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There are concerns about the negative consequences of non‐native livestock grazing of sagebrush communities, especially since these communities are experiencing unpreceded threats from invasive annual grasses, altered fire regimes, and climate change. The narrative around grazing often focuses on the effects of heavy, repeated growing season use that were common historically but now are rare or localized (e.g., near water sources). At the same time, the potential for ecological benefits of strategically applied grazing is often overlooked, limiting management options that may promote desired outcomes. To improve management in the face of unprecedented threats, we synthesized the literature to investigate and identify potential ecological benefits of strategically applied livestock grazing in sagebrush communities. We found that grazing can be used to modify fine fuel characteristics in ways that decrease fire probability and severity in sagebrush communities. Pre‐fire moderate grazing may be especially important because it decreases fire severity and, thereby, promotes biodiversity and reduces postfire annual grass invasion, fire‐induced mortality of native bunchgrasses, and fire damage to soil biocrusts. Grazing can create and maintain fine fuel breaks to improve firefighter safety and fire suppression efficiency. Strategic grazing can also be used to promote desirable plant community composition. Grazing can be a valuable tool, that is currently underutilized, for achieving desired management outcomes in the sagebrush and likely other ecosystems. Improper grazing can generate severe negative consequences; therefore, successful application of grazing to achieve desired outcomes will require careful attention to plant community response and balancing management objectives with community constraints. [ABSTRACT FROM AUTHOR]

Abstract There are concerns about the negative consequences of non‐native livestock grazing of sagebrush communities, especially since these communities are experiencing unpreceded threats from invasive annual grasses, altered fire regimes, and climate change. The narrative around grazing often focuses on the effects of heavy, repeated growing season use that were common historically but now are rare or localized (e.g., near water sources). At the same time, the potential for ecological benefits of strategically applied grazing is often overlooked, limiting management options that may promote desired outcomes. To improve management in the face of unprecedented threats, we synthesized the literature to investigate and identify potential ecological benefits of strategically applied livestock grazing in sagebrush communities. We found that grazing can be used to modify fine fuel characteristics in ways that decrease fire probability and severity in sagebrush communities. Pre‐fire moderate grazing may be especially important because it decreases fire severity and, thereby, promotes biodiversity and reduces postfire annual grass invasion, fire‐induced mortality of native bunchgrasses, and fire damage to soil biocrusts. Grazing can create and maintain fine fuel breaks to improve firefighter safety and fire suppression efficiency. Strategic grazing can also be used to promote desirable plant community composition. Grazing can be a valuable tool, that is currently underutilized, for achieving desired management outcomes in the sagebrush and likely other ecosystems. Improper grazing can generate severe negative consequences; therefore, successful application of grazing to achieve desired outcomes will require careful attention to plant community response and balancing management objectives with community constraints.

The United Nations Decade on Ecosystem Restoration aims to prevent, halt, and reverse the degradation of ecosystems on every continent. Disturbances stemming from anthropogenic or natural causes make plant community restoration challenging. The introduction of fast‐growing weeds that generate high biomass and produce copious seed is most threatening to plant communities. A paradigm shift in ecosystem restoration is needed that emphasizes traits and affected ecological processes similar to weeds. The repeated introduction of seed from native plants with weedy characteristics follows the propagule pressure and evolution of invasiveness hypotheses. In targeting areas with heavy weed populations, native plants could establish and more successfully develop into functioning plant communities. [ABSTRACT FROM AUTHOR]

Annual and perennial grasses are important not only as a source of green fodder, hay, silage, grass meal and haylage in feed production, but also as good forecrops, due to the ability to accumulate biological nitrogen in the soil (since it decreases the cost of mineral fertilizers), to disinfect the soil from micro zoo pests, to improve the physical condition of the soil (since it decreases soil density). Perennial grasses are also an important component of biologized crop rotations, since the amount of crop residues remaining in the soil after harvesting is several times greater than after winter crops. The field trials were conducted in 2009–2016 by the staff of the laboratory of row crop cultivation technology of the FSBSI “Agricultural Research Center “Donskoy”. The experimental plot is located in the southern soil-climatic zone of the Rostov region (with insufficient and unstable moisture). The soil of the experimental plot is ordinary heavy loamy chernozem on loesslike loams, with 3.2% humus, neutral pH, and a high content of movable phosphorus and exchange potassium according to Machigin. The current paper has presented a bioenergetic estimation of grain (4-crop rotation sequence with annual grasses included) and biologized (8-crop rotation sequence with 25% perennial grasses) crop rotations. It has been established that nutrients’ amount per 1 ha of crop rotation area of biologized crop rotation is higher than in grain crop rotation on 22% of dry matter, on 40% of raw protein and on 39% of metabolic energy. Energy consumption per 1 kg of raw protein is lower on 27%.

The aim of the research was to study the effect of diatomite norms from 4 to 10 t/ha and their combinations with poultry manure on the physical and chemical properties of gray forest soils and crop productivity. To fulfill the goal, field experiments were conducted in the Vadinsk-Mokshan agro-soil district of Penza region in the period from 2019 to 2021. The studies determined that the most significant effect on increasing the capacity of cation exchange, the amount of exchangeable bases, decrease in the concentration of hydrogen ions in the soil absorbing complex had the effect and aftereffect of diatomite in the complex with poultry manure. It was found that the highest effect on the productivity of corn, spring wheat and annual grasses was the use of diatomite in combination with poultry manure. At the same time, the efficiency of corn productivity increased by 47.8-59.6%; the productivity of spring wheat increased by 26.8-35.4%; the productivity of vetch-oats increased by 22.8-36.6%. The total productivity of crops in the grain and fallow crops rotation ranged from 13.03 to 14.11 t/ha g.u. exceeding the control by 34.75-45.92 %.

Questions: In Mediterranean‐type systems, invasive C3 annual grasses appear early in the season and can pre‐empt resources and attain a competitive dominance over native perennial grasses. Here, we investigated whether planting C3 and C4 native grasses (a) combined, so that resources are extracted over a longer period, or (b) at higher density would make planted communities more competitive against invasive species. Location: Para Woodlands Reserve, near Adelaide, South Australia. Methods: In 72 experimental plots, native grasses were planted in combinations of seasonal patterns (three levels; single‐season assemblages with either C3 or C4 and extended season with both C3 and C4) and planting density (two levels; high = 44 plants/m2 and low = 20 plants/m2). Data were collected on native plant survival and biomass, invasive biomass and soil properties. Results: Overall, C3 native grasses were superior competitors against both invasive C3 grasses and native C4 grasses. We found no interaction between the combination of C3 and C4 grasses planted together and density of planting. Assemblages with higher densities were successful at reducing exotic plant biomass; however, there was a trade‐off with reduced individual performance among the native plants. Even though individual plants were larger in the low‐density treatment, total biomass was lower in these plots suggesting that density limits the growth of native communities as a whole. The C3 native plants were planted earlier than the C4 native plants because of differences in phenology and therefore likely pre‐empted resources and gained a size advantage, making them the superior competitor. Conclusion: Native perennial grasses can outcompete exotic plants for resources if planted earlier in the season. This resource pre‐emption appears to be more important than resource use over a longer period with C3 and C4 plants together and could be an effective restoration strategy. [ABSTRACT FROM AUTHOR]

Non-native plant invasions are often catalyzed by wildfires and may alter the structure, function, and composition of ecosystems. Of particular concern are non-native annual grasses that promote increased fire frequency and compete with native vegetation for early season moisture. While these effects are well studied in non-forested ecosystems, relatively few studies document invasions of non-native annual grasses in forested ecosystems. We document non-native plant invasion following repeated high-severity wildfire in mixed-conifer/hardwood forests dominated by Douglas-fir (Pseudotsuga menziesii) in the Klamath Mountains of northern California. Despite great concern regarding the loss of conifer dominance and transitions to non-forested states related to recent and projected increases in wildfire activity, there is little known about invasions of non-native plant species following fire in this region. Non-native plant species capable of long-distance dispersal had an average total cover of 26% and were ubiquitous across a systematic, gridded sample of twenty 800 m2 plots. Non-native forbs included multiple species of common post-disturbance invaders (e.g. Cirsium vulgare, Senecio sylvaticus, Lactuca serriola). Non-native annual grasses comprised more of the vegetative cover than non-native forbs (17% vs. 9%), and were dominated by two species, Aira caryophyllea and Vulpia myuros, which reached as high as 80% cover. Our findings indicate that non-native annual grasses are a novel stressor that may accelerate projected loss of conifer dominance in the Klamath Mountains by facilitating fire spread and increasing competition for early season soil moisture. Additional monitoring will be crucial to understanding the impacts of non-native plants as fire activity in this region continues to increase. [ABSTRACT FROM AUTHOR]

Biological invasions are responsive to changing wildfire regimes related to human activities that are altering biological communities. Our objective was to investigate how fire, rodent activity, and competition among plant species modify plant community structure, invasion patterns, and vulnerability to altered fire regimes. We imposed experimental fires, and reduced rodent density using fencing in a full factorial design and quantified competitive interactions among plant species in the northeast Mojave Desert that has experienced dramatic increases in plant invasion and fire in recent years. Vegetation surveys were conducted in the experimental plots to determine plant density, cover, and biomass of herbaceous plants over a 5-year period. Rodent exclusion increased the density, cover, and biomass of Bromus rubens, an invasive annual grass, and density of forb species. In contrast, rodent exclusion decreased the density, cover, and biomass of Schismus spp. another dominant annual invader. Fire increased Schismus spp. and forb species density, cover, and biomass but decreased B. rubens density. Negative spatial correlation between B. rubens and Schismus spp., and forbs indicated interspecific competition among the dominant plant species. Fire reduced rodent community diversity (Shannon's) 2.5-fold, which was correlated with increases in B. rubens cover and biomass, and native forb diversity. Fire, high rodent diversity, and competition from the other plant species may decrease fire potential in our study system by reducing the density and biomass of B. rubens, which because of its taller growth form tends to ignite and carry fire better than Schismus spp. and forbs. [ABSTRACT FROM AUTHOR]

Highlights • The aDGVM2 model was updated to distinguish annual and perennial grasses based on traits. • A new scheme for selective grazing was implemented and tested for South African sites. • Increasing grazing intensity reduced productivity and perennial grass abundance. • Heavy grazing and drought had similar effects on simulated grass communities. • Simulated rangeland recovery after grazing exclusion took between 2 and 15 years. Abstract Semi-arid tropical rangelands substantially contribute to livelihoods of subsistence farmers, but are threatened by undesired vegetation shifts due to climate change and overgrazing. Grazing-induced shifts of the grass community composition are often associated with rangeland degradation. To identify sustainable management strategies, a process-based understanding of grass functional diversity and rangeland dynamics is required. We present a new scheme for aDGVM2, a dynamic vegetation model for tropical ecosystems, that distinguishes annual and perennial grasses based on trait trade-offs to improve the representation of rangeland communities. Additionally, the model includes a new scheme that describes selective grazing and grazing effects on grass-layer composition. We tested the new model version for various grazing intensities along a precipitation gradient in South Africa. Mean annual precipitation below 500 mm constrained rangeland productivity and carrying capacity. Increasing grazing intensity reduced rangeland productivity and increased annual grass abundance. Heavy grazing resulted in annual grass dominance. Livestock preferred perennial over annual grasses at low grazing intensities at all except the two driest sites; preference switched to annual grasses at intermediate intensities, and became non-discriminating at high grazing intensities. Rangeland recovery after removal of grazers required 2–15 years. We conclude that management intervention reducing or eliminating grazing pressure during and after stress years is crucial to allow rangeland recovery and avoid permanent degradation. [ABSTRACT FROM AUTHOR]

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

It has been hypothesized that annuals of unpredictable arid deserts produce dormant seeds as a strategy for risk spreading, but weedy annuals have lower dormancy and positively photoblastic seeds. I tested this hypothesis by comparing dormancy, and photoperiod and temperature requirements during germination in annual grasses of unpredictable arid deserts and other grasses from disturbed sites. Seeds were collected from four annual grasses of natural sandy deserts and other four from disturbed sites of an arid Arabian desert. Seeds were germinated in three incubators adjusted at daily night/day temperature regimes of three temperatures in both continuous darkness and alternating 12 h light/12 h darkness. The four sandy desert grasses had greater dormancy, compared to those of disturbed sites. Light and temperature ranges of germination were narrower and species specific for sandy desert grasses. Seeds of the grasses of disturbed sites germinated at wider range of temperatures and all were positively photoblastic, except Chloris virgata . Negative photoblastism was very rare, recorded only in seeds of Coelachyrum brevifolium at lower and moderate temperatures. Seed photoblastism depended more on habitat types than seed mass. The light and temperature requirements of the studied grasses can explain their adaptation and distribution in natural habitats. [ABSTRACT FROM AUTHOR]

A higher competitive advantage of polyploid plants compared with their parental diploids is frequently invoked to explain their establishment success, colonization of novel environments and cytotypic ecological segregation, yet there is scarce experimental evidence supporting such hypotheses. Here, we investigated whether differential competitive ability of species of the Brachypodium distachyon (Poaceae) species complex, a model system for genomic, ecological and evolutionary studies of temperate grasses, contributes to explaining their ecological segregation as well as their coexistence in diploid/allotetraploid contact zones., We conducted two field experiments in dry and humid localities to evaluate the tolerance to competition of diploids and allotetraploids in densely occupied environments, and to parameterize models of intra- and intercytotype competition as a mechanism for species exclusion/coexistence., We provide experimental evidence supporting the hypothesis that, under natural field conditions, allotetraploids have superior ecological success compared with one of their parental diploids in terms of both colonizing competitive habitats and intercytotypic competition, with the balance of intra/intercytotype competition favoring polyploid population establishment., These findings, together with previous data on ecogeographic segregation and adaptive response to water stress, suggest that the interplay between aridity and competitive outcome determines the ability to colonize competitive environments, the exclusion of diploids, especially in arid localities, and species geographic segregation. [ABSTRACT FROM AUTHOR]

Frequent and extensive fires are becoming increasingly common throughout the tropical savannas of northern Australia. This fire regime has been implicated in both habitat alteration and losses of biodiversity. Granivorous birds are particularly affected because of the effect of fire on grass seed availability. The endemic Gouldian finch (Erythrura gouldiae) has experienced population declines in recent decades, potentially in response to changed fire regimes. Using breeding data from monitored artificial nest-boxes, this study examined the choice of breeding site by Gouldian finches in response to several attributes of the prevailing fire regime. The fire regime was characterised using remote sensing analysis of annual fire scars. Time since last fire and fire frequency were the most useful predictors of breeding site occupancy. Gouldian finches favoured recently burnt sites (previous dry season), but also sites that were infrequently burnt (return time of 2–3 years). Consequently, under the current regime of many frequent fires, Gouldian finches move among breeding sites and display low seasonal site fidelity. Our findings provide support for the notion that the Gouldian finch favours a fine-grain patch-mosaic fire regime and that contemporary large-scale fire regimes are likely contributing to their decline. [ABSTRACT FROM AUTHOR]

Rangelands occupy over a third of global land area, and in many cases are in less than optimum condition as a result of past land use, catastrophic wildfire, and other disturbances, invasive species, or climate change. Often the only means of restoring these lands involves seeding desirable species, yet there are few cost effective-seeding technologies, especially for the more arid rangeland types. The inability to consistently establish desired plants from seed may indicate that seeding technologies being employed are not successful in addressing the primary sources of mortality in the progression from seed to established plant. Seed enhancement technologies allow for the physical manipulation and application of materials to the seed that can enhance germination, emergence, and/or early seedling growth. In this article, we examine some of the major limiting factors impairing seedling establishment in North America's sagebrush steppe ecosystem and propose seed enhancement technologies that may have the potential to overcome these restoration barriers. We discuss specific technologies for: (1) increasing soil water availability; (2) enhancing seedling emergence in crusting soil; (3) controlling the timing of seed germination; (4) improving plantability and emergence of small-seeded species; (5) enhancing seed coverage of broadcasted seeds; and (6) protecting seedlings from pre-emergent herbicide. Concepts and technologies in this article for restoring the sagebrush steppe ecosystem may apply generally to semiarid and arid rangelands around the globe. [ABSTRACT FROM AUTHOR]

Multi-species pastures have been viewed as a means to increase forage production relative to monocultures through enhanced three-dimensional occupation of the canopy, which will intercept and use the incident radiation more efficiently. For this to occur, increased production of photosynthetically active tissues such as leaves is required. We tested the hypothesis that intercropping of black oats (Avena strigosa Schum.) and annual ryegrass (Lolium multiflorum Lam.) can increase total and leaf forage production compared with their monocultures. Monocultures and mixed pastures of black oat and annual ryegrass were established, and their tiller morphogenetic and structural traits, as well as components of herbage production, were measured throughout the usage period of the pastures. There was no difference between treatments for total growth rate (77.1 kg dry matter (DM) ha-1 day-1), but annual ryegrass pastures presented the greatest stem growth rate (38.1 kg DMha-1 day-1). Taking into account only the vegetative phase, the intercropped pasture produced 20% more leaf than the monocultures. There were no differences between species, either in monoculture or intercropped, for phyllochron, final leaf length, leaf elongation duration and leaf elongation rate. The most important modification in morphogenetic variables due to the inter-specific competition was an increase in senescence rate of annual ryegrass leaves. The average specific green leaf weight in the intercropping pastures corresponded to 84.6% and 137.5% of those values observed for black oat and annual ryegrass pastures, respectively. On the other hand, the intercropping pastures presented 43.5% more tillers than the black oat pastures and 17.8% fewer tillers than the annual ryegrass pastures. It is suggested that intercropping black oat and annual ryegrass does not change tiller ontogenetic processes and that the association of their different size and shape in intercropped pastures could increase pasture leaf production over their monocultures. [ABSTRACT FROM AUTHOR]

Foi avaliado o desempenho de novilhas de corte dos três aos doze meses de idade, mantidas em pastagem cultivada logo após o desmame (experimento 1) e no primeiro inverno pós-desmame (experimento 2), com ou sem o fornecimento de suplementos energéticos. No período de 16/02 a 21/04/2001, as novilhas permaneceram em pastagem de milheto, exclusivamente sob pastejo (PAST1), suplementadas com grão de milho moído (PAST1/M) ou com polpa cítrica peletizada e moída (PAST1/P). No período de 13/07 a 09/10/2001, as novilhas foram mantidas em pastagem de aveia preta e azevém, sem suplementação (PAST2), suplementadas com grão de milho moído (PAST2/M) ou suplementadas com casca de soja (PAST2/C). Peso vivo (PV), ganho de peso diário médio (GDM) e escore de condição corporal (ECC) foram avaliados. No experimento 1, os animais suplementados apresentaram maior PV final, GDM e ECC que os não-suplementados, não diferindo entre si. No experimento 2, as novilhas suplementadas com casca de soja apresentaram maior GDM e PV final que as não-suplementadas, enquanto as suplementadas com grão de milho ficaram em posição intermediária. O maior ECC foi obtido pelos animais de PAST2/C, seguidos de PAST2/M e, por último, de PAST2. Novilhas de corte desmamadas aos 60-90 dias devem ser suplementadas no período inicial pós-desmama, para que atinjam desenvolvimento satisfatório nesta fase do crescimento. Os subprodutos polpa cítrica e casca de soja podem substituir o grão de milho como suplementos energéticos para recria de novilhas de corte.It was evaluated beef heifers performance from three until twelve months of age, when they were reared in cultivated pasture soon after their weaning (experiment 1) and in the first winter post-weaning (experiment 2), with or without the supply of energy supplements to the animals. From 02/16 to 04/21/2001, the heifers stayed in Pearl Millet pasture, exclusively under grazing (PAST1); supplemented with milled corn grain (PAST1/C) or supplemented with pellet citric pulp (PAST1/P). From 07/13 to 10/09/2001, the heifers were maintained in oat plus italian ryegrass pasture without supplementation to the animals (PAST2); supplemented with milled corn grain (PAST2/C) or supplemented with soy hull (PAST2/H). The evaluated variables of animal performance were live weight (LW), average daily gain (ADG) and body condition score (BCS). In the experiment 1, supplemented animals presented larger values of final LW, ADG and BCS in relation to the non supplemented, ones the supplemented treatments not differing to each other. In experiment 2, the soy hull supplemented heifers showed greater ADG and final LW than non supplemented heifers, with the corn grain supplemented group in an intermediary position. The highest BCS was obtained by the animals of PAST2/H, followed by PAST2/C and, at last, of PAST2. Beef heifers weaned at 60-90 days should be supplemented in the initial post-weaning period, enabling them to reach satisfactory development in this phase of growth. The by-products citric pulp and soy hull can substitute the corn grain as energy supplements for rearing of beef heifers.

Aims (1) To investigate the temporal response of semi-arid Mediterranean grasslands to multiple disturbances as well as P fertilization and irrigation; and (2) to determine the reaction of single species or groups of species as well as the extent of recovery of the grassland community following cessation of the above interventions. Location North Greece. Methods In a fenced area, six treatments (burning, irrigation, digging, cutting, P fertilization and control) were applied, for three growing seasons, in a completely randomized block design with four blocks. Biomass was sampled in five (0.5 × 0.5 m) quadrats per plot at the end of the growing season and sorted into the following functional groups: annual grasses, perennial grasses, annual legumes and forbs (that included all the other species). Measurements were repeated 1 and 7 yr after cessation of the treatments. Results Annual grasses and legumes were positively favoured by cutting, burning and digging, which produced changes in vegetation composition over time. P fertilization had a positive influence on total legume biomass. Effects on individual species were not uniform. Plant composition after cessation of the disturbance treatments was quite different. Total legume biomass remained high 1 yr after the cessation of P fertilization but declined thereafter. Annual grasses and legumes constituted the largest portion of the total biomass in the first year of the experiment. Disturbance (burning, cutting and digging) gradually reduced their biomass in favour of forbs. Seven years after cessation of the treatments, the tall annual, as well as perennial grasses constituted more than 80% of the total biomass. Under conditions of disturbance, short annual species had an advantage over perennials, while cessation of disturbance enables perennial grasses to dominate. Conclusions Disturbance promotes the dominance of annuals, especially species with a persistent seed bank. Repeated disturbance encourages an increase of small or prostrate species. Cessation of disturbance leads to the rapid recovery of biomass production. Tall annuals are promoted. P fertilization clearly favours legumes in the short term. [ABSTRACT FROM AUTHOR]

Abstract: Vegetation change and anthropogenic development are altering ecosystems and decreasing biodiversity. Successful management of ecosystems threatened by multiple stressors requires development of ecosystem conservation plans rather than single species plans. We selected the big sagebrush (Artemisia tridentata Nutt.) ecosystem to demonstrate this approach. The area occupied by the sagebrush ecosystem is declining and becoming increasingly fragmented at an alarming rate because of conifer encroachment, exotic annual grass invasion, and anthropogenic development. This is causing range-wide declines and localized extirpations of sagebrush associated fauna and flora. To develop an ecosystem conservation plan, a synthesis of existing knowledge is needed to prioritize and direct management and research. Based on the synthesis, we concluded that efforts to restore higher elevation conifer-encroached, sagebrush communities were frequently successful, while restoration of exotic annual grass-invaded, lower elevation, sagebrush communities often failed. Overcoming exotic annual grass invasion is challenging and needs additional research to improve the probability of restoration and identify areas where success would be more probable. Management of fire regimes will be paramount to conserving sagebrush communities, as infrequent fires facilitate conifer encroachment and too frequent fires promote exotic annual grasses. Anthropogenic development needs to be mitigated and reduced to protect sagebrush communities and this probably includes more conservation easements and other incentives to landowners to not develop their properties. Threats to the sustainability of sagebrush ecosystem are daunting, but a coordinated ecosystem conservation plan that focuses on applying successful practices and research to overcome limitations to conservation is most likely to yield success. [Copyright &y& Elsevier]

Abstract: Restoration treatments are based on the largely untested notion that desired recovery of plant communities following disturbance wouldn’t occur in the absence of active intervention. We identified rate of short-term (10 year) floristic changes following removal of plant functional groups in Wyoming big sagebrush plant communities in 1999–2005 and 2008. Treatments imposed on 6 × 6 m plots were: 1) removal of all plant functional groups, 2) perennial grass removal, 3) shrub removal and 4) control. Our data suggest recovery of the shrub component on shrub removal plots could take decades. Similarly, perennial grass cover and density on perennial grass removal plots was less than half that of unaltered plots 10 years after treatment. When all functional groups were removed, cover of annual forbs, annual grasses, and shrubs returned to unaltered levels within ten years or less. Perennial forbs were unaffected (p > 0.05) by treatment. The fact that natural recovery of some components occurred within a relatively short post-disturbance time interval (i.e. <10 years) suggests that intervention may not be necessary for some functional groups. Restoring shrubs in areas dominated by perennial grasses may require targeted reductions of competing perennial grasses. Conversely, shrub dominance may limit perennial grass re-establishment. [Copyright &y& Elsevier]

Domestic animals potentially affect the reproductive output of plants by direct removal of aboveground plant parts but also could alter the structure and fertility of the upper soil and the integrity of biological crusts through trampling. We asked whether sheep selectivity of plant patches along grazing paths could lead to negative changes in biological crusts and soil seed banks. We randomly selected ten floristically homogeneous vegetation stands distributed across an area (1250 ha) grazed by free ranging sheep. Vegetation stands were differently selected by sheep as estimated through sheep-collaring techniques combined with remote imagery mapping. At each stand, we extracted 15 paired cylindrical soil cores from biological crusts and from neighboring soil without crusts. We evaluated the crust cover enclosed in each core and incubated the soil samples at field capacity at alternating 10–18 °C during 24 months. We counted the emerged seedlings and identified them by species. Sheep selectivity along grazing paths was largest at mid-distances to the watering point of the paddock. Increasing sheep selectivity was associated with the reduction of the cover of biological crusts and the size and species number of the soil seed bank of preferred perennial grasses under biological crusts. The size of the soil seed bank of annual grasses was reduced with increasing sheep selectivity under both crust and no crust soil conditions. We did not detect changes in the soil seed banks of less- and non- preferred species (shrubs and forbs) related to sheep selectivity. Our findings highlight the negative effects of sheep selectivity on biological crusts and the soil seed bank of preferred plant species and the positive relationship between biological crusts and the size of the soil seed bank of perennial grasses. Accordingly, the state of conservation of biological crusts could be useful to assess the state of the soil seed banks of perennial grasses for monitoring, conservation and planning the sustainable management of grazing lands. [Copyright &y& Elsevier]

The article presents a study which evaluates the impact of soil nitrogen (N) management on the growth and competitive ability of annual and perennial grass seedlings through meta-analysis. It states that annual grasses had maintained their high growth rates, great biomass, and tiller production than perennials under low and high nitrogen availability. It adds that there was no evidence that indicates that low nitrogen availability affects the competitive interactions between the seedlings.

Abstract: Fuel reduction in the wildland–urban interface is a widely used international strategy for assisting human communities regarding wildfire threats, but very little research has examined whether certain fuel reduction methods and their seasonal timing promote nonnative invasion. To address this issue, we evaluated nonnative and native plant response to five of the most commonly-practiced shrubland fuel reduction methods in Mediterranean climates, including (a) fall prescribed fire, (b) winter prescribed fire, (c) spring prescribed fire, (d) fall mastication (slashing) and (e) spring mastication. Treatments were replicated four times in mature northern California chaparral and surveyed for three years after treatment; treatment type was randomly assigned. We found that the effects of treatment type (fire/mastication) were more apparent than the effects of treatment season (fall/winter/spring), but there were some differences among seasons of prescribed fire. Mastication treatments had the highest number of nonnative invasive species. Mastication treatments also had 34% higher nonnative annual grass abundance than the fire treatments. Winter and spring prescribed fire treatments were most resistant to nonnative invasion since these areas had the fewest nonnative species, lowest nonnative species abundances, and highest relative proportions of native plants. In shrublands where controlling nonnative annual grass is an important objective, managers should consider cool season prescribed fire as a viable fuel reduction treatment. In cases where prescribed fire is not feasible, mastication provides an alternative that can exacerbate nonnative grass production in the short term but may maintain native plant seedbanks over the long term if the site remains undisturbed for several decades. Results from this study could be applicable to other areas of Mediterranean shrublands. [Copyright &y& Elsevier]

Floods have huge impacts on biodiversity of terrestrial plants, with the degree of the impacts being affected by various factors, which is evaluated by many methods. The widely used field investigation method is energy and time consuming and not applicable for evaluating the impact of floods on all plants. The weight scoring method and risk index analysis method are less accurate because the influencing factors are ignored. A more convenient and accurate evaluation method is needed. Here, the main influencing factors were sorted into temperature (T), geomorphic change (G), ratio of flood depth to plant height (D), and ratio of flood duration to waterlogging tolerance time of plant (F). The species number of different plants and monthly distribution of annual grasses in each land cover type were calculated. After establishing the impact functions of T , G , D , and F on plants, we proposed an assessment method using the total biodiversity impact index (TBI) and average biodiversity impact index (ABI) representing the total and average impact degree of floods on plant biodiversity. The feasibility of this method was verified using a case study. We concluded that (1) TBI and ABI varied with space; (2) the ABIs of different plants in the descending order were perennial grasses, annual grasses, shrubs, and trees; (3) the monthly average ABIs of different land cover types in the descending order were grassland, shrubland, cropland, forest, town, and floodplain, that of the monthly average TBIs were grassland, shrubland, forest, cropland, town, and floodplain, which are all high in summer and low in winter. This method can be used for pre-evaluation and rapid evaluation of the impact of floods on biodiversity of plants in inundated areas. It can also be used to evaluate the environmental flood risk of dams and embankments and provide quantitative indicators for risk management. [Display omitted] • The factors influencing the impact of floods on plant biodiversity were sorted into four. • TBI and ABI were used to represent the total and average impact degree of floods on plant biodiversity. • We established the impact functions of the four factors and proposed the calculation methods of TBI and ABI. • The ABIs of different plants in the descending order were perennial grasses, annual grasses, shrubs, and trees. [ABSTRACT FROM AUTHOR]

In savanna environments, fire and grass are inextricably linked by feedback loops. In the Darwin area of northern Australia, flammable tall annual grasses of the genus Sarga (previously Sorghum') have been implicated in a savanna fire-cycle. We examined the relationship between fire history, the grass layer and distance from settlement using LANDSAT images and plot-based surveys. Areas more than 500 m from settlement were burnt almost twice as often, the additional fires being concentrated late in the dry season and in areas dominated by annual Sarga and even more so where dominated by short annual grasses. Grass cover was a stronger correlate of fire frequency than grass biomass, the two showing a non-linear relationship. Sites dominated by short annual grasses had similar cover to, but markedly lower biomass than those dominated by annual Sarga or perennial grasses. Our results reflect the success of fire suppression in the vicinity of settlements, but little effective management of late dry-season wildfires in remoter areas. We evaluate several hypotheses for the association of frequent fire with annual grasses regardless of their growth form and conclude that fuel connectivity and possibly other fuel characteristics are key issues worthy of further investigation. [ABSTRACT FROM AUTHOR]

A high relative growth rate (RGR) is thought to be an important trait allowing invasive annual grasses to exploit brief increases in nitrogen (N) supply following disturbance in the Intermountain West. Managing soils for low N availability has been suggested as a strategy that may reduce this growth advantage of annual grasses and facilitate establishment of desirable perennials grasses. The objective of this study was to examine the degree to which soil N availability affects RGR and RGR components of invasive annual and desirable perennial grasses. It was hypothesized that (1) invasive annual grasses would demonstrate a proportionately greater reduction in RGR than perennial grasses as soil N stress increased, and (2) the mechanism by which low N availability decreases RGR of annual and perennial grasses would depend on the severity of N stress, with moderate N stress primarily affecting leaf mass ratio (LMR) and severe N stress primarily affecting net assimilation rate (NAR). Three annual and three perennial grasses were exposed to three levels of N availability. RGR and components of RGR were quantified over four harvests. Moderate N stress reduced RGR by decreasing LMR and severe N stress lowered RGR further by decreasing NAR. However, reduction in RGR components was similar between invasive and natives, and as a consequence, annual grasses did not demonstrate a proportionately greater reduction in RGR than perennials under low N conditions. These results suggest managing soil N will do little to reduce the initial growth advantage of annual grasses. Once perennials establish, traits not captured in this short-term study, such as high tissue longevity and efficient nutrient recycling, may allow them to compete effectively with annuals under low N availability. Nevertheless, if soil N management does not facilitate the initial establishment of perennials in annual grass infested communities, then there is little likelihood that such techniques will provide a long-term benefit to restoration projects in these systems. [ABSTRACT FROM AUTHOR]

Abstract: In glyphosate-tolerant crops, weed control may be improved and glyphosate dose may be reduced when ammonium sulfate (AMS) is added to the spray mixture. Much research has investigated how AMS may reduce antagonism between salt ions present in the carrier water and glyphosate molecules, especially when hard water is used as the spray carrier. However, little information is available describing whether glyphosate dose may be reduced when soft water is used. Field trials were established at two Ontario and one Michigan location in 2003 and 2004 to evaluate control of several annual weeds when 0.25, 0.5, 0.75 and 1× label doses of glyphosate ±2% AMS were applied in glyphosate-tolerant maize. The concentration of salt and metal ions in the spray water at Harrow and Ridgetown were low, and the concentrations at East Lansing were moderate. Crop tolerance was excellent in all treatment plots. The addition of AMS only improved weed control at the Ridgetown location. Control of Abutilon theophrasti was improved at the 0.25 and 0.5× glyphosate doses; however, improvements in control did not exceed 65%. Percent weed control below 80% is generally considered unacceptable. Control of Amaranthus retroflexus, Chenopodium album, and several annual grasses was not improved by AMS addition at any glyphosate dose in comparison to the application of glyphosate alone. Overall, the addition of AMS to a soft water carrier improved control of some weed species only at below-label glyphosate doses. Nonetheless, because weed control was not improved beyond 70% when AMS was added, we continue to recommend that the full label dose of glyphosate be applied to reduce the necessity for additional glyphosate applications to maintain acceptable weed control. [Copyright &y& Elsevier]

A 3-year study was conducted to investigate the major nutrient dynamics in soil receiving swine effluent as the sole source of plant nutrients for warm-season perennial bermudagrass and cool-season annuals. Berseem and crimson clovers, ryegrass, and wheat were seeded in common bermudagrass for a year-round nutrient uptake and spring through summer haying. Bermudagrass dry matter of 9.0 mg ha-1 (3-yr average) was not impacted by the overseeding treatments. Most of the soil nutrient element concentrations increased during the study, particularly phosphorus in top 5 cm of the soil surface. The increase of Fe and NO3-N concentration at the 0-5 cm depth was high. Double cropping can be a better practice than growing bermudagrass alone, but, the effluent nutrient application must be coordinated with the nutrient requirements of the growing forages in order to minimize the build up of any nutrient in the soil. [ABSTRACT FROM AUTHOR]

Abstract: Hand weeding is still by far the most widely practised cultural weed control technique in vegetable production throughout the tropics because of the prohibitive costs of herbicides and fear of toxic residue coupled with the lack of knowledge about their use. Field experiments were conducted in 2000 and 2001 to examine the frequency of weeding conducive to optimum growth and yield of jute in Nigeria. Results indicated that weeding once as early as 2, 3 or 4 weeks after sowing (WAS) was not as beneficial to the growth and yield of jute as two weedings conducted at 2 and 5 WAS or 3 and 6 WAS. Weeding once every week throughout the duration of crop growth significantly () enhanced all growth and yield parameters over most of the treatments. Both the final and cumulative weed weights at harvest were found to be negatively correlated with increasing frequency of weeding with an average correlation coefficient (r) of −0.73 in both years. In contrast, all growth and yield parameters were linearly and positively correlated with increasing frequency of weeding (). Bearing in mind the economics of labour input and yield, two weeding operations at 2 and 5 WAS was the most promising of all the treatments. [Copyright &y& Elsevier]

Abstract: Annual grasses are stronger competitors for available soil N than blue oak seedlings and soil microorganisms. However, little is known about the dynamics of N competition during annual grass senescence. We conducted a field experiment in a California oak woodland to study effects of annual grass senescence on N uptake by grasses, blue oak seedlings and soil microorganisms. Labeled N was applied at the beginning of April, May and of June in the form of 15NH4 + or 15N-glycine. Plants and soils were harvested after 5 days (15NH4 + and 15N-glycine treatments) and after 26 days (15NH4 + treatment only). We evaluated effects of N form, season and labeling period on N competition among oak seedlings, annual grasses and soil microorganisms. N forms did not affect competition among grasses, oak seedlings and soil microorganisms, but more 15N was incorporated into the soil organic N pool in the 15N-glycine treatments than in the 15NH4 + treatments. There were no seasonal (May vs June) effects on 15N recovery in blue oak seedlings and soil microorganisms. Plant samples from April harvest were lost. In June, when grasses were senescing, more 15N was found in the soil inorganic pool than in May. Extremely dry soils in June may have limited inorganic N availability to oak seedlings and soil microorganisms. After 26-day labeling period, 15N recovery in blue oak seedlings and the soil organic N pool significantly increased, while 15N recovery in both the soil microbial and inorganic N pools decreased compared to the 5-day labeling period. Although blue oak seedling biomass changed little from early May to late June, N concentrations in oak roots increased 53%. In contrast, annual grass biomass peaked in May, and then decreased rapidly. Our results suggest that blue oak seedlings and annual grasses have different temporal competitive abilities. Blue oak seedlings appear to have a long-term strategy for N competition. Blue oaks take up N slowly but steadily, increasing N uptake from 5 to 26 days. This extended time period has a greater positive effect on N uptake than does reduced grass uptake caused by senescence. [Copyright &y& Elsevier]

Land-use changes and biological invasions have converted the vegetation of California''s Central Valley and surrounding foothills from a mixture of perennial forbs and grasses and spring- and summer-flowering annuals to vegetation dominated by Eurasian spring-flowering annual grasses. The exotic annual grass communities are now rapidly being invaded by a Eurasian summer-flowering annual thistle that has caused losses of soil moisture resources on invaded sites of 15–25% of mean annual precipitation. A rough preliminary estimate indicates that the value of the lost water may range from 16 to 75 million dollars per year in the Sacramento River watershed alone. [Copyright &y& Elsevier]

Red brome is a Mediterranean winter annual grass that has invaded south-western USA deserts. Unlike native annuals, it does not maintain a soil seed bank, but exhibits early and uniform germination. Above-average winter precipitation in these regions allows red brome to reach high density and biomass. These are time for concern, as large numbers of easily dispersed seeds increase the likelihood that it may spread into new areas. However, early and uniform germination can also lead to population crashes when drought precludes seed production. Winter droughts dramatically reduce densities of red brome, but provide opportunities for management of this exotic grass. [Copyright &y& Elsevier]

The southern African Mopane savanna is a water-limited ecosystem and an increase in woody plant abundance often results in the suppression of herbaceous plants. In an attempt to counter this effect, the thinning or even total clearing of all woody plants is a common practise in South Africa. Since the outcome of woody plant removal is determined by both negative and positive responses to tree removal, a study was conducted to establish if all tree woody species have the same impact on the herbaceous layer. The study area featured a dense stand of Colophospermum mopane, interposed with isolated colonies of Salvadora australis, each forming its own characteristic habitat. Seven plots (65 m×180 m) were subjected to different intensities of tree thinning, ranging from a totally cleared plot (0%) to plots thinned to the equivalent of 10%, 20%, 35%, 50% and 75% of the leaf biomass of a control plot (100%) with a tree density of 2711 plants ha−1. The S. australis-habitat, in comparison to the larger C. mopane-habitat, supported a superior cover of herbaceous plants. The S. australis-habitat supported a larger proportion of perennial grasses, acting as valuable seed resources of these and other herbaceous plants. Differences in the soil nutrient status and soil water between the C. mopane- and S. australis-habitats are likely determinants of these differences. A poor ground cover existed at high tree densities of the larger C. mopane-habitat. A rapid colonization of bare ground by herbaceous plants resulted with increasing intensity of tree thinning of the major C. mopane-habitat, but the opposite appeared to happen on the S. australis-habitat. The S. australis trees are considered critical in maintaining conditions favourable for the persistence of the associated herbaceous component. Thinning or removal of S. australis is therefore considered undesirable. [Copyright &y& Elsevier]