We monitored the radial distribution of sap flux density (v; g H2O m(-2) s(-1)) in the sapwood of six plantation-grown Pinus taeda L. trees during wet and dry soil periods. Mean basal diameter of the 32-year-old trees was 33.3 cm. For all trees, the radial distribution of sap flow in the base of the stem (i.e., radial profile) was Gaussian in shape. Sap flow occurred maximally in the outer 4 cm...

A unified nomenclature for use in heat pulse measurement of sap flow is proposed. This unified nomenclature overcomes fundamental misunderstandings of the physics of heat and sap movement in wood. The nomenclature is also appropriate to other methodologies for sap flow measurement, such as heat balance methods.

Sap flow from excised maple stems collected over the winter (1986/87) was correlated with stem water content. Stem water content was high in the fall (>0.80) and decreased rapidly during 2 weeks of continuous freezing temperatures in late winter (<0.60). Exudation of sap from stem segments subjected to freeze/thaw cycles was small (<10 mL/kg) in the fall, but substantial exudation (45-50 mL/kg)...

Mountain ash (Eucalyptus regnans F.J. Muell.) forest catchments exhibit a strong relationship between stand age and runoff, attributed inter alia to differences in tree water use. However, the tree water use component of the mountain ash forest water balance is poorly quantified. We have used the sap flow technique to obtain estimates of daily water use in large mountain ash trees. First, the s...

Some confusion was observed during the 7 International Workshop on Sap Flow (Seville, Spain, 21-24 October 2008) with respect to the use of symbols, units and physical quantities in presentations and during discussions. It was therefore decided at the end of the workshop that a technical note would be very useful with the aim to summarize the basics of the “Système International des Unités (SI)...

Sap flow in plants takes place in the xylem, a hydraulic system that is usually under negative pressure and in which gas and liquid phases are separated by nanoporous, fibrous pit membranes. It has long been known that this system is at risk of drawing gas nanobubbles through these membranes into the xylem sap, a process referred to as “air seeding”. These bubbles then can cavitate and create e...

This work provides a design for two types of sensors, based on the thermal dissipation and heat ratio methods of sap flow calculation, for moderate to large scale deployments for the purpose of monitoring tree transpiration. These designs include a procedure for making these sensors, a quality control method for the final products, and a complete list of components with vendors and pricing info...

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 agr...

A multi-year, multi-technique study was conducted to measure evapotranspiration and its components within an uneven-aged mixed deciduous forest in the Southeastern United States. Four different measurement techniques were used, including soil water budget (1 year), sap flow (2 years), eddy covariance (5 years), and catchment water budget (31 years). Annual estimates of evapotranspiration were s...