The effects of collared pika grazing on alpine tundra vegetation in southwestern Yukon, Canada
grantor: University of Toronto In alpine tundra vegetation, rates of plant production were as low in 15-17 day short-term 'in situ' pika removal exclosures as they were in control, unexclosed plots. After nearly two seasons of herbivore exclusion, sites with a history of grazing had much h...
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| Format: | Thesis |
| Language: | English |
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1999
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| Online Access: | http://hdl.handle.net/1807/14084 http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ45889.pdf |
| Summary: | grantor: University of Toronto In alpine tundra vegetation, rates of plant production were as low in 15-17 day short-term 'in situ' pika removal exclosures as they were in control, unexclosed plots. After nearly two seasons of herbivore exclusion, sites with a history of grazing had much higher production than sites with no history of grazing, demonstrating an important influence of past grazing pressures. I also found that the pattern of pika grazing influence changed between two disjunct field sites separated by 40km: pikas had a detectable impact up to 7 m from talus in one site, but only up to 2 m in the other. When the effect of grazing on leaf demography for three species was examined, grazing history, rather than current season grazing, was found to affect growth traits. In a common garden experiment, grazing history affected plant response to simulated pika herbivory in a sedge but not in a composite. In all three experiments, grazing history was found to have a profound and very important impact on plant growth. M.Sc. |
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