METHODS 



Fieldwork 



Sampling design. --The study was designed to provide data for four different skid- 

 ding methods: 



1. Ground lead. --Crawler tractor and rubber-tired skidder, entire log dragged. 



2. Skyline . --One end of log elevated. 



3. Helicopter. --Limited skidding. 



4. Preaommercial thinning . - -No skidding. 



For each skidding method, two species groups were desired and for each species 

 group, two age classes of slash. For each combination of skidding method, species, and 

 age, we attempted to locate two study sites on areas represented by each of three aver- 

 age loading levels: low (sparsely distributed), medium (nominally about half of ground 

 covered by slash), and heavy (uniformly distributed). 



Study sites were located in areas having different loadings to assure that any 

 differences in skidding patterns due to loading would be reflected in the data. 



Species were partitioned into the following two groups, based on similarity of 

 lopped depths as observed by Fahnestock and Dieterich (1962) : 



1. Douglas-fir {Pseudotsuga menziesii (Mirb.) Franco) 

 Grand fir {Abies grandis (Dougl.) Lindl.) 



Alpine fir (Abies lasioaarpa (Hook.) Nutt.) 

 Western redcedar (Thuja plioata Donn) 

 Western hemlock (Tsuga heterophylla (Raf.) Sarg.) 

 Western larch (Larix ooaidentalis Nutt.) 

 Engelmann spruce (Pioea engelmannii Parry) 



2. Lodgepole pine (Pinus oontorta Dougl.) 

 Ponderosa pine (Pinus ponderosa Laws.) 

 Western white pine (Pinus montioola Dougl.) 



All slash was at least one-half year old and had existed through at least part of 

 a winter. Two age classes were recognized: 0- to 1-year and 3- to 4-year. Some combin- 

 ations of skidding, species, and age were not found. Because skyline and helicopter 

 logging has received substantial use only recently in the Intermountain area, the 0- to 

 1-year and 3- to 4-year lodgepole pine and 3- to 4-year Douglas-fir were unavailable for 

 sampling. Surprisingly, 0- to 1-year precommercially thinned stands other than pines 

 were also unavailable. All other skidding, species, and age combinations were sampled. 



Within study areas that were a minimum of several acres in size, two primary tran- 

 sects were established. Along each primary transect, a total of 50 or more sampling 

 points were located at 2-foot intervals. Points without slash were not sampled. 



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