Because the distribution of mortality is often 

 clustered and because of the large size of some 

 areas to be inventoried, a sampling design making 

 use of large-scale aerial photography would 

 appear to offer advantages. Heller and others 

 (1 964) and Sayn-Wittgenstein (1 960) determined 

 that tree species can be identified to acceptable 

 accuracy standards on large-scale color aerial 

 photography. This paper investigates the use of 

 aerial photography in mortality sampling. The 

 study objectives, stated as questions, are: 



1 . Can 1 - and 2-year-old mortality be accurately 

 identified on large-scale aerial photography? 



2. Can species identification of mortality trees 

 and of green trees be accurately done on 

 large-scale aerial photography? 



METHODS 

 Photography Obtained 



For this study, 70 mm aerial photography was 

 taken with 60 percent end lap on two flight lines on 

 one subcompartment and a single flight line on a 

 second subcompartment of the Coeur d'Alene 

 National Forest (administered as part of the Idaho 

 Panhandle National Forests). The flight lines 

 varied in length from 1.5 miles (2.4 km) to slightly 

 over 2 miles (3.2 km). The photographs were taken 

 and processed in June 1971 by John Wear and 

 Richard Myhre, who at the time were with the 

 Remote Sensing Research Work Unit of the 

 Pacific Southwest Forest and Range Experiment 

 Station. The combinations of scale and film type 

 used in this study were 1:1600 and 1:2400 true 

 color transparencies. However, because the 

 photographs were taken over rough terrain, there 

 is considerable variability in scale in different 

 segments of the photo strips. Because 70 mm 

 photography at scales of 1 :1 600 and 1 :2400 fre- 

 quently does not include a broad enough area to 

 be used to locate specific photo plots on the 

 ground, 1 :4800 blackand white photographs were 

 taken simultaneously. The 1 :4800 blackandwhite 

 photographs were not used in the identification of 

 green or mortality trees. Instead, they were en- 

 larged, printed, and used to locate photo plots for 

 ground examination. 



Photo Interpretation 



The subcompartments photographed fell pri- 

 marily in the grand fir-cedar-hemlock ecosystem. 

 Species growing on the photographed portions of 

 the subcompartments were Douglas-fir, grand fir, 

 white pine, western larch, western hemlock, pon- 

 derosa pine, lodgepole pine, and western red- 

 cedar. Stand density conditions on the two sub- 

 compartments ranged from low density, poorly 

 stocked stands to high density, well stocked 

 stands. 



All photo interpretation was done in stereo. On 

 each photo frame all 1 - and 2-year mortality trees 

 were identified by species: the 1 -year mortality by 

 brightly discolored foliage and retention of most of 

 this foliage; and the 2-year mortality by dully 

 discolored foliage with very little of it retained 

 (Millerand Keen 1 960). These characteristics vary 

 both among species and from year to year be- 

 cause of climatic variation. However, these char- 

 acteristics are an acceptable average descriptor 

 for general use in dating mortality on large-scale 

 aerial photography. 



On every 12th frame of 1:1600 scale photo- 

 graphy, a 0.6 inch by 0.6 inch (1 .52 cm by 1 .52 cm) 

 subplot was established near the center of the 

 frame. Although this resulted in unequal sized 

 plots on the ground (because of variation on scale 

 on each flight line) it did assure that a constant 

 proportion of the photographs were sampled. A 

 total count of green trees by species was made on 

 each subplot. In addition, five trees were selected 

 on each subplot to test species identification on 

 an individual tree basis. 



Ground Examination 



Every sixth frame of 1 :1 600 scale photography 

 was used for ground examination. All 1 - and 2-year 

 mortality trees identified on the photographs were 

 checked on the ground. Discrepancies were ex- 

 amined again both on the ground and on the 

 photos in an effort to explain the error and thus 

 improve future photo interpretation. 



Each photo subplot used to sample green trees 

 was located on the ground. All green trees on 

 these plots were counted by species. The five 



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