J. Čermák

A new method of sap flow rate determination in trees

A new method of sap flow rate determination in stems of adult trees is described in which mass flow (the transpiration flux in the present case) is estimated from a heat-transfer measurement. The device used includes a couple of thermometers in a differential connection and plate electrodes, through which a controlled heat input flows into a denned studied segment of the xylem. The present method was tested first with a laboratory simulating system, then with the stem of a living adult treePrunus avium L. The data are registered continually and automatically; continuous measurement of sap flow rate of long duration with a greater number of trees is thus made possible.AbstractByla navržena nová metoda stanovenÍ vedenÍ vody v kmeni adultnÍch stromÜ, založená na principu mčřeni hmotného toku (transpiraeniho proudu) na základĚ prenosu tepla. ZařÍzčnÍ se skládá z dvojice diferenciálnč zapojených teplomčrů a deskových elektrod, kterými je přiváděn kontrolovaný tepelný výkon do zkoumané části aktivnÍho xylemu (definovaného segmentu), Navrženà metoda byla vyzkoušena na simulátoru v laboratornÍch podminkàch a na kmeni živého adultnÍho stromuPrunus avium L. Data jsou plnč automaticky a kontinuálnč registre-vána: to umožňuje kontinuámÍ sledovànÍ intensity transpiračnÍho proudu po dlouhá časová údobÍ simultánč u vĚtšÍho počtu stromů.

Improved thermal method of continual recording the transpiration flow rate dynamics

The analysis of the dynamic properties of thermal methods of transpiration flow measurement was performed and the measuring system developed, capable of quantitative measurements of fast flow changes (in minutes). The system is specified with a constant automatically maintained temperature difference between the heated and reference points in the measured part of the plant. System’s output signal related to measured quantity is linear. The system has been under longterm testing in full grown trees using the method of heat balance with direct electric heating of the xylem. The results obtained so far may be considered very good.

Sap flow rate and transpiration dynamics in the full-grown oak (Quercus robus L.) in floodplain forest exposed to seasonal floods as related to potential evapotranspiration and tree dimensions

Sap flow rate and transpiration dynamics were studied in the course of 3 years in a dominant tree species in the floodplain forest,i.e. in the full-grown oak (Quercus robur L.) tree, using the method of trunk heat balance devised by the authors. The investigations were carried out at a period at which regular and marked fluctuation in a relatively high water table usually occurred, culminating in seasonal flooding. High sap flow rate values in the tree were established under conditions of non-limiting water supply in soil (up to 400 kg per day or up to 39 000 kg per vegetation period) and characteristic daily flow curves (rounded with a large amplitude and with the maximum at noon), corresponding to those described theoretically. Relationships were inferred by means of which tree water consumption can be calculated under these conditions on the basis of data measured at meteorological stations. From these equations it follows that the transpiration of the tree canopy amounted to 80% of the potential evapotranspiration. The amount of the used daily tree water reserve was assessed to be 0.4 mm in the seasonal average. The transpiration coefficient reached in climatically distinct years the values of 400 to 700 of the increase in tree dry matter. The area of the so-called effective tree-crown ground plan approximated to the area determined geodetically. The results obtained are useful for both ecophysiological and hydrological studies. Some of the described procedures are convenient for the evaluation of functional tree dimensions and according to them also of the forest stand structure.

The compensation of natural temperature gradient at the measuring point during the sap flow rate determination in trees

The study summarizes the results of the influence of outer temperature gradient on the accuracy of sap flow rate measurements in tree trunks by means of thermic-based methods. Particularly it deals with those methods based on the continual accurate measurements of temperature differences between the heated part and the part with natural temperature, at the measuring point. The battery of thermometers significantly compensating the mentioned temperature gradient effect is described.

Improvement of the method of sap flow rate determination in full-grown trees based on heat balance with direct electric heating of xylem

Several improvements of the method of sap flow rate determination in full-grown trees elaborated by the authors are described. The method is based on heat balance with direct electrical heating of the xylem. The accuracy of the relationship for the calculation of flow rate was improved, the influence of unevennesses of flow in different annual rings was reduced. A method of extrapolation of the results obtained by measuring an individual xylem segment against the whole tree and of interpolation to a unit segment was elaborated, a simplified method of connecting the electrodes supplying the thermal input to the segment is described and an indicator of the relative water content of the xylem was derived.AbstractBylo popsáno několik zdokonalení metody stanovení transpiračního proudu u vzrostlých stromů vyvinuté autory, která je založena na tepelné bilanci s přímým elektrickým ohřevem xylemu; byl zpřesněn vztah pro výpočet toku, omezen vliv nerovnoměrností toku v různých letokruzích, uveden způsob extrapolace výsledků získaných měřením v daném segmentu xylemu na celý strom a interpolace na jednotkový segment, popsáno zjednodušené zapojení elektrod dodávajících tepelny vykon do segmentu a odvozen ukazatel relativního obsahu vody v xylemu.

Transpiration flow rate in a full-grown tree ofPrunus avium L. estimated by the method of heat balance in connection with some meteorological factors

The course of the transpiration flow rate (Qw), of transpiration flow acceleration (Qw/dt) and of the integrated transpiration flow was determined during an average summer day by repeated measurements according to the method of heat balance and the free water capacity of the tree trunk was estimated. The relations between the transpiration flow rate and the temperature and relative humidity of the air and the vapour pressure deficit measured at the same time in their diurnal course, as well as at the single diurnal terms during the whole time at which measurements were carried out were determined by correlation analysis. The problems linked with the effect of various meteorological conditions during different times of the day, of rain showers, solar radiation and soil water content are discussed. The possibilities of explaining the midday depression of transpiration on the basis of repeated measurements of the transpiration flow rate are evaluated.AbstractNa základě opakovaných měření metodou tepelné bilance u vzrostlého stromuPrunus avium L. v letmím období byl stanoven průběh intenzity transpiračního proudu (Qw) během průměrného dne, jeho zrychlení (Qw/dt) i denní sumy a odhadnuta volná vodni kapacita kmene stromu. Korelační analyzou byly stanoveny vztahy mezi intenzitou transpiračnflío proudu a současně měřenou teplotou vzduchu, relativní vlhkostí vzduchu a sytostním doplňkem a to jednak v dennim průběhu, jednak v jednotlivých denních termínech za celou dobu měření. Byla diskutována problematika vlivu jednotlivých meteorologických prvků v různých obdobích dne, vliv dešt’ovych přcháněk, sluneční radiace a vody v p°dě. Hodnoceny možnosti postižení polední deprese transpirace na základě opakovaných měření transpiračnflío proudu.

The electric conductance of seedling stems and the water content of spruce and pine seedlings in the course of desiccation

The dependence of electric conductance (admittance) of the stem on seedling water content (on the relative water content related to dry matter, or on the water saturation deficit, respectively) was followed in spruce and pine seedlings. The dependence was statistically highly significant and strong:r = 0.80 when individual plants were evaluated andr = 0.97 when mean values of twenty-seedlmg sets were taken into account. Electric conductance values can be used as a substitute) for water content determinations in plant tissues under defined conditions, although tho exact interpretation, especially of absolute values of those quantities with regard to their capacity component, remains to be offered.

Transpiration flow rate in a full-grown tree ofPrunus avium

The course of the transpiration flow rate (Qw), of transpiration flow acceleration (Qw/dt) and of the integrated transpiration flow was determined during an average summer day by repeated measurements according to the method of heat balance and the free water capacity of the tree trunk was estimated. The relations between the transpiration flow rate and the temperature and relative humidity of the air and the vapour pressure deficit measured at the same time in their diurnal course, as well as at the single diurnal terms during the whole time at which measurements were carried out were determined by correlation analysis. The problems linked with the effect of various meteorological conditions during different times of the day, of rain showers, solar radiation and soil water content are discussed. The possibilities of explaining the midday depression of transpiration on the basis of repeated measurements of the transpiration flow rate are evaluated.AbstractNa základě opakovaných měření metodou tepelné bilance u vzrostlého stromuPrunus avium L. v letmím období byl stanoven průběh intenzity transpiračního proudu (Qw) během průměrného dne, jeho zrychlení (Qw/dt) i denní sumy a odhadnuta volná vodni kapacita kmene stromu. Korelační analyzou byly stanoveny vztahy mezi intenzitou transpiračnflío proudu a současně měřenou teplotou vzduchu, relativní vlhkostí vzduchu a sytostním doplňkem a to jednak v dennim průběhu, jednak v jednotlivých denních termínech za celou dobu měření. Byla diskutována problematika vlivu jednotlivých meteorologických prvků v různých obdobích dne, vliv dešt’ovych přcháněk, sluneční radiace a vody v p°dě. Hodnoceny možnosti postižení polední deprese transpirace na základě opakovaných měření transpiračnflío proudu.

Transpiration flow rate in a full-grown tree ofPrunus avium L. estimated by the method of heat balance in connection with some meteorological factors@@@Transpirační proud u adultniho stromuPrunus avium L. stanoveny metodou tepelné bilance ve vztahu k některým meteorologickým prvkům

The course of the transpiration flow rate (Qw), of transpiration flow acceleration (Qw/dt) and of the integrated transpiration flow was determined during an average summer day by repeated measurements according to the method of heat balance and the free water capacity of the tree trunk was estimated. The relations between the transpiration flow rate and the temperature and relative humidity of the air and the vapour pressure deficit measured at the same time in their diurnal course, as well as at the single diurnal terms during the whole time at which measurements were carried out were determined by correlation analysis. The problems linked with the effect of various meteorological conditions during different times of the day, of rain showers, solar radiation and soil water content are discussed. The possibilities of explaining the midday depression of transpiration on the basis of repeated measurements of the transpiration flow rate are evaluated.AbstractNa základě opakovaných měření metodou tepelné bilance u vzrostlého stromuPrunus avium L. v letmím období byl stanoven průběh intenzity transpiračního proudu (Qw) během průměrného dne, jeho zrychlení (Qw/dt) i denní sumy a odhadnuta volná vodni kapacita kmene stromu. Korelační analyzou byly stanoveny vztahy mezi intenzitou transpiračnflío proudu a současně měřenou teplotou vzduchu, relativní vlhkostí vzduchu a sytostním doplňkem a to jednak v dennim průběhu, jednak v jednotlivých denních termínech za celou dobu měření. Byla diskutována problematika vlivu jednotlivých meteorologických prvků v různých obdobích dne, vliv dešt’ovych přcháněk, sluneční radiace a vody v p°dě. Hodnoceny možnosti postižení polední deprese transpirace na základě opakovaných měření transpiračnflío proudu.