34 



ECOLOGY 



called geographic influences. They ex- 

 hibit aggregation and migration, reac- 

 tion upon the environment and increas- 

 ing control of it. Competition has been 

 rife between and within them, and out 

 of this has gradually emerged a new 

 function, cooperation, first within the 

 family and then spreading to larger and 

 larger units under a slow but inevitable 

 compulsion. 



Succession has been less clearly per- 

 ceived in human communities, though 

 ever\ where prevalent in prehistoric and 

 ancient times, while modern rivalries 

 disclose certain aspects of it. Tlie first 

 recorded succession is that of Chellean, 

 Achulean, Mousterian, Solutrian and 

 Magdalenian peoples in Europe, while 

 the most complex has been the se- 

 quence of races in Mesopotamia, from 

 Sumerian to Akkadian, Amorite, Baby- 

 lonian, Assyrian, Chaldean, Persian, 

 Macedonian, Mongol, Tatar and Turk. 



Better known to us is the series of 

 invasions that have swept over Eng- 

 land, involving Pict, Goidel, Br}'thon, 

 Roman, Angle and Saxon, Dane, and 

 Norman. A similar succession on our 

 own continent is illustrated by the 

 Maya, Toltec, Aztec and Spaniard in 

 Mexico, by various Pueblan cultures of 

 the Southwest, and by the trapper, 

 hunter, pioneer, homesteader, and ur- 

 banite in the Middle West. 



SUCCESSION AS A TOOL 



The applications of succession to 

 human problems and natural indus- 

 tries are manifold. They are exemplified 

 in all the disturbances wrought by man 

 in the vegetation of the globe, as al- 

 ready suggested in the case of fire and 

 clearing. 



Succession is invoked for its bene- 

 fits in the rotation of crops, and it lies 

 at the root of systems of forest man- 

 agement, and particularly of afforesta- 

 tion and reforestation. It is indispen- 

 sable to land classification, and hence 

 to regulated grazing and the utilization 

 of the public domain. It is the chief 

 tool in the control of run-off, erosion 

 and floods, and the conservation of 

 water supplies for irrigation and urban 

 use, as in the maintenance of all sur- 

 face natural resources, including game. 



How varied is its service may be 

 shown by the appeal to it in the litiga- 

 tion between Texas and Oklahoma 

 over the location of boundary formed 

 by the Red River in which millions of 

 dollars in the Burkbumett oil field were 

 involved. The decision of the United 

 States Supreme Court in favor of Texas 

 was based upon the evidence obtained 

 from succession studies made possible 

 by the researches of the Carnegie Insti- 

 tution of Washington. 



QUESTIONS 



1. Define and illustrate a climax com- 

 munity. 



2. Define and illustrate succession. 



4. Name some of the factors comprising 

 the environment of plants. 



5. What are the two most extensive cli- 

 maxes in the United States? 



3. What determines, largely, the type 6. Describe the main events in any one 

 and speed of succession? prominent t)'pe of succession. 



