Bromus Rubens Research Articles

Phenology forecasting models for detection and management of invasive annual grasses

AbstractNon‐native annual grasses can dramatically alter fire frequency and reduce forage quality and biodiversity in the ecosystems they invade. Effective management techniques are needed to reduce these undesirable invasive species and maintain ecosystem services. Well‐timed management strategies, such as grazing, that are applied when invasive grasses are active prior to native plants can control invasive species spread and reduce their impact; however, anticipating the timing of key phenological stages that are susceptible to management over vast landscapes is difficult, as the phenology of these species can vary greatly over time and space. To address this challenge, we created range‐wide phenology forecasts for two problematic invasive annual grasses: cheatgrass (Bromus tectorum), and red brome (Bromus rubens). We tested a suite of 18 mechanistic phenology models using observations from monitoring experiments, volunteer science, herbarium records, timelapse camera imagery, and downscaled gridded climate data to identify the models that best predicted the dates of flowering and senescence of the two invasive grass species. We found that the timing of flowering and senescence of cheatgrass and red brome were best predicted by photothermal time models that had been adjusted for topography using gridded continuous heat‐insolation load index values. Phenology forecasts based on these models can help managers make decisions about when to schedule management actions such as grazing to reduce undesirable invasive grasses and promote forage production, quality, and biodiversity in grasslands; to predict the timing of greatest fire risk after annual grasses dry out; and to select remote sensing imagery to accurately map invasive grasses across topographic and latitudinal gradients. These phenology models also have the potential to be operationalized for within‐season or within‐year decision support.

Characterization and Comparative Analysis of Complete Chloroplast Genomes of Four Bromus (Poaceae, Bromeae) Species.

Bromus (Poaceae Bromeae) is a forage grass with high adaptability and ecological and economic value. Here, we sequenced Bromus ciliatus, Bromus benekenii, Bromus riparius, and Bromus rubens chloroplast genomes and compared them with four previously described species. The genome sizes of Bromus species ranged from 136,934 bp (Bromus vulgaris) to 137,189 bp (Bromus ciliates, Bromus biebersteinii), with a typical quadripartite structure. The studied species had 129 genes, consisting of 83 protein-coding, 38 tRNA-coding, and 8 rRNA-coding genes. The highest GC content was found in the inverted repeat (IR) region (43.85-44.15%), followed by the large single-copy (LSC) region (36.25-36.65%) and the small single-copy (SSC) region (32.21-32.46%). There were 33 high-frequency codons, with those ending in A/U accounting for 90.91%. A total of 350 simple sequence repeats (SSRs) were identified, with single-nucleotide repeats being the most common (61.43%). A total of 228 forward and 141 palindromic repeats were identified. No reverse or complementary repeats were detected. The sequence identities of all sequences were very similar, especially with respect to the protein-coding and inverted repeat regions. Seven highly variable regions were detected, which could be used for molecular marker development. The constructed phylogenetic tree indicates that Bromus is a monophyletic taxon closely related to Triticum. This comparative analysis of the chloroplast genome of Bromus provides a scientific basis for species identification and phylogenetic studies.

Homogenization of soil seed bank communities by fire and invasive species in the Mojave Desert

Soil seed banks help maintain species diversity through temporal storage effects and function as germination pools that can optimize fitness across varying environmental conditions. These characteristics promote the persistence of native plant communities, yet disturbances such as fire and associated invasions by non-native species can disrupt these reserves, fundamentally altering successional trajectories. This may be particularly true in deserts, where native plant communities are less adapted to fire. While studies of fire effects on desert plant communities are not uncommon, information regarding the short- and long-term effects of fire on seed banks is less available. To better understand the influence of fire and invasive species on desert seed banks, we investigated soil seed bank biodiversity from 30 wildfires that burned between 1972 and 2010 across the Mojave Desert ecoregion of North America. We assessed how characteristics of fire regimes (frequency, time since fire, and burn severity) interacted with climate and invasive plants on measures of α-, β-, and γ-diversities. Because β-diversity is a direct measure of community variability and reveals important information about biodiversity loss, we further examined the nestedness and turnover components of β-diversity. Mean α- and γ-diversities were generally higher for burned locations than in unburned reference sites, however individual fire variables had little influence on patterns of seed bank diversity. Burned area seed banks tended to be dominated by non-native invasive species, primarily two grasses, (Bromus rubens, Bromus tectorum), as well as an invasive forb (Erodium cicutarium). The most striking pattern we observed was a collective sharp decline in α-, β-, and γ-diversities with increased invasive species dominance, indicating the homogenization of seed bank communities with the colonization of invasive species after fire. Evidence of homogenization was further supported by reduced turnover and increased nestedness in burn areas compared to reference areas indicating potential biodiversity loss. Our findings highlight how biological processes such as plant invasions can combine with disturbance from fire to alter patterns of seed bank composition and diversity in desert ecosystems.

Plant networks are more connected by invasive brome and native shrub facilitation in Central California drylands

Dominant vegetation in many ecosystems is an integral component of structure and habitat. In many drylands, native shrubs function as foundation species that benefit other plants and animals. However, invasive exotic plant species can comprise a significant proportion of the vegetation. In Central California drylands, the facilitative shrub Ephedra californica and the invasive Bromus rubens are widely dispersed and common. Using comprehensive survey data structured by shrub and open gaps for the region, we compared network structure with and without this native shrub canopy and with and without the invasive brome. The presence of the invasive brome profoundly shifted the network measure of centrality in the microsites structured by a shrub canopy (centrality scores increased from 4.3 under shrubs without brome to 6.3, i.e. a relative increase of 42%). This strongly suggests that plant species such as brome can undermine the positive and stabilizing effects of native foundation plant species provided by shrubs in drylands by changing the frequency that the remaining species connect to one another. The net proportion of positive and negative associations was consistent across all microsites (approximately 50% with a total of 14% non-random co-occurrences on average) suggesting that these plant-plant networks are rewired but not more negative. Maintaining resilience in biodiversity thus needs to capitalize on protecting native shrubs whilst also controlling invasive grass species particularly when associated with shrubs.

Studying Floristic Composition for the Conservation of Parque das Camélias (Braga Municipality) Biodiversity

The conservation of biodiversity and the understanding of its distribution patterns play a crucial role in promoting effective land management. The present study aimed to identify herbaceous species in Parque Urbano das Camélias located in the city of Braga. The research was conducted as part of an ongoing collaboration between the School of Sciences at the University of Minho and the Municipal Council of Braga. The site was sampled using the quadrant method, employing a 1m2 measurement, to encompass 12 strategically selected locations throughout the park. The findings encompassed 28 distinct specimens, with identification achieved at the genus level for 27 and at the species level for 25. The study area harbors both native species from mainland Portugal and exotic species, with the Poaceae family being predominant, accounting for 50% of the identified individuals. Some of the species identified in the park include Avena spp., Bromus madritensis, and Plantago lanceolata. The study discusses preservation strategies and biodiversity enhancement for the Parque Urbano das Camélias.

Wildfire and cattle legacies on gradients of soil nitrogen underlie patterns of annual brome invasion.

Human activities are increasing wildfires and livestock activity in arid ecosystems with potential implications for the spread of invasive grasses. The objective of this study was to test whether fire history and cattle activity alter soil resource gradients, thereby affecting patterns of Bromus rubens L. (red brome) invasion. Six paired burned and unburned transect lines (1-km long) were established in the northeast Mojave Desert along the boundaries of four independent wildfire scars. At 100-m transect increment points, we measured the distance to the two nearest cowpats, and two random points and measured the density, height, biomass, and seed production of red brome, soil moisture and inorganic nitrogen (N). Cattle activity was 29% greater along burned transects compared to unburned transects (P < 0.05). Red brome height, density, and seed production were 11-34% greater along burned transects than unburned transects (P < 0.05). Red brome height, biomass, density, and seed production were twofold to tenfold greater next to cowpats compared to random points (P < 0.05). Soils along burned transects and beneath cowpats had greater soil inorganic N (P < 0.05), which was positively correlated with red brome density, height, biomass, and seed production (R2 = 0.60-0.85, P < 0.0001). Transgenerational effects were evident as seeds from red brome next to cowpats had 27% higher germination than seeds collected from random points. Positive responses of red brome to increased inorganic N related to fire and cattle activity may contribute fine fuel infill that drives invasive grass-fire cycles in deserts.

Herbicide resistance in Bromus spp.: a global review

AbstractThis review summarizes what is currently known about herbicide resistance in Bromus spp. worldwide. Additional information on the biology and genetics of Bromus spp. is provided to further the understanding of resistance evolution and dispersal of the different species. Cases of herbicide resistance have been confirmed in Bromus catharticus Vahl., Bromus commutatus Schrad. (syn.: Bromus racemosus L.), Bromus diandrus Roth, Bromus japonicus Thunb. (syn.: Bromus arvensis L.), Bromus madritensis L., Bromus rigidus Roth (syn.: Bromus diandrus Roth ssp. diandrus), Bromus rubens L., Bromus secalinus L., Bromus sterilis L., and Bromus tectorum L. in 11 countries. Bromus spp. populations have evolved cross- and multiple resistance to six herbicide sites of action: acetyl-coenzyme A carboxylase, acetolactate synthase, photosystem II, very-long-chain fatty-acid, 5-enolpyruvylshikimate-3-phosphate synthase, and 4-hydroxyphenylpyruvate dioxygenase inhibitors. Resistance mechanisms varied from target-site to non–target site or a combination of both. Bromus spp. are generally highly self-pollinated, but outcrossing can occur at low levels in some species. Bromus spp. have different ploidy levels, ranging from diploid (2n = 2x = 14) to duodecaploid (2n = 12x = 84). Herbicide resistance in Bromus spp. is a global issue, and the spread of herbicide-resistance alleles primarily occurs via seed-mediated gene flow. However, the transfer of herbicide-resistance alleles via pollen-mediated gene flow is possible.

First report of a wide distribution of glyphosate-resistant compact brome (Bromus madritensis) in the Iberian Peninsula: confirmation and field management

AbstractGlyphosate resistance is spreading in Spain and Portugal due to excessive herbicide use, in both annual and perennial crops. Compact brome (Bromus madritensis L.) is increasing in frequency in these different cropping systems when under conservation agriculture, particularly when glyphosate fails to control it. Fourteen populations from different areas in the Iberian Peninsula were confirmed as being B. madritensis using simple sequence repeat markers and clearly separated from the closely related species red brome (Bromus rubens L.) and ripgut brome (Bromus diandrus Roth). Six B. madritensis populations were classified as resistant, according to both their shikimic acid accumulation levels and their resistance factors based on LD50 or GR50 (values between 4 and 8). Populations with higher resistance factors also showed lower shikimic acid concentrations. Moreover, these resistant populations were able to survive the minimum registered dose for glyphosate in Spain in perennial crops (1,080 g ae ha−1, five populations) or in arable crops before seeding for annual weeds (540 g ae ha−1, one population), under both greenhouse and field conditions. The trials carried out in a glyphosate-resistant field during 2 consecutive years showed that acceptable control (≥90%) was only consistently achieved 90 d after application for preemergence treatment with flazasulfuron in a tank mix with glyphosate, while control with postemergence treatments, such as propaquizafop plus glyphosate, was below 80%. This research describes the first herbicide-resistance report for the weed species B. madritensis, confirming the presence of glyphosate-resistant populations mainly in perennial cropping systems but also in winter cereals from Spain. Due to the limited chemical tools to manage these populations, there is an urgent need for farmers to implement integrated weed management strategies.

Field evaluation of selected autochthonous herbaceous species for cover crops in Mediterranean woody crops

This study evaluated under two contrasting field conditions, and during two seasons, four autochthonous species, Bromus rubens (Br), Brachypodium distachyon (Bd), Medicago truncatula (Mt) and Anthemis arvensis (Aa), as single species and in mixtures of Br + Mt, Br + Aa and Br + Mt + Aa, to determine their suitability as temporary cover crops (CCs) for Mediterranean woody crops. Br, Bd and Mt reached above 90 % ground cover (GC) in spring, while Aa reached a maximum of 80 %; in early winter GC varied from 0 % to 40 %, approximately, depending on the sowing date in the fall. The thermal time required to reach 30 % GC and seed maturity appeared as two key traits to evaluate the suitability of autochthonous species as temporary CCs for Mediterranean woody crops. Our experiment showed that early seeding (no later than mid-October) is critical to exploit these traits into effective CCs under Mediterranean conditions. Phenologic models developed for the tested species, based on temperature, are capable of predicting their development properly under field conditions, and they might be used to predict the evolution of GC when calibrated from field experiments. Aboveground biomass was affected by edaphic conditions, with higher values being observed in the most fertile soil, in Córdoba, in the range of 300–700 g m−2, compared to Adamuz with 150–350 g m−2. When used as monospecific CCs, Br, Bd and Mt had a higher aboveground biomass than Aa. We observed no differences in aboveground biomass among mixtures within each of the two locations. Differences in fine root biomass (RB) and fine root length density (RLd) resembled those of aboveground biomass, albeit with a higher variability. When used as monospecific CCs, fine RB and fine RLd were higher for Br and Bd, followed by Mt, with Aa having the lower values. Fine RB, or fine RL, in the top 0–30 cm of soil is also a relevant trait for selecting temporary CCs for Mediterranean woody crops. Our results show that they are also greatly affected by edaphic-climatic conditions and that they have a moderate correlation with aboveground biomass. The analysis of soil water uptake in the Córdoba plot showed no significant differences among the monospecific species and the mixtures, with ET values during the 2014/15 and 2015/16 growing seasons in the range of 325–300 mm.

Phytochemical Screening, Allelopathic and Bioherbicidal Potentialities of Euphorbia Guyoniana Boiss. and Reut. Leaf Extract

Euphorbia guyoniana Boiss. & Reut. (Euphorbiaceae) is well known for the chemical diversity of its phytoconstituents, and toxicological properties that have been found in literature. However, research articles about their allelopathic characteristics are rarely reported. The current research study was conducted to explore phytochemical screening, allelopathic effects and their potential uses as natural herbicide of Euphorbia guyoniana Leaf extract, harvested from Oued Metlili, Algerian Sahara, on germination and seedling growth of four adventitious species (Bromus rubens L., Phalaris minor Retz., Plantago lagopus L., Ammi visnaga L.) and one cultivated species (Triticum durum L.) in laboratory conditions. The analyses of crude plant extract confirmed the flavonoids, anthocyanins, phenols and tannins, steroids, saponins, free quinone, sterols and triterpenes as well as carohydrates in the extract. Our results show that the leaf extract of Euphorbia guyoniana had significant allelopathic and bioherbicidal activity on germination and seedling growth of adventitious species and stimulatory activity on cultivated species at lower concentrations.

Weed Flora of Man-Made river agriculture project (Masiklo)1

&#x0D; Abstract&#x0D; The goals of the present work were to document the weed species in Triticum aiestivum L. (Wheat) fields in MR agricultural project Masiklo and to provide quantitative data that could be used to estimate losses due to weeds, also to attract the attention to the economically important weeds in MR agricultural project Masiklo and to develop methods for their control. In this study, a survey was conducted to identify weed species naturally occurring in MR agricultural Wheat fields in Masiklo Libya. A checklist including 41 species was prepared. The checklist includes the scientific name for each species. Reported species were belonging to 37 genera and 19 families of angiosperms. Dicotyledons were represented by 32 species, 30 genera, and 17 families, and Monocotyledons were represented by 9 species, 7 genera, and 2 families. The dominant families according to the number of species were Poaceae (8 species), Fabaceae (6 species), Asteraceae and Brassicaceae (5 species), and Apiaceae (3species). The results of this survey showed that Lolium rigidum, Fumaria officinalis, Hordeum murinum ssp. glaucum, Medicago polymorpha, Bromus madritensis, Bromus rigidus and Sinapis flexuosa were the dominant species in studied fields.

Phenological patterns of herbaceous Mediterranean plant communities in spring: is there a difference between native and formerly-cultivated grasslands?

Background and aims – Plant phenology, defined as the timing of recurring life events like leaf flushing, flowering, or fruiting, is highly sensitive to environmental factors such as photoperiod, temperature, and moisture. Phenological synchrony between interacting species – such as plants and their pollinators – is of major importance to the structure and functioning of ecosystems. Plant phenology might also be affected by changes in edaphic conditions. However, whether former agricultural activities may shift phenological patterns of plant communities remains poorly understood. In this study, we evaluated the impact of past agricultural practices on herbaceous plant community phenology in the protected Mediterranean xeric grassland of La Crau (France). Material and methods – We compared (1) species composition, and (2) phenological patterns of annuals, perennials, Bromus rubens (annual), and Lobularia maritima (perennial), in formerly-cultivated plots – abandoned for 30 years – and intact native grassland plots (steppe), both subjected to itinerant sheep grazing. Key results and conclusion – Our results suggest that former agricultural activities can affect species composition of Mediterranean xeric grassland communities with differences visible after 30 years of abandonment, but only altered phenological patterns slightly. We suggest that climatic factors and sheep grazing acted as strong habitat filters constraining community assembly at the phenological level.

Transgenerational responses to climate change in Mediterranean annual species with contrasting functional strategies

Increasing temperature and aridity predicted by climate change models in the Mediterranean region will pose a significant challenge for the survival of some plant species. The mechanisms by which species modify their phenotype across generations in response to the environment have been identified as essential to cope with the new climatic conditions. However, this transgenerational transfer remains unexplored for species with contrasted resource-use strategies (fast-growing or acquisitive versus stress-tolerant or conservative species). For this purpose, transgenerational responses to warming and drought of annual plant species with different resource-use strategies were assessed by conducting three experiments. In a field experiment, climatic treatments of increased temperature and rainfall exclusion were imposed on five herbaceous species typical of Mediterranean grasslands. The descendants of the individuals sampled in the field were employed in two greenhouse experiments to: (1) analyze the transgenerational response by re-imposing warming and drought conditions, and (2) identify possible maternal effects by maintaining them at optimal conditions of air temperature and water availability and comparing with maternal performance. We measured reproductive output, plant growth and survival variables as plant performance indicators. We found contrasting transgenerational responses to warming and drought depending on the functional strategy of the species. Direct effects of the abiotic stressors on parental plants were retained or new ones appeared in their offspring, with special negative impact on one of the most acquisitive species ( Crepis capillaris ). In contrast, the most conservative species ( Bromus madritensis ) highly tolerated increased climatic stress but deleterious maternal effects were registered, given the high negative impact on the performance of the descendants of maternal plants that were subjected to climatic treatments. Our study highlights the importance of evaluating plant responses to stress across generations to better understand their potential ability to face new environmental conditions in species with different functional strategies. • Transgenerational response to climate change varies with plant functional strategy. • Acquisitive plant species are highly sensitive to warming and drought. • Maternal effects compromise the response to climate change of conservative species.

Biocrusts do not differentially influence emergence and early establishment of native and non‐native grasses

AbstractBiological soil crusts (biocrusts) cover the soil surface of global drylands and interact with vascular plants. Biocrusts may influence the availability and nature of safe sites for plant recruitment and the susceptibility of an area to invasion by non‐native species. Therefore, to investigate the potential role of biocrusts in invasive species management, we sought to determine whether native and non‐native grass recruitments in two North American deserts were differentially affected by biocrusts. We conducted a series of coordinated experiments in field, semi‐controlled, and controlled environment settings in the Colorado Plateau and Sonoran Desert using contrasting biocrust and grass functional types. Experiments in field environments focused on early establishment of grass seedlings whereas controlled environment experiments focused on seedling emergence. Within each experiment, we compared responses (frequency, magnitude, and timing of emergence/establishment) both across species (biocrust types pooled) and across species and levels of biocrust development. Native grasses varied by experiment and included Aristida purpurea, A. purpurea var. longiseta, Bouteloua gracilis, and Vulpia octoflora. Emergence of non‐native Bromus tectorum was similar to that of native grasses on the Colorado Plateau. Differences in emergence of native vs. non‐native grasses in the Sonoran Desert were species‐ and response‐specific. Emergence of the non‐native Bromus rubens was comparable to that of native grasses whereas emergence frequency and magnitude of the non‐native Pennisetum ciliare was lower compared with two of four native species. Within a grass species, emergence was higher and faster on bare soil compared with biocrusts in the Sonoran Desert semi‐controlled and greenhouse environment experiments. However, the pattern was not consistent across other experiments. When comparing across Colorado Plateau and Sonoran Desert biocrusts in greenhouse experiments, we found that emergence of native grasses was higher on Colorado Plateau biocrusts. Based on the lack of consistent results across our experiments, grass recruitment on biocrusts appears to be driven more by species‐specific traits than species provenance. Our greenhouse experiments suggest that biocrust topographic relief is an important safe site trait influencing plant recruitment.

Probing behavior of Neophilaenus campestris on various plant species

AbstractThe recent history of Xylella fastidiosa Wells et al. introduction in Europe illustrates how the lack of knowledge about the bacterium‐vector‐host interactions hinders the application of effective containment strategies, with the bacterial spread that currently appears relentless. Vector behavior is a key component in plant pathogen transmission; therefore, detailed knowledge of vector probing behavior on various host plants would furnish useful data for containing the bacterium. Aiming at this goal, we carried out electrical penetration graph (EPG)‐assisted probing behavior observations of the spittlebug, Neophilaenus campestris (Fallen) (Hemiptera: Aphrophoridae), a candidate vector widespread in all the areas where X. fastidiosa is currently established. Spittlebug probing was first characterized on one of its preferred host plants, Bromus madritensis L. (Poaceae), over short (6 h) and long (16 h) time spans. Thereafter, we performed comparative observations of the spittlebug probing on B. madritensis, olive, and grapevine. Overall, the probing behavior of N. campestris, that is, the main characteristic waveforms, did not differ substantially from that of Philaenus spumarius (L.) (Hemiptera: Aphrophoridae); however, here we report and describe a new kind of xylem activity interruption, provisionally termed N2, not previously observed in P. spumarius. Considering the time spent in xylem ingestion as a percentage of the total probing time (host‐suitability indicator used for spittlebugs), grapevine and B. madritensis are the preferred hosts for N. campestris, with olive as the least suitable among the plants tested. Successful probes, that is, probes during which xylem ingestion occurred, on grapevine were 2.5× greater than olive. Therefore, our data on N. campestris probing behavior suggest that the spittlebug role in X. fastidiosa epidemiology in European vineyards should be given more attention. In the present manuscript, we also discuss the current difficulties in interpreting and analyzing the outcomes of EPG studies on spittlebugs.

ОСОБЕННОСТИ ФЛУКТУАЦИЙ ЭФЕМЕРОВО-ЭФЕМЕРОИДОВОЙ СИНУЗИИ В ПОЛУПУСТЫННЫХ ФИТОЦЕНОЗАХ КУРА-АРАЗСКОЙ НИЗМЕННОСТИ В СВЯЗИ С КЛИМАТИЧЕСКИМИ ИЗМЕНЕНИЯМИ

The dynamics of semi-desert herbaceous phytocenoses was studied under the conditions of the Kura-Araz lowland on permanent model sites (10×10 m). Based on seven-year (2014–2020) stationary observations, regularities of seasonal and annual fluctuations of cereal-forb and legume-forb phytocenoses were revealed in connection with weather conditions. The analysis of data on the long- term dynamics of their species composition, structure, stock of the raw above-ground part is carried out. The α-diversity is estimated by generally accepted indices, the results of phenological observations are given. It was found that in the seasonal dynamics of plants, the beginning of the growing season depends on the air temperature in March, and the end of the cycle depends on the air temperature in May-early June. The optimal dates for the mass development of grasses are the beginning and the middle of May. In the case of an increased norm of atmospheric precipitation and a late onset of summer heat, this pattern may be violated, and the dates are shifted to the end of May – beginning of June. Over the years of observations in the cereal-forb phytocenosis of 19 species, 9, and in the legume-forb phytocenosis of 17 species, 5 turned out to be constant. The total projective cover ranged from 50 (dry years) to 100 % (wet years). The assessment of α-diversity showed that the species diversity of phytocenoses increased in years with a high amount of atmospheric precipitation in May. A linear dependence of phytomass on the total amount of atmospheric precipitation for March-June was revealed. It was found that the best accumulation of herbal phytomass is influenced by the amount of precipitation in late spring. The most resistant to warming plant species have been identified. These are mainly cereals with an average feed value: Avena eriantha, Bromus japonicus, Bromus rubens, Eremopyrum orientale, Lolium rigidum and weed herbs – Capsella bursa- pastoris, Carduus pycnocephalus, Convolvulus arvensis, Erodium cicutarium, Lepidium draba, Xanthium strumarium, the last species is an invasive plant. Among the representatives of legumes, only one species, Medicago minima, turned out to be relatively resistant to high air temperatures. It was found that of the total herbage, only 35.5 % of species can withstand a warming of 1.5–2 °C.

Glyphosate Resistance Confirmation and Field Management of Red Brome (Bromus rubens L.) in Perennial Crops Grown in Southern Spain

The excessive use of the herbicide glyphosate on annual and perennial crops grown in Southern Spain has caused an increase in resistant weed populations. Bromus rubens has begun to spread through olive and almond cultivars due to low glyphosate control over these species, whereas previously it had been well controlled with field dose (1080 g ae ha−1). Characterization using Simple Sequence Repeat (SSR) markers confirmed the presence of B. rubens collected in Andalusia. A rapid shikimic acid accumulation screening showed 17 resistant (R) populations with values between 300 and 700 µg shikimate g−1 fresh weight and three susceptible (S) populations with values between 1200 and 1700 µg shikimate g−1 fresh weight. In dose–response experiments the GR50 values agreed with previous results and the resistance factors (RFs: GR50 R/GR50 S (Br1)) were between 4.35 (Br9) and 7.61 (Br19). Foliar retention assays shown no differences in glyphosate retention in both R and S populations. The tests carried out in a resistant field (Br10) demonstrated the control efficacy of pre-emergence herbicides since flazasulfuron in the tank mix with glyphosate had up to 80% control 15 to 120 days after application (DAA) and grass weed postemergence herbicides, such as propaquizafop + glyphosate and quizalofop + glyphosate, had up to 90% control 15 to 90 DAA. Results confirm the first scientific report of glyphosate-resistant B. rubens worldwide; however, the use of herbicides with another mode of action (MOA) is the best tool for integrated weed management.

Cover–biomass relationships of an invasive annual grass, Bromus rubens, in the Mojave Desert

AbstractEstimates of plant biomass are helpful for many applications in invasive plant science and management, but measuring biomass can be time-consuming, costly, or impractical if destructive sampling is inappropriate. The objective of this study was to assess feasibility of developing regression equations using a fast, nondestructive measure (cover) to estimate aboveground biomass for red brome (Bromus rubens L.), a widespread nonnative annual grass in the Mojave Desert, USA. At three study sites, including one measured for three consecutive years, B. rubens cover spanned 0.1% to 85% and aboveground biomass 1 to 321 g m−2. In log10-transformed linear regressions, B. rubens cover accounted for 68% to 96% of the variance in B. rubens biomass among sites, with all coefficients of determination significant at P &lt; 0.05. For every doubling of percent cover, biomass was predicted to increase by 78%, 83%, and 144% among the three sites. At the site measured for three consecutive years, which ranged in rainfall from 65% to 159% of the long-term average, regression slopes each year differed from other years. Regression results among sites were insensitive to using cover classes (10 classes encompassing 0% to 100% cover) compared with simulated random distribution of integer cover within classes. Biomass of B. rubens was amenable to estimation in the field using cover, and such estimates may have applications for modeling invasive annual plant fuel loads and ecosystem carbon storage.

Positive associations with native shrubs are intense and important for an exotic invader but not the native annual community across an aridity gradient

AbstractAim and LocationPositive interactions influence the assembly of plant communities globally, particularly in stressful environments such as deserts. However, few studies have measured the intensity and relative importance of positive interactions involving native and invasive species along aridity gradients. These measures are essential for predicting how dryland communities will respond to biological invasions and environmental change. Here, we measured the intensity and importance of positive associations formed between native shrubs and the annual plant community, which included highly invasive Bromus madritensis ssp. rubens (“B. rubens”) and native neighbours, along an aridity gradient across the Mojave and San Joaquin Deserts.MethodsAlong the gradient, we sampled metrics of abundance and performance for invasive B. rubens, native annual species (pooled), exotic annual species (pooled) and all annual species (pooled) during peak flowering at 120 pairs of shrub and open microsites.ResultsAcross the gradient, B. rubens occurred at far greater abundance, cover, biomass and fitness near shrubs than away from shrubs. When Larrea tridentata was the focal shrub, positive effects on B. rubens abundance and cover were least intense at the most arid sites under the shortest shrubs. The native annual community occurred at greater abundance, cover and species richness away from shrubs, regardless of relative aridity or shrub traits. Community‐level species richness was greatest away from shrubs, but exotic species richness was similar in shrub and open microsites.Main conclusionsAcross two deserts, B. rubens formed intense and important positive associations with native shrubs that consistently improved its abundance, cover, biomass and fitness, and for abundance and cover, the intensity of B. rubens–L. tridentata associations depended upon relative aridity and shrub height. By strongly facilitating a dominant invader but not native‐ or community‐level biodiversity, native shrubs provided the wrong kind of help to the annual plant community.

Meteorological factors driving airborne grass pollen concentration in central Iberian Peninsula

Grasses are a taxonomic group of considerable environmental importance, playing a major ecological role as well as making a significant contribution to the world’s economy, since they include valuable crop and pasture species. Grass pollen allergens are also among the main causes of respiratory allergies worldwide. The interpretation of airborne grass pollen concentrations is a particularly complex task, given the marked diversity of pollen-emitting species and the influence of weather-related variables. This paper examines the influence of meteorological variables on flowering in the species contributing most to airborne grass pollen concentrations. This study was carried out in the surroundings of the city of Toledo (Spain), a Mediterranean city located in the center of the Iberian Peninsula. Temperature was the variable most influencing flowering onset, which was also affected by relative humidity, rainfall and hours of sunlight. The flowering period of grass species that flower at the start of spring (Bromus rubens and Hordeum leporinum) began earlier in years with higher mean winter temperatures, while the species that flower from mid to late spring (Trisetaria panicea and Dactylis glomerata subsp. hispanica), the flowering period began earlier in years with higher cumulative rainfall in winter and spring, which were also the years with the highest mean temperatures. Research into the influence of weather-related variables on grass phenology can shed important light on variations in airborne pollen concentrations, which determine the potential period of exposure for allergy sufferers.