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Brno, Czech Republic

Krofta K.,Hop Research Institute Co. | Kuera J.,EMS Brno | Urban J.,Mendel University in Brno
Acta Horticulturae | Year: 2013

Transpiration of the Czech hop 'Premiant' (Humulus lupulus L.) plantation was investigated during three consecutive growing seasons and compared with Penman-Monteith based reference evapotranspiration and transpiration estimated by FAO dual crop approach. We measured the sap flow of the twelve individual bines (using the stem heat balance sensors type EMS SF 62). Actual bine transpiration peaked in August, when the crop was fully developed, at less than 3 mm day-1, which was 60% of the reference evapotranspiration and only 65% of the transpiration estimated by dual crop approach. Seasonally, most of the water was potentially evaporated from the soil surface and transpired by the understory vegetation (i.e. weeds). Less than half of the total amount of vaporized water was transpired (the partitioning depended on a stage of crop development), which makes space for the water-saving techniques in hop growing. Source


Urban J.,Mendel University in Brno | Bednarova E.,Mendel University in Brno | Plichta R.,Mendel University in Brno | Gryc V.,Mendel University in Brno | And 4 more authors.
IForest | Year: 2015

Over the course of a year, tree physiological processes are not only directly affected by environmental conditions, but also by the tree’s own phenological stages. At the same time, phenological stages should, to a certain degree, reflect tree physiology. However, we have rather poor knowledge of the details of the interplay between phenology and ecophysiology. The objective of this study was to develop a better understanding of the links between phenology and ecophysiology. We investigated the degree to which various physiological processes are synchronized both with each other and with phenology and what information related to phenology can be obtained from instrumental ecophysiological measurements. Phenological observations, along with measurements of transmittance of photosynthetically active radiation (PAR), stem volume changes, sap flow and xylogenesis were conducted in a 45-year old European beech (Fagus sylvatica) stand in the Czech Republic. Results indicated that ecophysiology was tightly related with the phenological stage of the tree. Early spring phenological stages were closely linked with the beginning of cambial activity and the onset of sap flow, i.e., the first leaves were produced simultaneously with the beginning of stem radial growth. The highest xylem growth rates occurred in June, simultaneously with the highest sap flow rates. Cambial activity ceased with the onset of summer leaf coloring at the end of July, at the same time as the permanent decrease in sap flow rate. The end of cell wall maturation was linked to the onset of autumn leaf coloring. We conclude that instrumental measurements of tree and stand ecophysiology provided additional information better specifying the onset of particular phenostages. In our case, twelve permanently located sensors used to measure PAR transmittance captured leaf area development with acceptable accuracy, thus limiting the need for frequent visits to the forest site in the spring and autumn. Moreover, data from dendrometers showed linkages to bud break and the onset of leaf coloring. Therefore, ecophysiological measurements increased the effectiveness and accuracy of phenological observations and provided additional information about tree development in particular external conditions. © SISEF. Source


Kucera J.,EMS Brno | Urban J.,Mendel University in Brno
Acta Horticulturae | Year: 2012

The aim of this contribution is to describe the step-wise improvement of the trunk heat balance method (THB) from the first idea to the actual sophisticated instrumentation. Both technical and theoretical aspects of the development of the method are considered. The original idea of heating trunk tissues with an electrical current passing between inserted plate electrodes has been accepted as an optimal arrangement despite the misleading original idea of energy distribution. The first important improvement eliminated the significant influence of highly electrically conductive phloem on the accuracy of the measurement in trunks with thick phloem tissues. Following fundamental physical analysis of both power field and heat field showed false conception of the homogeneous energy distribution between two parallel plate electrodes in an electrically conductive environment. Besides, the physical analysis confirmed the presumption that the stability of the flow measurement based on heat balance increases with the size of heated volume. The actual measuring layout uses three stainless plates for direct heating of plant tissues and the needle temperature sensors are inserted in slots of those plates. This way uses the averaging effect of metal plates and reduces an error caused by a radial temperature gradient that makes a lot of troubles especially by point-shaped temperature sensors. The electronics maintains stable temperature difference between heated and non-heated parts of the measuring points. This arrangement substantially improves the response of the measuring system to fast sap flow changes and last but not least greatly reduces the power consumption. Source


Urban J.,Mendel University in Brno | Krofta K.,Hop Research Institute Co. | Kucera J.,EMS Brno
Acta Horticulturae | Year: 2012

Evapotranspiration of the Czech hop cultivar Agnus (Humulus lupulus L.) plantation was investigated during three consecutive growing seasons. We measured two components of the water balance: total evapotranspiration (using the Bowen ratio energy balance method) and transpiration of the bines (using the stem heat balance sensors type EMS SF 62). Actual evapotranspiration peaked when the crop was fully developed, at 80 - 90% of the potential evapotranspiration. Most of the water was evaporated and less than half of the total amount of vaporized water was transpired (the partitioning depended on a stage of crop development). EMS heat balance sensors don't require any empirical calibration. However, to ensure the correctness of the sap flow measurements, a calibration of the sap flow sensors was performed. Just before the harvest, a total of eighteen bines were removed from the plants and their water uptake was measured potometrically (volumetrically). Accuracy of the sap flow measurement was -3 % when compared against potometry. Source


Senfeldr M.,Mendel University in Brno | Urban J.,Mendel University in Brno | Madera P.,Mendel University in Brno | Kucera J.,EMS Brno
Trees - Structure and Function | Year: 2016

Key message: We measured sap flow and shoot water potentials in clonally connected parent and daughter trees. We found bidirectional flow patterns in branches mediating the connection between parent and daughter trees. Abstract: Layering is an important mode of vegetative reproduction at treeline, in which clonal daughter trees are formed by the rooting of lower (“layering”) branches of the parent tree. These branches mediate the connection between parent (PT) and daughter tree (DT). Here, we measured quantity and direction of sap flow in layering branches as well as PT and DT, and measured shoot water potentials in the crowns of a connected PT and DT. We found bidirectional sap flow pattern in layering branches, with the bidirectionality of the flow resulting from water potential dynamics of the parent and daughter trees varying diurnally. We found that 4.3 % of the total water transpired by the DT was supplied by the PT root system, with up to 25 % of the instantaneous daughter tree sap flow coming from the parent tree. In contrast, water provided by the daughter’s root system to the parent tree comprised only a negligible amount, less than 1 % of the parent’s entire sap flow. Additionally, after experimental excavation of part of the DT roots, layering branch flow towards the DT increased, while flows in the opposite direction almost vanished. This study showed that aboveground clonal connections can facilitate a new type of hydraulic redistribution where water is transported bidirectionally through branches. This transfer of water and nutrients is vital especially in the first years of the daughter tree but supplies considerable amounts of water even several years after the establishment of a new clonal tree. © 2015, Springer-Verlag Berlin Heidelberg. Source

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