Xylem hydraulic properties in subtropical coniferous trees influence radial patterns of sap flow: implications for whole tree transpiration estimates using sap flow sensors

Guyot, Adrien, Ostergaard, Kasper T., Fan, Junliang, Santini, Nadia S. and Lockington, David A. (2014) Xylem hydraulic properties in subtropical coniferous trees influence radial patterns of sap flow: implications for whole tree transpiration estimates using sap flow sensors. Trees - Structure and Function, 29 4: 961-972. doi:10.1007/s00468-014-1144-5


Author Guyot, Adrien
Ostergaard, Kasper T.
Fan, Junliang
Santini, Nadia S.
Lockington, David A.
Title Xylem hydraulic properties in subtropical coniferous trees influence radial patterns of sap flow: implications for whole tree transpiration estimates using sap flow sensors
Journal name Trees - Structure and Function   Check publisher's open access policy
ISSN 0931-1890
1432-2285
Publication date 2014-12-21
Year available 2014
Sub-type Article (original research)
DOI 10.1007/s00468-014-1144-5
Open Access Status
Volume 29
Issue 4
Start page 961
End page 972
Total pages 12
Place of publication Heidelberg Germany
Publisher Springer
Collection year 2015
Language eng
Formatted abstract
Key message

A high spatial resolution dataset of sap flux density in subtropical conifers is used to assess the minimum number and location of sap flow sensors required to monitor tree transpiration accurately.

Abstract

Tree transpiration is commonly estimated by methods based on in situ sap flux density (SFD) measurements, where the upscaling of SFD from point measurements to the individual tree has been identified as the main source of error. The literature indicates that the variation in SFD with radial position across a tree stem section can exhibit a wide range of patterns. Adequate capture of the SFD profile may require a large number of point measurements, which is likely to be prohibited. Thus, it is of value to develop protocols, which rationalize the number of point measurements, while retaining a satisfactory precision in the tree SFD estimates. This study investigates cross-sectional SFD variability within a tree and successively for six individual trees within a stand of Pinus elliottii var. elliottii × caribaea var. hondurensis (PEE × PCH). The stand is part of a plantation in subtropical coastal Australia. SFD is estimated using the Heat Field Deformation method simultaneously for four cardinal directions with measurements at six depths from the cambium. This yields a reference value of single tree SFD based on the twenty-four point measurements. Large variability of SFD is observed with measurement depth, cardinal direction and selected tree. We suggest that this is linked to the occurrence of successive narrow early and latewood rings with contrasting-specific hydraulic conductivities and wood water contents. Thus, an accurate placement of sensors within each ring is difficult to achieve in the field with the sensor footprint covering several rings of both early and latewood. Based on the reference dataset, we identified both an “ideal” setup and an “optimal” setup in terms of cost effectiveness and accuracy. Our study shows the need of using a systematic protocol to optimize the number of sensors to be used as a trade-off between precision and cost. It includes a preliminary assessment of the SFD variability at a high spatial resolution, and only then based on this, an appropriate placement of sensors for the long-term monitoring.
Keyword Pinus elliottii × caribaea
Plant water relations
Sap flux density
Sapwood
Tree water use
Upscaling
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ
Additional Notes Published online ahead of print 21 Dec 2104

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Civil Engineering Publications
Official 2015 Collection
 
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Created: Tue, 30 Dec 2014, 00:25:36 EST by System User on behalf of School of Civil Engineering