THE BIOLOGY OF LODGEPOLE PINE 413 



the species has adapted itself very slightly to its new conditions. In 

 short, then, it is both a recent and rapid migrant from a northern 

 source. 



Consider now the facts that the tree produces some seed almost 

 every year, that a good crop of seed means at least 200,000 germinable 

 seeds per acre of forest, and that, in addition, there are always held 

 on the trees cones amounting to two to ten times the volume of an 

 average crop, and the possibility of its rapid migration is readily 

 seen. It appears, also, that the keeping quality of the cones must be 

 a large factor, making them especially attractive to squirrels and 

 other rodents which cache their winter's food supply. 



All writers" ' on lodgepole, I believe, have agreed that this species 

 is extremely partial to siliceous soils. Certain it is that within its main 

 range it has invaded almost all granitic and glacial soils, while leaving 

 J3ouglas fir to hold lava and limestone soils in many instances. Our 

 field sowings of lodgepole seed have shown that, under average climatic 

 conditions for this region, germination occurs readily in sandy or 

 gravelly soils whose capillarity^ is 10 or 15 per cent, but -is prac- 

 tically prohibited by a capillarity of 30 per cent, which would be met 

 with in some limestone, lava, and alluvial soils and those of large 

 humus content. Echard tests of these same soils, using lodgepole 

 seedlings, show that the wilting coefiicient for this species is very 

 high, amounting usually to 23 per cent of the capillary moisture of 

 the several soils, while Douglas fir and Engelmann spruce coefficients 

 are only 12 and 16 per cent, respectively. The nonavailable percentage 

 for lodgepole also rises very rapidly with the presence of alkali in 

 the soil. These facts bespeak, physiologically, a small power for 

 drawing moisture from the soil, and point to the fact that lodgepole 

 in its native habitat unquestionably grew almost wholly on siliceous 

 soils. Of greater present import, however, is the relation of these facts 

 to the poor quality of lodgepole when growing, particularly on lime- 

 stone soils, its inability to invade the so-called "parks" within its type, 

 which are usually slight depressions having more or less alluvial soil. 

 and finally the importance of exposing the mineral soil to secure 

 reproduction. 



« Mason, D. T., "The Life History of Lodgepole Pine in the Rocky Mountains." 

 Bull. 154, U. S. D. A., F. S. 



" Tower, G. E., "Study of the Reproductive Characteristics of Lodgepole Pine." 

 Proc. vSoc. Am. For., IV, 1. 



8 This expression refers to the moisture-holding capacity of a 5-inch column of 

 soil against the force of gravity, 48 hours being allowed for drainage after saturating. 



