278 



SUCCESSION IN ETJKASIA. 



These are called "cogonales," and are covered chiefly with Imperata exaliata 

 and Saccharum spontaneum. After a small portion of the original or second- 

 growth forest has been cut, it is planted, and cultivation then ceases. The 

 growth of the jungle overcomes the planted crops in 1 to 3 years, and the 

 clearing is abandoned for a new one. If the jungle-growth is set on fire, as is 

 frequently the case, nearly all the plants except the grasses are killed. As a 

 consequence vast areas of forest have been converted into grassland, which is 

 maintained by repeated burning. Where fire does not occur, the woody 

 species quickly gain the upper hand and shade out the grass, species of Maca- 

 ranga and Malotes being characteristic at first. In the natural reforestation of 

 the grasslands, Pinus insularis is often the pioneer species, while in lowlands 

 Baiihinia, Eugenia, and others play this rfile. 



Bews (1912, 1913) has dealt incidentally with the development of a number 

 of subtropical formations in Natal and has noted the effect of man upon grass- 

 land in particular: 



The high veld consists of species of Anthistiria and Andropogon. Early 

 burning of the grass causes these to be replaced primarily by Aristida jund- 

 formis, which also invades along paths where Anthistiria has been killed. 

 Eragrostis curvula and Cynodon dactylon form consocies along paths or where 

 the ground has been otherwise disturbed by man or by cattle. When the 

 low veld is changed, Eragrostis and Cynodon enter in the same areas as in the 

 high veld. Aristida is not important, but Spordbolus indicus forms an exten- 

 sive community. When bush-land is cleared, fire sweeps through and destroys 

 the young trees, tending to produce grassland. The author notes the following 

 stages of "retrogression" in the bush: (1) smaller scattered areas of bush, 

 similar to the margin of the larger midland bush; (2) bush clearing due to fire; 

 (3) veld or grassland due to constantly recurring fires. 



Gates (1915 : 26) has described a Sphagnum bog in the crater of Mount San 

 Cristobal in the Philippines, and has indicated the course of succession by 

 figure 22. Priseres are indicated by continuous lines and fire subseres by 

 dotted lines. 



Sphagnum Association. 



Isachne Assoc. 



I 



Paspaium-Kyllinga Assoc. 



Qaultheria or.»-' 

 Ericad Assoc 



Melastpma Assoc. 



Mossy Forest.' 

 Fig. 22.— Prisere and subsere in the Philippines. After Gates. 



