VEGETATION MANAGEMENT — EGLER 



309 



reinvasion by new trees. If this reinvasion can be slowed down only 

 by half (for example, the time for removal of new trees postponed 

 from 5 to 10 years hence) then the yearly maintenance costs will be 

 halved, a matter of considerable economic importance. As will be 

 shown later, this, and much more, can be done. 



PHYSIOGNOMIC DEVELOPMENT 



By physiognomy is meant the gross morphologic appearance of the 

 vegetation, as grassland, shrubland, or forest. Though there are 

 many exceptions, the normal course of development from open land 

 to forest is through an orderly sequence of stages, starting with (1) 

 annual weeds, such as ragweed and pigweed, and progressing through 

 (2) grasslands with forbs, such as goldenrods and asters, (3) shrub- 

 lands, and (4) forests, often themselves composed of a sequence of 

 stages, such as gray birch at the start, then a white-pine forest, and 

 lastly, a hundred or more years later, a forest of oaks, maples, beeches, 

 hemlocks, and others. For rights-of-way and roadsides, stages 1 

 and 4 are not wanted, and choices may be made from among those in 

 stages 2 and 3. 



There are two mechanical interpretations of this physiognomic 

 development, "relay floristics" and "initial floristic composition." 



Relay floristics is the conventional and commonly accepted view- 

 point on vegetation development. The theory assumes (fig. 2) that 



crop 



veeds 



grassland 



shrub/and 



fores h 



^- ' ' ' ' ' ' I ' ' i ' ' ' ' ' ' ' ' ' I ' I I ■ I I I I I I I I I I t I ^ 



ijears 



Figure 2. A diagrammatic presentation of vegetation development in terms of relay 

 floristics. According to this theory, a relay of plants invades the previous stage, and is 

 in turn replaced by a succeeding stage. 



