Measuring sap flow with the heat balance approach using constant and variable heat inputs

Kjelgaard, Jim; Stöckle, Claudio O.; Black, Robert; Campbell, Gaylon S.

doi:10.1016/s0168-1923(96)02397-0

Cited by 52 publications

(48 citation statements)

References 25 publications

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“…On the other hand, the MARD between the sap flow estimates obtained from the Dayau-type sensors and transpiration estimates obtained from gravimetric data was very low (only 6.2%) for day-time measurements, in accordance with the results of several previous investigations (e.g. Higgs, 1994;Kjelgaard et al, 1997;Sakuratani, 1981). With some exceptions (Gerdes et al, 1994;Shackel et al, 1992), most relevant previous studies have reported lower variations (Weibel and de Vos, 1994), in measurements over 24-hour periods, than we found here over 24-and 48-h periods.…”

Section: Discussionsupporting

confidence: 91%

“…In previous evaluations of the accuracy of sap flow measurements using stem heat balance methods the transpiration rates in the examined material have sometimes been considerably higher (e.g., Dugas et al, 1993;Grime et al, 1995;Ishida et al, 1991;Valangogne and Nasr, 1993). When comparing the variation in the same ranges of transpiration speed during day time, we have approximately the same magnitude of variation compared to other studies (Dugas et al, 1993;Grime et al, 1995aGrime et al, , 1995bKjelgaard et al, 1997;Weibel and de Vos, 1994). However, measuring sap flow in relation to gravimetrical data and using material with higher transpiration rates during measurements over 24-hour periods or longer lead to higher accumulated sap flows and consequently lower variations in regressions than those we found.…”

Section: Discussionsupporting

confidence: 82%

“…10 g per h or less), resulting in a substantial underestimation of total transpiration in all seedlings of approximately 100 g or more over 48-h periods. Kjelgaard et al (1997) found similar trends when they compared variable power with constant power input methods. Therefore, in order to correctly evaluate water relations in seedlings during establishment in the field using the EMS-type system, corrections are required for this systematic error, possibly using measurements of the weight of a reference seedling planted in a pot.…”

Section: Discussionmentioning

confidence: 65%

“…Few comparisons have been made between methods using constant and variable power inputs (Grime et al, 1995;Kjelgaard et al, 1997), and sap-flow methods have seldom been applied for evaluating water use in seedlings during the establishment phase (Barnes, 2002;Messina and Duncan, 1993), when transpiration rates are normally low. Further, to our knowledge, no previous study has evaluated the accuracy of the EMS-type system using gravimetric data or comparing its accuracy during various light intensities with other sap flow methods.…”

Section: Introductionmentioning

confidence: 99%

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Estimation du flux de sève à partir du bilan thermique de la tige de plants de Quercus robur L. en relation avec l’intensité de la lumière : comparaison de deux méthodes au cours de la phase d’installation

Löf¹,

Welander²

2009

Ann. For. Sci.

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Abstract• Knowledge of whole tree seedling water fluxes is important in ecological and forestry research, especially under conditions with low transpiration, but no standard method has yet been established that provides reliable in situ measurements.• The aims were: (1) to assess the performance of two methods for estimating sap-flows in oak seedlings following planting by correlating the data they provided with natural light intensities over a three-week period, and (2) to compare the estimates with transpiration data obtained by weighing pots.• Estimates of sap flows obtained from data provided by constant power (Dayau-type) heat balance gauges under low light conditions (100-450 μmol m −2 s −1 ) were less variable than estimates from variable power (EMS-type) heat balance gauges. The EMS-type system yielded data with little between-gauge variation, but consistently underestimated transpiration on a daily basis, a systematic error that should be corrected by other methods. The Dayau-type gauges yielded data with substantial variations, and several gauges are probably needed in research to cover these variations. Further, both systems provide rather uncertain estimates of short-time (hour) transpiration rates.• However, provided that these considerations are taken into account, we conclude that it should be possible to use either system in various research contexts. Mots-clés :racines / flux de sève / transpiration / bilan hydrique / relations hydriques Résumé -Estimation du flux de sève à partir du bilan thermique de la tige de plants de Quercus robur L. en relation avec l'intensité de la lumière : comparaison de deux méthodes au cours de la phase d'installation.• La connaissance des flux d'eau de l'arbre entier est importante dans la recherche en écologie et en foresterie, en particulier dans des conditions de faible transpiration, mais jusqu'à présent, aucune méthode standard ne procure des mesures fiables in situ.• Les objectifs étaient : (1) d'évaluer la performance de deux méthodes d'estimation des flux de sève en suivant une plantation de semis de chêne et en corrélant les données fournies par ces dernières avec les intensités de lumière naturelle sur une période de trois semaines, et (2) de comparer les estimations de transpiration avec des données obtenues par pesée des pots.• Les estimations de flux de sève obtenues à partir des données fournies par une alimentation constante (Dayau-type) des jauges de bilan thermique sous des conditions de faible luminosité (100-450 μmol m −2 s −1 ) sont moins variables que les estimations des jauges de bilan thermique à puissance variable (EMS-type). Le système EMS-type a fourni des données avec peu de variation entre les jauges, mais a toujours sous-estimé la transpiration sur une base quotidienne, une erreur systéma-tique qui doit être corrigé par d'autres méthodes. Les jauges de type Dayau ont fourni des données avec des variations importantes, et plusieurs jauges sont probablement nécessaires pour la compré-hension de ces variations. En outre, les deux systèmes ...

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Section: Discussionsupporting

confidence: 91%

Section: Discussionsupporting

confidence: 82%

Section: Discussionmentioning

confidence: 65%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Estimation du flux de sève à partir du bilan thermique de la tige de plants de Quercus robur L. en relation avec l’intensité de la lumière : comparaison de deux méthodes au cours de la phase d’installation

Löf¹,

Welander²

2009

Ann. For. Sci.

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“…Sap flow was measured by the tissue-heat-balance method as described in Sala et al [31], Grime and Sinclair [36], Kjelgaard et al [37] and Nagler et al [8,38,39]. We used home-made sensors described in Scott et al [40], which were field-validated by measurements of ET actual by flux towers [40].…”

Section: Sap Flow Measurementsmentioning

confidence: 99%

An Empirical Algorithm for Estimating Agricultural and Riparian Evapotranspiration Using MODIS Enhanced Vegetation Index and Ground Measurements of ET. I. Description of Method

et al. 2009

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Abstract:We used the Enhanced Vegetation Index (EVI) from MODIS to scale evapotranspiration (ET actual ) over agricultural and riparian areas along the Lower Colorado River in the southwestern US. Ground measurements of ET actual by alfalfa, saltcedar, cottonwood and arrowweed were expressed as fraction of potential (reference crop) ET o (ET o F) then regressed against EVI scaled between bare soil (0) and full vegetation cover (1.0) (EVI*). EVI* values were calculated based on maximum and minimum EVI values from a large set of riparian values in a previous study. A satisfactory relationship was found between crop and riparian plant ET o F and EVI*, with an error or uncertainty of about 20% in the mean estimate (mean ET actual = 6.2 mm d

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Evapotranspiration partitioning in semiarid shrubland ecosystems: a two‐site evaluation of soil moisture control on transpiration

2011

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Vegetation of dryland ecosystems is sensitive to precipitation pulses. Future climate scenarios suggest that the frequency and magnitude of precipitation events will change. How much and to what extent will these changes impact the hydrological cycle in creosotebush (Larrea tridentata) shrublands that dominate the three North American hot deserts? In this study, we examine the partitioning of precipitation inputs into bare soil evaporation (E) and transpiration (T) within creosotebush ecosystems at sites characterized by bimodal precipitation regimes: the Santa Rita Experimental Range (SRER) and the Walnut Gulch Experimental Watershed (WGEW). At both sites, during summer 2008, we measured evapotranspiration (ET) using eddy covariance, whole plant T using the heat-balance sap flow, and soil moisture at several depths. During the dry period preceding the summer monsoon, both ET and soil moisture were very low. With the onset of summer rains, E dominated ET; shrub transpiration did not respond to increases in soil moisture for approximately 3 more weeks. A series of large precipitation events increased moisture at deeper soil layers, and triggered T. Overall, ET was largely correlated to moisture levels in shallow soil layers typical of dryland ecosystems dominated by dry conditions, high evaporative demand, and poor soil infiltration. Under the current precipitation regime, characterized by many small storms and few large storms, soil moisture is low with most precipitation inputs lost as E. However, if climatic changes lead to less frequent but larger precipitation events, dryland communities could experience shifts in the partitioning of ET affecting the hydrologic budget of the ecosystem.

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Measuring sap flow with the heat balance approach using constant and variable heat inputs

Cited by 52 publications

References 25 publications

Estimation du flux de sève à partir du bilan thermique de la tige de plants de Quercus robur L. en relation avec l’intensité de la lumière : comparaison de deux méthodes au cours de la phase d’installation

Estimation du flux de sève à partir du bilan thermique de la tige de plants de Quercus robur L. en relation avec l’intensité de la lumière : comparaison de deux méthodes au cours de la phase d’installation

An Empirical Algorithm for Estimating Agricultural and Riparian Evapotranspiration Using MODIS Enhanced Vegetation Index and Ground Measurements of ET. I. Description of Method

Evapotranspiration partitioning in semiarid shrubland ecosystems: a two‐site evaluation of soil moisture control on transpiration

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