Papers on biology and agriculture 2ii 



That the growth rate in height for the same species 

 on similar sites is very uniform is brought out by study 

 of pin oak (Quercifs palustris). Measurements were 

 taken in Gallatin county on pin oak growing on gray clay 

 subject to flooding from the Wabash, and in Union county 

 for the same species on drab clay subject to flooding from 

 the Mississippi. The height growth of the average tree 

 for each at 50 years is 68 feet, and at no period between 

 5 and 65 years is there a variation of more than one foot 

 in the height of the average tree for these widely separat- 

 ed stands. 



Comparing the rate of growth in height for the com- 

 mon upland commercial species with that of the bottom- 

 land species of the state, the studies show that the up- 

 land species grow in height about 709c as fast as the bot- 

 tomland species and in diameter about 55% as fast. Thus 

 it is apparent that if the growing of hardwood timber 

 crops is going to be profitable anywhere the bottomlands 

 present the more favorable conditions. 



Comparing the height growth of the eight bottomland 

 species studied there is a noticeable grouping. The in- 

 tolerant Cottonwood (Populus deltoides) and sycamore 

 (Platanus occidentalis) show an average annual height 

 growth of more than two feet for the first 50 years. The 

 honey locust (Gleditsia triacanthos), soft maple (Acer 

 saccharinum), and pin oak (Quercus palustris) have an 

 average height growth of 1.4 feet for the same period. 

 The elm (Ulmus Americana), ash (Fraxiims Americana) 

 and hackberry (Celtis Mississippi ensis) average slightly 

 less than 1 foot per year. Thus in rate of volume 

 growth for average individual trees the listing would be 

 in order of importance, cottonwood, sycamore, pin oak, 

 honey locust, soft maple, ash, elm and hackberry. 



Where these studies were made the soils are rich and 

 moisture abundant. Thus the factor controlling both 

 the occurrence of any one species in the mixture and its 

 rate of volume growth is available sunlight. Abandoned 

 river channels generally have seedlings in abundance of 

 several species, but the rapid growth rate of cottonwood 

 and sycamore soon places these above their competitors 

 and results in a belt of these intolerant trees. But the 



