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Stable isotopic composition of carbon and nitrogen and nitrogen content in vascular epiphytes along an altitudinal transect*
Author(s) -
Hietz P.,
Wanek W.,
Popp M.
Publication year - 1999
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1046/j.1365-3040.1999.00502.x
Subject(s) - epiphyte , crassulacean acid metabolism , nitrogen , botany , transect , biology , ecology , chemistry , photosynthesis , organic chemistry
The foliar content of nitrogen and the relative abundances of 13 C and 15 N were analysed in vascular epiphytes collected from six sites along an altitudinal gradient from tropical dry forests to humid montane forests in eastern Mexico. The proportion of epiphyte species showing crassulacean acid metabolism (CAM) (atmospheric bromeliads, thick‐leaved orchids, Cactaceae, and Crassulaceae) decreased with increasing elevation and precipitation from 58 to 6%. Atmospheric bromeliads, almost all of which had δ 13 C values indicating CAM, were more depleted in 15 N ( x = − 10·9‰ ± 2·11) than the C 3 bromeliads which form water‐storing tanks ( − 6·05‰ ± 2·26). As there was no difference in δ 15 N values between C 3 and CAM orchids, the difference in bromeliads was not related to photosynthetic pathways but to different nitrogen sources. While epiphytes with strong 15 N depletion appear to obtain their nitrogen mainly from direct atmospheric deposition, others have access to nitrogen in intercepted water and from organic matter decomposing on branches and in their phytotelmata. Bromeliads and succulent orchids had a lower foliar nitrogen content than thin‐leaved orchids, ferns and Piperaceae. Ground‐rooted hemi‐epiphytes exhibited the highest nitrogen contents and δ 15 N values.