Decline in biological soil crust N-fixing lichens linked to increasing summertime temperatures.

Biological soil crusts (biocrusts), comprised of mosses, lichens, and cyanobacteria, are key components to many dryland communities. Climate change and other anthropogenic disturbances are thought to cause a decline in mosses and lichens, yet few long-term studies exist to track potential shifts in these sensitive soil-surface communities. Using a unique long-term observational dataset from a temperate dryland with initial observations dating back to 1967, we examine the effects of 53 y of observed environmental variation and Bromus tectorum invasion on biocrust communities in a grassland never grazed by domestic livestock. Annual observations show a steep decline in N-fixing lichen cover (dominated by Collema species) from 1996 to 2002, coinciding with a period of extended drought, with Collema communities never able to recover. Declines in other lichen species were also observed, both in number of species present and by total cover, which were attributed to increasing summertime temperatures. Conversely, moss species gradually gained in cover over the survey years, especially following a large Bromus tectorum invasion at the study onset (ca. 1996 to 2001). These results support a growing body of studies that suggests climate change is a key driver in changes to certain components of late-successional biocrust communities. Results here suggest that warming may partially negate decades of protection from disturbance, with biocrust communities reaching a vital tipping point. The accelerated rate of ongoing warming observed in this study may have resulted in the loss of lichen cover and diversity, which could have long-term implications for global temperate dryland ecosystems.

Diverse ALS mutations and cross-and multiple-resistance to ALS and EPSPS inhibitors in flucarbazone­sodium-resistant Bromus japonicus populations from Hebei province, China.

Japanese brome (Bromus japonicus) has become one of the main weeds in wheat fields in Hebei province of China and causes a large decrease of wheat production. A total of 44 putative resistant and 2 susceptible Japanese brome populations were collected in the 2021/2022 crop season from Hebei province of China to determine resistance levels to flucarbazone­sodium and to investigate the diversity of acetolactate synthase (ALS) mutations, as well as to confirm the cross-and multiple-resistance levels to ALS and EPSPS (5-enolpyruvate shikimate-3-phosphate synthetase) inhibitors. Whole plant bioassay results showed that 15 out of 44 populations tested or 34% were resistant to flucarbazone­sodium. The resistance indices of Japanese brome to flucarbazone­sodium ranged from 43 to 1977. The resistant populations were mainly distributed in Baoding and Shijiazhuang districts, and there was only one resistant population in Langfang district. Resistant Japanese brome had diverse ALS mutations, including Pro-197-Ser, -Thr, -Arg and Asp-376-Glu. The incidence of Pro-197-Ser mutation was the highest at 68%. Application of the CYP450 inhibitor malathion suggested that CYP450 was involved in metabolic resistance in a population without an ALS mutation. The population with Pro-197-Thr mutation evolved weak cross-resistance to mesosulfuron-methyl and pyroxsulam, and it is in the process of evolving multiple-resistance to glyphosate.

Ecosystem resilience to invasion and drought: Insights after 24 years in a rare never-grazed grassland.

Understanding the resilience of ecosystems globally is hampered by the complex and interacting drivers of change characteristic of the Anthropocene. This is true for drylands of the western US, where widespread alteration of disturbance regimes and spread of invasive non-native species occurred with westward expansion during the 1800s, including the introduction of domestic livestock and spread of Bromus tectorum, an invasive non-native annual grass. In addition, this region has experienced a multi-decadal drought not seen for at least 1200 years with potentially large and interacting impacts on native plant communities. Here, we present 24 years of twice-annual plant cover monitoring (1997-2021) from a semiarid grassland never grazed by domestic livestock but subject to a patchy invasion of B. tectorum beginning in ~1994, compare our findings to surveys done in 1967, and examine potential climate drivers of plant community changes. We found a significant warming trend in the study area, with more than 75% of study year temperatures being warmer than average (1966-2021). We observed a native perennial grass community with high resilience to climate forcings with cover values like those in 1967. In invaded patches, B. tectorum cover was greatest in the early years of this study (1997-2001; ~20%-40%) but was subsequently constrained by climate and subtle variation in soils, with limited evidence of long-term impacts to native vegetation, contradicting earlier studies. Our ability to predict year-to-year variation in functional group and species cover with climate metrics varied, with a 12-month integrated index and fall and winter patterns appearing most important. However, declines to near zero live cover in recent years in response to regional drought intensification leave questions regarding the resiliency of intact grasslands to ongoing aridification and whether the vegetation observations reported here may be a leading indicator of impending change in this protected ecosystem.

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.

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

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

Fuel Properties of Effective Greenstrips in Simulated Cheatgrass Fires.

Invasive annual grasses alter fire regime in steppe ecosystems, and subsequent trends toward larger, more frequent wildfires impacts iconic biodiversity. A common solution is to disrupt novel fuel beds comprising continuous swaths of invasive annual grasses with greenstrips-linear, human-maintained stands of less-flammable vegetation. But selecting effective native species is challenged by the fact that identifying the optimal combination of plant traits that interrupt wildfire spread is logistically difficult. We employed fire behavior simulation modeling to determine plant traits with high potential to slow fire spread in annual Bromus-dominated fuelbeds. We found species with low leaf:stem (fine:coarse) ratios and high live:dead fuel ratios to be most effective. Our approach helps isolate fuelbed characteristics that slow fire spread, providing a geographically-agnostic framework to scale plant traits to greenstrip effectiveness. This framework helps managers assess potential native species for greenstrips without needing logistically-difficult experimental assessments to determine how a species might affect fire behavior.

Marker-trait association analysis for drought tolerance in smooth bromegrass.

BACKGROUND: Little information is available on the application of marker-trait association (MTA) analysis for traits related to drought tolerance in smooth bromegrass. The objectives of this study were to identify marker loci associated with important agronomic traits and drought tolerance indices as well as fining stable associations in a diverse panel of polycross derived genotypes of smooth bromegrass. Phenotypic evaluations were performed at two irrigation regimes (normal and deficit irrigation) during 2 years; and association analysis was done with 626 SRAP markers. RESULTS: The results of population structure analysis identified three main subpopulations possessing significant genetic differences. Under normal irrigation, 68 and 57 marker-trait associations were identified using general linear model (GLM) and mixed linear mode1 (MLM), respectively. While under deficit irrigation, 61 and 54 markers were associated with the genes controlling the studied traits, based on these two models, respectively. Some of the markers were associated with more than one trait. It was revealed that markers Me1/Em5-11, Me1/Em3-15, and Me5/Em4-7 were consistently linked with drought-tolerance indices. CONCLUSION: Following marker validation, the MTAs reported in this panel could be useful tools to initiate marker-assisted selection (MAS) and targeted trait introgression of smooth bromegrass under normal and deficit irrigation regimes, and possibly fine mapping and cloning of the underlying genes and QTLs.

Transcriptomic resources for prairie grass (Bromus catharticus): expressed transcripts, tissue-specific genes, and identification and validation of EST-SSR markers.

BACKGROUND: Prairie grass (Bromus catharticus) is a typical cool-season forage crop with high biomass production and fast growth rate during winter and spring. However, its genetic research and breeding has remained stagnant due to limited available genomic resources. The aim of this study was to generate large-scale genomic data using high-throughput transcriptome sequencing, and perform a preliminary validation of EST-SSR markers of B. catharticus. RESULTS: Eleven tissue samples including seeds, leaves, and stems were collected from a new high-yield strain of prairie grass BCS1103. A total of 257,773 unigenes were obtained, of which 193,082 (74.90%) were annotated. Comparison analysis between tissues identified 1803, 3030, and 1570 genes specifically and highly expressed in seed, leaf, and stem, respectively. A total of 37,288 EST-SSRs were identified from unigene sequences, and more than 80,000 primer pairs were designed. We synthesized 420 primer pairs and selected 52 ones with high polymorphisms to estimate genetic diversity and population structure in 24 B. catharticus accessions worldwide. Despite low diversity indicated by an average genetic distance of 0.364, the accessions from South America and Asia and wild accessions showed higher genetic diversity. Moreover, South American accessions showed a pure ancestry, while Asian accessions demonstrated mixed internal relationships, which indicated a different probability of gene flow. Phylogenetic analysis clustered the studied accessions into four clades, being consistent with phenotypic clustering results. Finally, Mantel analysis suggested the total phenotypic variation was mostly contributed by genetic component. Stem diameter, plant height, leaf width, and biomass yield were significantly correlated with genetic data (r > 0.6, P < 0.001), and might be used in the future selection and breeding. CONCLUSION: A genomic resource was generated that could benefit genetic and taxonomic studies, as well as molecular breeding for B. catharticus and its relatives in the future.

Genetic analysis of Bromus tectorum (Poaceae) in the Mediterranean region: biogeographical pattern of native populations.

Genetic diversity within and among 42 native populations of Bromus tectorum (cheatgrass) was characterized within two regions, the eastern Mediterranean and the western Mediterranean. Two hypotheses were tested for the genetic diversity of these populations: (1) populations from the eastern Mediterranean are more genetically diverse compared with populations to the west, a potential consequence of the species' westward dispersal with the spread of agriculture, and (2) populations across the Mediterranean contain comparable genetic diversity but display high genetic differentiation, a potential consequence of both regions having served as refugia during glacial advances in the late Quaternary Period. Populations in the eastern Mediterranean possess 16 polymorphic loci and 37 multilocus genotypes. In contrast, populations from the western Mediterranean include a subset of these polymorphic loci (9) and fewer multilocus genotypes (19), consistent with the dispersal of B. tectorum with the east-west Holocene spread of agriculture. Among the 19 multilocus genotypes identified in populations from the western Mediterranean, 13 are undetected among eastern Mediterranean populations. Average genetic diversity within populations from the eastern Mediterranean is nonetheless comparable to the genetic diversity in populations from the Iberian Peninsula, whereas diversity is the lowest in the populations from southern France. Our results suggest a prominent role for agriculture in the grass's western spread, although glacial history and environmental heterogeneity also could have influenced the grass's genetic diversity. The exceptionally high level of self-pollination (>99%) in B. tectorum has contributed to preserving the genetic signature associated with the species' biogeographical history across the Mediterranean region.

Nitrogen addition, not heterogeneity, alters the relationship between invasion and native decline in California grasslands.

The presence of invasive species reduces the growth and performance of native species; however, the linear or non-linear relationships between invasive abundance and native population declines are less often studied. We examine how the amount and spatial distribution of experimental N deposition influences the relationship between non-native, invasive annual grass abundance (Bromus hordeaceus and Bromus diandrus) and a dominant, native perennial grass species (Stipa pulchra) in California. We hypothesized that native populations would decline as invasion increased, and that high nitrogen availability would cause native species to decline at lower invasion levels. We predicted that the rate of population decline would be slower in heterogeneous, compared to homogeneous, environments. We employed a field experiment that manipulated the amount and spatial heterogeneity of N addition across a range of invasive/native-dominated communities. There were strong negative and non-linear associations between level of invasion and S. pulchra proportional change (PC). Stipa pulchra PC was more negative and seedling survival was lower when N was added, and the negative effects of N addition on PC became larger in the final year of the study when S. pulchra had the largest declines. There was not strong evidence showing reduced competition in heterogeneous, compared to homogeneous, N treatments. Soil moisture was similar between S. pulchra and B. hordeaceus plots under ambient N, but B. hordeaceus under added N reduced soil moisture. Under N addition, Bromus spp. take up N earlier, reduce soil moisture, and create dry conditions in which S. pulchra declines.

Phytochemical screening and biological activities of Bromus pectinatus Thunb.

The present research study investigates the phytochemical and pharmacological importance of Bromus pectinatus. Qualitative phytochemical analysis of this plant was carried out to use standard method for the presence of various bioactive constituents. Results showed the ethanolic extract contain natural product such as steroids, alkaloids, tannins, coumarin, saponins, flavonoids and phenols. These compounds play a key role to reducing various disease and microbial inhibition. The ethanolic extract also showed the antimicrobial and antifugal activity against different pathogenic bacterial strains e.g Escherichia coli, Micrococus leutus, Protus vulgarus, and Kelebsela pneumona and three fungal strains Aspergillus fumigatus, Aspergillus flavous, Aspergillus niger. The antioxidant assay was performed as % inhibition of DPPH (1, 1-diphenyl-2-picryl-hydrazyl) free radicals. The plant extract has more antioxidant activity as compared to ascorbic acid. The maximum concentration (800µg/ml) is the most effective of all. The plant extract showed the high cytotoxicity activity against Brine shrimp. Moreover, the plant extract exhibited allelopathic effect on different growth parameters of wheat plant mostly at higher concentration. These results indicate that the BPEE have a potential broad-spectrum antimicrobial, cytotoxic, antioxidant and phytotoxic activity due to the presence of bioactive compounds.

Differential stoichiometric homeostasis and growth in two native and two invasive C3 grasses.

Global changes interact with plant invasions by differentially impacting native and invasive species. For example, invasive plants often benefit from eutrophication to a greater degree than native plants. While this is well-documented, a broad, trait-based explanation for this phenomenon is lacking. Recent research shows that stoichiometric homeostasis predicts plant species responses to eutrophication and drought, but this research has not been extended into an invasion ecology paradigm. We tested the hypotheses that stoichiometric homeostasis would differ between native and invasive plants, that expressed levels of stoichiometric homeostasis would respond to water availability, and that differences in stoichiometric homeostasis would match differences in growth. In a nutrient and water manipulation study, we found that stoichiometric homeostasis differed between native grasses (Elymus canadensis and Pascopyrum smithii) and invasive grasses (Agropyron cristatum and Bromus inermis), that differences in stoichiometric homeostasis matched differences in growth in well-watered grasses, and that expressed levels of stoichiometric homeostasis were stable across the water supply treatments. These results suggest that invasive plants maintain growth advantages over native plants in eutrophic conditions because of differential homeostatic requirements. We argue that stoichiometric homeostasis is therefore a useful functional trait to explain and predict differential native and invasive plant responses to global change.

Differences in growth-economics of fast vs. slow growing grass species in response to temperature and nitrogen limitation individually, and in combination.

BACKGROUND: Fast growing invasive alien species are highly efficient with little investment in their tissues. They often outcompete slower growing species with severe consequences for diversity and community composition. The plant economics trait-based approach provides a theoretical framework, allowing the classification of plants with different performance characteristics. However, in multifaceted background, this approach needs testing. The evaluation and prediction of plant performance outcomes in ecologically relevant settings is among the most pressing topics to understand and predict ecosystem functioning, especially in a quickly changing environment. Temperature and nutrient availability are major components of the global environmental change and this study examines the response of growth economic traits, photosynthesis and respiration to such changes for an invasive fast-growing (Bromus hordaceus) and a slow-growing perennial (Bromus erectus) grass species. RESULTS: The fully controlled growth chamber experiment simulated temperature-and changes in nitrogen availability individually and in combination. We therefore provide maximum control and monitoring of growth responses allowing general growth trait response patterns to be tested. Under optimal nitrogen availability the slow growing B. erectus was better able to handle the lower temperatures (7 °C) whilst both species had problems at higher temperatures (30 °C). Stresses produced by a combination of heat and nutrient availability were identified to be less limiting for the slow growing species but the combination of chilling with low nutrient availability was most detrimental to both species. CONCLUSIONS: For the fast-growing invader B. hordeaceus a reduction of nitrogen availability in combination with a temperature increase, leads to limited growth performance in comparison to the slow-growing perennial species B.erectus and this may explain why nutrient-rich habitats often experience more invasion than resource-poor habitats.

Infection of the Native California Grass, Bromus carinatus, by Fusarium circinatum, the Cause of Pitch Canker in Pines.

At Point Reyes National Seashore in California, Fusarium circinatum, the causal agent of pitch canker in pines, was isolated from Pinus muricata, the California native grass, Bromus carinatus, and the introduced grass, Holcus lanatus. All grass plants from which F. circinatum was isolated were symptomless. Pathogenicity of grass isolates was confirmed by inoculation of P. radiata trees, which developed symptoms similar to trees inoculated with a pine isolate of F. circinatum. Isolates from grasses were somatically compatible with isolates recovered from symptomatic pines. B. carinatus grown in a growth chamber was inoculated with a green fluorescent protein-expressing strain of F. circinatum. Segments of inoculated leaves were incubated in moist chambers; after 1 to 2 days, sporulating hyphae were observed growing from leaf tissue. Spores of F. circinatum removed from B. carinatus leaves were confirmed to be fluorescent when illuminated with ultraviolet light. These results raise the possibility that B. carinatus cryptically infected by F. circinatum may be a source of propagules capable of infecting pines.

Biochemical and genetic polymorphism of Bromopsis inermis populations under chronic radiation exposure.

MAIN CONCLUSION: For the subsequent assessment of the genetic mechanisms responsible for the resistance of plants to chronic irradiation, the analysis of RAPD-cDNA with the subsequent isolation, cloning, and sequencing of expressed polymorphic sequences is a promising technique. A study was conducted on Bromopsis inermis populations that have been growing for a long time in the EURT area. Using RAPD primers, we studied the genetic spectra of plants. In analysing the UPGMA algorithm, we identified two well-distinguishable clusters with a high level of bootstrap support (> 85%): background samples hit the first, and impact samples hit the second. Our data indicate a decrease in diversity in the most polluted population, as well as the appearance of new alleles in chronically irradiated samples of the B. inermis. Smooth brome seedlings were characterised by the content of anthocyanins, comparable with other types of cereals. In the gradient of chronic irradiation, the relative content of anthocyanins was not significantly changed. For the first time, the partial nucleotide sequences of the key genes of anthocyanin biosynthesis (Chi and F3h) in the brome were determined, these sequences were found to be 191 and 356 bp in length, respectively, and were cloned and sequenced. Three copies of the Chi gene were identified in the B. inermis genome. One copy (BiChi-1) clustered with the sequences of the Aegilops tauschii gene (D genome), and the other two copies (BiChi-2 and BiChi-3) formed a separate cluster in the Pooideae subfamily adjacent to Hordeum vulgare. In the copy of BiChi-1, a complete deletion of intron 1 was detected. For the F3h gene, one copy of the B. inermis gene was obtained, which forms a separate branch in the subfamily Pooideae.

Importance of considering soils in seed transfer zone development: evidence from a study of the native Bromus marginatus.

Seed transfer zones, which define the geographical relationship between adaptive traits and environmental factors, are increasingly used to determine the source populations that can be combined in restoration and revegetation. Climatic variables have been the most commonly used environmental data in transfer zone development, even though soils are also a primary selective force on plants. We assessed the importance of including soils in seed transfer zones using Bromus marginatus, a native grass used for restoration and revegetation in the western United States, as an example. Seeds were collected from 64 populations across Montana and Idaho and grown in a common garden for two years. We assessed among-population variation based on 11 traits related to germination rate, plant size, vigor, inflorescence number, survival, and carbon isotope discrimination (∆13 ), and used this variation to develop seed transfer zone maps using two approaches: (1) a conventional approach, using only climatic variables (climate only) and (2) an expanded approach that included soils and climatic variables (soils + climate). The most influential drivers of trait variation were factors related to soil water availability: soil order, available water content (AWC), and organic carbon levels. Populations from areas with andic soils, which have high soil AWC and soil organic carbon, had low germination, limited first-year survival, low ∆13 , and small seeds. Growing season length and winter temperatures were also predictive of trait variation. In comparison to climate-only models, soils + climate models explained 11% more variance (120% relative increase) for ∆13 and an average of 4.5% more (27% relative increase) for growth traits and survival. The transfer zone map developed using soils + climate differed from the climate-only map in both spatial pattern of ecotypic variation and number of transfer zones; the soils + climate map had more zones and a higher proportion of small (<4 km2 ) transfer zone patches, while the climate-only map had more large patches >37 km2 . Including soils in transfer zone development may identify adaptive trait variation that is obscured by large-scale differences in climate and could improve plant materials used for ecosystem management.

The study of inter-specific relationships of Bromus genus based on SCoT and ISSR molecular markers.

The genus of Bromus is one of the most important collection of rangeland plants, which are distributed in a wide range of natural areas of Iran. Interspecific relationships were evaluated in 90 accessions of 18 Bromus species based on 15 ISSR and 15 SCoT primers. SCoT markers separated the accessions better than ISSR marker. In addition, there was a high interspecific diversity between surveying germplasm. The sections of Bromus genus completely separated based on DNA molecular markers. SCoT markers could separate the accessions in each species. The primers of SC5 and SC35 from SCoT marker and UBC861, UBC857 and UBC844 primers from ISSR marker were identified as the best primers in revealing of genetic diversity between accessions. The sections of Ceratochloa, Genea, Pnigma and Bromus were monophyletic and were placed in one cluster. The section Bromus had a direct relationship with section Genea. In other words, section Ceratochloa has a direct relationship with Pnigma. B. tectorum and B. sericeus. B. sterilis had the most distance with other species in section Genea. B. squarrosus and B. japonicus had the most similarity and B. briziformis with B. danthoniae and B. scoparius with B. rechingeri had a moderate relationship in section Bromus. B. tomentosus and B. persicus had the highest similarity and B. riparius with B. biebersteinii and B. tomentellus with B. inermis had a moderate similarity in section Pnigma.

Biotic filtering of endophytic fungal communities in Bromus tectorum.

The assembly of horizontally transmitted endophytic fungi within plant tissues may be affected by "biotic filtering". In other words, only particular endophytic fungal taxa from the available inoculum pool may be able to colonize a given plant species. We tested that hypothesis in Bromus tectorum, an important invasive species in the arid, western United States. We collected seed from Bromus tectorum and sources of inoculum for endophytic fungi including soil and various kinds of plant litter at a field site in central Utah. We characterized, using Illumina sequencing, the endophytic fungal communities in the various inoculum sources, inoculated Bromus tectorum seedlings under gnotobiotic conditions with the various sources, and then characterized the communities of endophytic fungi that assembled in their roots and leaves. Different inoculum sources containing significantly different endophytic fungal communities produced complex communities of endophytic fungi in leaves and roots of Bromus tectorum. In leaves, the communities assembling from the various inoculum sources were not significantly different from each other and, in roots, they were only slightly different from each other, mainly due to variation in a single fungal OTU, Coprinopsis brunneofibrillosa. Consequently, there was significantly more variation in the structure of the communities of endophytic fungi among the inoculum sources than in the resultant endophytic fungal communities in the leaves and roots of Bromus tectorum. These results are consistent with biotic filtering playing a significant role in endophytic fungal community assembly.

The effect of consumer pressure and abiotic stress on positive plant interactions are mediated by extreme climatic events.

Environmental extremes resulting from a changing climate can have profound implications for plant interactions in desert communities. Positive interactions can buffer plant communities from abiotic stress and consumer pressure caused by climatic extremes, but limited research has explored this empirically. We tested the hypothesis that the mechanism of shrub facilitation on an annual plant community can change with precipitation extremes in deserts. During years of extreme drought and above-average rainfall in a desert, we measured plant interactions and biomass while manipulating a soil moisture gradient and reducing consumer pressure. Shrubs facilitated the annual plant community at all levels of soil moisture through reductions in microclimatic stress in both years and herbivore protection in the wet year only. Shrub facilitation and the high rainfall year contributed to the dominance of a competitive annual species in the plant community. Precipitation patterns in deserts determine the magnitude and type of facilitation mechanisms. Moreover, shrub facilitation mediates the interspecific competition within the associated annual community between years with different rainfall amounts. Examining multiple drivers during extreme climate events is a challenging area of research, but it is a necessary consideration given forecasts predicting that these events will increase in frequency and magnitude.

Maternal experience and soil origin influence interactions between resident species and a dominant invasive species.

Invasive species dominance in invaded communities may not be long-lasting due to regulatory processes, such as plant-soil feedbacks and neighboring species adaptation. Further, the change in species competitive ability may be contingent upon neighbor identity (i.e., specialized response) or consistent across neighbors (i.e., generalized response). Specialized responses can facilitate overall coexistence, while generalized responses may result in competitive exclusion. We set up a greenhouse experiment to test, in three species, the effect of soil conditions (non-invaded vs. invaded soil) and maternal experience (offspring of maternal plants from invaded vs. non-invaded areas) on species competitive ability against the invader Bromus inermis and conspecifics. If changes in species competitive ability against B. inermis were also evident when interacting with conspecifics, it would suggest a generalized increased/decreased competitive ability. Maternal experience resulted in reduced suppression of B. inermis in the three species and no change in tolerance. On the other hand, tolerance to B. inermis was enhanced when plants grew in soil from invaded areas, compared to non-brome soil. Importantly, both the decreased suppression due to maternal experience with B. inermis and the increased tolerance in invaded soil appear to be invader specific, as no such effects were observed when interacting with conspecifics. Specialized responses should facilitate coexistence, as no individual/species is a weaker or stronger competitor against all other neighbors or under all local soil conditions. Further, the negative plant-soil feedback for B. inermis should facilitate native species recovery in invaded areas and result in lower B. inermis performance and dominance over time.