COMMUNITY ORGANIZATION: STRATIFICATION 



489 



The opposite extreme is in the tropical 

 evergreen forest communities. Here there is 

 no general period of inactivity, no sharply 

 defined decrease in stratification, but in- 

 stead periodic changes in the over-all vege- 

 tation and animal life as this or that plant 

 constituent passes through its specific 

 flowering, fruiting, and leafing-out. 



We need a vast amount of exact in- 

 formation on the taxonomic and ecologic 

 composition of the animals of the higher 

 strata of forests. Especially desirable would 

 be complete studies of all strata for a 

 period of several consecutive years, in 

 which both plants and animals are studied 



given species, usually as a consequence of 

 specific food requirements, is found in only 

 one stratum during its normally active 

 period. 



The third type of organization is rela- 

 tively frequent. In a study of an elm-maple 

 forest near Nashville, Tennessee, Adams 

 (1941) found nine species of leaf-hoppers 

 (Cicadellidae) of the genus Ertjthroneura. 

 All nine species were taken from the 

 herbaceous, shrub, and canopy levels, but 

 the three most common species (comes, 

 tricincta, and vulnerata) of the canopy 

 were taken in the lower levels only oc- 

 casionally. 



Table 39. Relative Stratal Abundance of Birds in Bagleij Wood (After Colquhoun and 



Morley, 1943) 



Bird 



Wood pigeon. . 



Nuthatch 



Blue tit 



Long-tailed tit. 

 Treecreeper . . . 



Coal tit 



Marsh tit 



Great tit 



Goldcrest 



Blackbird 



Robin 



Wren 



Figures in italics indicate stratum of highest density for each species. 



qualitatively and quantitatively. Such a 

 program should be cooperative and closely 

 integrated. Otherwise there will be no 

 general comprehension, and certain groups 

 (for example, bacteria and birds) might 

 be given close attention, while others (for 

 example, soil protozoans and scale-insects) 

 might be forgotten. When such analyses are 

 available for synthesis, forest stratification 

 can be examined more critically. 



In general, epipatomic strata have several 

 types of organization of their animal con- 

 stituents. For example, there are (1) 

 seasonal and (2) diurnal changes in popu- 

 lation. There are (3) patterns of stratal 

 distribution in which species are found in 

 all epipatomic strata, but are abundant in 

 only one stratum. Then there are (4) 

 specific stratal localizations in which a 



A second example will suffice. Colquhoun 

 and Morley (1943), in their study of 

 Bagley Wood, in an almost pure stand of 

 Quercus robiir, found five strata: (1) upper 

 canopy (above 35 feet), (2) tree (15 to 35 

 feet), (3) shrub (4 to 15 feet), (4) herb 

 (3 inches to 4 feet), and (5) ground. They 

 were concerned with the birds of Bagley 

 Wood and, as Table 39 shows, found that 

 the majority of species utilized several strata 

 with a particular stratum of abundance for 

 each kind of bird. 



This type of distributional pattern, ex- 

 emplified here by leaf-hoppers and birds, 

 is to be expected in forest animals generally. 

 It is equally common in tropical forests. 

 Thus Allee (1926a, p. 462), discussing 

 the Barro Colorado forest in the Panama 

 Canal Zone: "The type of stratification 



