CONVERSION OF FOREST. 155 



Hole's definition makes it clear why it was necessary for him to recognize a 

 parallel succession. From the basic standpoint of development, parallel 

 succession is but the universal progression from lower to higher phyads char- 

 acteristic of all seres. This is clear from the citation given above, but it is 

 also shown by the following: 



"A very clear case where an area of recent alluvium has been first colonized 

 by munj (Saccharum munja) in this way, but from which it has later been 

 driven out again by the khair (Acacia catechii), has been seen by the writer in 

 an area at the foot of the southern slopes of the Siwaliks near Mohan. In 

 part of the area, munj is still dominant and vigorous, but young plants of 

 khair are just appearing scattered here and there; in other portions the khair 

 are more numerous, larger and older, and many of the munj clumps between 

 them can be seen dead and djdng, while elsewhere a dense pure polewood of 

 khair has become established under the shade of which can still be seen the 

 decayed remains of the munj cliunps which had first colonized the spot." 



Regression is defined as the "reverse succession from a highly developed to a 

 more simple type." The illustrations given have been quoted above. It is 

 again evident in these examples that the process is merely one of destruction 

 by lumbering, fire, grazing, or erosion, with subsequent colonization by lower 

 types. There is no succession, no development from forest to grassland, but 

 a replacement of forest by grassland as a consequence of more or less complete 

 destruction of the trees. As in all cases of supposed regression, the actual 

 facts, in partially denuded areas especially, can be obtained only by quadrat 

 and instrumental methods lasting through several years. 



Conversion of forest.— The foregoing accounts seem to make it clear that 

 nearly all cases of so-called retrogression or regression are not processes of devel- 

 opment at all. They are really examples of the initiation of normal progres- 

 sive development in consequence of destruction or denudation. Hence it is 

 incorrect to speak of retrogressive succession or development, as well as of 

 retrogressive formations or associations. The latter are merely those stages 

 m which the production of a bare area occurs, with the concomitant origin of 

 a new sere. Furthermore, the diverging views upon the subject indicate that 

 the analysis has been superficial and extensive rather than intensive and 

 developmental. 



There remain to be considered those cases in which a change from a higher 

 clunax conununity to a lower subclimax community actually occurs Such 

 are the actual and supposed cases of the conversion of forest into scrub 

 heath, grassland, or swamp. The supposed examples of this change are 

 numerous, but the process of conversion has been seen and studied in verv few 

 iMtances. This does not mean that the process may not be as universalis iu 

 advocates assume, but it does indicate that the final acceptance of this ^ew 

 must await intensive quantitative study of typical cases in each associaZT 

 n this comiection there are three distinct questions to be coiSdSed (S 

 it actu^y proven that the conversion of forest into heath or grassland Hn.^ 

 occur ; (2) can this change be produced by natural as weU as aS agencS 

 (3) IS It an actual successional development in a backward direction ^ ^' 



Superficial evidence of the change of forest into grassland or heath'is abnnH 

 ant in all countries where lumbering, grazing, and cultivation have been nur' 

 sued for centuries. The rise of ecology is so recent, however, and the numbe; 



