The Wind River Experimental Forest 



171 



mostly within a year after it falls. 

 Forests that supposedly grew from this 

 duff -stored seed following logging and 

 slash burning were found to come from 

 seed brought in considerable distances 

 by the wind. Measurements of the seed 

 flight of Douglas-fir and its associates, 

 made by releasing seed at tree heights 

 from a box kite over snow fields and 

 also by catching the natural seed fall in 

 seed traps, still stand as the most ac- 

 curate and complete records ever made 

 of tree-seed flight. 



Fire studies made there on weather 

 and fuel relationships, slash disposal, 

 and so on have formed much of the 

 background for the fire-protection 

 system in this forest region. 



Meteorological and biological stud- 

 ies that disclosed surface temperatures 

 lethal to seedlings (both from heat and 

 frost) and the seedling losses from ex- 

 cessive drought, lack of cover, competi- 

 tion, and rodent damage explained 

 why seedlings came in thickly on some 

 areas, while others refused to restock. 

 These were supplemented by cone- 

 crop records, which showed that sev- 

 eral years elapsed between medium 

 and heavy seed crops. 



Thirty years of life history, recorded 

 on sample plots after early cutting and 

 burning, shows the gradual decrease in 

 rate of restocking as the distance from 

 the seed source of uncut timber in- 

 creases. Ten years was required to 

 stock adequately the first cut-over 

 quarter of a mile from green timber, 

 and 20 years for the second on cool, 

 favorable northerly exposures ; the hot 

 southerly exposures and flat bottoms, 

 where brush and grass competition was 

 heavy, are still irregularly stocked or 

 nonstocked. 



A measure of the second period in 

 the life history of Douglas-fir stands 

 consists of 35 years of records on per- 

 manent growth plots in young stands; 

 these show an average annual net 

 growth of 645 board feet an acre 

 despite an annual loss of half that 

 amount that occurs as these stands ap- 

 proach and attain commercial size and 

 maturity. Studies now indicate that 



most of the annual loss can be saved by 

 light improvement cuts. 



Pruning studies showed that 25- to 

 30-year old stands could be pruned 

 to clear the first 18-foot log of knot- 

 producing branches with no reduction 

 of growth rate or entrance of decay 

 resulting from the operations. The 

 difference in value between a pruned 

 and an unpruned tree, when projected 

 50 years into the future, was calculated 

 to equal several times the cost of prun- 

 ing plus 3 -percent compound interest. 



Spacing- test plantations of 2 3 -year- 

 old Douglas-fir show volume growth, 

 stem-quality development, and fire 

 hazard for spacings from 4 by 4 feet 

 to 12 by 12 feet. They indicate that 6 

 by 6 feet to 8 by 8 feet spacing should 

 give the most satisfactory combination 

 of quality and volume growth. The 

 widest spacing had the largest trees, 

 but those large trees also had the larg- 

 est limbs, which makes the largest knots 

 in lumber. 



Heredity plantations of Douglas-fir, 

 now 35 years old, show a 33-percent 

 variation in growth rate between the 

 best and the poorest of 13 selected 

 strains of stock and indicate that local 

 strains may not be the best unless seed 

 is taken from good trees in good stands. 



A similar plantation of ponderosa 

 pine, produced from seed from various 

 parts of the Western States, shows that 

 trees of the best strains are nearly 

 double the size of the poorest, and also 

 that young trees from limby, crooked 

 parent stock or tall, clean-boled parent 

 stock retain these parental character- 

 istics when planted side by side in test 

 plantations. 



Light stand-improvement cuts in 

 100-year-old stands reduced mortality 

 losses, increased net growth, and made 

 possible the salvage of trees attacked 

 by bark beetles and Poria weirii a 

 serious root rot that complicates the 

 production of timber crops. 



Experimental partial cuts in over- 

 mature old-growth stands have indi- 

 cated that in most cases concentrations 

 of old-growth trees might better be 

 clear-cut. In stands having an under- 



