| Summary: | In an effort to identify the influence of light and temperature on the physiology and leaf structural characteristics of three species of Quercus from Coahuila, Mexico, we measured a comprehensive suite of plant traits as functions of light and temperature intensity. We tested the hypotheses that 1) species' physiological responses to light and temperature were related to their distributions in their native habitats; and 2) that species' physiological responses corresponded to similar variation in leaf anatomical and morphological traits. Quercus sideroxyla was adapted to high elevation forest over stories as evidenced by its high photosynthetic rate, transpiration rate, relative water content (RWC), leaf density (LD), and thick palisade and spongy parenchyma. Quercus rugosa displayed typical characteristics of a forest understory species including a low photosynthetic rate and light saturation point, thick spongy parenchyma tissue and high RWC, leaf density, and leaf mass per unit area. Quercus laceyi was adapted to hot, dry sites based on its lower RWC and LD, intermediate photosynthetic rate, thick cuticle and upper epidermis, and low transpiration rates at high temperatures. Our results suggest that the physiological and structural adaptations of Mexican oaks to changing environmental conditions across resource gradients are key regulators of plant community structure.
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