THE ROLE OF ASPEN IN THE REFORESTATION 



OF MOUNTAIN BURNS IN ARIZONA AND 



NEW MEXICO 



G. A. PEARSON 

 Fort Valley Experiment Station, Flagstaff, Arizona 



A characteristic feature of the timbered mountains in Arizona 

 and New Mexico at altitudes above 8000 feet is the occurrence of 

 extensive burns. The original forests below 9500 feet were com- 

 posed mainly of western yellow pine {Pinus ponderosa), Douglas 

 fir (Pseudotsuga taxifolia), limbei' pine (Pinus flexilis), Mexican 

 white pine (Pinus strobiformis) , and white fir (Abies concolor). As 

 the altitude increases these species are gradually supplanted by 

 Engelmann spruce (Picea engelmanni) , bristle cone pine {Pinus 

 aristata), and in some localities Alpine fir (Abies lasiocarpa). 

 The greater portions of the burns have grown up to quaking aspen 

 (Populus tremuloides) , but extensive areas are practically bare. 

 Scattering trees of the original forest usually remain, and where 

 this condition exists or where the burn is comparatively small 

 conifers are generally restocking the land. Douglas fir, white 

 fir and Engelmann spruce thrive in the shade of the aspen and 

 eventually overtop it, reestablishing the original association or 

 forest type. On burned areas not occupied by aspen or oak brush, 

 which occasionally takes the place of aspen, coniferous reproduc- 

 tion is usually, though not always, deficient. 



The absence of aspen on many of the burns within the natural 

 range of the species is in some instances difficult to explain. On 

 certain areas it is almost entirely wanting, and where it does occur 

 the stands are broken by frequent openings. On exposed slopes 

 and certain other sites the absence of aspen can be readily account- 

 ed for on the basis of unfavorable moisture conditions. Repeated 

 fires have undoubtedly in some instances entirely exterminated the 

 aspen, despite its great capacity for propagation by root suckers. 



249 



THE PLANT WORLD, VOL. 17, NO. 0, 1914 



