Historical structure and composition of ponderosa pine and mixed-conifer forests in south-central Oregon

摘要: We summarized structure and composition of dry forests from a 90-year-old timber inventory collected by the Bureau Indian Affairs on former Klamath Reservation (now part FremontWinema National Forest). This analysis includes data 424,626 conifers P15 cm dbh 3068 transects covering 6646 ha. The represent 10–20% sample 38,651 ha forest growing sites that are classified as ponderosa pine (Pinus ponderosa) mixed-conifer habitat types distributed within 117,672 study area. Large, drought- fire-tolerant dominated these forests. Large tree (>53 dbh) basal area (13 ± 7 m 2 /ha) contributed 83 16% total area; 81 20% large-tree was pine. Composition were very similar to those sites. Variability in recorded all highest moist Stand densities (trees per hectare, tph) have more than tripled over past 90 years 68 28 tph current density 234 122 Current Vegetation Survey United States Forest Service. Mean area, however, increased less 20%. Basal large trees has declined >50%, abundance proportion number hectare decreased factor five. landscape-level record historical conditions allows inferences about across tens thousands hectares. A landscape emerges which supports working hypotheses frequent, low- moderate-severity wildfires maintained predominantly low-density large, fire- drought-tolerant pines significant moisture productivity gradient driest types.