292 JOURNAL OF FORESTRY 



these requirements normally approached in Nature? (3) To what ex- 

 tent can adverse natural conditions be ameliorated by silvicultural prac- 

 tice? 



At present the above questions can be answered onl}- in general 

 terms. Specific and accurate data, which can be secured only by most 

 detailed investigations, are required. Such investigations present many 

 difficulties because of the complexity of the factors involved, and be- 

 cause the road has not been paved by investigations in allied sciences. 

 Since the problem of plant relations to habitat factors is now absorbing 

 the best talent in botanical science, it is to be hoped that before many 

 years new discoveries will come to our assistance. With the methods 

 of investigation now available, however, much can be learned regard- 

 ing the reproduction of western yellow pine. 



SUMMARY 



This article should be regarded as a progress report on an investi- 

 gation which is barely begun. Although valuable data have already 

 been secured, the chief value of the work up to the present time lies in 

 the development of methods and the establishment of records for fu- 

 ture reference. Full returns will begin to be realized only after 20 or 

 30 years. 



The western yellow-pine forests in this region are as a rule not fully 

 stocked. The main reason for this is poor natural reproduction. Most 

 prominent among the agents responsible for the death or injury of 

 trees past the sapling stage are mistletoe, insects, porcupine, lightning, 

 and wind. 



Increment data cover too short a period to furnish a reliable basis 

 for calculating yield. The indications are, however, that an annual in- 

 crement of 2 per cent of the growing stock on cut-over areas is a con- 

 servative figure. In average stands this means an annual growth 

 amounting to from 50 to 75 board feet. Where natural reproduction 

 brings about rapid restocking, the above figures may be greatl}^ ex- 

 ceeded during the first 40 years after cutting. 



Natural reproduction is the greatest and most far-reaching silvicul- 

 tural problem with which the forester has to contend in this region. 

 In certain sections reproduction is good, but on the National Forests, 

 where exploitation has been greatest, reproduction is generally unsat- 

 isfactory. This situation is due largely to natural conditions, fore- 

 most among which is insufficient or poorly distributed precipitation. 

 Silviculture can never wholly overcome the difficulty. /VU it can rea- 



