VEGETATION OF BRAZOS CANYON 1S1 



vegetation is replaced by weeds, such as that omnipresent 

 southwestern plant, Ximenesia exauriculata, which in spite of 

 its abundance apparently has never received a common name. 

 In many places the alluvial flats are carpeted with a dense brown 

 mat of some Polygonum, probably P. litorale. This short 

 valley is not to be taken as typical of grazing conditions in Rio 

 Arriba County, for the low mountains in this part of New Mexico 

 are probably' the best stock ranges in the state. 



The Rio Brazos is a tributary of the Chama River, flowing 

 into it near Tierra Amarilla. From its mouth eastward for 

 about nine miles it flows through an open valley between low 

 hills, but farther up it traverses a high plateau, through which 

 it has cut a sinuous canyon from two to three thousand feet 

 deep, and often less than a hundred yards in width. The can- 

 yon is bounded by perpendicular granitic cliffs, and ends 

 abruptly at the southern escarpment of the plateau. For nearly 

 a mile on the north side of the stream this escarpment is as 

 abrupt as the walls of the -canyon, then it changes into steep 

 forested hillsides. At its foot is a great talus slope, along whose 

 base the Brazos runs. The opposite side of the valley is inclosed 

 by steep slopes, which rise to a level plateau, this finally falling 

 gradually toward the west to the Chama Valley. The Brazos 

 itself is a typical Rocky Mountain stream, swift, clear, cold, 

 dashing over polished boulders, deepening here and there into 

 great green pools which are the favorite haunts of trout. As it 

 comes out into the wider valley toward Tierra Amarilla, it 

 slackens, of course, and becomes wider and shallow. 



In the region about the Brazos Canyon two life zones are 

 represented, the Canadian and Transition, and on the highest 

 summits there are faint traces of the Hudsonian. The Cana- 

 dian Zone embraces the plateaus and all the higher slopes of 

 the mountains, the "box" or the canyon proper, and the north- 

 ward lower sides of the mountains, extending in narrow strips 

 well down into the Transition along the streams, while the 

 Transition Zone covers all the lower slopes, except the more 

 abrupt northward ones, and spreads, in a modified form, down 

 to the Chama River. Near Tierra Amarilla the Upper Sonoran 



