Analysis of riparian vegetation age structure among the forest land owners of the central Oregon Cascades

Vegetation along the banks of mountain streams in the western OregonCascades comprises the transition zone between land and water basedecosystems, and as such, is a vitally important and unique natural resource.Forestry is a major land use in this region, and harvesting riparian vegetationhas serious and well documented impacts on natural ecological andhydrological processes. In order to protect riparian vegetation, "buffer strips"are often required by the presiding management agency. However, buffer stripmanagement regulations and enforcement varies substantially among themany owners of forest land in the region. Given the substantial differences inforest management practices among owners that result in part from differingforest practice regulations that apply, it was unclear what the general ecologicalcondition of riparian vegetation was. This study examined the forest standstructure and age characteristics, as identified from Landsat Thematic Mapperimagery, among five different land ownership classes. The study alsoexamined the pattern of change in the occurrence of old-growth conifers thatoccurred with increasing lateral distance from the stream, across various landownership classes.: It was found that there was typically a predominance ofyounger mixed open canopy riparian conditions on low elevation privateindustrial and interspersed federal lands. In contrast, older conifers tendeddominate riparian vegetation on higher elevation federal lands. Furthermore,it was found that change from an older to younger seral stage with increasinglateral distance from the stream tended to occur more rapidly on low elevationprivate industrial and interspersed federal lands.
This study provides insight about how the condition of riparian vegetationcorrelated to the corresponding ownership or management regime. Vegetationinventories across large regions such as the study area have only recentlybecome feasible with advances in remote sensing technology, digital imageprocessing techniques, and geographic information systems. The employmentof these new technologies has. introduced a scale of investigation which enableslandscape scale patterns, processes, and human influences on riparian systemsto be better understood.