30 



ECOLOGY 



Frederic E. Clements 



The Nature and Role of Plant Succession 



Reprinted by permission of the Carnegie Insti- 

 tute of Washington from News Service Bul- 

 letin 3(30):241-244, 1935. 



Dar\vin once said that every traveler 

 should be a botanist, since plants fur- 

 nish the chief embellishment of all 

 landscapes. Today it may be asserted 

 with equal warrant that the traveler 

 should be an ecologist if he is to under- 

 stand the changes wrought by nature 

 and by man upon the countenance of 

 Mother Earth. 



Even the everlasting hills are not 

 ageless, for thev are worn down by wind 

 and water; lakes are filled, rivers grow 

 old, and swamps become dry land sub- 

 ject to the plow. Intimately connected 

 with these changes, hastening or retard- 

 ing them and in turn being modified 

 by them, are the populations of living 

 things, interacting in a maze of causes 

 and effects to render the mantle of life 

 a veritable kaleidoscope. 



Most responsive of these is the plant 

 cover, forming the pattern of a complex 

 community in which animals and prim- 

 itive man in particular find shelter 

 and homes and from which they draw 

 food and materials. Ever\' such com- 

 munity is essentially an organism, of 

 a higher order than an individual 

 geranium, robin, or chimpanzee, but 

 possessing structure and development, 



and a coordination of functions and 

 parts similar in many respects. Like 

 them, it is a unified mechanism in 

 which the whole is greater than the 

 sum of its parts and hence it constitutes 

 a new kind of organic being with novel 

 properties. 



Communities arise, grow, mature, 

 attain old age and die from natural 

 causes or h\ accident. They regularly 

 reproduce themselves after partial de- 

 struction bv fire, lumbering, clearing, or 

 other disturbance, regenerating new 

 parts, not altogether unlike the process 

 by which a lobster grows a new claw 

 or a lizard a tail. Tlie final or adult 

 community is termed a climax, bv rea- 

 son of the fact that it is the highest 

 t}'pe of social organism capable of grow- 

 ing in a particular climate, and its proc- 

 ess of growth is known as succession, 

 from the series of transient populations 

 that pass across the scene. 



The driving force behind succession 

 is climate, operating directly or more 

 often indircctlv through soil or terrain. 

 Like the individual plant, the com- 

 munity is acted upon by the environ- 

 ment and in turn reacts upon the latter, 

 modif)'ing such ruling factors as water, 



