Premium
Water vapour isotopic exchange by epiphytic bromeliads in tropical dry forests reflects niche differentiation and climatic signals
Author(s) -
REYESGARCÍA CASANDRA,
MEJIACHANG MONICA,
JONES GLYN D.,
GRIFFITHS HOWARD
Publication year - 2008
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 - 10.1111/j.1365-3040.2008.01789.x
Subject(s) - epiphyte , humidity , crassulacean acid metabolism , relative humidity , chemistry , water vapor , tropical and subtropical dry broadleaf forests , environmental chemistry , water content , environmental science , botany , ecology , photosynthesis , biology , geology , meteorology , geography , organic chemistry , geotechnical engineering
The 18 O signals in leaf water ( δ 18 O lw ) and organic material were dominated by atmospheric water vapour 18 O signals ( δ 18 O vap ) in tank and atmospheric life forms of epiphytic bromeliads with crassulacean acid metabolism (CAM), from a seasonally dry forest in Mexico. Under field conditions, the mean δ 18 O lw for all species was constant during the course of the day and systematically increased from wet to dry seasons (from 0 to +6‰), when relative water content ( RWC ) diminished from 70 to 30%. In the greenhouse, progressive enrichment from base to leaf tip was observed at low night‐time humidity; under high humidity, the leaf tip equilibrated faster with δ 18 O vap than the other leaf sections. Laboratory manipulations using an isotopically depleted water source showed that δ 18 O vap was more rapidly incorporated than liquid water. Our data were consistent with a Craig–Gordon (C‐G) model as modified by Helliker and Griffiths predicting that the influx and exchange of δ 18 O vap control δ 18 O lw in certain epiphytic life forms, despite progressive tissue water loss. We use δ 18 O lw signals to define water‐use strategies for the coexisting species which are consistent with habitat preference under natural conditions and life form. Bulk organic matter ( δ 18 O org ) is used to predict the δ 18 O vap signal at the time of leaf expansion.