NATURAL REFORESTATION IN THE MOUNTAINS OF 



NORTHERN IDAHO 



HARRY B. HUMPHREY 



Bureau of Plant Industry, Washington, D. C. 



AND 



JOHN ERNST WEAVER 



University of Minnesota 



The factors affecting the natural reforestation of a fire-denuded 

 area may, in general, be said to be the same in Idaho and Ore- 

 gon as in Maine or Minnesota. There may be and actually 

 are differences in detail as to what species of herbaceous and 

 shrubby plants may prepare the way for the more delicate seed- 

 lings of those trees native to the particular locality. But the 

 principle prevails everywhere that certain plants or plant socie- 

 ties are antecedent and probably essential to the appearance and 

 permanent establishment of a forest. The first step in the 

 reforestation of a fire-swept area is the restoration of the condi- 

 tions necessary to insure the germination and vigorous early 

 development of the tree seedlings. The presence of humus in 

 the soil insures a certain degree of moisture conservation and 

 the retention of certain ingredients of plant food so easily lost by 

 drainage. 



Experience and observation teach us that however hardy, 

 however well equipped, may be such trees as those which come 

 to occupy the most trying situations, they were doubtless so 

 sensitive to environmental factors during their first years as to 

 have perished but for the fact that there must have prevailed a 

 proper and essential balance of physiologic factors. To estab- 

 lish this balance may have required but a year, or it may have 

 taken a much longer time. 



In this paper it is not our purpose to discourse on the laws 

 which regulate natural reforestation in different sections of the 



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