Xylem sap flux density (Fd) was measured, on a 43-year-old (mature) and three 4-year-old (young) mango (Mangifera indica L.) trees, using Granier-type probes. The relative influences of environmental variables were examined under well-watered condition. Circumferential variation in Fd was also investigated by placing sensors on the north, south-west and south-east sides of the mature tree. Sap ...

Robust thermal dissipation sensors of variable length (3 to 30 cm) were developed to overcome limitations to the measurement of radial profiles of sap flow in large-diameter tropical trees with deep sapwood. The effective measuring length of the custom-made sensors was reduced to 1 cm at the tip of a thermally nonconducting shaft, thereby minimizing the influence of nonuniform sap flux density ...

Bamboos are grasses (Poaceae) that are widespread in tropical and subtropical regions. We aimed at exploring water use patterns of four tropical bamboo species (Bambusa vulgaris, Dendrocalamus asper, Gigantochloa atroviolacea, and G. apus) with sap flux measurement techniques. Our approach included three experimental steps: (1) a pot experiment with a comparison of thermal dissipation probes (T...

Many researchers are using sap flux to estimate tree-level transpiration, and to scale to standand catchment-level transpiration; yet studies evaluating the comparability of sap flux-based estimates of transpiration (Et) with alternative methods for estimating Et at this spatial scale are rare. Our ability to accurately scale from the probe to the tree to the watershed has not yet been demonstr...

Calibration of the Granier thermal dissipation technique for measuring stem sap flow in trees requires determination of the temperature difference (DeltaT) between a heated and an unheated probe when sap flow is zero (DeltaT(max)). Classically, DeltaT(max) has been estimated from the maximum predawn DeltaT, assuming that sap flow is negligible at nighttime. However, because sap flow may continu...

Sap flow measurements conducted with thermal dissipation probes (TDPs) are vulnerable to natural temperature gradient (NTG) bias. Few studies, however, attempted to explain the dynamics underlying the NTG formation and its influence on the sensors' signal. This study focused on understanding how the TDP signals are affected by negative and positive temperature influences from NTG and tested the...

Sap flow measurements conducted with thermal dissipation probes (TDPs) are vulnerable to natural temperature gradient (NTG) bias. Few studies, however, attempted to explain the dynamics underlying the NTG formation and its influence on the sensors’ signal. This study focused on understanding how the TDP signals are affected by negative and positive temperature influences from NTG and tested the...

Accurately scaling sap flux observations to tree or stand levels requires accounting for variation in sap flux between wood types and by depth into the tree. However, existing models for radial variation in axial sap flux are rarely used because they are difficult to implement, there is uncertainty about their predictive ability and calibration measurements are often unavailable. Here we compar...

Uncertainties in ecophysiological responses to environment, such as the impact of atmospheric and soil moisture conditions on plant water regulation, limit our ability to estimate key inputs for ecosystem models. Advanced statistical frameworks provide coherent methodologies for relating observed data, such as stem sap flux density, to unobserved processes, such as canopy conductance and transp...

Granier-type thermal dissipation probes are common instruments for quantifying tree water use in forest hydrological studies. Estimating sapflow using Granier-type sapflow sensors requires determining the maximum temperature gradient (∆Tmax) between the heated probe and the reference probe below. ∆Tmax represents a state of zero sap flux, which was originally assumed to occur each night leading...