93 



The even-aged plots were divided between the three upland types — 

 post oak, scrub oak, and upland mixed hardwoods — and the one bottom- 

 land type : and the data were worked up to show, for each decade between 

 the second and tenth, the total number of trees for a fully stocked acre, 

 the average height of the dominant trees, the D. B. H. of the average tree, 

 the basal area per acre, the total cubic feet contents exclusive of branch- 

 wood, and the average annual growth per acre. (Tables 4-8, pp. 95-9T.) 



A comparison of growth on these even-aged upland stands in Illi- 

 nois and the even-aged second growth hardwoods in Connecticut and 

 Massachusetts indicates that the Illinois post oak type has about the same 

 number of trees per acre at a given decade as the poorest upland type in 

 Connecticut — Quality III Oak (Frothingham '12), but that the diameter 

 growth averages less on the post oak, and that the height growth averages 

 decidedly lower. This Quality III Oak type in Connecticut represents 

 thin-soiled upper slopes. It is very poor land, yet it produces better trees 

 than the post oak type in Illinois. 



A study of the scrub oak stands on the sands in Illinois shows that 

 these sands produce trees of an average diameter and height-growth com- 

 parable to that of the better sites in Connecticut — between Quality I and 

 Quality II Oak sites — but that the fully stocked Illinois stands do not have 

 nearly as many trees per acre as the eastern forests. 



A study of the upland mixed hardwoods type of Illinois shows that 

 the diameter growth for such fully stocked even-aged stands averages 

 about the same as the better sites in Connecticut (Quality I Oak), that 

 the height growth of dominant trees averages about the same as that of 

 the medium sites in Connecticut (Quality II Oak), and that the number 

 of trees per acre for a given decade is again very low in Illinois. At 70 

 years these fully stocked stands in Illinois have but 70 per cent as many 

 trees as such stands on the Quality I Oak site in Connecticut, and but 45 

 per cent as many trees as fully stocked even-aged stands of 70 years on 

 Quality I sites in Massachusetts. (Spaeth '20.) 



The annual rainfall of Connecticut is about 47 inches, and of Illinois 

 about 37 inches. The annual evaporation for Connecticut amounts to 

 about 39 inches, for Illinois to approximately 41 inches. The lesser 

 amount of rain and the greater evaporation in Illinois is thus reflected in 

 the decrease in the number of trees supported on an acre. This indicates 

 that, in the management of the hardwood forests on the uplands of Illi- 

 nois, the conservation of moisture is one of the important factors. 



Post Oak Type 



The post oak plots selected were on the heavy acidulous soils com- 

 mon to the level uplands of south-central Illinois described in Part I under 

 the post oak type, p. 32. Post oak constitutes 74 per cent of the trees on 

 the plots measured, scrub oak 12, with various black oaks and hickories 

 totaling 14 per cent. An examination of the tables 4-6, pp. 95, 96, shows 

 that these post-oak stands have a greater number of trees per acre, a 

 smaller total basal area per acre and consequently a smaller average 



