139. 



trees, in density, and therefore in tillage and in the mulch produced. 

 It stinulates soil life, owing to the variety of mulch. Where the mixture 

 is part deciduous there is the advantage of greater soil formation, ae- 

 ration, and soil moisture, and herbaceous plants come in and assist in 

 working up the humus, therefore the action is beneficial. This is valu- 

 able in spruce woods, as it affords a means of cleaning out the debris. 



TD. In an all-aged stand, even if pure, there is a variety of 

 tree sizes, from brush to timber; therefore there is a variety of cover, 

 shape, protection from wind and rain, a difference in tillage and use of 

 soil, and a difference in mulch production. Unf ourtunately, lean sands 

 are driven to pine; others vfill not cone. Pines do not do well as un- 

 even-aged stands. An extreme case of this is the Jack pine in the north. 

 It will not grow in uneven-a^e<l stands; it will come in on burns, but not 

 under an old stnd. It gives the least amount of help to the forester. 

 This is also true of hard pinos, It is largely a matter of tolerance. 



K) Physiography of Soil. 



i. Depth of soil depends on its origin and manner of building up. 



a,. Y'ater and wind transportation give large areas of uniform 

 deep soils, sands, and silts. 



b,. Water transportation gave and gives smaller areas of such 

 uniform soTls in valleys, etc. 



di. Glacial drift gave large areas of unusually deep soil 

 accumulations, very variable in kind and structure of material, 



ei. Soils in place usually vary in wide limits, even on small 

 areas, in keeping vdth the variation of the rock material itself. 



e_. Shallow soils are more variable than deep soils; this vari- 

 ation is felt more by plants. This is also true of hardpan. 



j2. Topography affects soils. 



ji. Steep grounds tend to wash off bodily. Agriculture ceases 

 at 3/ slopes, cultivated forest at 6o/ . Beyond this point woods are 

 "protected forests* 1 , rocks holding the sand, etc. 



b.. All slopes wash (this 10 axiomatic), and the best soil 



tends to go down to the bottom. 



. Soil on slopes is normally over-drained/ water moves faster 

 and soils Teach more than on the l 



<1. Slope affects soil temperature. Cold and warm sites on east 

 and west slopes. Following is the order of the different exposures in 

 regard to warmth and coldness, beginning with the warmest and ending witli 

 the coldest; SW, S, SS, W, a, NB f NW, H. 



The effect of the direct sun in latitude 48 K. is practically 

 nil in January, when the angle of slope is 55 <> r more, for north slopes. 

 The soil warms up in summer: 



June : Jan. :: 8 : 7 



Sept. : Jan. :: 3 : 1 on the level. 



e,. Slope, by affecting temperature, affects soil evaporation, 



