A new method of sap flow rate determination in trees

Čermák, Jan; Deml, Miroslav; Penka, Miroslav

doi:10.1007/bf02922390

Cited by 249 publications

(60 citation statements)

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“…For symmetrical measurements, they are placed above and below and at equal distance from the heater in the axial direction (Daum 1967, Vieweg & Ziegler 1960, Sakuratani 1981, Tikhov 1979, Nadezhdina 1989, 1999, Burgess et al 2001, while for asymmetrical measurements, the above thermometer is substituted by one placed together with the heater. (Ittner 1968, Cermák et al 1973, Granier 1985.The majority of methods using thermometers arranged symmetrically around a heater produce accurate sap flow measurement with good dynamic resolution with the true sap flow under low flow conditions (Vieweg & Ziegler 1960, Leyton 1970, Saddler & Pitman 1970, Nadezhdina 1999. The situation can be different, however, under high flow rate conditions when a symmetrical sensor output does not correlate linearly with flow rates and renders a diurnal variation with two peaks, corresponding to one in the morning and one in the afternoon, with a drop at around midday (e.g., Ittner 1968 in spruce, Tikhov 1979 in pine, Nadezhdina 1992, 1999 in apple).…”

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Revisiting the Heat Field Deformation (HFD) method for measuring sap flow

Nadezhdina¹

2018

iForest

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The Heat Field Deformation (HFD) technique is a thermodynamic method for measuring sap flow. Based on continuous heating the HFD method allows for high time resolution measurements which are highly important when studying plant responses to abrupt environmental changes. This work provides a succinct review of previously described features of the HFD methodology. Analyzing symmetrical and asymmetrical temperature differences around a measured linear heater (dTsym and dTas) relative to their ratio dTsym/dTas (so called a K-diagram) is at the heart of this methodology. This key concept, however, has to date only been generally described in previous works on the HFD technique. My objective here is to provide a comprehensive overview describing different types of K-diagrams, their interpretation and application for determining Kvalues or dTas for a zero flow condition. The K-value is a measured parameter which is particularly important for objectively characterizing heat conducting properties at the sensor insertion point under specific local measurement conditions. Correctly determining the K-value is critical for accurately calculating sap flow based on recorded temperature measurements. I have included in this review several examples demonstrating how the K-value is dependent upon changes to the environment and its important role in sap flow estimation. Keywords: K-diagram, K/R-diagram, K-value, Sap Flow per Section, Sap Flux Density, Sensor IntroductionThermodynamic methods for measuring sap flow are widely used in forestry, hydrology, agronomy and eco-physiological studies to accurately estimate tree water use, to identify specific drought stress conditions or to understand plant functionality. These methods which depend on heat transfer, however, differ fairly widely in their capabilities and limitations, notably in their sensitivity to low, zero and reverse flow rates. Reverse sap flow is particularly important for understanding the whole plant physiology and tree architecture, and acts as an indicator of hydraulic redistribution (Nadezhdina 1999, 2010, Burgess et al. 1998. In thermodynamic methods, thermometers are commonly used to gauge temperature changes of the heat field around a heater in response to sap movement. Thermometers may be arranged around the heater either symmetrically or asymmetrically. For symmetrical measurements, they are placed above and below and at equal distance from the heater in the axial direction (Daum 1967, Vieweg & Ziegler 1960, Sakuratani 1981, Tikhov 1979, Nadezhdina 1989, 1999, Burgess et al. 2001, while for asymmetrical measurements, the above thermometer is substituted by one placed together with the heater. (Ittner 1968, Cermák et al. 1973, Granier 1985.The majority of methods using thermometers arranged symmetrically around a heater produce accurate sap flow measurement with good dynamic resolution with the true sap flow under low flow conditions (Vieweg & Ziegler 1960, Leyton 1970, Saddler & Pitman 1970, Nadezhdina 1999. The situation can be different, however, under hig...

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Revisiting the Heat Field Deformation (HFD) method for measuring sap flow

Nadezhdina¹

2018

iForest

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“…In this paper, data from the oldest site (Coulissenhieb) [7] with constants from Smithsonian Meteorological Tables [50]. Standard [5,35]. Sapflux density (J) of five additional trees was measured by constant heating flowmeters according to Granier [18,19].…”

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Estimating tree canopy water use via xylem sapflow in an old Norway spruce forest and a comparison with simulation-based canopy transpiration estimates

et al. 1998

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-Tree xylem sapflow rates of 140-year-old Norway spruce (Picea abies) were scaled to the stand level and compared to canopy transpiration predicted by the stand gas exchange model STANDFLUX. Variation in sapflux densities between individual sensors was high (coefficient of variance = 0.4) and included both variation within and between trees, but it was not different between two applied sapflow methodologies (radial flowmeter

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“…épicéa / modèle tridimentionnel STANDFLUX / flux de sève / transpiration de la canopée / efficience d'utilisation de la lumière / interaction biosphère-atmosphère method of Cermák et al [14,15]; Kucera et al [37]; and Schulze et al [62].…”

Section: Observations Of Sap Flowunclassified

Modelling age- and density-related gas exchange of Picea abies canopies in the Fichtelgebirge, Germany

et al. 2000

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-Differences in canopy exchange of water and carbon dioxide that occur due to changes in tree structure and density in montane Norway spruce stands of Central Germany were analyzed with a three dimensional microclimate and gas exchange model STANDFLUX. The model was used to calculate forest radiation absorption, the net photosynthesis and transpiration of single trees, and gas exchange of tree canopies. Model parameterizations were derived for six stands of Picea abies (L.) Karst. differing in age from 40 to 140 years and in density from 1680 to 320 trees per hectare. Parameterization included information on leaf area distribution from tree harvests, tree positions and tree sizes. Gas exchange was modelled using a single species-specific set of physiological parameters and assuming no influence of soil water availability. For our humid montane stands, these simplifying assumptions appeared to be acceptable. Comparisons of modelled daily tree transpiration with water use estimates from xylem sapflow measurements provided a test of the model. Estimates for canopy transpiration rate derived from the model and via xylem sapflow measurements agreed within ± 20%, especially at moderate to high air vapor pressure deficits. The results suggest that age and density dependent changes in canopy structure (changes in clumping of needles) and their effect on light exposure of the average needle lead to shifts in canopy conductance and determine tree canopy transpiration in these managed montane forests. Modelled canopy net photosynthesis rates are presented, but have not yet been verified at the canopy level.norway spruce / xylem sapflow / canopy transpiration / canopy light use efficiency / biosphere-atmosphere interactions Résumé -Effet de l'âge et de la densité sur la modélisation des échanges gazeux dans la canopée de peuplements de Picea abies (L) Karst. dans le Fichtelgebirge (Allemagne). Les différences d'échange d'eau et de dioxyde de carbone au niveau de la canopée qui se produisent à la suite de changements dans la structure et la densité des arbres dans des peuplements d'Epicéa commun en zone de montagne de l'Allemagne centrale, ont été analysées selon le modèle tridimensionnel de microclimat et d'échange gazeux STANDFLUX. Le modèle a été utilisé pour calculer l'absorption du rayonnement par la forêt, le bilan photosynthétique net et la transpiration d'arbres individuels, et les échanges gazeux au niveau de la canopée. La paramétrisation du modèle a été effectuée à partir des mesures dans six peuplements de Picea abies (L.) Karst. dont l'âge variait de 40 à 140 ans et la densité des peuplements de 1680 à 320 arbres par hectare. La paramétrisation incluait l'information sur la distribution de la surface foliaire à partir de l'exploitation d'arbres, la position des arbres et leurs dimensions. Les échanges gazeux ont été modélisés en utilisant une série de paramètres physiologiques spécifiques de l'espèce, et en supposant qu'il n'y avait aucune influence de la disponibilité en eau. Pour les peuplements consi...

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A new method of sap flow rate determination in trees

Cited by 249 publications

References 8 publications

Revisiting the Heat Field Deformation (HFD) method for measuring sap flow

Revisiting the Heat Field Deformation (HFD) method for measuring sap flow

Estimating tree canopy water use via xylem sapflow in an old Norway spruce forest and a comparison with simulation-based canopy transpiration estimates

Modelling age- and density-related gas exchange of Picea abies canopies in the Fichtelgebirge, Germany

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