APPENDIX A. 



Scheme of Graphic Representation of Environmental 

 Factors for the Forests of Alabama. 



ON page 17 it was pointed out that the character of 

 the forest at any place is determined by the joint 

 action of many different factors, some more potent than 

 others, some acting directly and some indirectly, some 

 essentially uniform over considerable areas and some 

 varying much in short distances, some simple and some 

 complex. The diagram on the next page seeks to bring 

 out some of these relations more clearly than it can be 

 done by words alone; though of course it is still far from 

 perfect. 



For the sake of simplicity some factors whose effects 

 are not very well understood, and some which are much 

 less noticeable in Alabama than elsewhere, or affect 

 herbs much more than they do trees, or do not vary 

 enough within the limits of our state to make much dif- 

 ference, are omitted. (It should be borne in mind that 

 for fjeof/rapJiicdl purposes it is only variahle factors that 

 have any significance.) 



Factors which vary too much in short distances to be 

 used in defining forest regions are enclosed in dotted cir- 

 cles, and those which are complex, i. e., which can vary 

 in more than one direction, are enclosed in double circles. 

 If space permitted some of the complex factors could be 

 separated into simple ones. For example, soil chemistry 

 is a complex factor, because of the large number of dif- 

 ferent substances contained in soils ; and if we were con- 

 sidering that alone we might have a separate circle for 

 each mineral or element that is found in our soils, 



A combination of a smooth and a dotted circle means 

 that some phases of the enclosed complex factor vary 

 greatly in short distances and some do not. In the case 

 of topography, for example, several hills and valleys, 



(185) 



13 G 



