Notes on Forestry Uses in Aerial Photo Interpretation
Timber type mapping -- delineation and identification of homogenous stands of timber or other vegetation cover on aerial photographs
Now often fits into larger ecological classification schemes
See Figure 21.1 for a typed photograph
Decisions to make:
Relates to objectives, photo scale, and scale of the final map desired
Can map without field verification but it is risky
Field verification done to:
Combining field checking with photo interpretation:
∑ Pre-typing, make type lines on the photos before going into the field. Questionable areas can be checked after typing a small area, and then type larger areas as experience gained.
∑ Post-typing, field reconnaissance first. Travel as many roads and paths as possible, then type the map
Critical to take advantage of local experience.
The PNW Ecoclass Identification System
Computer compatible, links into a larger ecosystem classification system. Based on climax vegetation, not necessarily what is there.
Used for many years. Not originally computer compatible, but has been modified. Based on current use, not climax vegetation.
Usually easy to distinguish. Can be some difficult cases such as grown in farmland
How to define commercial vs. noncommercial: forest characteristics, ownership, intention, etc.
Commercial Forestland Classes and Symbols
Type classifications based on species composition, tree size, age class, degree of stocking, understory conditions, and stand history. System uses a six part symbol
Predominant species type.
On smaller scale photos need to know where various types are likely to be located.
Can have species combinations.
Requires knowledge of the forest ecology of the region.
Figures 24.5, 24.6, and 24.7 show coniferous
species identification on large-scale photos in western
Figures 21.2 and 21.3 show drawings of silhouettes and aerial view of selected hardwoods and conifers.
Tree diameter is the most common basis.
Can relate crown diameter to tree diameter. Not always a straight line relationship.
Need distinct category delineations: seedlings & saplings, pole timber, small saw timber, large mature timber, and large over-mature timber.
Good forest inventory data critical.
In stands with two distinct classes can indicate that too. See Figure 21.1 and Table 21.1
Crown closure (the proportion of the area covered by tree crowns) is best measure of stocking See Figure 24.2 for scale.
Can also use a broad classification system.
For regeneration can also make a classification of stocking
Species Composition Symbols
Can recognize the composition of the stands according to agreed upon rules such as:
Data of Stand Origin
System shows date of origin of young stands to the nearest decade, rounding up if greater than five.
Used to indicate some condition describing the origination of a stand of management.
†Aerial photos provide input to an ongoing information management system that would be used for timber sale planning and execution. A geographic information systems (GIS) is critical for forest management. Timber sales need to be part of the overall planning process.
Photos previously taken can help locate sales in the off-season. Especially when field recon difficult or impossible.
†Development of a cutting priority map. Part of a GIS.
Topographic features visible in stereo viewing can influence location of sales.
Initial sale compartment delineations can be made on photos.
The overview of a photo view reduces the possibility of illogical sales compartments.
Final sales boundaries must be made surveyed on the ground since photos donít show enough details.
Rough estimates of sales volume can be made from photos.
The type of logging practiced can be evaluated on photos.
Photos can be used in selective cutting operations.
Salvage sales can be estimated from photos, both in pre-damage and post-damage photos. Color infrared photos can be helpful.
Stereo views give more detail than topographic maps for planning roads.
Photos can help keep the timber harvesting on track.
Photos can document progress of a sale. See Figure 21.6
Often used for small-scale coverage flown after the completion of the sale to map the cutting units and the new road system.
Sometimes special oblique photos of cutting units to plan
slash-burning are done in
Includes fire prevention and detection. Also planning, preparation, and training activities.
Thermal scanning can penetrate smoke and is used (not the same as IR photography). See Figure 21.7
Panchromatic and regular color vertical and oblique photos used for planning.
Can also use photo mosaics
Fuel mapping another procedure using aerial photos. Fuel maps prepared from photos, ground recon, and air recon.
Aerial recon including photos essential to fire fighting. Photos canít penetrate smoke. Need to use thermal imaging in combination with pre-existing aerial photos.
Aerial photos used for damage assessment. Can do aerial photo timber inventories.
Canít detect all insect and disease problems from the ground. Photos can:
Color infrared film very important in this process.
Murthaís classification system for† identification and detection of damage based on the physiological changes in the foliage as detected from aerial photos:
Type I: Trees that are completely or almost completely defoliated
Type II: Trees that show some defoliation through the presence of bare branches or malformation
Type III: Trees that show the foliage as some other color that is not consistent with normal foliage color of the species involved
Type IV: Trees that show no visible sign of damage but have a deviation from the normal reflectance pattern in the nonvisible light range.