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Bromus tectorum is a dominant winter annual weed in cold deserts of western North America. We followed patterns of seed carry-over and abundance of the pathogen Pyrenophora semeniperda over 5 years at B. tectorum-dominated shadscale (Atriplex confertifolia) and sagebrush (Artemisia tridentata) sites in southern Idaho. We hypothesised that more seeds could potentially carry over at the drier shadscale site because of minimal autumn precipitation, but that P. semeniperda, a pathogen that primarily kills dormant seeds, would have more impact at the drier site, where a higher density of dormant seeds would likely be present in the early spring seedbank. Successful first-year seed carry-over was higher in years with...
Categories: Publication;
Types: Citation,
Journal Citation;
Tags: Drechslera campanulata,
Weed Research,
biological control,
cheatgrass,
dormancy, All tags...
downy brome,
drooping brome,
germination,
sagebrush,
shadscale, Fewer tags
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Long-lived desert shrubs exhibit infrequent, episodic recruitment from seed. In spite of this long time scale, selection on life history attributes that affect seedling recruitment should be strong. We studied factors affecting germination phenology and seedling establishment for Coleogyne ramosissima, a dominant shrub species in the ecotone between warm and cold deserts in western North America. We also examined ecotypic differentiation in establishment strategy in response to selection regimes in two contrasting habitats. We followed patterns of dormancy loss, germination, emergence, and survival in reciprocal field experiments at warm winter Mojave Desert and cold winter Colorado Plateau study sites. Seed germination...
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Seed gennination of Atriplex confertifolia (shadscale) has been studied sporadically since 1900, with little progress in understanding the mechanisms responsible for seed donnancy or in overcoming these obstacles for the purpose of successfully seeding shadscale in restoration projects. Most work has concentrated on the indurated bracteoles and their role in inhibiting gennination, but no conclusive evidence has been presented to show that the bracts must disintegrate to allow germination. Experiments show that moist chilling offresh seeds for 12 weeks allowed gennination of up to 66 percent offresh fruits and up to 85 percent of 3 year old fruits. No gennination occurred in unchilled fruit. A preliminary trial...
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1. Pathogen spillover occurs when disease levels for a given population are driven by transmission from a reservoir species that carries a high pathogen load. Pathogen spillover is widely documented in crop systems, but has been little studied in natural plant communities. 2. The abundant seed production of weedy species may create a scenario where spillover of a generalist seed pathogen onto less abundant seeds of native hosts is possible. The invasive annual weed cheatgrass (Bromus tectorum) is a potential reservoir species for Pyrenophora semeniperda, a multiple-host fungal seed pathogen that naturally occurs in the semi-arid western United States. 3. To investigate potential community-level consequences of spillover...
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After-ripening, the loss of dormancy under dry conditions, is associated with a decrease in mean base water potential for germination of Bromus tectorum L. seeds. After-ripening rate is a linear function of temperature above a base temperature, so that dormancy loss can be quantified using a thermal after-ripening time (TAR) model. To incorporate storage water potential into TAR, we created a hydrothermal after-ripening time (HTAR) model. Seeds from two B. tectorum populations were stored under controlled temperatures (20 or 30 �C) and water potentials (?400 to ?40 MPa). Subsamples were periodically removed from each storage treatment and incubated at 15 or 25 �C to determine germination time courses. Dormancy status...
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