Ancillary data are summarized for each wildlife habitat type, but are not divided by subregion or structural condition class.
Figures and Tables are referred to with an "*" followed by ".sp-" and a figure or table number. In the summary narratives the "*" is replaced by the wildlife habitat code (e.g., WLCH). The methods and caveats for each figure and table number apply to all wildlife habitat types.
When it was possible to distinguish the height of dead trees used from live trees, only heights of snag species were tabulated. However, many studies did not do this, so heights of live trees are included in this analysis. When we discuss tree height here, we mean the total height of the tree, not the height at which the observed activity of the wildlife species occurred.
Within a habitat type, a weighted mean height was calculated for all records of the same species with the same use (e.g. nesting, foraging, etc.). Means were weighted by sample size. These means were then graphically displayed within each habitat type (Figure *.sp-8).
When reviewed papers indicated the species of snags or trees used by wildlife, these species were recorded by frequency of use, if possible. When it was possible to distinguish the species of dead trees used from live trees, only snag species were tabulated. Many studies did not do this however, so there are species of live trees included in this analysis. In Table *.sp-10, the tree species used most often was noted under the column “Primary use". The tree species used second most often was noted under the column “Secondary use", and third most often was noted under “Tertiary use". Some studies listed more than 3 species used; the full list of additional species is available in the Annotate Bibliography for each study. If studies indicated selection, then tree species were recorded in order of selection rather than frequency. Some studies showed only a single tree species used; in those cases, it wasn’t always clear whether that was the only species used, or just the species most often used.
The number of wildlife species using individual tree species and level of use within a particular habitat type is summarized in Figure *.sp-9.
The studies we reviewed used a wide array of methodologies to classify the decay stage of snags. The classification schemes used had from two to nine categories of snag decay. In order to compare decay stages across studies, we took all the snag categories and, based on the author’s description of these categories, re-classed the snags as either soft, moderate or hard, similar to Bull et al.’s (1997) classification scheme (Table *.sp-11). A common decay classification system is the 5-classes described by Cline et al. (1980). For studies that reported decay in those 5 classes, they were re-classified as follows: class 1 to hard, classes 2 and 3 to moderate, and classes 4 and 5 to soft.
Where studies of wildlife species use of trees indicated the proportion of trees that were alive or dead, this was recorded and displayed in (Table *.sp-12). Some studies may have only looked at snag use by wildlife species, and would therefore not have recorded any live tree use. This was probably particularly true of earlier studies. We did not attempt to distinguish those studies from others, so studies that showed 100% use of either live or dead trees may be more a reflection on the study design rather than a reflection of species use.
Our main point in this section was to illustrate the importance of live trees, especially dead or decayed portions of live trees, as important habitat features for certain species or certain life stages of a species. Cavity nesters will use decayed portions of live trees, especially larch, aspen, and other hardwoods. The use of defective trees was recorded if indicated by author; these data are displayed in Table *sp-12.
Where hollow trees were noted in studies, these data were recorded (Table *.sp-12). Very few studies addressed wildlife use of hollow trees and snags.
If the studies we reviewed noted whether or not the top of the tree was broken out or intact, we recorded that information (Table *.sp-12). When available, we also noted the proportion of the trees in each study that were in the recorded condition.
Within a habitat type, a weighted mean length was calculated for all records of the same species with the same use (e.g., nesting, foraging, etc.). Means were weighted by sample size. These means were then graphically displayed within each habitat type (Figure *.sp-13).
When reviewed papers indicated the species of down wood used by wildlife, these species were recorded by order of use, if possible. In Table *.sp-14, the down wood species used second most often was noted under the column “Secondary use", and third most often was noted under “Tertiary use". Some studies listed more than 3 species used; the full list of additional species is available in the Annotate Bibliography for each study. If studies indicated selection, then down wood species were recorded in order of selection rather than frequency. Some studies showed only a single down wood species used; in those cases, it wasn’t always clear whether that was the only species used, or just the species most often used.
The number of wildlife species using individual down wood species and level of use within a particular habitat type is summarized in Figure *.sp-11.
The studies we reviewed used a wide array of methodologies to classify the decay stage of down wood (Table *.sp-15). In order to compare decay stages across studies, we took all the snag categories and, based on the author’s description of these categories, re-classed the logs as either decayed, moderate or hard, similar to Bull et al.’s (1997) classification scheme (able *.sp-11T). A common decay classification system is the 5-classes described by Cline et al. (1980). For studies that reported decay in those 5 classes, they were re-classified as follows: class 1 to hard, class 2 to moderate, and classes 3 through 5 to decayed. Other classifications reported in the literature were from Sollins (1982) and Maser et al. (1979). For these classification systems, decay was re-classified as follows: class 1 to hard, classes 2 and 3 to moderate, and classes 4 through 5 to decayed.
Where hollow down wood was noted in studies, these data were recorded (Table *.sp-16). Most of the data we found on hollow down wood were associated with two studies conducted by the same principle author in the Blue Mountains of northeast Oregon (Evelyn Bull). Authors tended to be silent on whether or not down wood in their study area was hollow.