96 IOWA ACADEMY OF SCIENCES. 



NOTES ON FOREST DISTRIBUTION IN IOWA. 



BY T. H. MACBRIDE. 



The peculiar character of our American forest geography- 

 early attracted the attention of intelligent observers. Civilized 

 men, Frenchmen, crossing the continent from the Atlantic 

 seaboard, after threading for two hundred leagues a forest 

 almost unbroken, suddenly found themselves in the presence of 

 vast treeless plains, extending westward across a large portion 

 of the central Mississippi valley. In wonder and admiration 

 the vcnjageur looked upon these great plains, grass-grown and 

 flower- bedecked, and found them counterpart to the green 

 meadows of France; to them he gave the name prairie, a word 

 now so familiar as to have long lost for all Eaglish- speaking 

 men e^ery vestige of foreign origin. How these great mead- 

 ows ever came to exist or persist in the region where they 

 first were seen, or why the forests of the east should so sud- 

 denly stop was a problem the voyageur could not solve, and has 

 been a problem from the days of the voijageur until now. 



In these times of almost universal forest extermination, 

 when we are in sight of the era in which Americans must 

 laboriously undertake the work of re-forestration, it is well that 

 we should closely attend to conditions once established by- 

 nature, that we may hereafter act with her assistance, for in 

 plant distribution, whatever our blunders may be or have been, 

 nature we may be sure has seldom made a mistake. 



In general, two factors are said to control forest distribution 

 on the planet; the one, rainfall, the other, temperature. If the 

 rainfall is deficient there can be no forest, rainfall seems never 

 to be excessive, and if a region is too cold there is no forest. 

 In proof of this we have but to look at the high altitudes and 

 latitudes of the earth. What makes our Iowa problem there- 

 fore peculiar, is the fact that forest distribution here, as else- 

 where in prairie regions, does not accord with these general 



