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Plant transpiration, entropy production and gross primarily productivity
Šír, M. ; Tesař, Miroslav ; Lichner, Ľ.
The Earth is a self-organized system. The source of information for self-organization is the degradation of solar radiation. The solar energy is highly organized and carried by photons. Earth absorbs this energy and then releases it back to the Universe. However, energy released to the environment is in the form of electromagnetic radiation, which is on average at longer wavelengths than the absorbed photons. The flow of the entropy associated with the energy conversion, which is at disposal for the self-organization, is approximately equal to 1.16·10.sup.38./sup. bit·.sub.s./sub..sup.-1./sup. (Roland-Mieskowski, 1994). The nature of self-organization is a theme of contemporary scientific discussion. The core of this discussion is the role of biotic processes. Lovelock and Margulis (1974) formulated a theory that the self-organization in a global scale is an emergent characteristic of the Earth’s biota (Gaia theory).
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Formation of extreme rains in the Krkonoše Mts. in summer 2002 and 2006
Tesař, Miroslav ; Šír, Miloslav ; Fišák, Jaroslav
In the article, hydrological and meteorological conditions preceding two extreme rains in the Krkonoše Mts. in summer 2002 and 2006 are discussed. Both were caused by cyclones, which moved from Hungary to Poland. Meteorological conditions preceding the rains were very similar in both cases – long-lasting lack of precipitation and extraordinary high air temperatures. We analyze the role of insufficient plant transpiration in the rise of both extreme rains.
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Hydrologic extremes and gross primary productivity in the Liz catchment
Šír, Miloslav ; Tesař, Miroslav ; Lichner, Ľ. ; Váchala, J. ; Krejča, M.
The synergy between hydrologic extremes, plant transpiration, gross primary productivity, and soil water retention was studied in the experimental area Zábrod – meadow in the Bohemian Forest. Heat balance, potential and actual transpiration, entropy production and gross primary productivity were evaluated. It was found that the soil water retention is the crucial factor determining hydrologic pattern and gross primary productivity. Insufficient soil water retention leads to small entropy production by evaporation and small gross primary productivity, which results in the extremalization of the hydrologic cycle. On the other hand, in the case of sufficient soil water retention, high entropy production by transpiration and high gross primary productivity leads to the stability of the hydrologic cycle.
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Vliv vegetace na tepelnou bilanci a výměnu entropie
Šír, Miloslav ; Weger, J. ; Tesař, Miroslav ; Lichner, Ľ.
The aim of this study is to quantify the synergy between the vegetation cover, solar radiation, air temperature and soil moisture. Heat balance, potential and actual transpiration, and net entropy exchange at three localities under different plant cover was studied in order to determine crucial factors determining phytomass productivity in cold climatic areas of Bohemian Forest. The phytomass productivity can be quantified by the entropy exchange associated with the latent heat flux. Water shortage is a crucial factor determining phytomass productivity in dry and warm seasons in cold climatic conditions of Czech mountains.
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Comparison of two models of forest transpiration
Šír, Miloslav ; Čermák, J. ; Naděždina, N. ; Naděždin, V. ; Tesař, Miroslav
Two transpiration models were tested in the paper, one is with plant control, and another without plant control. Principle of the (1) model with plant control was, that physical mechanism of transpiration is evaporation actively controlled by plants. The supposed mechanism is: part of the heat (heat equivalent of the energy absorbed from solar radiation), which would cause overheating the plant above 25 ºC is dissipated by evaporation. The model has five physical parameters, which are in principle measurable. (2) The model without plant control is based on the assumption, that transpiration dissipates a constant fraction of the heat from the heat equivalent of absorbed solar radiation (about 45 %). The model needs only one measurable physical parameter. Both models were tested by comparing their results with results actually measured daily totals of transpiration (via sap flow) in the floodplain forest Pohansko (near the town of Břeclav, southernmost Moravia), which was typical with almost non-limiting soil water supply over the period May 1 to Sept. 30, 1998. Results of both models were almost equal. We discussed their physical differences evaluating their goals and weak points and specified a program for further testing the physical mechanism of transpiration.
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Plant transpiration and self-organization of hydrologic cycle
Šír, Miloslav ; Lichner, Ľ. ; Tesař, Miroslav
We quantified the influence of plant transpiration on the entropy production associated with the degradation of solar energy on the Earth’s surface covered by plants. Two surfaces were studied: (1) biotic surface – plant transpiration taken as equal to the potential one, (2) abiotic surface – plant transpiration taken as if equal to zero. Two sources of entropy were taken into account – the entropy production associated with the conversion of solar radiation into (1) the sensible heat, and (2) latent heat. Surface processes in hydrologic cycle were examined in the experimental watershed Liz located in the Bohemian Forest (Czech Republic). We found that in the growing season 1992 the entropy production in humid hydrologic cycle (the Earth’s surface is biotic) was considerably higher than in the arid one (in 39 % of days the Earth’s surface behaved as biotic, in 61 % of days behaved as abiotic). Considering that the biotic effect on the Earth’s functioning can be assessed using the entropy production, we can assume that the hypothesis that biota – represented as a biotic surface – regulates Earth’s environment is proved in the watershed scale.
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Climate change and plant transpiration
Šír, Miloslav ; Tesař, Miroslav ; Lichner, Ľ. ; Syrovátka, O.
The article shows how the plant transpiration cools the boundary level of the atmosphere. In a summer day, when the heat input is 5 to 6 kWh/m2 per day, in the mountainous and submontane areas of the Czech Republic (600 to 1400 m a.s.l.) the plant transpiration decreases: (1) maximum temperature of plant cover from 47 to 25 degrees C, (2) maximum temperature of boundary level of the atmos-phere from 29 to 21 degrees C, (3) maximum temperature of the soil in the depth of 15 cm from 15 to 8 degrees C. The cooling caused by plant transpiration substantially af-fects the energy balance of the land surface. Insufficient transpiration caused an increment of thermal energy of about 23
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