- The management Pf forest resources is a complex task. A thorough and up-to-date inventory is an important part of forest management. Aerial photography is one of the important tools used to facilitate the design of a forest inventory. Aerial photographs are used to determine acreages, to locate roads and sample plots, and to stratify the forest area if a stratified sampling design is to be used. Aerial photographs can further be utilized in conjunction with aerial photo volume tables to conduct a combined photo-field cruise, thus reducing costs. However, aerial photo cruising is sometimes limited in practice, because insufficient aerial photo volume tables are available for specific species and for different geographic areas of the country.
In this study six stand aerial photo volume tables were tested to determine their reliability to predict volume for three different timber types (even-aged Douglas-fir, even-aged ponderosa pine and all-aged ponderosa pine). These six tables represented four different species groups (Douglas-fir, ponderosa pine, hardwoods and mixed conifers) arid four different geographic locations (Western Oregon and Washington, Minnesota, California and the Intermountain states). Four of the six stand photo volume tables predicted volume with similar reliability at the 95 percent confidence level for the even-aged and the all-aged ponderosa pine types. Three of those same four stand photo volume tables reliably predicted volume at the 95 percent confidence level for the even-aged Douglas-fir type.
This study demonstrated that three of the six tables could be used equally well for any of the three different timber types, regardless of species, stand structure or geographic location. Further investigation may show that many photo volume tables may be used interchangeably from species to species or area to area. This presupposes that double sampling with regression analysis will be used to remove systematic errors in photo volume estimates caused by inaccurate photo measurements and discrepancies within the photo volume tables.