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Historical vegetation of central southwest Oregon, based on GLO survey notes : final report to USDI Bureau of Land Management, Medford District

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  • Final report to USDI Bureau of Land Management. Medford District, Oregon.
  • Historical vegetation at the time of European settlement is of great interest to both the public and land managers, but is poorly documented. One source of data are the earliest land survey records of the General Land Office (GLO). Rectangular township surveys in Southwest Oregon were initiated in the mid 1850’s as settlers began to claim homesteads in the Bear Creek Valley surrounding what is now Medford. We examined GLO land survey field notes and plats (maps) accompanying the surveys, transcribed GLO landscape data into an Access database, and classified the data set into very general vegetation types for mapping. About 89 vegetation types (subclasses) were described for mapping historic vegetation, distinguished by major differences in plant composition and topographic features. Tree density was estimated from section line descriptions and witness tree spacing at corners, and was used to classify stands into tree classes. These types then were combined into broad “Vegetation Classes” for mapping (i.e. savanna, shrubland, forest, prairie). Classifying and mapping historical vegetation occurred on about 418,500 acres in an earlier OSU study, and about 720,700 acres in this BLM study, located in Jackson and Josephine Counties. The authors merged results from these adjacent GLO studies, expanding the coverage to approximately 1.14 million acres (49 townships). Modern soil surveys of the study area helped the authors interpret GLO data and draw vegetation boundaries. About 44% of the landscape was closed upland forest, 41% woodland, 1.4% riparian forest, 2% oak or conifer savanna, 1% shrublands, and 11% bottomland meadow or upland prairie. Forest types ranged from moist, mixed conifer uplands to dry valley ponderosa pine-hardwood grassland. Large areas of prairie and mixed oak-conifer woodland dominated many low elevation locations on plains, foothills, and especially clayey terraces or southern slopes near what is now Medford. Nearly 115 plant species or plant groups were identified by the surveyors, mostly trees and shrubs. Some were misidentified and not easily interpreted by the authors when archaic names were used by the surveyors. Grazing quality was frequently noted as surveyors attempted to describe land productivity for livestock. Historic baseline plant data is presented for broad landscape transects and sometimes by topographic positions, but is limited by the sketchy nature of the original surveyor notes. Nearly 350 homestead parcels of various sizes were claimed in the study, as identified in GLO survey notes and on Donation Land Claim maps, showing how quickly settlement occurred in the study area after gold was discovered in 1851. Most early homesteads included prairie or oak savanna, which was open and more easily converted to farmland or pasture. Early saw mills, grist mills, fields, roads, water diversions and major Indian trails were also identified and transcribed from the GLO records.
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  • Hickman, O. Eugene and John A. Christy. 2011. Historical Vegetation of Central Southwest Oregon Based on GLO Survey Notes. Final Report to USDI Bureau of Land Management. Medford District, Oregon. 124 pp.
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  • Joint Fire Science Council (BLM study, 2007-2009)
  • Oregon Watershed Enhancement Board (OSU study, 2002-2003)
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