12 VEGETATION IN CENTRAL AMERICA. 



In some localities it is evident that the woody vegetation may make a 

 slow and gradual conquest, even in spite of occasional fires, if suffi- 

 cient time is allowed and no new clearings are made. Many localities 

 which are now open grass country or are covered with scattering 

 pines, oaks, or Curatella trees are being reforested by dense tropical 

 vegetation, wherever the opportunity is afforded by a cessation of 

 cutting and burning. (See Pis. IV, V, and VI.) 



Where the grasses are suitable for cattle and are eaten and trampled 

 by grazing animals the fires are rendered less severe and less frequent, 

 and there is more rapid progress toward reforestation. In districts 

 where sheep are grazed, as in the highlands of the Department of 

 Quiche, Guatemala, the grass is kept too short to protect the land, 

 and a very destructive erosion can then take place. Surfaces which 

 retained their gently sloping contours under the native system of 

 agriculture are now becoming thickly gashed with gullies and ravines 

 whose steep, crumbling slopes remain naked of all vegetation. The 

 complete devastation of such areas seems likely to ensue unless the 

 sheep are withdrawn. 



BOTANICAL INDICATIONS THAT MANY FORESTS ARE OF RECENT 



GROWTH. 



Reforestation can be traced through a succession of temporary 

 types of vegetation, such as pines, oaks, Curatella, Acrocomia, Cecro- 

 pia, Castilla, and Attalea. These are abundant in regions undergoing 

 reforestation, but are extremely rare in virgin forests or in those 

 sufficiently old for the tropical hard-wood trees to have grown to 

 maturity and occupied the land, along with their attendant hosts of 

 epiphytes and shade-tolerant undergrowth. It thus becomes evident 

 that many of the existing forests are not permanent or primeval, but 

 show the intermediate stages of a process of reforestation which 

 probably requires several centuries to reach a stable condition. 



While this permanent forest covering is becoming established the 

 temporary and intermediate types are gradually crowded out and 

 may be almost completely exterminated in districts where the forests 

 have remained undisturbed for sufficiently long periods of time. 

 Thus the absence of rubber trees (Castilla) and of Attalea palms 

 from the forests along the Rio Dulce region of eastern Guatemala 

 may be taken as evidence that this district has not been occupied by 

 Indians for many centuries. 



Such facts have to be taken into account in estimating the agri- 

 cultural possibilities of a locality. Scarcity of wild rubber trees 

 does not prove, for instance, that a place is unsuited to rubber plant- 

 ing, but may mean merely that there has been no agricultural occu- 



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