Cellulose (delta)18O is an index of leaf-to-air vapor pressure difference (VPD) in tropical plants.
Cellulose in plants contains oxygen that derives in most cases from precipitation. Because the stable oxygen isotope composition, δ(18)O, of precipitation is associated with environmental conditions, cellulose δ(18)O should be as well. However, plant physiological models using δ(18)O suggest that cellulose δ(18)O is influenced by a complex mix of both climatic and physiological drivers. This influence complicates the interpretation of cellulose δ(18)O values in a paleo-context. Here, we combined empirical data analyses with mechanistic model simulations to i) quantify the impacts that the primary climatic drivers humidity (e(a)) and air temperature (T(air)) have on cellulose δ(18)O values in different tropical ecosystems and ii) determine which environmental signal is dominating cellulose δ(18)O values. Our results revealed that e(a) and T(air) equally influence cellulose δ(18)O values and that distinguishing which of these factors dominates the δ(18)O values of cellulose cannot be accomplished in the absence of additional environmental information. However, the individual impacts of e(a) and T(air) on the δ(18)O values of cellulose can be integrated into a single index of plant-experienced atmospheric vapor demand: the leaf-to-air vapor pressure difference (VPD). We found a robust relationship between VPD and cellulose δ(18)O values in both empirical and modeled data in all ecosystems that we investigated. Our analysis revealed therefore that δ(18)O values in plant cellulose can be used as a proxy for VPD in tropical ecosystems. As VPD is an essential variable that determines the biogeochemical dynamics of ecosystems, our study has applications in ecological-, climate-, or forensic-sciences.
Center for Stable Isotope Biogeochemistry, Department of Integrative Biology, University of California, Berkeley, CA 94720, USA. kahmena@ethz.ch
Ansgar
A
Kahmen
Dirk
D
Sachse
Stefan K
SK
Arndt
Kevin P
KP
Tu
Heraldo
H
Farrington
Peter M
PM
Vitousek
Todd E
TE
Dawson
D000399:Air Pressure; D002482:Cellulose / Q000378:metabolism*; D017753:Ecosystem; D027822:Myrtaceae / Q000378:metabolism*; D010103:Oxygen Isotopes / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism*; D013696:Temperature
D010103:Oxygen Isotopes; D002482:Cellulose
New Phytol. 2009;181(3):553-62
19154318
Science. 1977 Dec 23;198(4323):1209-15
17741685
Science. 1979 Apr 6;204(4388):51-3
17816736
Nature. 2006 Apr 27;440(7088):1179-82
16641993
Funct Plant Biol. 2005 May;32(4):293-303
32689132
Plant Cell Environ. 2008 Jun;31(6):738-51
18208514
Radiat Environ Biophys. 1974 Mar 29;11(1):41-52
4832051
Plant Physiol. 1986 Oct;82(2):423-7
16665045
Tree Physiol. 2001 Jan;21(1):43-50
11260823
New Phytol. 2009 Nov;184(3):619-630
19761496
Plant Physiol. 1990 May;93(1):325-32
16667454
Tree Physiol. 2005 Feb;25(2):129-46
15574395
Plant Cell Environ. 2007 Aug;30(8):892-909
17617818
Funct Plant Biol. 2007 Mar;34(2):83-94
32689335
Science. 1981 Mar 27;211(4489):1417-9
17731182