Carbon Isotope Ratios of Plants of a Tropical Dry Forest in Mexico

Carbon isotope ratios were measured on leaves of the dominant species within a tropical dry forest in Mexico, which was characterized as being strongly drought deciduous. A variety of succulent epiphytes from diverse microsites had carbon isotope ratios indicating obligate crassulacean acid metabolism. All woody species examined had isotope ratios indicative of the C3 photosynthetic pathway, although there was a wide range of isotopic values. Two of the woody species that retained leaves during the dry season showed a large variation in carbon isotope ratios (up to 6 %o) that was dependent on microsite location. Key-words: Epiphytes, isotope ratios, crassulacean acid metabolism, water-use-efficiency, succulents