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Susan E. Meyer - One of the best experts on this subject based on the ideXlab platform.
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Niche specialization in Bromus Tectorum seed bank pathogens
Seed Science Research, 2018Co-Authors: Susan E. Meyer, J. Beckstead, Phil S. AllenAbstract:Niche theory predicts that when two species exhibit major niche overlap, one will eventually be eliminated through competitive exclusion. Thus, some degree of niche specialization is required to facilitate coexistence. We examined whether two important seed bank pathogens on the invasive winter annual grass Bromus Tectorum (cheatgrass, downy brome) exhibit niche specialization. These pathogens utilize seed resources in complementary ways. Pyrenophora semeniperda is specialized to attack dormant seeds. It penetrates directly through the seed coverings. Hyphae ramify first through the endosperm and then throughout the seed. Seed death results as the embryo is consumed. In contrast, the Fusarium seed rot pathogen ( Fusarium sp.) is specialized to attack non-dormant seeds in the early stages of germination. It cannot penetrate seed coverings directly. Instead, it responds to a cue emanating from the radicle end with directional hyphal growth and subsequent penetration at the point of radicle emergence, causing seed death. Non-dormant seeds usually escape P. semeniperda through germination even if infected because it develops more slowly than Fusarium . When water stress slows non-dormant seed germination, both P. semeniperda and Fusarium can attack and cause seed mortality more effectively. The Fusarium seed rot pathogen can sometimes reach epidemic levels and may result in B. Tectorum stand failure (‘die-off’). Stands usually re-establish from the persistent seed bank, but if P. semeniperda has also reached high levels and eliminated the seed bank, a die-off can persist indefinitely.
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Development of single‐nucleotide polymorphism markers for Bromus Tectorum (Poaceae) from a partially sequenced transcriptome
Applications in plant sciences, 2016Co-Authors: Keith R. Merrill, Susan E. Meyer, Elizabeth A. Leger, Craig E. Coleman, Katherine A. CollinsAbstract:Premise of the study: Bromus Tectorum (Poaceae) is an annual grass species that is invasive in many areas of the world but most especially in the U.S. Intermountain West. Single-nucleotide polymorphism (SNP) markers were developed for use in investigating the geospatial and ecological diversity of B. Tectorum in the Intermountain West to better understand the mechanisms behind its successful invasion. Methods and Results: Normalized cDNA libraries from six diverse B. Tectorum individuals were pooled and sequenced using 454 sequencing. Ninety-five SNP assays were developed for use on 96.96 arrays with the Fluidigm EP1 genotyping platform. Verification of the 95 SNPs by genotyping 251 individuals from 12 populations is reported, along with amplification data from four related Bromus species. Conclusions: These SNP markers are polymorphic across populations of B. Tectorum, are optimized for high-throughput applications, and may be applicable to other, related Bromus species.
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Community Ecology of Fungal Pathogens on Bromus Tectorum
Springer Series on Environmental Management, 2016Co-Authors: Susan E. Meyer, J. Beckstead, Janalynn PearceAbstract:Bromus Tectorum L. (cheatgrass or downy brome) presents a rich resource for soil microorganisms because of its abundant production of biomass, seeds, and surface litter. Many of these organisms are opportunistic saprophytes, but several fungal species regularly found in B. Tectorum stands function as facultative or obligate pathogens. These organisms interact dynamically with abiotic factors such as interannual variation in weather, with other soil microorganisms, with their hosts, and with each other to create spatially and temporally varying patterns of endemic or epidemic disease. Five principal soilborne pathogens, Ustilago bullata Berk. (head smut pathogen), Tilletia bromi (Brockm.) Nannf. (chestnut bunt pathogen), Pyrenophora semeniperda (Brittlebank & Adams) Shoemaker (black fingers of death pathogen), Fusarium Link sp. n. (Fusarium seed rot pathogen), and a new species in the Rutstroemiaceae (bleach blonde syndrome pathogen), are known to have sometimes major impacts on B. Tectorum seed bank dynamics, seedling emergence, and seed production. These pathogens exhibit niche specialization, so that they are rarely in direct competition. They sometimes interact to increase the total impact on B. Tectorum stand structure, which can result in stand failure or “die-off.” Die-offs represent areas where B. Tectorum has been controlled by natural processes, suggesting that these areas might be suitable targets for restoration. Naturally occurring fungal pathogens that can have a strong negative impact on B. Tectorum success have also been considered as candidate organisms for B. Tectorum biocontrol using an augmentative mycoherbicidal strategy.
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Identification of the Infection Route of a Fusarium Seed Pathogen into Nondormant Bromus Tectorum Seeds.
Phytopathology, 2014Co-Authors: Janalynn Franke, Brad Geary, Susan E. MeyerAbstract:ABSTRACT The genus Fusarium has a wide host range and causes many different forms of plant disease. These include seed rot and seedling blight diseases of cultivated plants. The diseases caused by Fusarium on wild plants are less well-known. In this study, we examined disease development caused by Fusarium sp. n on nondormant seeds of the important rangeland weed Bromus Tectorum as part of broader studies of the phenomenon of stand failure or “die-off” in this annual grass. We previously isolated an undescribed species in the F. tricinctum species complex from die-off soils and showed that it is pathogenic on seeds. It can cause high mortality of nondormant B. Tectorum seeds, especially under conditions of water stress, but rarely attacks dormant seeds. In this study, we used scanning electron microscopy (SEM) to investigate the mode of attack used by this pathogen. Nondormant B. Tectorum seeds (i.e., florets containing caryopses) were inoculated with isolate Skull C1 macroconidia. Seeds were then exposed...
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Exposure to Low Water Potentials and Seed Dormancy Favour the Fungus in the Pyrenophora semeniperda-Bromus Tectorum Pathosystem
Plant Protection Science, 2013Co-Authors: Heather Finch-boekweg, Phil S. Allen, Susan E. MeyerAbstract:Finch H., Allen P., Meyer S. (2013): Exposure to low water potentials and seed dormancy favour the fungus in the Pyrenophora semeniperda–Bromus Tectorum pathosystem. Plant Protect. Sci., 49 (Special Issue): S15–S20. In semi-arid regions of the United States, Pyrenophora semeniperda kills seeds of the winter annual Bromus Tectorum . We report on pathosystem outcomes under manipulated water potential and temperature environments commonly observed within semi-arid environments for dormant and non-dormant seeds. We propose a range of outcomes for infected seeds. During summer, seeds remain dormant and are killed across a range of water potentials. During au tumn, seeds survive by rapidly germinating or are killed if radicle emergence is delayed by intermittent hydration. In winter/spring, secondarily dormant seeds can be killed by the fungus. The only likely scenarios where seeds escape death include absence of infection (autumn, spring, or following autumn, germination) or infection in autumn when seeds germinate rapidly.
Thomas H. Deluca - One of the best experts on this subject based on the ideXlab platform.
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fire native species and soil resource interactions influence the spatio temporal invasion pattern of Bromus Tectorum
Ecography, 2008Co-Authors: Michael J. Gundale, Steve Sutherland, Thomas H. DelucaAbstract:Bromus Tectorum (cheatgrass) is an invasive annual that occupies perennial grass and shrub communities throughout the western United States. Bromus Tectorum exhibits an intriguing spatio-temporal pattern of invasion in low elevation ponderosa pine Pinus ponderosa/bunchgrass communities in western Montana where it forms dense rings beneath solitary pines following fire. This pattern provides a unique opportunity to investigate several indirect effects of native vegetation that influence the invasion pattern of B. Tectorum, and specifically how native species, disturbance, and soil resources interact to influence the spatio-temporal pattern of invasion. We established four replicate field sites, each containing burned-tree, burned-grass, unburned-tree, and unburned-grass sampling locations, and initiated a series of field sampling and greenhouse experiments utilizing these locations. The objective of our first greenhouse experiment was to identify whether belowground factors contributed to the pattern of B. Tectorum biomass observed in these field locations. This experiment generated a B. Tectorum biomass response that was nearly identical to the invasion pattern observed in the field, suggesting further investigation of belowground factors was necessary. We measured resin-sorbed NH + 4 and NO - 3 during one generation of B. Tectorum, and measured a suite of P fractions through a sequential extraction procedure from these soils. These data revealed that a resource island of high N and P exists beneath pine trees. Through a second greenhouse experiment, we determined that N limited B. Tectorum biomass in tree soil, whereas P limited biomass in bunchgrass soil. Finally, through a germination experiment we determined that pine litter strongly inhibited B. Tectorum germination. These data suggest B. Tectorum is regulated by P in bunchgrass soil, and by N and inhibition by pine litter beneath trees, effects that are likely alleviated by fire. These data demonstrate the combined role of direct and indirect interactions between native and invasive species in regulating biological invasions.
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Fire, native species, and soil resource interactions influence the spatio‐temporal invasion pattern of Bromus Tectorum
Ecography, 2008Co-Authors: Michael J. Gundale, Steve Sutherland, Thomas H. DelucaAbstract:Bromus Tectorum (cheatgrass) is an invasive annual that occupies perennial grass and shrub communities throughout the western United States. Bromus Tectorum exhibits an intriguing spatio-temporal pattern of invasion in low elevation ponderosa pine Pinus ponderosa/bunchgrass communities in western Montana where it forms dense rings beneath solitary pines following fire. This pattern provides a unique opportunity to investigate several indirect effects of native vegetation that influence the invasion pattern of B. Tectorum, and specifically how native species, disturbance, and soil resources interact to influence the spatio-temporal pattern of invasion. We established four replicate field sites, each containing burned-tree, burned-grass, unburned-tree, and unburned-grass sampling locations, and initiated a series of field sampling and greenhouse experiments utilizing these locations. The objective of our first greenhouse experiment was to identify whether belowground factors contributed to the pattern of B. Tectorum biomass observed in these field locations. This experiment generated a B. Tectorum biomass response that was nearly identical to the invasion pattern observed in the field, suggesting further investigation of belowground factors was necessary. We measured resin-sorbed NH + 4 and NO - 3 during one generation of B. Tectorum, and measured a suite of P fractions through a sequential extraction procedure from these soils. These data revealed that a resource island of high N and P exists beneath pine trees. Through a second greenhouse experiment, we determined that N limited B. Tectorum biomass in tree soil, whereas P limited biomass in bunchgrass soil. Finally, through a germination experiment we determined that pine litter strongly inhibited B. Tectorum germination. These data suggest B. Tectorum is regulated by P in bunchgrass soil, and by N and inhibition by pine litter beneath trees, effects that are likely alleviated by fire. These data demonstrate the combined role of direct and indirect interactions between native and invasive species in regulating biological invasions.
Michael J. Gundale - One of the best experts on this subject based on the ideXlab platform.
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fire native species and soil resource interactions influence the spatio temporal invasion pattern of Bromus Tectorum
Ecography, 2008Co-Authors: Michael J. Gundale, Steve Sutherland, Thomas H. DelucaAbstract:Bromus Tectorum (cheatgrass) is an invasive annual that occupies perennial grass and shrub communities throughout the western United States. Bromus Tectorum exhibits an intriguing spatio-temporal pattern of invasion in low elevation ponderosa pine Pinus ponderosa/bunchgrass communities in western Montana where it forms dense rings beneath solitary pines following fire. This pattern provides a unique opportunity to investigate several indirect effects of native vegetation that influence the invasion pattern of B. Tectorum, and specifically how native species, disturbance, and soil resources interact to influence the spatio-temporal pattern of invasion. We established four replicate field sites, each containing burned-tree, burned-grass, unburned-tree, and unburned-grass sampling locations, and initiated a series of field sampling and greenhouse experiments utilizing these locations. The objective of our first greenhouse experiment was to identify whether belowground factors contributed to the pattern of B. Tectorum biomass observed in these field locations. This experiment generated a B. Tectorum biomass response that was nearly identical to the invasion pattern observed in the field, suggesting further investigation of belowground factors was necessary. We measured resin-sorbed NH + 4 and NO - 3 during one generation of B. Tectorum, and measured a suite of P fractions through a sequential extraction procedure from these soils. These data revealed that a resource island of high N and P exists beneath pine trees. Through a second greenhouse experiment, we determined that N limited B. Tectorum biomass in tree soil, whereas P limited biomass in bunchgrass soil. Finally, through a germination experiment we determined that pine litter strongly inhibited B. Tectorum germination. These data suggest B. Tectorum is regulated by P in bunchgrass soil, and by N and inhibition by pine litter beneath trees, effects that are likely alleviated by fire. These data demonstrate the combined role of direct and indirect interactions between native and invasive species in regulating biological invasions.
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Fire, native species, and soil resource interactions influence the spatio‐temporal invasion pattern of Bromus Tectorum
Ecography, 2008Co-Authors: Michael J. Gundale, Steve Sutherland, Thomas H. DelucaAbstract:Bromus Tectorum (cheatgrass) is an invasive annual that occupies perennial grass and shrub communities throughout the western United States. Bromus Tectorum exhibits an intriguing spatio-temporal pattern of invasion in low elevation ponderosa pine Pinus ponderosa/bunchgrass communities in western Montana where it forms dense rings beneath solitary pines following fire. This pattern provides a unique opportunity to investigate several indirect effects of native vegetation that influence the invasion pattern of B. Tectorum, and specifically how native species, disturbance, and soil resources interact to influence the spatio-temporal pattern of invasion. We established four replicate field sites, each containing burned-tree, burned-grass, unburned-tree, and unburned-grass sampling locations, and initiated a series of field sampling and greenhouse experiments utilizing these locations. The objective of our first greenhouse experiment was to identify whether belowground factors contributed to the pattern of B. Tectorum biomass observed in these field locations. This experiment generated a B. Tectorum biomass response that was nearly identical to the invasion pattern observed in the field, suggesting further investigation of belowground factors was necessary. We measured resin-sorbed NH + 4 and NO - 3 during one generation of B. Tectorum, and measured a suite of P fractions through a sequential extraction procedure from these soils. These data revealed that a resource island of high N and P exists beneath pine trees. Through a second greenhouse experiment, we determined that N limited B. Tectorum biomass in tree soil, whereas P limited biomass in bunchgrass soil. Finally, through a germination experiment we determined that pine litter strongly inhibited B. Tectorum germination. These data suggest B. Tectorum is regulated by P in bunchgrass soil, and by N and inhibition by pine litter beneath trees, effects that are likely alleviated by fire. These data demonstrate the combined role of direct and indirect interactions between native and invasive species in regulating biological invasions.
Phil S. Allen - One of the best experts on this subject based on the ideXlab platform.
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Niche specialization in Bromus Tectorum seed bank pathogens
Seed Science Research, 2018Co-Authors: Susan E. Meyer, J. Beckstead, Phil S. AllenAbstract:Niche theory predicts that when two species exhibit major niche overlap, one will eventually be eliminated through competitive exclusion. Thus, some degree of niche specialization is required to facilitate coexistence. We examined whether two important seed bank pathogens on the invasive winter annual grass Bromus Tectorum (cheatgrass, downy brome) exhibit niche specialization. These pathogens utilize seed resources in complementary ways. Pyrenophora semeniperda is specialized to attack dormant seeds. It penetrates directly through the seed coverings. Hyphae ramify first through the endosperm and then throughout the seed. Seed death results as the embryo is consumed. In contrast, the Fusarium seed rot pathogen ( Fusarium sp.) is specialized to attack non-dormant seeds in the early stages of germination. It cannot penetrate seed coverings directly. Instead, it responds to a cue emanating from the radicle end with directional hyphal growth and subsequent penetration at the point of radicle emergence, causing seed death. Non-dormant seeds usually escape P. semeniperda through germination even if infected because it develops more slowly than Fusarium . When water stress slows non-dormant seed germination, both P. semeniperda and Fusarium can attack and cause seed mortality more effectively. The Fusarium seed rot pathogen can sometimes reach epidemic levels and may result in B. Tectorum stand failure (‘die-off’). Stands usually re-establish from the persistent seed bank, but if P. semeniperda has also reached high levels and eliminated the seed bank, a die-off can persist indefinitely.
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Postdispersal Infection and Disease Development of Pyrenophora semeniperda in Bromus Tectorum Seeds
Phytopathology, 2016Co-Authors: Heather Finch-boekweg, Phil S. Allen, John S. Gardner, Brad GearyAbstract:The Ascomycete fungus, Pyrenophora semeniperda, attacks a broad range of cool-season grasses. While leaf and predispersal infection of seeds (i.e., florets containing caryopses) have been previously characterized, little is known about the pathogenesis of mature seeds following dispersal. In this study, we examined infection and disease development of P. semeniperda on dormant seeds of Bromus Tectorum. Inoculated seeds were hydrated at 20°C for up to 28 days. Disease development was characterized using scanning electron and light microscopy. P. semeniperda conidia germinated on the seed surface within 5 to 8 h. Hyphae grew on the seed surface and produced extracellular mucilage that eventually covered the seed. Appressoria formed on the ends of hyphae and penetrated through the lemma and palea, stomatal openings, and broken trichomes. The fungus then catabolized the endosperm, resulting in a visible cavity by 8 days. Pathogenesis of the embryo was associated with progressive loss of cell integrity and pro...
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Exposure to Low Water Potentials and Seed Dormancy Favour the Fungus in the Pyrenophora semeniperda-Bromus Tectorum Pathosystem
Plant Protection Science, 2013Co-Authors: Heather Finch-boekweg, Phil S. Allen, Susan E. MeyerAbstract:Finch H., Allen P., Meyer S. (2013): Exposure to low water potentials and seed dormancy favour the fungus in the Pyrenophora semeniperda–Bromus Tectorum pathosystem. Plant Protect. Sci., 49 (Special Issue): S15–S20. In semi-arid regions of the United States, Pyrenophora semeniperda kills seeds of the winter annual Bromus Tectorum . We report on pathosystem outcomes under manipulated water potential and temperature environments commonly observed within semi-arid environments for dormant and non-dormant seeds. We propose a range of outcomes for infected seeds. During summer, seeds remain dormant and are killed across a range of water potentials. During au tumn, seeds survive by rapidly germinating or are killed if radicle emergence is delayed by intermittent hydration. In winter/spring, secondarily dormant seeds can be killed by the fungus. The only likely scenarios where seeds escape death include absence of infection (autumn, spring, or following autumn, germination) or infection in autumn when seeds germinate rapidly.
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Secondary Dormancy of Seeds in Relation to the Bromus Tectorum-Pyrenophora semeniperda Pathosystem
Plant Protection Science, 2013Co-Authors: Katie Karen Hawkins, Phil S. Allen, Susan E. MeyerAbstract:Hawkins K.K., Allen P., Meyer S. (2013): Secondary dormancy of seeds in relation to the Bromus tecto rum–Pyrenophora semeniperda pathosystem. Plant Protect. Sci., 49 (Special Issue): S11–S14. Bromus Tectorum is a highly invasive annual grass. The fungal pathogen Pyrenophora semeniperda can kill a large frac tion of B. Tectorum seeds. Outcomes in this pathosystem are often determined by the speed of seed germination. In this paper we extend previous efforts to describe the pathosystem by characterising secondary dormancy acquisition of B. Tectorum . In the laboratory approximately 80% of seeds incubated at –1.0 MPa became dormant. In the field, seeds were placed in the seed bank in late autumn, retrieved monthly and dormancy status determined. The field study confirmed the laboratory results; ungerminated seeds became increasingly dormant. Our data suggest that secondary dormancy is much more likely to occur at xeric sites.
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Environmental factors influencing Pyrenophora semeniperda-caused seed mortality in Bromus Tectorum
Seed Science Research, 2012Co-Authors: Heather Finch, Phil S. Allen, Susan E. MeyerAbstract:AbstractTemperature and water potential strongly influence seed dormancy status and germination of Bromus Tectorum. As seeds of this plant can be killed by the ascomycete fungus Pyrenophora semeniperda, this study was conducted to learn how water potential and temperature influence mortality levels in this pathosystem. Separate experiments were conducted to determine: (1) if P. semeniperda can kill dormant or non-dormant seeds across a range of water potentials (0 to − 2 MPa) at constant temperature (20°C); and (2) how temperature (5–20°C) and duration at reduced water potentials (0–28 days) affect the outcome. When inoculated with the fungus at 20°C, all dormant seeds were killed, but fungal stromata appeared more quickly at higher water potentials. For non-dormant seeds, decreasing water potentials led to reduced germination and greater seed mortality. Results were similar at 10 and 15°C. Incubation at 5°C prevented stromatal development on both non-dormant and dormant seeds regardless of water potential, but when seeds were transferred to 20°C, dormant seeds evidenced high mortality. For non-dormant seeds, exposure to low water potential at 5°C resulted in secondary dormancy and increased seed mortality. Increasing incubation temperature, decreasing water potential and increasing duration at negative water potentials all led to increased mortality for non-dormant seeds. The results are consistent with field observations that pathogen-caused mortality is greatest when dormant seeds imbibe, or when non-dormant seeds experience prolonged or repeated exposure to low water potentials. We propose a conceptual model to explain the annual cycle of interaction in the Bromus Tectorum–Pyrenophora semeniperda pathosystem.
Steve Sutherland - One of the best experts on this subject based on the ideXlab platform.
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fire native species and soil resource interactions influence the spatio temporal invasion pattern of Bromus Tectorum
Ecography, 2008Co-Authors: Michael J. Gundale, Steve Sutherland, Thomas H. DelucaAbstract:Bromus Tectorum (cheatgrass) is an invasive annual that occupies perennial grass and shrub communities throughout the western United States. Bromus Tectorum exhibits an intriguing spatio-temporal pattern of invasion in low elevation ponderosa pine Pinus ponderosa/bunchgrass communities in western Montana where it forms dense rings beneath solitary pines following fire. This pattern provides a unique opportunity to investigate several indirect effects of native vegetation that influence the invasion pattern of B. Tectorum, and specifically how native species, disturbance, and soil resources interact to influence the spatio-temporal pattern of invasion. We established four replicate field sites, each containing burned-tree, burned-grass, unburned-tree, and unburned-grass sampling locations, and initiated a series of field sampling and greenhouse experiments utilizing these locations. The objective of our first greenhouse experiment was to identify whether belowground factors contributed to the pattern of B. Tectorum biomass observed in these field locations. This experiment generated a B. Tectorum biomass response that was nearly identical to the invasion pattern observed in the field, suggesting further investigation of belowground factors was necessary. We measured resin-sorbed NH + 4 and NO - 3 during one generation of B. Tectorum, and measured a suite of P fractions through a sequential extraction procedure from these soils. These data revealed that a resource island of high N and P exists beneath pine trees. Through a second greenhouse experiment, we determined that N limited B. Tectorum biomass in tree soil, whereas P limited biomass in bunchgrass soil. Finally, through a germination experiment we determined that pine litter strongly inhibited B. Tectorum germination. These data suggest B. Tectorum is regulated by P in bunchgrass soil, and by N and inhibition by pine litter beneath trees, effects that are likely alleviated by fire. These data demonstrate the combined role of direct and indirect interactions between native and invasive species in regulating biological invasions.
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Fire, native species, and soil resource interactions influence the spatio‐temporal invasion pattern of Bromus Tectorum
Ecography, 2008Co-Authors: Michael J. Gundale, Steve Sutherland, Thomas H. DelucaAbstract:Bromus Tectorum (cheatgrass) is an invasive annual that occupies perennial grass and shrub communities throughout the western United States. Bromus Tectorum exhibits an intriguing spatio-temporal pattern of invasion in low elevation ponderosa pine Pinus ponderosa/bunchgrass communities in western Montana where it forms dense rings beneath solitary pines following fire. This pattern provides a unique opportunity to investigate several indirect effects of native vegetation that influence the invasion pattern of B. Tectorum, and specifically how native species, disturbance, and soil resources interact to influence the spatio-temporal pattern of invasion. We established four replicate field sites, each containing burned-tree, burned-grass, unburned-tree, and unburned-grass sampling locations, and initiated a series of field sampling and greenhouse experiments utilizing these locations. The objective of our first greenhouse experiment was to identify whether belowground factors contributed to the pattern of B. Tectorum biomass observed in these field locations. This experiment generated a B. Tectorum biomass response that was nearly identical to the invasion pattern observed in the field, suggesting further investigation of belowground factors was necessary. We measured resin-sorbed NH + 4 and NO - 3 during one generation of B. Tectorum, and measured a suite of P fractions through a sequential extraction procedure from these soils. These data revealed that a resource island of high N and P exists beneath pine trees. Through a second greenhouse experiment, we determined that N limited B. Tectorum biomass in tree soil, whereas P limited biomass in bunchgrass soil. Finally, through a germination experiment we determined that pine litter strongly inhibited B. Tectorum germination. These data suggest B. Tectorum is regulated by P in bunchgrass soil, and by N and inhibition by pine litter beneath trees, effects that are likely alleviated by fire. These data demonstrate the combined role of direct and indirect interactions between native and invasive species in regulating biological invasions.
