80 MAN ON THE LANDSCAPE 



wet, cold, hungry and perhaps lost, can start a fire with the peeled 

 branches of sumac. There is not much loss when the crabapple shades 

 out this link in the succession. 



By now perhaps twenty, perhaps fifty or seventy-five years have 

 passed since the last scrawny cow grazed the field. The period de- 

 pends on many factors. After the wild crab comes the ash, the first 

 good harwood invader, and after another fifty years or so the ash has 

 shaded out the crabapple. (Fig. 36.) Then other hardwoods appear, 

 according to ecological conditions the oaks, hickories, maples, 

 beeches, walnuts creeping clowly because their seed dispersal is re- 

 stricted in distance. (Fig. 37.) 



And so, maybe, with luck in a hundred and fifty years the climax 

 forest may be well on its way back. Without luck, who knows?; it 

 may take a thousand years. 



Animal Succession. Little has been said about animals, but it is 

 obvious that, as environment goes through its developmental phases, 

 food, shelter and moisture conditions favorable to various animals 

 are changing. Usually, successive animal associations proceed along 

 with plant successions, ending in a climax co-terminal with the plant 

 and environmental climaxes. Animals react on the environment in 

 various ways and contribute to its development. Earthworms exert 

 a tremendous influence on soil, when conditions favor their existence. 

 Ants, field mice, shrews, moles, groundhogs, gophers, chipmunks and 

 other burrowing animals aid in soil formation by mixing, aerating, 

 irrigating and fertilizing it. Springtails, snails, centipedes, milli- 

 pedes, beetles, spiders, ants, mites, termites, bumblebees, etc., are pres- 

 ent in surface litter and soil in the magnitude of hundreds of thou- 

 sands up to millions per acre. Field mice, shrews and moles, with 

 their mazes of subsurface runways, are usually present to the extent 

 of dozens up to a hundred or more per acre. Microscopic animals 

 must be thought of in billions. 



Birds and game mammals are present in smaller numbers, but 

 their reaction may be very significant in developing or maintaining 

 the bio-climax. There will probably be, on an acre of average fer- 

 tility and suitable vegetation, one pair of birds, with young. There 

 may be ten pairs of small mammals with ten young per pair. Of other 

 mammals, there might be as many as four or five vegetarian rabbits 

 per acre, one browsing deer to seven acres, one meat eating fox to the 

 square mile. Of game birds, quail may average one, probably less, 

 per acre ; pheasants may average one or two per acre, with concentra- 

 tions on good feeding or watering areas up to 200 per acre at certain 

 times, such as in severe winter weather or drought. 



The truth is that dealing with life and environment solely from 

 the viewpoint of plants is an artificial distinction; and, while useful 

 for simplification of the study area, cannot be a wholly true picture of 

 what is encountered in the field. The serious student of life is intellec- 

 tually obligated to investigate animal ecology, or the combined fields 

 of plant and animal ecology called bio-ecology. 



