Graduate Thesis Or Dissertation


Phytosociology of the ponderosa pine type on pumice soils in the Upper Williamson River Basin, Klamath County, Oregon Public Deposited

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  • The study was conducted over approximately 191,000 acres in central Klamath County, Oregon. The research had three objectives: first, to describe and classify the seral and near-climax vegetation by using polyclimax principles; secondly, to determine the southern extension of five plant associations and one plant associes as previously described by C. T. Dyrness within the Weyerhaeuser Antelope Unit; and thirdly, to determine the inherent variability of these and other plant communities on young pumice soils over various elevation and relief patterns. The sampling was limited to those soils derived from aerially deposited pumice of Mt. Mazama origin. These included the widely distributed Lapine soil series and the less prevalent Longbell and Shanahan soil series. Their profiles are characterized by an A00, Al, AC, C, and D horizon sequence. A qualitative reconnaissance method permitted the gathering of vegetation, soil and physiographic data from a large number of variable-sized sample locations. These locations were statified to obtain a homogeneous vegetation-soil sampling unit. The association table was used to synthesize the analytical stand data into units of similar ecology. The mechanics of association table construction are described. The Pinus ponderosa/Purshia tridentata, the Pinus ponderosa/Purshia tridentata/Festuca idahoensis, the Pinus ponderosa/Purshia tridentata-Arctostaphylos parryana var. pinetorum, the Pinus ponderosa/Ceanothus velutinus-Purshia tridentata, the Pinus ponderosa/Arctostaphylos parryana var. pinetorum-Ceanothus velutinus and the Abies concolor/Ceanothus velutinus association plus the Pinus ponderosa/Ceanothus velutinus associes are defined and characterized as they occur in the study area. Factor compensation plays a significant role in determining the location of these classification units since any single plant community may occur over several different soil and physiographic situations. The appearance of these associations over the landscape is presently determined by the young soils and the local physiographic features. Therefore, their representative stands are designated as edaphic or topo-edaphic climaxes depending upon the location of these stands in relation to the typical elevational range of the association. The Pinus ponderosa/Ceanothus velutinus associes is considered to be an early successional stage of the Abies concolor/Ceanothus velutinus association as evidenced by the rapid encroachment in the Pinus ponderosa/Ceanothus velutinus understory of mesic-tending tree and herbaceous species. In addition, the characteristic species which are common to both communities express similar presence and dominance values, and their physical environments are similar. Heavy seed pressure from mesic species on locally favorable, micro-environments permit fragmentary expressions of the Abies concolor/Ceanothus velutinus association to appear in the adjacent ecosystems representative of more xeric-tending effective environments. The variability in the species' presence and relative dominance as they occur among and within ecological units can be partially explained by the species' autecological requirements in relation to the physical environments typical of each ecological unit. The influence of an effective environment upon some species is reflected in the growth form, vigor and phenology of these species and their competitive relationships to other species in the stand. The utilization of this ecological knowledge is related to the timber, range and wildlife resources of the Upper Williamson River Basin. As emphasized, however, effective resource management is achieved only by an understanding of the plant and animal environment, a realization of the biological principles related to these environments, and the economical regulation of resource use within the framework of these biological limitations.
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