Establishment Of Perennial Grasses Research Articles

Integration of Prescribed Burning, Aminopyralid, and Reseeding for Restoration of Yellow Starthistle (Centaurea solstitialis)-Infested Rangeland

AbstractYellow starthistle (Centaurea solstitialis) is among the most invasive plant species in the western United States. The long-term management of yellow starthistle should include an integrated approach that incorporates establishment of competitive vegetation. In this study, conducted in two locations at Fort Hunter Liggett in Monterey County, California, we evaluated the combination of prescribed burning, the herbicide aminopyralid, and reseeding of native broadleaf and grass species on both yellow starthistle control and native plant restoration. Both study sites were burned in late October 2009. Over the following season, aminopyralid was applied at three timings and native plant species were seeded at three timings, using both a drill-seeder and broadcast spreader. Evaluations over the next 3 yr showed that aminopyralid provided complete to nearly complete control of yellow starthistle when applied between January and March, and this level of control was maintained for two seasons. Native plants failed to establish when broadcast seeded, regardless of the timing. December and January drill seeding timings were the most successful in establishing native species. There was a strong herbicide and drill seed timing interaction effect on native grass cover at both study sites. Over the course of the study the native perennial grass Stipa cernua was the most successful seeded species to establish, but establishment was slow and required 3 yr. Our results indicate that a January or March aminopyralid treatment integrated with a native perennial grass drill seeding program in January offers the greatest probability of both successful yellow starthistle control and perennial grass establishment.

Plant Establishment in Masticated Utah Juniper Woodlands

Juniper (Juniperus spp.) encroachment into sagebrush (Artemisia spp.)-bunchgrass communities has reduced understory cover on millions of hectares of semiarid rangelands. Mechanical masticators shred trees to restore desirable vegetation and reduce the potential for catastrophic wildfire. Mechanical mastication where juniper density is high and perennial grass cover is low brings a risk of invasive weed dominance unless perennial species are established. To determine whether juniper mastication favors annual- or perennial-grass establishment, we compared seedling emergence, tillers, and aboveground biomass of cheatgrass (Bromus tectorum L.) and Anatone bluebunch wheatgrass (Pseudoroegneria spicata [Pursh] A. Löve). Comparisons were made among hand-planted rows between and under juniper canopies of masticated and adjacent untreated control areas at three locations in Utah. Bluebunch wheatgrass had 16% (95% CI: 11–21) and cheatgrass had 10% (95% CI: 5–15) fewer seedlings emerge per row in masticated than untreated areas (P < 0.001). However, bluebunch wheatgrass had 3.2 (95% CI: 2.0–5.2) times more tillers and 1.9 (95% CI: 1.6–2.2) times more aboveground biomass per row in masticated than untreated areas (P < 0.001). Similarly, cheatgrass had 2.3 (95% CI: 1.5–3.8) times more tillers, 2.0 (95% CI: 1.7–2.4) times more aboveground biomass, and 11.4 (95% CI: 6.3–20.7) times more spikelets per row in masticated than untreated areas (P < 0.001). This increased seedling growth in masticated areas was associated with increased inorganic nitrogen and soil water compared to untreated areas. Because mastication improves the growth of both cheatgrass and bluebunch wheatgrass seedlings, it could support dominance by either annual- or perennial-life forms. To avoid cheatgrass dominance where perennial understory cover is limited and cheatgrass propagule pressure is high, mastication should be accompanied by seeding desirable perennial species such as Anatone bluebunch wheatgrass.

Stand Establishment and Persistence of Perennial Cool-Season Grasses in the Intermountain West and the Central and Northern Great Plains

The choice of plant materials is an important component of revegetation following disturbance. To determine the utility and effectiveness of various perennial grass species for revegetation on varied landscapes, a meta analysis was used to evaluate the stand establishment and persistence of 18 perennial cool-season grass species in 34 field studies in the Intermountain and Great Plains regions of the United States under monoculture conditions. Combined across the 34 studies, stand establishment values ranged from 79% to 43% and stand persistence values ranged from 70% to 0%. Intermediate wheatgrass (Thinopyrum intermedium [Host] Barkworth & D. R. Dewey), tall wheatgrass (Thinopyrum ponticum [Podp.] Z.-W. Liu & R.-C. Wang), crested wheatgrass (Agropyron spp.), Siberian wheatgrass (Agropyron fragile [Roth] P. Candargy), and meadow brome (Bromus riparius Rehmann) possessed the highest stand establishment (≥ 69%). There were no significant differences among the 12 species with the largest stand persistence values. Basin wildrye (Leymus cinereus (Scribn. & Merr.) Á. Löve), Altai wildrye (Leymus angustus [Trin.] Pilg.), slender wheatgrass (Elymus trachycaulus [Link] Gould ex Shinners), squirreltail (Elymus spp.), and Indian ricegrass (Achnatherum hymenoides [Roem. & Schult.] Barkworth) possessed lower stand persistence (≤ 32%) than the majority of the other species, and Indian ricegrass (0%) possessed the lowest stand persistence of any of the species. Correlations between environmental conditions and stand establishment and persistence showed mean annual study precipitation to have the most consistent, although moderate effect (r = ∼0.40) for establishment and persistence. This relationship was shown by the relatively poor stand establishment and persistence of most species at sites receiving less than 310mm of annual precipitation. These results will be a tool for land managers to make decisions concerning the importance of stand establishment, stand persistence, and annual precipitation for revegetation projects on disturbed sites.

Grassland Response to Herbicides and Seeding of Native Grasses 6 Years Posttreatment

AbstractHerbicides are the primary method used to control exotic, invasive plants. This study evaluated restoration efforts applied to grasslands dominated by an invasive plant, sulfur cinquefoil, 6 yr after treatments. Of the five herbicides we evaluated, picloram continued to provide the best control of sulfur cinquefoil over 6 yr. We found the timing of picloram applications to be important to the native forb community. Plots with picloram applied in the fall had greater native forb cover. However, without the addition of native perennial grass seeds, the sites became dominated by exotic grasses. Seeding resulted in a 20% decrease in exotic grass cover. Successful establishment of native perennial grasses was not apparent until 6 yr after seeding. Our study found integrating herbicide application and the addition of native grass seed to be an effective grassland restoration strategy, at least in the case where livestock are excluded.

Leaf and tiller dynamics in two competingC3grass species: influence of neighbours and nitrogen on morphogenetic traits

AbstractThe objective of this work was to analyse the competitive interactions betweenBromus willdenowiiKunth. (BW = prairie grass) and a perennialC3grassDactylis glomerataL. (DG = cocksfoot) through morphogenetic traits, during pasture establishment. Four combinations of species (pureBW, pureDG,DGflanked byBWandBWflanked byDGplants), with and without winter nitrogen fertilization, were factorially arranged in a complete random block design. Data were recorded on three tiller age cohorts of the central target plant: the main stem and those that appeared 20 and 30 days after fertilization (daf). Leaf elongation rate (LER) of the older tillers was the only variable affected by nitrogen addition. Annual neighbours, which showed higherLERthan perennial ones, caused a decrease in leaf lifespan in the younger tillers and a delay in the leaf appearance rate on the main stem and on 20‐daf tillers, and the tiller appearance rate. Annual neighbours controlled leaf and tiller dynamics and therefore restricted the vertical and horizontal space occupation of the target plant. These results reinforce the advantage of using a low seeding rate for the annual species to avoid negative effects on perennial grass establishment and persistence.

Effects of nitrogen and phosphorus on vegetation dynamics of a degraded native grassland in semi-arid south-eastern Australia

The roles of nitrogen (N) and phosphorus (P) in controlling vegetation transitions in a degraded semi-arid grassland were investigated in a factorial experiment that combined two initial levels of perennial plant density (low and high), three levels of N (N+, N0 and N–) and two levels of P (P+ and P0). Increased levels of both N and P were achieved by fertiliser addition while sucrose was used to reduce the level of N. Vegetation dynamics were driven primarily by soil N rather than P. Addition of sucrose, which was inferred to result in the immobilisation of mineral N, reduced the growth of annual species and facilitated the establishment and growth of native perennial grasses. Addition of P generally had no significant effect on dry matter production, either in total or for species grouped as forbs, annual grasses and perennial grasses, or on recruitment and mortality of perennial grasses. However, at some times of observation addition of P increased ground cover and/or the basal circumference of some perennial grass species. Basal circumference for Enteropogon acicularis was also increased by addition of N. Soil biological activity, measured by decomposition of cotton strips, was increased by addition of N, which maintained vegetation in an annual-dominated condition, and was not affected by addition of P. Carbon addition has the potential to assist restoration of this grassland. However, the capacity of some native grass species to respond to increased fertility suggests that once restoration is achieved some increase in fertility may be beneficial for pastoral production.

Cultivation and Reseeding Effects on Soil Organic Matter in the Mixed Prairie

This study investigated how disturbances from cultivation and haying altered the soil organic C (SOC) at two sites: one (Lethbridge) in a Stipa–Agropyron–Bouteloua community (49°7″ N, 112°57″ W) and a second (Onefour) in a more xeric Stipa–Bouteloua community (49°3″ N, 110°27″ W). Seven disturbance treatments were established on previously uncultivated native grassland to assess their effect on SOC 12 or 13 yr after establishment. A randomized complete block design with four replicates was used. Soils were sampled in the fall of 1995, 1997, and 2006 at two increments (0–15 and 15–30 cm) and a third (30–90 cm) was sampled in 2006. The soils were all analyzed for their SOC and, in 2006, also for their light fraction organic C (LF OC) and mineralizable C. Breaking and immediate establishment of perennial grass monocultures had no effect on SOC, LF OC, or mineralizable C. Wheat (Triticum aestivum L.) cropping (either fallow or continuous) resulted in a 19% loss of SOC after 13 yr. The rate of loss varied from an average of about 1.7 Mg ha−1 yr−1 in the first 4 yr to about 0.32 Mg ha−1 yr−1 in the subsequent 9 yr. These results are consistent with a more rapid loss of SOC in the first decade of cropping virgin soils, a slowing rate of loss, and a new steady state within a few decades.

Five Basic Steps to Successful Perennial Pasture Grass Establishment From Vegetative Cuttings on South Florida Flatwoods

Revised! SSAGR24, a 4-page illustrated fact sheet by Joe Vendramini, Yoana Newman, Ann Blount, Martin B. Adjei, and Paul Mislevy, describes the different steps that minimize establishment failure and lead to a favorable outcome of dense stand of perennial pasture grass. Published by the UF Department of Agronomy, March 2010. SSAGR24/AG125: Five Basic Steps to Successful Perennial Pasture Grass Establishment From Vegetative Cuttings on South Florida Flatwoods (ufl.edu)

Use of Biosolids to Enhance Rangeland Forage Quality

Biosolids land application was demonstrated to be a potentially cost-effective means for restoring forage productivity and enhancing soil-moisture-holding capacity on disturbed rangelands. By land-applying aerobically digested, anaerobically digested, composted, and lime-stabilized biosolids on rangeland test plots at rates of up to 20 times (20X) the estimated nitrogen-based agronomic rate, forage yields were found to increase from 132.8 kg/ha (118.2 lb/ac) (control plots) to 1182.3 kg/ha (1052.8 lb/ac). Despite the environmental benefits associated with increased forage yield (e.g., reduced soil erosion, improved drainage, and enhanced terrestrial carbon sequestration), the type of forage generated both before and after biosolids land application was found to be dominated by invasive weeds, all of which were characterized as having fair to poor nutritional value. Opportunistic and shallow rooting invasive weeds not only have marginal nutritional value, they also limit the establishment of native perennial grasses and thus biodiversity. Many of the identified invasive species (e.g., Cheatgrass) mature early, a characteristic that significantly increases the fuel loads that support the increased frequency and extent of western wildfires.

Integrating Herbicide Use and Perennial Grass Revegetation to Suppress Weeds in Noncrop Areas

AbstractNoncropland such as levees, roadsides, field borders, fencerows, and wildlife areas are vulnerable to weed invasion. Many sites have undergone frequent human disturbance, such as manipulation from surrounding land uses, and lack competitive, desirable vegetation. This study addressed the importance of revegetation in an integrated weed management program including revegetation for noncrop areas. The study evaluated 14 cool-season perennial grasses (seven native species and eight introduced species) for their establishment, vigor, and ability to suppress weeds. It also evaluated the impact of herbicides on weed control and grass establishment. Treatments were applied at three noncrop sites in Northeast California that were heavily infested with weeds. Chemical weed control during the year of seeding and the following year was critical for perennial grass establishment. Weed cover was greater than 50% whereas average seeded grass cover was less than 6% in untreated plots at all sites 2 yr after seeding. In contrast, average seeded grass cover at all sites was 22 to 31% 2 yr after seeding for treatments where herbicide use resulted in wide-spectrum weed control and grass safety. Increasing perennial grass cover decreased total weed cover across perennial grass species 1and 2 yr after seeding. Individual grass species' cover differed among sites. Two introduced grasses (tall wheatgrass and crested wheatgrass) and three native grasses (western wheatgrass, bluebunch wheatgrass, and thickspike wheatgrass) showed broad adaptation and had &gt; 20% cover at all sites 2 yr after seeding. In herbicide-treated plots, these grasses reduced total weed cover by 43 to 98% compared to unseeded plots 2 yr after seeding.

Shrub Microsite Influences Post-Fire Perennial Grass Establishment

Woody plants can cause localized increases in resources (i.e., resource islands) that can persist after fire and create a heterogeneous environment for restoration. Others have found that subcanopies have increased soil organic matter, nitrogen, and carbon and elevated post-fire soil temperature. We tested the hypothesis that burned sagebrush subcanopies would have increased seedling establishment and performance of post-fire seeded perennial bunchgrasses compared to burned interspaces. We used a randomized complete block design with five study sites located in southeast Oregon. The area was burned in a wildfire (2007) and reseeded in the same year with a seed mix that included non-native and native perennial bunchgrasses. Seedling density, height, and reproductive status were measured in October 2008 in burned subcanopy and interspace microsites. Non-native perennial grasses had greater densities than native species (P , 0.001) and were six times more abundant in burned subcanopies compared to burned interspaces (P , 0.001). Density of natives in burned subcanopies was 24-fold higher than burned interspaces (P 5 0.043). Seedlings were taller in burned subcanopies compared to burned interspaces (P 5 0.001). Subcanopy microsites had more reproductive seedlings than interspace microsites (P , 0.001). Our results suggest that under the fire conditions examined in this study, pre-burn shrub cover may be important to post-fire restoration of perennial grasses. Determining the mechanisms responsible for increased seeding success in subcanopy microsites may suggest tactics that could be used to improve existing restoration technologies. Resumen

Effects of a New Waste‐Processing By‐product on Soil and Vegetation at Fort Campbell, Tennessee

A garbage‐processing technology has been developed that sterilizes and separates inorganic and organic components of municipal solid waste. A study was initiated to evaluate the uncomposted organic by‐product of this process as a soil amendment for establishing native prairie grasses on disturbed Army training lands. The waste was incorporated into a silt loam soil at Fort Campbell Military Reservation in the central United States. The waste material was applied at rates of 0, 4.5, 9, 18, and 36 Mg ha−1 and seeded with native prairie grasses to assess its effects on vegetation for two growing seasons, with an additional unseeded control treatment for comparison to natural recovery. Treatments receiving the highest rate of application had significantly more native grass basal cover and percent composition than the controls. Plant phosphorus accumulation increased significantly with increasing pulp application. Soil phosphorus and lead concentrations increased in the top 10 cm of the highest application rates where pulp was mixed in the soil. Because minimal environmental effects were detected and the pulp improved perennial grass establishment and nutrition at the 36 Mg ha−1 rate, land application should be considered a viable and beneficial alternative to current waste‐management practices.

Field studies of the effects of pre-sowing weed control and time of sowing on tropical perennial grass establishment, North-West Slopes, New South Wales

Two separate experiments on the North-West Slopes of New South Wales investigated: (1) the effects of differing lengths of pre-sowing weed control (2 years, 1 year, and 3–4 months in the spring immediately before sowing) on the soil seed density of liverseed grass (Urochloa panicoides) from November 2005 to November 2007 and its seedling density at establishment (December 2007), as well as on subsequent herbage mass and plant frequency of this species and Panicum coloratum var. makarikariense cv. Bambatsi (Expt 1); and (2) the effects of cultivar, time of sowing (November 2006, January 2007, and March 2007), and defoliation in the autumn after sowing, on the over-wintering ability of 5 tropical perennial grasses (Expt 2). The cultivars sown in Expt 2 were Bambatsi, Dichanthium aristatum cv. Floren, Chloris gayana cv. Katambora, Digitaria eriantha var. eriantha cv. Premier, and Bothriochloa bladhii var. glabra cv. Swann. At sowing (November 2007), liverseed grass seed and seedling densities in Expt 1 were lowest (P &lt; 0.05) in the 2-year pre-sowing weed control treatment (15 and 13/m2, respectively), and the subsequent herbage mass of Bambatsi (January and October 2008) was highest (P &lt; 0.05) in this treatment. In Expt 2, 59 frosts occurred in 2007, and Floren, Bambatsi, and Swann sown in March of that year over-wintered poorly and had lower (P &lt; 0.05) herbage mass and plant frequency in the following spring compared with the other sowing times. These differences were also evident in autumn and spring 2008, up to 23 months after sowing.

Establishment and persistence of perennial grass and herb cultivars and lines in a recharge area, North-West Slopes, New South Wales

Two adjacent sites, one previously cropped and the other a native pasture, were sown with perennial temperate and tropical grasses and herbs (Expt 1), Phalaris aquatica (phalaris) and Festuca arundinacea (tall fescue) cultivars or lines (Expt 2), and perennial tropical grasses (Expt 3) near Manilla, NSW. Establishment, herbage mass and plant frequency were assessed in 2003–06 to (i) identify cultivars/lines with superior persistence, (ii) detect possible mechanisms required for successful production and persistence in a summer-dominant rainfall environment, and (iii) examine the comparative performance of the species groups when sown into previously cropped and native pasture areas. Plots were fertilised annually and grazed or mown at least seasonally. Most cultivars/lines persisted at the previously cropped site, while those on the native pasture site had to be resown and generally failed to persist beyond the first year. At the previously cropped site, summer-dormant tall fescue cv. Resolute MaxP® was the most persistent of the grasses evaluated in Expt 1. Grasses such as Lolium perenne cv. Avalon and Bromus stamineus cv. Gala did not perenneate, but regenerated annually from seed. Native grasses generally had poor establishment; however, Austrodanthonia richardsonii and A. fulva tended to increase in plant frequency over time. Chloris gayana (Rhodes grass) cv. Katambora and Panicum maximum (panic) cv. Gatton were the only tropical grasses that established in Expt 1, and both had plant frequencies similar (P &gt; 0.05) to the temperate grasses at the final assessment. In Expt 2, Resolute MaxP again was the most persistent cultivar/line. Several experimental lines of phalaris (e.g. T39 and M225) had high herbage mass and good persistence compared with commercial cultivars. In Expt 3, Katambora Rhodes grass and Digitaria eriantha ssp. eriantha (digit grass) cv. Premier were the most persistent cultivars and had the highest herbage mass. These data highlighted summer dormancy in temperate grasses and frost tolerance in tropical grasses as two possible mechanisms important for persistence of grasses on the North-West Slopes of NSW and the risks associated with sowing perennial grasses into established native pastures.

Native Perennial Grasses in Highway Medians: Pre- and Postplant Techniques for Establishment in a Mediterranean Climate

AbstractWithin highway rights-of-way, native perennial grasses provide desirable services to support natural and human constructed ecosystems. However, native perennial grass establishment in annual grass dominated roadsides of semiarid and Mediterranean climates of the western United States requires specific cultural and chemical management treatments to control weeds. In 2004, field studies were conducted in Sacramento Valley, California to determine the effect of herbicide, disc cultivation, and species selection on native perennial grass establishment and annual weed persistence. Perennial grass species mixes common to drier and wetter upland areas in northern California were drill seeded at two sites (I-5 North and I-5 South) that had been burned in 2003 and received weed control (i.e., herbicide, cultivation, mowing) in spring 2004. Herbicides were the most important treatments for native perennial grass establishment and weed reduction. Native perennial grass species persistence was largely unaffected by cultivation or native plant accessions at these sites. Native perennial grass density increased at I-5 North in the second year of growth (2006) resulting in a plant density totaled across all herbicide regimes of 3.9 plants m−1 compared to 2.5 plants m−1 at I-5 South. Vigorous native perennial grass growth in the more fertile and less droughty soils of I-5 North helped to limit annual weeds through competition, which is anticipated to reduce the need for chemical and mechanical control in years following early establishment.

Integrated Management of Perennial Pepperweed (Lepidium latifolium)

AbstractPerennial pepperweed is invasive throughout California. It thrives in a wide range of environments and is a common weed in floodplains, pastures, wetlands, and roadsides. In disturbed areas, perennial pepperweed rapidly forms monotypic stands with a thick litter layer. These infestations not only out-compete other vegetation, but prevent re-establishment of desirable species even after perennial pepperweed control. This experiment examined integrated management strategies with the goal of maximizing perennial pepperweed control and establishment of desirable native vegetation. The experiment was conducted at two sites in Lassen County, CA. Both sites were heavily infested with perennial pepperweed and lacked competing vegetation. The experimental design was a split-split-randomized block with four replications. Site preparation treatments included winter burning, summer and fall mowing, winter grazing, and fall disking. These treatments were designed to remove thatch to facilitate herbicide application and reseeding of desirable perennial grasses. Herbicide treatments included chlorsulfuron, 2,4-D, or glyphosate applied at the flower bud stage. Revegetation treatments included no seeding and no-till seeding of native perennial grasses. Most site preparation plus herbicide combinations reduced perennial pepperweed cover &gt; 85% compared to the untreated control, although treatment efficacy was variable between sites and years. Burning, grazing, mowing, or disking in combination with herbicide treatment and no-till seeding was necessary for successful native perennial grass establishment. Burning or mowing with yearly 2,4-D applications for 3 yr gave the best combination of perennial pepperweed control and native grass establishment. Chlorsulfuron caused chlorosis and stunting to western wheatgrass, basin wildrye, and beardless wildrye at both sites when applied the spring before seeding. No treatment offered complete weed control, suggesting follow-up spot herbicide applications are needed for long-term perennial pepperweed suppression. These results provide several successful integrated strategies for control of perennial pepperweed and revegetation to a desired native perennial grass community.

RESTORING NATIVE GRASSES AS VEGETATIVE BUFFERS IN A COASTAL CALIFORNIA AGRICULTURAL LANDSCAPE

ABSTRACT We investigated changes in vegetation composition of different grass buffer strips in a fragmented coastal agricultural landscape to evaluate the potential for native grass restoration of sites that receive agricultural runoff. Vegetative buffers bordering Elkhorn Slough, draining into Monterey Bay, California, were either seeded with a non-native annual grass (Hordeum vulgare) or with a mix of native perennial grasses (Bromus carinatus, Deschampsia cespitosa, Nassella pulchra), and above-ground biomass and cover of vegetation were measured over a 4-yr period. Based on preliminary results, we initiated a second, smaller-scale experiment to test establishment of native perennial grasses (Bromus carinatus, Elymus glaucus, Hordeum brachyantherum) at different seeding densities with combinations of non-native annual grasses (H. vulgare or Lolium multiflorum and Vulpia myuros) to optimize erosion control. In the first experiment, plots seeded with non-native annual grasses had greater biomass than nat...

Non-Composted Municipal Solid Waste Processing Byproduct Effect on Soil Reclamation

ABSTRACT A new garbage processing technology has been developed that sterilizes and separates inorganic and organic components of municipal solid waste. The non-composted byproduct of this process, Fluff®, has the potential to be utilized as a soil amendment to improve soil conditions in highly degraded soils. A study was initiated to evaluate Fluff as a soil amendment for establishing native grasses on disturbed US Army training lands. The Fluff was incorporated into a sandy loam soil at Fort Benning Military Reservation, GA on two sites: a moderately degraded and a highly degraded soil. The Fluff was incorporated at rates of 0, 18, 36, 72, and 143 Mg ha− 1 to assess the effects on soil properties for two growing seasons. The addition of Fluff improved available plant nutrients and soil pH levels at both sites. Also, Fluff reduced the level of soil bulk density and increased soil concentration of carbon (C) and nitrogen (N). Because no adverse environmental effects were detected and Fluff improved soil physical and nutrient conditions as well as improving perennial grass establishment with increasing application rates, land application of Fluff to degraded US Army training grounds could be considered a viable and beneficial alternative to current waste management practices.

Soil Erosion Thresholds and Alternative States in Northeastern Patagonian Rangelands

In semiarid rangelands, continuous grazing may decrease vegetation cover, accelerating soil erosion and eventually causing a transition to an alternative, degraded state. State-and-transition models invoke process-based explanations of alternative states, but there are few examples that use empirical data on key factors and processes. We used rainfall simulation to determine 1) the relationships between soil surface characteristics and interrill erosion in 3 spatially related plant communities: stable grass with scattered shrubs (GS), degraded grass with scattered shrubs (DGS), and degraded shrub steppes (DSS), and 2) the site conservation threshold (SCT) of this rangeland. We also analyzed the effect of past erosion on soil and vegetation characteristics. In the GS, sediment production and sediment concentration were significantly lower (p < 0.05) than in the DGS and the DSS. The main soil protection factors in the GS and in the DGS were perennial grass and litter cover, while in the DSS, gravel cover became the main soil protection factor. The SCT, the point at which the rate of soil erosion increases markedly, corresponded to a plant-and-litter cover close to 90% and occurred within the DGS. Although this plant community may reverse back to the conserved GS, long-term accelerated erosion may result in enough soil loss to trigger irreversible changes and prompt the transition to the DSS. The threshold underlying this transition would be reached when the A horizon is severely reduced by erosion. Under these conditions, the soil hydrological properties are affected irreversibly, preventing perennial grass establishment. While the GS represents a resource conserving plant community, desirable for both forage production and soil protection, the DSS represents a dysfunctional state with a minimum forage value. The DGS represents an unstable and transitional community that, without management intervention to halt soil erosion, will likely change into the DSS. En los pastizales naturales semiáridos, el pastoreo continuo puede disminuir significativamente la cobertura de la vegetación, acelerar la erosión del suelo y eventualmente causar una transición hacia estados alternativos degradados. Los modelos de estados y transiciones generalmente explican estados alternativos en función de distintos procesos, sin embargo hay pocos ejemplos que usen datos empíricos. Nosotros empleamos lluvia simulada a los fines de determinar 1) las relaciones entre las características superficiales del suelo y la vegetación y la erosión laminar en 3 comunidades vegetales espacialmente relacionadas: una estepa herbácea con arbustos (EH), una estepa herbácea degradada con arbustos (EHD), y una estepa arbustiva degradada (EAD), y 2) el umbral de conservación del sitio (UCS) en éste pastizal. También analizamos el efecto de la erosión histórica sobre las características superficiales del suelo y la vegetación. En la EH la producción y la concentración de sedimentos fueron significativamente más bajos (p < 0.05) que en la EHD y la EAD. Los principales factores de protección del suelo en la EH y la EHD, fueron los pastos perennes y el mantillo, mientras que en la EAD, la cobertura de gravas fue el principal factor de protección del suelo. El UCS, definido como el punto donde la tasa de erosión de suelo aumenta notablemente, se correspondió con una cobertura de pastos perennes y mantillo cercana al 90% y ocurrió dentro de la EHD. Si bien ésta comunidad puede revertir hacia la EH, la erosión acelerada mantenida durante largo tiempo puede producir una pérdida de suelo tan importante como para provocar cambios irreversibles e iniciar la transición hacia la EAD. El umbral subyacente a la transición se alcanzaría cuando, como consecuencia de la pérdida de suelo, el horizonte A es severamente reducido. Bajo estas condiciones, las propiedades hidrológicas del suelo son afectadas irreversiblemente, limitando el establecimiento de pastos perennes. Mientras que la EH tiene una alta capacidad para conservar los recursos del suelo, representa la comunidad vegetal deseable tanto para la producción de forraje como para la protección del suelo, la EAD representa una comunidad con baja capacidad para conservar los recursos del suelo y bajo valor forrajero. La EHD es una comunidad inestable y transicional que, sin un plan de manejo tendiente a detener la erosión acelerada del suelo, cambiará irreversiblemente a una estepa arbustiva degradada.

Effects of an Uncomposted Municipal Waste Processing By‐Product on Prairie Grass Establishment

A garbage processing technology has been developed that sterilizes and separates inorganic and organic components of municipal solid waste. A study was initiated to evaluate the uncomposted organic by‐product of this process as a soil amendment for establishing native prairie grasses on disturbed Army training lands. The waste was incorporated into sandy soils at Fort Benning Military Reservation on two sites: a moderately degraded and a highly degraded soil. The waste material was applied at rates of 0, 17.9, 35.8, 71.6, and 143 Mg ha−1 and seeded with native prairie grasses to assess its effects on vegetation for two growing seasons, with an additional unseeded control treatment for comparison to natural recovery. The addition of uncomposted waste increased percent composition and basal cover of switchgrass (Panicum virgatum L.) at both sites and percent composition of big bluestem (Andropogon gerardii Vitman) at one site. Indiangrass [Sorghastrum nutans (L.) Nash] was negatively affected by the addition of the waste material at both sites. Biomass in the 143 Mg ha−1 treatment increased 4180% compared to the seeded control at the highly degraded site. Plant uptake of P and Na increased at both sites and an apparent Fe toxicity problem was alleviated at the highly disturbed site with increasing application rates. Because perennial grass establishment improved so dramatically with increasing application rates, land application of this uncomposted waste material could be considered a viable and beneficial alternative to current waste management practices for degraded Army lands.