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Evapotranspiration of selected agricultural and forest species
Kučera, J. ; Urban, J. ; Trnka, Miroslav ; Fischer, Milan ; Krofta, K. ; Duffková, R.
The aim of this article is a comparison of evapotranspiration (ET) of different covers (turf grass, clover (Trifolium pratense), winter wheat (Triticum aestivum), hops (Humulus lupulus) and the high density poplar stand (J-105, Populus nigra x Populus Maximowiczii)) with the potential evapotranspiration (PET) and the general description the ET rates dynamic during the season. The second goal is to quantify the ratio of the transpiration and the whole evapotranspiration for the two contrasting cultures – the hops and poplars stand. The daily maximal sum of the grass ET reached, similarly like for the other species, up to 5–6 mm per day, which comprises 85–93 % of PET. Significantly higher ET was showed by the culture of clover. On the other hand, the lowest values were performed by the poplar stand in the first year after coppicing. The transpiration to evapotranspiration ratio resulted in 40–70 % by the hops and 80–90 % in case of the poplars.
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Water-use effeciency-different computation strategies
Slípková, Romana
Water use efficiency (WUE) of the plants can be expressed as a ratio weight of biomass increment and consumed water. Two Norway spruce (Picea abies (L.) Karst) in density 1820 individuals ha-1 (FS) and 2440 individuals ha-1 (FD) in Bílý Kříž study site were studied during growing season 2003. WUE (g l-1) in this study was calculated as a ratio of total aboveground biomass increment (TB) defined by two approaches and stand transpiration. TB was defined by (i) one allometric relationship of diameter of the trunk in breast height and total aboveground biomass and (ii) as a sum of increment of stem, branch and leaves biomass allometrically obtained separately. Resulted WUE was marked as WUEI and WUEII. Mean WUEI was in FS 6,5 g l-1 and FD 14,0 g l-1; in case of WUEII FS 4,9 g.l-1 and FD 10,1 g.l-1, any difference was not significant. TBI was significantly higher than TBII in FD. We recommend WUEII approach for long term WUE evaluation.
Fulltext: content.csg -  PDF
Plný tet: Slípková_SylvaNet WoodNet 2010 - PDF
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The effect of elevated air CO2 concentration on water regime and transpiration of Norway spruce
Valouch, Ludvík ; Pokorný, Radek ; Tomášková, Ivana
Under the elevated CO2 air concentration, changes in physiological processes and morphology were evident in relatively short time. Direct measurement via heat pulse method proved reduction of specific sap flux throw the stem in the first year of cultivation in elevated CO2. SSF in both treatments was comparable in the next tree years. During the sixth year of fumigation, higher transpiration rate in trees growing under elevated CO2 was recorded. It was implication of larger bearing leaf area, larger conducting vessels area on the in crosscut stems section and larger root absorbed area. Continuously sap flow measuring of sun and shaded part of the crown was found that SSF of higher crown part was higher in both treatments. Average hydraulic conductance soil-leaf (GTsa) was 1,4 times higher in sunny part of the crown than estimated for the whole crown in ambient treatment A (ambient [CO2] concentration). Difference in hydraulic conductance between the upper and lower crown part of the E treatment (doubled [CO2] concentration of A treatment) was not so pronounced.
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