72 " JOURNAL OF FORESTRY 



practitioner is. How shall he decide in a specific case what measures to 

 adopt? The guiding rule in answer to this question is. that where the 

 humus is comparatively loose, being composed largely of moss and 

 needles, nitrification may be expected to take place when the stand is 

 opened up by cutting. Another good criterion is the type of herbaceous 

 vegetation. Hesselman names a list of plants which are termed nitro- 

 phylous and whose presence is regarded as an indication of a soil rich 

 in available nitrates. 



Among these plants are the following : 



Epilobium augustifolinm Rubus saxatilis 



Rnbus idseiis Urtica dioica 



Senecio silvaticns Arenaria trinervia 



Taraxacum officinale Fragaria 



Galeopsis bifida Rumex acetosella 



Luzula pilosa Sonchus arvensis 



Rubus strigosus Cirsium lanceolatum 



A type of soil in which nitrification is not taking place is indicated by 

 the presence of a ground cover made up of mosses and lichens which 

 do not wilt on exposure to sunlight, or where the ground is covered by 

 a mat of Aira flcxuosa. Other indicators of nitrogen deficiency are 

 P olytrichiiim juniperinum, Vaccinium, and Arctostaphylos nva ursa. 

 Under such conditions a light burning is advocated. 



Failure to recognize these two general types of soil is thought to 

 account for many of the dift'erences of opinion in regard to silvicul- 

 tural practice. The author cites examples to show that the advocates 

 of shelter-wood systems, particularly Wagner's "border-cutting." have 

 worked mainly on relatively good soils, where cutting alone suffices to 

 bring about nitrification. On the other hand, foresters who have advo- 

 cated heavy cuttings followed by burning or cultivation have, as a rule, 

 dealt with soils in which nitrification is difficult. 



The findings of this investigation, if not directly applicable to Amer- 

 ican forestry, should at least prove suggestive. They probably will 

 find application in the more humid forests of this country, where there 

 is a large amount of decaying organic matter in the forest floor. For 

 such conditions this investigation seems to offer an explanation of the 

 beneficial action universally attributed to exposing the mineral soil by 

 burning or partial cultivation. It is interesting to note in this connec- 

 tion that a system of heavy cutting followed by slash burning is now 

 practised in the Douglas fir forests of the Pacific Northwest. 



In open stands, such as the yellow pine forests of Arizona and New 

 Mexico, this investigation can have only a remote application. Here 



