386 



COMMUNITY ECOLOGY: 



BOREAL REGION 

 Arctic Alpine 

 HudsonJon 

 Canadion 



Transition 



AUSTRAL REGION 

 Upper Austral 

 Lower Austral 



TROPICAL REGION 



Figure 19.24 Merriom's Life Zones. 



in the northeastern Great Plains Grassland and con- 

 tinues eastward into the Deciduous Forest. Gommon 

 animals are the fox squirrel, prairie vole, eastern 

 wood rat, many warblers, lark sparrow, cardinal, and 

 Carolina wren. The western, or Upper Sonoran ^one, 

 has areas of sagebrush, chaparral, and woodland 

 characterized by the gray fox, ring-tailed cat, grass- 

 hopper mouse, valley quail, scrub jay, Bewick wren, 

 plain titmouse, and bushtit. The Lower Austral ^one 

 also has humid eastern and arid western subunits. 

 The Austronpartan ^one is in the Southern Pine Forest 

 of the Atlantic and Gulf Coastal Plains; it features the 

 cotton rat, rice rat, boat-tailed grackle, chuck-will's 

 widow, and Swainson's warbler. The Lower Sonoran 

 ^one includes southwestern Desert Scrubs, kangaroo 

 rats, pocket mice, desert quail, vermilion flycatcher, 

 cactus wren, and the verdin. 



In the small Tropical Region of southern Florida, 

 the vegetation is typified by palms, orchids, man- 

 groves, and many plants of climbing habit. The com- 

 mon animals are mostly birds, especially the great 

 white heron, reddish egret, caracara. Everglade kite, 

 white-crowned pigeon, and mangrove cuckoo. 



CRITICISMS 



Life Zones were defined solely on the basis of tem- 

 perature. However, temperature is associated with 

 many other ecological factors. For this reason. Life 

 Zones can be said to approximate the effects of lati- 

 tude, altitude, slope, slope exposure, prevailing winds 

 and air currents, nearness to water and deserts, 

 amount of water, type of substrate and rock outcrops 

 as related to heat absorption and reflection, and size 

 of mountains (small, isolated elevations show little 

 zonation). Moreover, because temperature is a fair 

 environmental indicator, Life Zones are related to the 

 distribution of plants and, therefore, animals. 



The Life Zone scheme once was the only available 

 scheme. Certain newer ones exist and generally are 

 used much more frequently by biogeographers. How- 

 ever, these newer concepts mostly supplement the 

 ideas of Merriam. Most supplements — perhaps all of 

 them — could have fitted within his Life Zone concept. 

 In many respects, it is unfortunate that they were not. 

 Perhaps most unfortunate is the possibility of Mer- 

 riam's major contribution being overlooked. His Life 



