Graduate Thesis Or Dissertation
 

Influence of cow age/experience and landscape thermal regimes on distribution and grazing patterns of cattle in northeastern Oregon mixed conifer forested rangelands

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  • Two studies were conducted to determine the factors influencing distribution of cattle on northeastern Oregon mixed-conifer forested rangelands. The objective of the first study was the quantification of differences in distribution of cattle of different ages. Beginning in 1991, and continuing through 2001, radio telemetry collars were placed on a minimum of 30 cattle per year, prior to turnout. Cattle graze the forest from approximately 15 Jun until 15 Oct each year, and were grouped into four age classes: two and three year old cattle (group 1), four and five year old cattle (group 2), six and seven year old cattle (group 3), and cattle eight years of age and older (group 4). The objective of the second study was to determine differences in landscape thermal regimes between riparian and upland areas. Ambient and "black body" thermal probes were placed in a grid pattern in riparian and upland areas at a height of one meter (mid height of a cow), to encompass the entire pasture. For study 1, all groups of cattle preferred areas with shallow slopes (P<0.05), westerly aspects (P<0.05). All age classes of cattle also preferred areas farther from water than the mean distance to water in the pasture (P<0.05) as well as areas with higher quantities of forage (kg/ha) than the mean value of forage production for the pasture (P<0.05). Cattle in age classes two, three and four selected areas with lower percent canopy closure of trees greater than 12 cm diameter, breast height (dbh), than the mean value for the pasture (P<0.05) Cattle in age class one selected for areas of lower elevation and slightly steeper slopes than cattle in age class four (P<0.05). Cattle in age class two were not affected by slope or elevation in their distribution (P<0.05). Cattle in age class three were not influenced by elevation in their distribution, but selected areas of the pasture with shallower slopes (P<0.05). For the second study, the trial was conducted from 5 Aug to 25 Sep in 2001, and from 15 Jul to 1 Sep in 2002. Year was found to be significant (P<0.0001), therefore results from each year were analyzed separately. Each six week grazing period was divided into three-week intervals, and deemed early and late season for each year. Season was found to be highly significant (P<0.0001), and therefore analyzed separately within each year. Least significant means were utilized to determine differences in temperatures. Differences were considered significant at the P<0.05 level for all analysis. Thermal probes were divided into two types within two areas; ambient and blackball, within riparian and upland areas. Analysis conducted examined the differences between riparian and upland ambient and blackball thermal probes. Area and type of probe were both highly significant (P<0.0001) for all classifications, however, there was not an area by type interaction.
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