Graduate Thesis Or Dissertation
 

Fire ecology and management in plant communities of Malheur National Wildlife Refuge, southeastern Oregon

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/j9602409f

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  • This research assesses prescribed burning as a habitat management technique in wetlands and associated upland communities of Malheur National Wildlife Refuge, southeastern Oregon. Experimental burns were conducted to evaluate fire behavior and effects in wetland and upland habitats, and, fire effects on Cirsium arvense. Wetland plant communities were monotypic stands of emergent macrophytes: Scirpus acutus, Sparganium eurycarpum, Carex atherodes, Juncus balticus, Eleocharis palustris. Upland communities studied included Chrysothamnus nauseosus/Elymus cinereus and Sarcobatus vermiculatus/Distichlis spicata shrub-grasslands and an Elymus triticoides mesic meadow. Burning was conducted during periods of vegetation dormancy. Stepwise multiple regression was used to evaluate the relative influence of various fuel and weather parameters on fire behavior, and, to quantify the relationship of the "best" independent variables to the response variables rate-of-spread (ROS) and flame length. Models incorporating windspeed alone, or in combination with a second variable, account for 50 to 90 percent of the variation in ROS. Successful burns were conducted with a wide range of conditions, provided the surface of fuels were dry and winds were steady. Burning prescriptions and techniques suitable for these fuel types are given. Fire effects on vegetation were measured for two years (Sarcobatus/Distichlis, one year). Vegetation response was largely insensitive to timing of burns within the dormant period. Comparisons with unburned treatments (=non-use) indicate fire significantly alters vegetation structure and community function; however, responses were often species-specific. Aboveground herbage production increased for one to two years in all but winter-burned Sparganium communities. Burning increased shoot density of rhizomatous species. Vigorous postburn sprouting-regrowth of shrubs resulted in rapid replacement of canopy cover and volume. Reproductive effort varied markedly among species and in response to fire. The observed dynamics of organic residues suggest these communities will return to preburn status after three to five years. Dormant season burning reduced relative abundance of Cirsium arvense. Changes in population structure and reproductive success, as well as increased production of associated species, indicate burning may be a useful means of halting Cirsium invasion or spread by maintaining a productive stand of native vegetation.
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