286 



THE XORTH AMERICAN GRASSLAND 



fornia well into Lower California were once grassland, as attested by 

 numerous relicts of the perennial dominants (Fig. 68). 



Climate. The climate of this prairie differs from all those previ- 

 ously considered in having a winter rainfall, the maximum occurring 

 in December, January, and February. It is reflected in the two grow- 

 ing seasons of the desert plains, the winter season being the counter- 

 part of the single growing season in California. Except in the neigh- 



FiG. 68. — California prairie composed of Si /pa pulchra; San Joaquin Vallej-. 

 (Plioto by Edith Clements.) 



borhood of the coast, the summers are hot, as in all southern grass- 

 lands, and the winters are mild, with little or no snow within the range 

 of this association. 



The annual rainfall varies from about 6 inches in the upper San 

 Joaciuin and in the Antelope Valley at the west end of the Mohave 

 Desert, to 25-30 inches along the coast. In view of the fact that most 

 of the grassland climax receives 70 per cent of the precipitation be- 

 tween Ai)ril first and October first, it has sometimes been doubted 

 whether the climate of California is favorable to such a climax, espe- 

 cially with the low minimum indicated above. However, the exten- 



