Vegetation change in Arizona Madrean pine-oak forests following high-severity wildfire: patterns and mechanisms

Authors: Andrew M Barton*, University of Maine - Farmington, Helen M. Poulos, Wesleyan University
Topics: Environmental Science
Keywords: climate change, drought tolerance, forest type conversion, high-severity wildfire, Horseshoe Two Fire, oaks, pines, plant physiology, resprouting, vegetation change
Session Type: Paper
Day: 4/4/2019
Start / End Time: 9:55 AM / 11:35 AM
Room: Regency Ballroom, Omni, West
Presentation File: No File Uploaded


Conversion of forests to shrublands and other vegetation types is common across forests of the Southwest in response to the increasing prevalence of high-severity wildfires. We examined post-fire regeneration of pines and oaks in two high-severity fires in the Chiricahua Mountains in the Sky Islands of Arizona. Under pre-Euro-American settlement fire conditions, thick-barked Pinus engelmannii and P. leiophylla survived typical, low-severity fires. In contrast, recent crown fires resulted in widespread mortality of pines, but oaks (Quercus hypoleucoides and Q. arizonica) have resprouted abundantly. Post-fire seedling establishment has been very low in P. engelmannii, which is largely restricted to moister, low-fire-severity sites. P. leiophylla has fared only slightly better, in part because of a modest amount of resprouting. The high performance of oaks in the post-fire landscape is tied to their high photosynthetic capacity and drought tolerance, while the poor regeneration of pines following high-severity wildfire is likely related to their drought intolerance and need to maintain positive water balance. In response to high-severity fire in the Chiricahua Mountains, therefore, differences in sprouting ability and physiology appear to favor oaks over pines in the post-fire landscape, which could lead to a long-term reduction in the abundance and distribution of pines in these formerly mixed Madrean pine-oak forests.

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