A Comparison of Sap Flow Measurements and Potometry in Two Tropical Lowland Tree Species with Contrasting Wood Properties

Marco V Gutiérrez,Louis S Santiago

doi:10.15517/rbt.v54i1.14000

Abstract

We evaluated the performance of the Heat Dissipation Technique (HDT) to measure sap flow in whole trees by comparison with potometric water uptake. Two tropical lowland species, Ochroma lagopus (balsa), a pioneer species with light wood and Hyeronima alchorneoides (pilón), a late-successional species with hard wood were examined. Diurnal courses of sap flow measured with the HDT showed good agreement with potometry. At the low sap flow rates (below 1 Kg h(-1)) occurring during nocturnal recharge HDT consistently underestimated sap flow rates. This resulted in the failure of the current version of the HDT to measure nocturnal water uptake, an important component of the water budget of at least one of the two species examined.

Highlights

Heat dissipation has been especially promising to those wishing to measure water use in very large trees growing in the field
We evaluated the performance of the Heat Dissipation Technique (HDT) to measure sap flow in whole trees by comparison with potometric water uptake
Our objective was to test the capacity of the Heat Dissipation Technique to accurately measure water use of tropical trees, by comparing it with water uptake of trees held in potometers

Summary

Introduction

Heat dissipation has been especially promising to those wishing to measure water use in very large trees growing in the field. Sap flow estimates based on heat dissipation measurements have shown errors in the range of 2-12% (Wullschleger et al 1998). Our objective was to test the capacity of the Heat Dissipation Technique to accurately measure water use of tropical trees, by comparing it with water uptake of trees held in potometers. Because of the low rates typically associated with nocturnal uptake (Green et al 1989), and the influence of wood density and stem capacitance on this process (Waring and Running 1978, Goldstein et al 1997), a specific objective was to asses the capacity of HDT to measure stem recharge in trees with contrasting wood properties

Objectives

Methods

Results

Conclusion