified. To assess these effects, we established a field experiment consisting of 288 plots (1 m2) in an eastern Oregon annual grass—dominated shrubsteppe ecosystem. In this study, the amount, timing, and frequency of perennial grass seeding events, soil moisture availability, and annual grass seed bank density were manipulated. We found that more frequent perennial grass seeding events combined with high perennial grass seeding rates produced the highest perennial grass density and biomass 2 years following seeding. However, we also found that if annual grass seed density was 1500 seeds · m-2 or higher, perennial grass density and biomass decreased, regardless of seeding strategy. Because of this finding, it appears that a threshold is crossed between...

Long‐term effects of seeding after wildfire on vegetation in Great Basin shrubland ecosystems

Summary Invasive annual grasses alter fire regimes in shrubland ecosystems of the western USA, threatening ecosystem function and fragmenting habitats necessary for shrub‐obligate species such as greater sage‐grouse. Post‐fire stabilization and rehabilitation treatments have been administered to stabilize soils, reduce invasive species spread and restore or establish sustainable ecosystems in which native species are well represented. Long‐term effectiveness of these treatments has rarely been evaluated. We studied vegetation at 88 sites where aerial or drill seeding was implemented following fires between 1990 and 2003 in Great Basin (USA) shrublands. We examined sites on loamy soils that burned only once since 1970 to eliminate confounding effects of recurrent fire and to assess soils most conducive to establishment of seeded species. We evaluated whether seeding provided greater cover of perennial seeded species than burned–unseeded and unburned–unseeded sites, while also accounting for environmental variation. Post‐fire seeding of native perennial grasses generally did not increase cover relative to burned–unseeded areas. Native perennial grass cover did, however, increase after drill seeding when competitive non‐natives were not included in mixes. Seeding non‐native perennial grasses and the shrub Bassia prostrata resulted in more vegetative cover in aerial and drill seeding, with non‐native perennial grass cover increasing with annual precipitation. Seeding native shrubs, particularly Artemisia tridentata, did not increase shrub cover or density in burned areas. Cover of undesirable, non‐native annual grasses was lower in drill seeded relative to unseeded areas, but only at higher elevations. Synthesis and applications. Management objectives are more likely to be met in high‐elevation or precipitation locations where establishment of perennial grasses occurred. On lower and drier sites, management objectives are unlikely to be met with seeding alone. Intensive restoration methods such as invasive plant control and/or repeated sowings after establishment failures due to weather may be required in subsequent years. Managers might consider using native‐only seed mixtures when establishment of native perennial grasses is the goal. Post‐fire rehabilitation provides a land treatment example where long‐term monitoring can inform adaptive management decisions to meet future objectives, particularly in arid landscapes where recovery is slow.

Role of propagule pressure and priority effects on seedlings during invasion and restoration of shrub-steppe

Plant invasion and restoration outcomes are largely driven by the timing and magnitude of seed dispersal, and by the performance of dispersed species in an environment. Because seed dispersal controls recruitment of newly arriving species and facilitates safe site occupation, assembly will differ depending on seed dispersal processes and variable environmental conditions. The objective of this study was to identify how annual and perennial grasses assembled when dispersal times, propagule pressure, and water availability were modified. To assess these effects, we conducted a field experiment in an annual grass invaded shrub-steppe ecosystem in eastern Oregon. We tested the effects of seeding annual and perennial grasses in autumn or delaying annual grass seeding until spring, adding water, and varying annual and perennial grass seeding rate by 150, 1,500, 2,500, or 3,500 seeds m−2 on perennial and annual grass seedling emergence through time and final density and biomass. Providing perennial grasses a priority effect by delaying annual grass seeding until spring initially facilitated perennial grass establishment, but this effect did not persist into the second growing season. We found that if annual grass propagule pressure exceeded 150 seeds m−2, perennial grass recruitment was limited. In addition, higher water availability increased perennial grass establishment, but was dependent upon annual grass propagule pressure. These findings suggest that seeding perennial grasses into annual grass dominated systems is more dependent upon the existing propagule pressure of annual grasses than the priority effects of perennial grasses, the propagule pressure of perennial grasses, or water availability.