THE PINON-CEDAR WOODLAND. 199 



The groupings of the pifion-cedar woodland have been noted in approxi- 

 mately a hundred localities throughout the climax area. In the majority of 

 these, Pinus edulis and Juniperus monosperma are the dominants. The pifion 

 occurs infrequently in pure stands, but this is regularly the case with cedar 

 at lower altitudes, where the pifion drops out. In such instances, however, 

 the climax woodland soon disappears and the cedar forms a savannah in sage- 

 brush or grassland. In addition to the Colorado plateaus already mentioned, 

 extensive climax areas of pifion-cedar have been studied in Colorado at Gar- 

 land, Arboles, Mancos, Cortez, Dolores, on the San Miguel plateau, and on 

 the plateau of Deadman's Cafion south of Cheyenne Mountain. In Utah 

 similar areas occur at Moab, La Sal, and Bluff. 



The pifions make greater demands than the cedars for water though not for 

 light. In the general absence of quantitative studies, the sequence must be 

 determined by the consideration of successional relations supplemented by 

 evidence from growth-forms and distribution. Upon this basis, Pinus edulis 

 is the least xerophytic, followed by P. monophylla, J. monosperma, and J. 

 utahensis. J. scopulorum seems to approach P. edulis more nearly, judging 

 from the fact that it usually makes its best growth in moist canyons. The habit 

 of P. monophylla and J. utahensis, as well as the nature of the community, 

 accords with the fact that the western portion of the climax receives several 

 inches of rain less than the eastern in general. The reduction of the fascicle 

 to a single leaf in the pifion also suggests the differentiation of this association 

 into two very closely related communities. 



SOCIETIES. 



Societies proper to the woodland are to be expected only where the climax 

 is more or less extensive. In subclimax areas and especially where the com- 

 munity is fragmentary or becomes converted into savannah, the herbs and 

 shrubs of the ground cover are derived from the adjacent or surrounding 

 climax, sagebrush, chaparral, or grassland. Moreover, the shade of the 

 typical woodland has reduced the scrub or grassland species which could 

 adapt themselves to it, just as the more xerophytic habitat has discouraged 

 invasion from the montane forest. As a consequence, the ground cover is 

 composed of a sparse community of shade species in the denser woodland, 

 while the more open areas are occupied by societies more or less common to 

 the adjacent formations. Aspects are little if at all developed in the former, 

 and no attempt has been made to distinguish them here. Several of the domi- 

 nants of the chaparral, sagebrush, and grassland have the appearance of 

 societies, as they are not only constant features, but also take on a habitat- 

 form more or less peculiar to the shady woodland. 



Shade societies. 



Chenopodium fremontii. Aster ericoides. Gutierrezia sarothrae. 



Draba caroliniana. Malvastrum coccineum. Senecio fendleri. 



Pentstemon linarioides. Gymnolomia multiflora. Astragalus flexuosus. 



Sisymbrium incisum. Allium acuminatum. Hymenopappus filifolius. 



Gilia aggregata. Grindelia squarrosa. Eriogonum umbellatum. 



Erysimum parviflorum. Pedicularis centranthera. Artemisia discolor, 



•'entstemon barbatus. Arabis drummondii. Artemisia frigida. 



Pentstemon coeruleus. Chenopodium leptophyllum. Actinella acaulis. 



Opuntia mesacantha. Cordylanthus wrightii. Physaria didymocarpa. 



Lesquerella argentea. Aster bigelovii. Yucca baccata. 



Hedeoma drummondii. Chrysopsis villosa. 



