488 



THE COMMUNITY 



Leptodactylus, of tropical America spends 

 the day in its deep subterranean burrows 

 and ascends to the floor at night for insect 

 food (Park, Barden, and Williams, 1940). 



In a study of the birds of Bagley Wood, 

 near Oxford, England (Colquhoun and 

 Morley, 1943), the species were divided 

 into three feeding groups: namely, upper 

 canopy, tree and shrub, and ground. The 

 last, again chiefly insect eaters, are typical 

 floor species. During vernal and autumnal 

 migrations many birds spend part of their 

 time in this stratum. The ovenbird is a 

 typical example. 



Few mammals Live continuously in or on 

 the floor and derive their sustenance from 

 its inhabitants; many pass a part of their 

 lives as floor transients. Some forest 

 mammals travel on the floor and feed on 

 the herbaceous and shrub strata (deer), or 

 dig through the floor into the subterranean 



For the interested reader this outline 

 of the floor stratum may be filled out 

 taxonomically by consulting the extensive 

 lists of Alice (1926a) for the Panama Canal 

 Zone rain forest, Adams (1941) for north 

 temperate deciduous forest, and Fichter 

 (1939) for north temperate coniferous 

 forest. 



From preceding pages it will be apparent 

 that the floor stratum ( 1 ) forms an essential 

 shield against meteorological and erosion 

 factors which would otherwise destroy 

 forest soil; (2) is the operational level at 

 which vital preliminary reductions are 

 initiated in soil formation; and (3) is the 

 cross roads of the community and, as such, 

 is used by many of the residents and tran- 

 sients of all strata. 



The remaining strata, although populated 

 by plants and animals, have a discontinuous 

 matrix formed almost wholly by plants. In 



Table 38. Forest Floor Populations of Macroscopic Invertebrates 



strata for roots and tubers (pigs, peccaries, 

 and the hke). Others feed in part on floor 

 animals, but ascend to it from subterranean 

 burrows (red-backed mice, shrews, less 

 commonly moles), or descend from higher 

 strata (squirrels). Chipmunks and deer 

 mice spend more of their lives on the floor, 

 and feed more on the fife of this level, but 

 both are often in higher strata. 



Study of data on population density of 

 forest floors suggests two conclusions: first, 

 that the population per unit area is larger 

 for forest floor than for grassland floor 

 in the same general latitude. This can be 

 seen by comparing the figures for grass- 

 land (Table 37) with those in Table 38. 

 Second, that in both forest and grassland 

 communities the population per unit area 

 tends to be larger in tropical regions as 

 contrasted with temperate regions at the 

 same general altitude. 



temperate deciduous forest communities 

 relatively few animals are permanent 

 residents, in the sense used in discussions 

 of the first two strata, since the annual loss 

 of foliage and the exposure are much 

 greater. Even in such forests there is never 

 an absolute loss of stratification. The 

 afoliated shrubs and trees remain; in their 

 skeletonized winter crowns are loosely con- 

 structed winter nests of tree squirrels. The 

 bark crevices, bark, and cambium of shrubs 

 and trees are crowded with hibernating in- 

 sects, as eggs, nymphs, larvae, pupae, or 

 imagines. Certain insects overwinter in 

 living sapwood and heartwood. Galls and 

 cocoons are attached to twigs. In such com- 

 munities stratification is permanent; it is less 

 active, and there are numerous hibernal ad- 

 ditions from more exposed communities. 

 The herbaceous stratum in these forests is 

 the most unstable. 



