• Condition Of Live Fire-Scarred Ponderosa Pine Eleven Years After Removing Partial Cross-Sections

      Heyerdahl, Emily K.; McKay, Steven J.; USDA Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory; University of Minnesota, Department of Horticultural Science (Tree-Ring Society, 2008-06)
      Our objective is to report mortality rates for ponderosa pine trees in Oregon ten to eleven years after removing a fire-scarred partial cross-section from them, and five years after an initial survey of post-sampling mortality. We surveyed 138 live trees from which we removed fire-scarred partial crosssections in 1994/95 and 387 similarly sized, unsampled neighbor trees of the same species. These trees were from 78 plots distributed over about 5,000 ha at two sites in northeastern Oregon. The annual mortality rate for sectioned trees from 1994/95 to 2005 was 3.6% compared to 2.1% for the neighbor trees. However, many of the trees that died between 2000 and 2005 were likely killed by two prescribed fires at one of the sites. Excluding all trees in the plots burned by these fires (regardless of whether they died or not), the annual mortality rate for sectioned trees was 1.4% (identical to the rate from 1994/95 to 2000) compared to 1.0% for neighbor trees. During these fires, a greater proportion of sectioned trees died than did catfaced neighbor trees (80% versus 64%) but the difference was not significant.
    • When Is One Core Per Tree Suffifcient To Characterize Stand Attributes? Results Of A Pinus Ponderosa Case Study

      Woodall, C. W.; USDA Forest Service, Northern Research Station, 1992 Folwell Avenue, St. Paul, MN 55108, USA (Tree-Ring Society, 2008-06)
      Increment cores are invaluable for assessing tree attributes such as inside bark diameter, radial growth, and sapwood area. However, because trees accrue growth and sapwood unevenly around their pith, tree attributes derived from one increment core may not provide sufficient precision for forest management/research activities. To assess the variability in a tree’s inside bark radius, sapwood radius, and 10-year radial growth estimated by tree cores, two increment cores at 90 degree angles were collected from ponderosa pine (Pinus ponderosa) trees in eastern Montana (n = 2,156). Paired core measurements varied substantially with 13% mean difference for inside bark radius, 19% mean difference for sapwood radius, and 23% mean difference for estimates of radial increment. Furthermore, decreasing crown ratio, decreasing diameter, and increasing site slope were all found to increase differences in estimates derived from paired cores. Whether for management or research purposes, the number of cores that should collected per tree depend on a stand’s susceptibility to reaction wood, required measurement precision, and budgetary constraints.