Water vapour isotopic exchange by epiphytic bromeliads in tropical dry forests reflects niche differentiation and climatic signals

The ¹⁸O signals in leaf water (δ¹⁸Olw) and organic material were dominated by atmospheric water vapour ¹⁸O signals (δ¹⁸Ovap) 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 δ¹...

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Published in:Plant, cell and environment cell and environment, 2008-06, Vol.31 (6), p.828-841
Main Authors: REYES-GARCÍA, CASANDRA, MEJIA-CHANG, MONICA, JONES, GLYN D, GRIFFITHS, HOWARD
Format: Article
Language:English
Subjects:
18O
Animal and plant ecology
Animal, plant and microbial ecology
Biological and medical sciences
Bromeliaceae
Bromeliaceae - physiology
Circadian Rhythm
Craig–Gordon model
Ecosystem
epiphytes
evaporative enrichment
Fundamental and applied biological sciences. Psychology
Oxygen - metabolism
Oxygen Isotopes
Seasons
Synecology
Terrestrial ecosystems
Trees
Tropical Climate
Water - metabolism
water vapour exchange
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Summary:The ¹⁸O signals in leaf water (δ¹⁸Olw) and organic material were dominated by atmospheric water vapour ¹⁸O signals (δ¹⁸Ovap) 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 δ¹⁸Olw for all species was constant during the course of the day and systematically increased from wet to dry seasons (from 0 to +6[per thousand]), 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 δ¹⁸Ovap than the other leaf sections. Laboratory manipulations using an isotopically depleted water source showed that δ¹⁸Ovap 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 δ¹⁸Ovap control δ¹⁸Olw in certain epiphytic life forms, despite progressive tissue water loss. We use δ¹⁸Olw 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 (δ¹⁸Oorg) is used to predict the δ¹⁸Ovap signal at the time of leaf expansion.
ISSN:0140-7791
1365-3040
DOI:10.1111/j.1365-3040.2008.01789.x