Spatial variations in xylem sap flux density in the trunk of orchard-grown, mature mango trees under changing soil water conditions

Abstract

Circumferential and radial variations in xylem sap flux density in trunks of 13-year-old mango (Mangifera indica L.) trees were investigated with Granier sap flow sensor probes under limiting and non-limiting soil water conditions. Under non-limiting soil water conditions, circumferential variation was substantial, but there was no apparent relationship between sap flux density and aspect (i.e., the radial position of the sensor probes on the trunk relative to the compass). Hourly sap flux densities over 24 hours at different aspects were highly pair-wise correlated. The relationships between different aspects were constant during well-watered periods but highly variable under changing soil water conditions. Sap flux density showed marked radial variation within the trunk and a substantial flux was observed at the center of the trunk. For each selected aspect on each tree, changes in sap flux densities over time at different depths were closely correlated, so flux at a particular depth could be extrapolated as a multiple of flux from 0 to 2 cm beneath the cambium. However, depth profiles of sap flux density differed between trees and even between aspects within a tree, and also varied in an unpredictable manner as soil water conditions changed. Nevertheless, over a period of non-limiting soil water conditions, depth profiles remained relatively constant. Based on the depth profiles obtained during these periods, a method is described for calculating total sap flow in a mango tree from sap flux density at 0-2 cm beneath the cambium. Total daily sap flows obtained were consistent with water use estimated from soil water balance.

Evaluation of heat balance and heat dissipation methods for sapflow measurements in pine and spruce

“…A sensor that covered the whole sapwood depth, and integrated the variation in sapflow, would probably best account for the radial variations in sapflow density. As this necessitates a large number of sensors of variable length, an acceptable compromise would be to distribute two or more 2 cm long sensors throughout the entire depth of the sapwood [30]. It has been suggested that measurements with sensors that partly cover the conducting xylem should be scaled using a correction factor [13,25].…”

Effet de la longueur de la portée des sondes de dissipation thermique de type Granier sur des mesures de densité de flux de sève

“…Iida et al (2006) indicated that transpiration activity at this site was depressed by the lack of soil water when REW was less than 0.4. Thus, the soil water was sufficient and the variations in u were likely constant (Lu et al, 2000).…”

“…Granier et al, 1996b;Köstner et al, 1998) and the azimuthal variations in u in the trunk, especially when growing in open canopy space like an orchard (Lu et al, 2000), must be determined. These variations of u can be measured by inserting a number of Granier sensors at the same height into a single tree.…”

“…These variations of u can be measured by inserting a number of Granier sensors at the same height into a single tree. Because heat transfer by conduction occurs in all directions, care must be taken to place the reference probes away from the influence of the heaters (Lu et al, 2000). Thus, as a prerequisite, the potential distance across which heat can be transferred by conduction must be determined, not only to define the span length between probes of a single sensor but to ensure the correct spacing of a number of sensors at the same height.…”

Fluxo de seiva xilemática em mamoeiro 'Golden' cultivado por microaspersão sobre copa: relações com as variáveis ambientais

“…Como se pode observar, em relação à bananeira, o mamoeiro representa um valor muito maior (˜11 vezes maior). Mesmo com valores de 0,06 m 2 de folha para cada cm 2 de área do xilema ativo, tal relação promoveu o valor bem elevado do fluxo de seiva (0,160 kg cm -2 de xilema ativo h -1 ), quando comparado a bananeira (0,015 kg cm -2 de xilema ativo h -1 ), pinheiro (0,019 kg cm -2 de xilema ativo h -1 ) (LU et al, 1995), em mangueira (0,035 kg cm -2 de xilema ativo h -1 ) (LU et al, 2000) e em algumas árvores tropicais (0,040 kg cm -2 de xilema ativo h -1 ) (GRANIER et al, 1996). Em bananeira, cultivada em condição de campo, LU et al (2002) realizaram medidas de FS as quais foram positivamente bem correlacionadas com algumas variaveis como radiação solar e evapotranspiração de referência.…”