A STUDY IN THE DIFFERENCE IN SOIL REQUIREMENTS OF PINE 



AND SPRUCE. 



L. J. YOUNG. 



An area on the Saginaw Forest, planted to Norway spruce in 1!X)4, lias 

 furnished an interesting and instructive demonstration of the great importance 

 in forest planting of choosing the proper species with reference to a given 

 ■ combination of site conditions. In order that the Imsiness of forestry shall 

 yield a profit, the rate of growth of the timber must not fall below a certain 

 minimum. The more it exceeds that minimum up to a reasonable limit, the 

 higher the profits. The proper species for a given site is, then, one which 

 will make the growth demanded by the general economic conditions existing 

 on any particular forest. To determine the right species is not always easy, 

 and in the case of this particular ai-ea a mistake seems to have been made, for 

 the growth over a considerable part of it has been far from satisfactory. 



At the southern border a narrow strip is practically level, and here the 

 growth of the spruce has been fairly good. To the north of this strip the 

 land slopes moderately toward the lake, and this slope comprises most of the 

 area. Here the growth has been poor, and on several spots rcri/ poor. At 

 the foot of the slope is a slight depression, which runs toward the east, becom- 

 ing somewhat deeper in that direction, and all the trees in the bottom of this 

 have made excellent growth. To the north of this depression the land rises 

 a few feet into a rounded knoll and here again the growth has been very poor. 

 The result of these varying conditions is a very irregular stand, in which the 

 present height of the trees varies from a minimum of 0.8 of a foot to a maxi- 

 mum of 21:1 feet, with an average of 6.5 feet. 



Up to the time of its acquisition by the university, this land had been 

 handled as a part of a farm and apparently had received little care, so that 

 the surface soil on the slope had washed badly and three large gullies had 

 been formed by erosion. The best of the soil from the slopes and the knoll 

 to the north had been carried into the depression at the foot of the slope, 

 forming a deposit of fine loam six inches thick without any admixture of 

 gravel. On the slopes, coarse gravel occurs plentifully in the soil from the 

 surface down. 



Examinations of samples taken from different parts of this area showed 

 that the soil on the slopes contains less moisture, very much less organic 

 matter, and less lime than that from the more level portions. Undoubtedly 

 the lack of these important plant foods is largely responsible for the unusually 



21st Mich. Acad. Sci. Kept., 1919. 



