BIOLOGICAL AND ECONOMIC ASPECTS OF CHAPARRAL 13 



very minor importance from an area with a dense stand of brush uni- 

 form over the area, but after a fire has destroyed the cover these sur- 

 face roots are killed and severe erosion takes place. 



Landslides in dense stands are relatively frequent on steep slopes 

 and are caused by a supersaturation of the soil mass. With plenty 

 of the heavier, deeper root .systems of the chaparral, these landslides 

 cannot occur, but frequently the species forming the cover on such 

 areas do not possess roots capable of anchoring the surface soil firmly 

 in place. Studies of these slips show that the genera in the order of 

 their importance in preventing these slips are: (i) oaks, (2) man- 

 zanitas, (3) sumacs, followed by other species, as the quinines, cas- 

 caras, and legumes, with greasewood bringing up the rear. In nearly 

 every case it was found that when oaks were destroyed in these slips 

 these deep roots were badly decayed, and it is well known that grease- 

 wood is weak, which would account for its place in the scale. It is 

 apparent, therefore, that there is a direct relationship between the 

 strength of these, deep taproots and the number of landslides. 



Another interesting thing in connection with the chaparral is the 

 change in vegetation that takes place on an area following the removal 

 of the chaparral cover: large numbers of herbaceous annuals and per- 

 ennials spring up whose presence before had not been noted. On two 

 areas, at an elevation of 4,300 feet,, from one of which all the chaparral 

 cover had been cleared, there were 37 species on the cleared area not 

 found in the brush, the increase in the number of individual plants 

 amounting to 164 per cent, while there were found in the chaparral five 

 species not found on the cleared areas. 



The same change in the character of the plants which spring up 

 after the removal of the brush is also to be noted on fire areas. Here 

 21 species occurred which were not found anywhere in the adjacent 

 brush. While the litter was not entirely destroyed, the number of 

 individual plants per unit area was 75 per cent greater than on the 

 area where it was entirely consumed. Similar studies were carried 

 on by sowing litter obtained in the brush in the open, and species sim- 

 ilar to those found on the burn and cleared areas were obtained, indi- 

 cating that there were a large number of dormant seeds of various 

 plants aw^aiting favorable conditions for germination, and also evinc- 

 ing the fact that the chaparral area formerly had been destroyed. 



On the economic side, chaparral holds a future which is just be- 

 ginning to be appreciated. For example, the yucca stem is being used 

 for surgeon's splints and for tree protectors, while from yucca leaves 



