Differences in leaf physiology among juvenile pines and oaks following high-severity wildfire in an Arizona Sky Island Mountain range

Recent increases in wildfire severity are converting pine-oak (Pinus-Quercus) woodland to oak shrubland in many sites in the southwestern United States. A key mechanism underlying this transition is the vigorous resprouting capacity of oaks compared to low regeneration rates in pines following wildfire. Differences among species in leaf physiological characteristics may also contribute to such vegetation type conversions, especially in the context of recent increased regional aridity. To that end, we evaluated variation in leaf functional traits in post-fire recruits five years after the 2011 Horseshoe Two in the Chiricahua Mountains, Arizona, USA. We measured a suite of functional traits in two pines (Pinus engelmannii and P. leiophylla) and two oaks (Quercus hypoleucoides and Q. arizonica), including leaf gas exchange, leaf pigment concentrations, leaf spectral reflectance, and wood xylem δ¹³C, δ¹⁸O isotopes, and integr