RELATIONS BETWEEN PLANTS AND ENVIRONMENT 77 



ever, fertility drops rapidly as the organic matter is oxidized and 

 leached by exposure to climate, and as erosion gets underway. After 

 a period of cropping, yields drop so far that the land is retired to 

 permanent pasture. (Fig. 26.) The period of cropping may range 

 from five or ten years of continuous row crops, up to fifty or seventy- 

 five years of rotated crops. 



The usual procedure in pasturing these lands is to attempt the 

 impossible, that is to make as much money from animals as was once 

 provided by small grains or row crops. In short, these pastures arc 

 overgrazed. Erosion continues. The grass cover becomes thinner. 

 Bare land meets the eye in many places. (Fig. 27.) Nature, abhorring 

 nakedness, starts to reclothe the now abandoned land. 



Here and there on the raw soil, filamentous mosses appear, along 

 with some micro-algae, and crustlike lichens. (Fig. 28.) These primi- 

 tive forms partially stop the erosion and begin to rebuild fertility. 

 They increase the chance that invading seeds will find a foothold, 

 instead of being washed off, blown off, or killed by dryness if they 

 sprout. 



What kind of seeds can meet the grade ? In spite of the humid cli- 

 mate, the high rate of runoff coupled with the lack of absorbent top- 

 soil have changed the soil climate to one of semi-aridity. In short, 

 the soil climate of this onetime Central Hardwood Forest has become 

 the soil climate of the Great Plains. And so it is not surprising that 

 a plains-like grass invades poverty grass. (Fig. 29.) But, unlike 

 grasses of the plains, poverty grass has about as much nutritional 

 value as excelsior. It has all it can do to keep itself alive, and while it 

 may be somewhat succulent for a brief period in the spring, it pro- 

 vides very little food for steer, lamb, rabbit or field mouse. These 

 animals relish poverty grass approximately in the degree you would 

 relish eating a damp broom. Along with this grass, another much 

 like it in character usually appears broomsedge. (Fig. 30.) 



After poverty grass has contributed its bit to preventing further 

 erosion, has wrested some minerals from their lockers in the poor 

 soil, and has added some humus to the land, the succession proceeds. 

 Running briars move in, particularly dewberry. Dewberry is a low- 

 growing, hardy plant. It produces fruit which is of some value to 

 animals such as rabbits, birds and others. By its shading effect it 

 begins the ousting of the poverty grass and other shorter plants which 

 need full sunlight. (Fig. 31.) 



Following dewberry, its taller cousin, blackberry comes into the 

 field. More wildlife is supported and protected. More humus accu- 

 mulates. Less erosion occurs. More shade is thrown. (Fig. 32.) 



Next come low-grade trees, such as sassafras, sumac, and wild 

 crabapple. (Figs. 33, 34, 35.) More roots grasp the soil. More ani- 

 mals can live on the new seeds and fruits. Man is still excluded, how- 

 ever. There is, as yet, little of use to him. As the trees grow, the 

 crabappple outgrows the sumac. Sumac is a no-account weed of a 

 tree, weak and pithy. Birds may eat its seeds, and the outdoorsmen, 



