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Oecologia (2008) 156:3141 DOI 10.1007/s00442-008-0974-5
PHYSIOLOGICAL ECOLOGY - ORIGINAL PAPER
Coordination of leaf and stem water transport properties in tropical forest trees
Frederick C. Meinzer David R. WoodruV Jean-Christophe Domec Guillermo Goldstein Paula I. Campanello M. Genoveva Gatti Randol Villalobos-Vega
Received: 2 August 2007 / Accepted: 11 January 2008 / Published online: 6 February 2008 Springer-Verlag 2008
Abstract Stomatal regulation of transpiration constrains leaf water potential ([afii9820]L) within species-speciWc ranges that presumably avoid excessive tension and embolism in the stem xylem upstream. However, the hydraulic resistance of leaves can be highly variable over short time scales, uncoupling tension in the xylem of leaves from that in the stems to which they are attached. We evaluated a suite of leaf and stem functional traits governing water relations in individuals of 11 lowland tropical forest tree species to determine the manner in which the traits were coordinated with stem xylem vulnerability to embolism. Stomatal regulation of [afii9820]L was associated with minimum values of water potential in branches ([afii9820]br) whose functional signiWcance was similar across species. Minimum values of [afii9820]br coincided with the
bulk sapwood tissue osmotic potential at zero turgor derived from pressurevolume curves and with the transition from a linear to exponential increase in xylem embolism with increasing sapwood water deWcits. Branch xylem pressure corresponding to 50% loss of hydraulic conductivity (P50) declined linearly with daily minimum [afii9820]br in a manner that caused the diVerence between [afii9820]br and P50 to increase from 0.4 MPa in the species with the least negative [afii9820]br to 1.2 MPa in the species with the most negative [afii9820]br.
Both branch P50 and minimum [afii9820]br increased linearly with sapwood capacitance (C) such that the diVerence between [afii9820]br and P50, an estimate of the safety margin for avoiding runaway embolism, decreased with increasing sapwood C.
The results implied a trade-oV between maximizing water transport and minimizing the risk of xylem embolism, suggesting a prominent role for the buVering eVect of C in preserving the integrity of xylem water transport. At the whole-tree level, discharge and recharge of internal C appeared to generate variations in apparent leaf-speciWc conductance to which stomata respond dynamically.
Keywords Capacitance Stomata Transpiration Turgor Xylem vulnerability
Introduction
Maintaining the integrity of the xylem hydraulic continuum running from the roots to...