Stand Structure of Old Growth Dry Mixed Conifer Forests in the Deschutes and Ochoco National Forests.

Old-growth dry-mixed conifer forests are valued as habitats for late seral forest species, for the\ud ecosystem services and landscape diversity they provide, and for their aesthetic appeal. The\ud structure of these forests has been heavily altered by historic logging of overstory ponderosa\ud pine and Douglas-fir. Additionally, changes in fire regime have altered understory density in\ud these forests to an unknown extent. Conserving remaining stands and facilitating old-growth\ud development in disturbed stands are objectives of the Deschutes and Ochoco National Forests.\ud This investigation addressed these objectives with two separate analyses. The first analysis was\ud an accuracy assessment of the GNN forest vegetation map’s ability to predict old-growth drymixed\ud conifer structure at a site scale and at a landscape scale. This analysis determined that\ud the GNN map is an adequate tool for identifying old-growth stands at a site scale, and was highly\ud accurate at predicting dry-mixed conifer forest vegetation at a landscape scale. The second\ud analysis characterized present day and historic stand structure of old-growth dry-mixed conifer\ud forests, and described how stand structure varied across the Deschutes and Ochoco National\ud Forests. The second analysis determined future research should investigate the growth rate of\ud understory ponderosa pine and Douglas-fir under varying density levels