9 6 A Study of the Vegetation of 



equally certain that others buried in the moister duff escaped burn- 

 ing. Hoffman (7) has shown that seeds of Thuja plicata may 

 remain dormant in the soil for two years, while those of Pinus 

 monticola and Pseudotsuga mucronata may be buried in the duff 

 for six years and still remain viable. 



The distribution of the seedlings was very irregular. In some 

 areas of a square meter or more none could be found, while in 

 other more favored spots the seedlings would average as many 

 as 8 per square meter. The ground occupied by these seedlings 

 was well covered with a mulch of the dead leaves and stems of 

 such herbaceous plants as have already been described for the 

 region. 



On the denuded south slopes where the original forest growth 

 consisted of an abundant stand of Pinus ponderosa with scattered 

 individuals of Pseudotsuga mucronata, notwithstanding the pres- 

 ence of a growth of Symphoricarpos, Pteridium, Epilobium, 

 Cirsium, Achillea, and other plants in considerable abundance 

 and so intermingled as to form a semi-shaded protected area, no 

 coniferous seedlings were present. Their absence was no doubt 

 due to insufficient soil moisture and excessive evaporation. 



These south mountain sides and their ravines and canyons will 

 in the course of time be reclaimed by a new growth of yellow pine 

 and Douglas fir unless ground fires occur and natural growth 

 conditions are obliterated. 



Reforestation studies in areas swept by fires of all degrees of 

 severity were made, especially in Thatuna Hills. In some cases 

 only very local areas were concerned, while in others the fires 

 covered considerable territory (Fig. 43). In practically all cases 

 sufficient seed trees were either left standing in the burned area 

 or on unburned ridges in close proximity to furnish the seed for 

 reforestation. 



About twenty-nine years ago, many square miles of these hills 

 were overrun by a fire which destroyed more or less completely 

 much of the virgin timber, leaving here and there a few living 

 trees representing the different species to serve as seed trees in 

 subsequent years. These burns covered chiefly the north and 

 northeast slopes of the mountains. In these mixed forests of 



