Virus infection and grazing exert counteracting influences on survivorship of native bunchgrass seedlings competing with invasive exotics
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Authors: C. M. Malmstrom, C. J. Stoner, S. Brandenburg, and L. A. Newton
Date: 2006
Journal: Journal of Ecology
Volume: 94
Number:
Pages: 264-275
Summary of Methods: To investigate the potential significance of virus-mediated mortality for early survivorship of bunchgrass seedlings, Malmstrom et al. compared the separate and combined effects of virus infection, competition and simulated grazing in a field experiment. Although virus infection alone did not reduce first-year survivorship, it halved the survivorship of bunchgrasses competing with exotics. Within an environment in which competition strongly reduces seedling survivorship, virus infection therefore has the power to cause additional seedling mortality and alter patterns of establishment. Clipping did not reduce bunchgrass survivorship further, but doubled it and disproportionately increased survivorship of infected bunchgrasses. This study suggests that barley and cereal yellow dwarf viruses can be potentially powerful agents in California grasslands. The findings demonstrate the potential significance of multitrophic interactions in virus ecology. Although sometimes treated as plant predators, viruses and herbivores may exert influences that are distinctly different, even counteracting.
Article Summary / Main Points: None
Vegetation Types:
MLRA Ecoregions:
Agrovoc Control Words: Riparian zones Rangelands Wildlife
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: apparent competition, barley yellow dwarf virus, invasive species, grazing, pathogen, native bunchgrasses
Annotation: The authors infected two species of young bunchgrass seedlings that showed different sensitivity to barely and cereal yellow dwarf virus infection, subjected them to competition with 3 different densities of exotic annuals crossed with 2 clipping treatments to monitor their growth and survivorship.,To simulate herbivory resulting from non-selective rotational grazing by sheep or cattle, one-half of the subplots (both competition subplots and those with bunchgrasses alone) were clipped three times in spring, beginning immediately after row covers were removed. At each clipping, all plants were clipped to an equal height. Plots were clipped to 5 cm on February 21 and on March 12-14, and to 7.6 cm on April 4.
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