J 



CONTRIBUTIONS TO WESTERN BOTANY NO. ^K :33 



LIFE ZONES 



Soon after my arrival in California to stay, in 1923, \vlien'I-ha3 

 gotten a clean-cut idea of the ecological conditions in southern Califoniia^ 



and of the views of Clements, Hall, Grinnell, and others as to life zorvt% 

 it became evident that either they or myself were radically at fault in 

 their conception of life zones. I have discussed at length the subject -of 

 life zones in Contributions No. 13, and my reasons for rejecting 'Merri- 

 am's terminology. There is no living botanist who has covered as much 

 of the ground in dispute as I, and for this reason I am prepared ^ to 

 defend my position. The various belts of Hall as given in his disrussion 

 of the botany of the San Jacinto Mountains are drainage areas for the 

 most part, good for local consumption but worthless for Avider use, and 

 of little zonal significance. As I have stated elsewhere temperature must 

 govern the limitations of life zones, tlxough humidity is the chief fac^^or 

 limiting plant formations^ In selection of zonal guides (certain species 

 of plants) we have to take into consideration the actual rer.ctions^ of 

 those guides to all ecoli _ 

 give of the life zones in which they are found so that v.e can evaluaVj 

 the evidence they give. For example, the aspen is a very valuaWe guide 



Tempera 

 alifomia 



(Wyoming to" Te>:as 

 Sierra regions) but worthless wherever the' humid- 

 westera Montana and westward. Piiius ponden^-sa 



good 



nc* 



region except in the southern Sierras and in Montana. Juniperus Utah- 



representative of the Lower Temperate life zone thro 



southern 



Californica,^1f it^be a 



guid 



iS far down into the Tropical. Larrea ISIexicana* is the be?t 

 we have for the Tropical, and never fails to tell correctly the 

 which it grows. But the Larrea does not grow on the western 

 slope of the Sierras nor on the plains (coastal) because of the high' humid- 

 ity, but its place is taken by Adenostoma fasciculatum. An acceptance of 

 these facts will lead to the unraveling of the apparently inextVicaVilc 

 tangle in which the botanists and zoologists of California are engiill'ed. 

 A^ a later date I may take up in detail the various areas affected^'bnt 

 this i's not my object here. As is well known Merr" 

 Larrea belt in the Temperate life zone, calling it Lower Sonoran/ a mis- 

 nomer, for it is largely crowded out in Sonora by Leguminosae. "Biu 

 vvherever local conditions permit the Larrea grows as far south as central 

 ^lexico, and ahvays in the Tropical life zone. If the Califorfaia botanists 

 were to extend the locally Califomian terminology of "Subtropical" it 

 would include the entire area where the Larra grows. But ^this would 

 completely disrupt their life zones. For at the south 'the^ Larrea grow^ 

 side by side with the Papaya, persimmon, sugar cane, 'date,- aid "^tther 



am 



