92 A Study of the Vegetation of 



reforestation has occurred, the new forest has usually about the 

 same composition as the old. In these cases, the composition 

 of the previous forest was determined, of course, by a study 

 of the stumps, by checking with the adjacent forest, especially 

 primeval forest areas on similar adjacent slopes. The following 

 case, found by repeated trials to be rather typical, is illustrative. 



Belt transects through a second growth forest occupying an 

 area in Thatuna Hills cut over about twenty-five years ago gave 

 the following percentage composition : 



Moist North Slope Dry South Slope 



Yellow pine 0.5 per cent. Yellow pine 36.0 per cent. 



Douglas fir 4.0 per cent. Douglas fir 14.0 per cent. 



Tamarack 30.0 per cent. Tamarack 10.0 per cent. 



White fir 26.0 per cent. White fir 40.0 per cent. 



Cedar 39.5 per cent. 



Superficially such moist slopes appear to be clothed with nearly 

 a pure tamarack forest, due to the more rapid height-growth of 

 this species. In such young forests the cedars are often small, 

 in fact, many are mere seedlings. A count of the annual rings 

 shows that they came in after the other trees had, by their shade, 

 made conditions less xerophytic. Their importance in the general 

 composition of the forest might be overestimated from their high 

 percentage. Farther up the slopes they are scattering, and only 

 near the moist base are they present in great abundance. Like- 

 wise, the white fir on the south slope occurs mostly in dense 

 thickets near the base. On the open south slope trees averaged 

 only i per square meter, while on the north slope the average was 

 3.5 per unit area. 



No less characteristic of the two types of forests are the shrubs 

 and herbs of the undergrowth. Opulaster pauciflorus, Ceanothus 

 velutinus, and Salix scouleriana make up the chief shrubby growth 

 on the south slope, often covering many square meters exclusively. 

 On the north slope both Opulaster pauciflorus and Ceanothus 

 velutinus occur but rarely, while Vaccinium macrophyllum is 

 more abundant than Salix scouleriana. Coptis occidentals, 

 Clintonia uniflora, Thalictrum Occident ale } Mitella stauropetala, 



92 



