Mesures thermiques des flux de sève dans les troncs et les racines et fonctionnement hydrique des arbres. I. Analyse théorique des erreurs sur la mesure des flux et validation des mesures en présence de gradients thermiques extérieurs

Cabibel, B.; Dô, Frédéric; Horoyan, Jacques

doi:10.1051/agro:19910804

Cited by 36 publications

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“…This assumption was confirmed by the good correlation between sap flow and gravimetric water loss in containerized mango trees. Sap flow appeared to underestimate the gravimetric water loss by less than 10 %, which was still within the confidence intervals of the relative incertitude (10 %) of Granier's method [2]. Granier sap flux sensor was found to be sensitive to both slow and abrupt alternations of the tree physiology.…”

Section: Discussionsupporting

confidence: 52%

“…Quality of sap flow measurements using Granier's sap flux sensors mainly depends on a) the accuracy of the sap flux sensor itself which has been thoroughly studied by Granier [8,9] and Cabibel and Do [2], and b) how well the sap flux density measured by the sensor represents the water conduction in the whole sapwood. Although the Granier's sensor demonstrated capacity of integrating sap flow over small scale [10], failure to sample a zone of sapwood with distinct sap flow from that explored by the sensor probe, could cause substantial error in total sap flow measurement using the Granier's sensors [7].…”

Section: Discussionmentioning

confidence: 99%

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Evaluation of Granier's sap flux sensor in young mango trees

Lü

Chacko

1998

Agronomie

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-Granier's technique of measuring sap flux density using a continuous heating system was tested on young mango trees. On containerized trees, sap flow underestimated transpiration measured gravimetrically by less than 10 %. In a 4-year-old field-grown tree, there was only a 5 % difference between cumulative summed sap flow in the branches and sap flow in the trunk over a 24-h period. Positioning of the sap flux sensor on the trunk was found to be non-critical for sap flow measurement in trees of diameter of less than 10 cm. Granier's sap flux sensor was sensitive to both slow and abrupt changes in canopy transpiration induced by successive branch girdling, defoliation and excision. A comparison of sap flow in the branches and water uptake by the tree measured using the 'cut-tree method' showed that sap flow method underestimated the actual water uptake by less than 6 %.

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Section: Discussionsupporting

confidence: 52%

Section: Discussionmentioning

confidence: 99%

Evaluation of Granier's sap flux sensor in young mango trees

Lü

Chacko

1998

Agronomie

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“…Esta calibração também foi confirmada posteriormente em três espécies arbóreas tropicais (Eucalyptus deglupta, Anacardium excelsum e Bursera simaruba) por Clearwater et al (1999) e Braun & Schmid (1999) em videira. Cabibel & Do (1991) se referem a uma calibração muito próxima desta, realizada em macieira, carvalho, castanheiro e em uma fibra sintética, obtendo-se:…”

Section: Equação Da Calibraçãounclassified

Estimativa da transpiração em cafeeiros utilizando-se sensores de dissipação térmica

Pimentel

Silva

Júnior

et al. 2010

Rev. bras. eng. agríc. ambient.

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RESUMOAlguns métodos são capazes de determinar diretamente a quantidade de água consumida por uma planta, entre eles o "método de dissipação de calor" ou método de Granier. Neste trabalho se propôs, como objetivo, construir e calibrar sensores de dissipação térmica, avaliar a transpiração em função da posição de inserção do sensor na planta (Norte, Sul, Leste ou Oeste) e comparar os resultados com os elementos meteorológicos e a evapotranspiração de referência. Em 24 cafeeiros se instalaram sensores de dissipação térmica, adaptados de Granier (1985), em que o conjunto termopar e resistência foi inserido na agulha. Obteve-se a densidade de fluxo de seiva a partir da variação da diferença de temperatura entre as sondas e se acompanhou a transpiração, em função da transição entre os períodos diurno e noturno. O experimento foi avaliado em 3 períodos: antecedente à floração, na floração e no início da frutificação. Não houve diferença significativamente entre os ângulos de inserção para o fluxo de seiva. Quanto aos elementos meteorológicos, a radiação e a umidade relativa foram os fatores mais determinantes da transpiração obtendo-se, por análises de regressão coeficientes R 2 entre 0,84 e 0,80. Palavra-chave: coffea arabica, fluxo de seiva, irrigação, evapotranspiração Estimation of transpiration in coffee crop using heat dissipation sensors ABSTRACT Some methods are capable of directly determining the amount of water consumed by a plant, among them, the "heat dissipation method" or Granier method. This study aimed to: build and calibrate sensors of thermal dissipation; to evaluate the transpiration as a function of the position of insertion of the sensor in the plant (North, South, East or West) and to compare the results with the meteorological elements and the evapotranspiration of reference. In 24 coffee plants, thermal dissipation sensors adapted from Granier (1985) were installed, where the whole thermocouple and resistance were inserted into the needle. Density of the sap flow was obtained from the variation of the difference in temperature between the probes and accompanied transpiration according to the transition between day and night periods. The experiment was evaluated during 3 periods: before flowering, during the flowering and at the beginning of fruiting. There was no significant difference between the angles of insertion to the sap flow. Regarding the meteorological elements, radiation and relative humidity were the most determinant factors in transpiration, obtained by analysis of regressions with, R 2 coefficients between 0.84 and 0.80.

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“…Due to its simplicity, low cost and reliability, Granier's stationary method has been widely used, particularly in forestry (Andrade et al, 1998;Braun and Schmid, 1999;Lüttschwager and Remus, 2007;Ma et al, 2008;Masmoudi et al, 2004;Meinzer et al, 1999;Oliveras and Llorens, 2001;Sevanto et al, 2008;Wilson et al, 2001;Wullschleger and Hanson, 2008). However, substantial errors on sap flow estimates are induced by heat storage, especially in small stems, and by natural thermal gradients in the wood (Cabibel and Do, 1991;Do and Rocheteau, 2001a). Additionally, the zero flow conditions needed for sap flow density calculation (often observed at predawn) may not occur under certain circumstances, such as during the slow restoration of internal tree water storage following a prolonged drought period (Lu et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

Mesure du flux de sève par sonde de dissipation thermique unique : exploitation du régime transitoire

et al. 2009

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Abstract• In thermal dissipation method the stationary regime is used to estimate sap flow density from the temperature difference between a heating probe and a non-heating one.• A new approach, based on the non-stationary regime of a single heating probe, is investigated on an olive tree branch. Probe temperature is monitored for different flow densities and for heating and cooling modes. Measurement sequences of 10 min using 5 s time steps are made just after the heating is switched on or off.• Results show that temperature variation has a quasi-exponential phase whose duration decreases for increasing flow densities. Thermal indices using temperature of the probe measured at initial, final, and intermediate times t i were developed. Relationships between sap flow density and thermal indices were found to be linear for t i = 10 s−60 s with better coefficients of determination in cooling mode (R 2 = 0.94−0.96) than in heating (R 2 = 0.83−0.93). Validation tests confirmed the robustness of the single probe method with lowest error obtained for t i = 20 s.• Single probe method seems to be a promising technique to measure tree sap flow. Its application could be considered under cooling mode using t i = 20 s and relatively short measurement sequences e.g. 5-10 min.Mots-clés : flux de sève / dissipation de chaleur / sonde unique / régime transitoire / olivier Résumé -Mesure du flux de sève par sonde de dissipation thermique unique : exploitation du régime transitoire.• La méthode de dissipation de chaleur utilise le régime stationnaire pour estimer la densité de flux de sève à partir de la température d'une sonde chauffée et une sonde non chauffée.• Une nouvelle approche exploitant le régime transitoire d'une seule sonde est testée sur une branche d'olivier. Des séquences de mesure de la température de la sonde sont réalisées pour différentes densités de flux. Les mesures sont effectuées toutes les 5 s pendant les 10 min qui suivent la mise en route ou l'arrêt du chauffage.• La variation de la température présente une phase quasi-exponentielle de durée inversement proportionnelle à la densité de flux. Des indices thermiques utilisant les températures de la sonde aux instants initial, final et intermédiaire t i ont été développés. Les relations entre les densités de flux et ces indices sont de type linéaire pour t i = 10 s−60 s avec des coefficients de détermination plus élevés en refroidissement (R 2 = 0.94−0.96) qu'en chauffage (R 2 = 0.83−0.93). Un travail de validation a confirmé la robustesse de la méthode, l'optimum étant t i = 20 s.• La méthode de la sonde unique semble être une technique prometteuse pour mesurer le flux de sève des arbres. Son application est envisageable en mode refroidissement avec t i = 20 s et des séquences de mesure relativement courtes : 5-10 min.

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Mesures thermiques des flux de sève dans les troncs et les racines et fonctionnement hydrique des arbres. I. Analyse théorique des erreurs sur la mesure des flux et validation des mesures en présence de gradients thermiques extérieurs

Cited by 36 publications

References 0 publications

Evaluation of Granier's sap flux sensor in young mango trees

Evaluation of Granier's sap flux sensor in young mango trees

Estimativa da transpiração em cafeeiros utilizando-se sensores de dissipação térmica

Mesure du flux de sève par sonde de dissipation thermique unique : exploitation du régime transitoire

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