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3. Photosynthetic traits and water use of tree species growing on abandoned pasture in different periods of precipitation in Amazonia

Creator:
Silva, C. E. M., Gonçalves, J. F. C., and Alves, E. G.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
botanika, botany, chronosequence, light-response curve, photosynthesis, secondary succession, and stomatal conductance
Language:
Multiple languages
Description:
Pasture soils in the Amazon become unsustainable after a short period of use, typically being replaced by emergent secondary vegetation (capoeira). The aim of this research was to investigate the photosynthetic capacity and water use in the most common tree species (Vismia japurensis, Vismia cayennensis, Bellucia grossularioides, Laetia procera, and Goupia glabra) in successional chronosequence. This study was carried out in secondary vegetation area with ages that vary between 1 and 19 years. Responses of gas exchange were determined during different periods of precipitation. The gas exchange decreased with advancing age of the vegetation (1-19 years), except for G. glabra. Negative relationships of PNmax as a function of aging observed for V. japurensis, V. cayennensis, B. grossularioides, and L. procera exhibited r2 equal to 0.59, 0.42, 0.33, and 0.58, respectively. The species of Vismia showed higher values for photosynthetic parameters in relation to other species across the chronosequence. Overall, there were differences in gas exchange only for some species between the different periods of precipitation. Therefore, our results suggest a distinct pattern of photosynthetic responses to species in early succession. Light decrease can exert a decisive role to reduce the photosynthetic rates in secondary succession species. On the other hand, the results of WUE showed weak evidence of changes for the species during dry and rainy periods in the abandoned pasture in central Amazonia. and C. E. M. Silva, J. F. C. Goncalves, E. G. Alves.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

4. The effect of soil tillage system on soil bulk density and other physical and hydrophysical characteristics of Gleyic Fluvisol

Creator:
Mati, Rastislav and Kotorová, Dana
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
conventional tillage, no-tillage system, gleyic fluvisol, soil hydrophysical characteristic, klasická agrotechnika, bezorbový systém, fluvizem glejová, and hydrofyzikálne charakteristiky pôdy
Language:
Slovak
Description:
Different sustainable systems of husbandry on soil with various protective technologies are frequently studied. Direct sowing without ploughing is one of the alternatives. This article presents results of the effect of conventional tillage (CT) and no-tillage system (NT) on soil bulk density, soil porosity, maximum capillary capacity and available water capacity of Gleyic Fluvisol in conditions of the East-Slovakian Lowland. Observed years 1999 - 2005 from point of wiev of annual sum of precipitation are valued as dry till humid and of annual average air temperature as normal or warm. The effect of used agrotechnical arrangements was statistically highly significant (α = 0.01) for porosity changes and statistically significant for soil bulk density (α = 0.05). Non-significant effect was found for maximum capillary capacity and available water capacity. In the soil layer 0 - 0.3 m during years 1999 - 2005 soil bulk density increased about 22 kg m-3 (1.54 %) at no-tillage system in comparison to conventional tillage. At no-tillage system average values of porosity decreased about 1.32 %, maximum capillary capacity and available water capacity non-significantly decreased about 0.32 % in comparison to conventional tillage. and V trvalo udržateľných sústavách hospodárenia na pôde sa do popredia dostávajú rôzne ochranné technológie obrábania pôdy, medzi ktoré patrí aj priama sejba bez orby. Predkladaný príspevok sa zaoberá vplyvom konvenčnej agrotechniky (CT) a bezorbového systému (NT) na objemovú hmotnosť, pórovitosť, maximálnu kapilárnu kapacitu a využiteľnú vodnú kapacitu fluvizeme glejovej v podmienkach Východoslovenskej nížiny. Sledované roky 1999 - 2005 sú z hľadiska ročných zrážkových úhrnov hodnotené ako suché až vlhké a z hľadiska priemerných ročných teplôt vzduchu ako normálne, resp. teplé. Vplyv použitých systémov agrotechnických opatrení sa štatisticky významne (α = 0,01) prejavil pri pórovitosti, štatisticky na hranici významnosti (α = 0,05) pri objemovej hmotnosti a štatisticky nevýznamne pri maximálnej kapilárnej kapacite a využiteľnej vodnej kapacite. V porovnaní s konvenčnou agrotechnikou sa pri bezorbovom systéme zvýšili priemerné hodnoty objemovej hmotnosti vo vrstve pôdneho profilu do 0 - 0,3 m za roky 1999 - 2005 o 22 kg m-3 (1,54 %); priemerné hodnoty pórovitosti sa znížili o 1,32 %, hodnoty maximálnej kapilárnej kapacity a využiteľnej vodnej kapacity o 0,32 %.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

5. Vliv sférické aberace na hloubku fokusu optické soustavy

Creator:
Mikš, Antonín and Pokorný, Petr
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
spherical aberration, depth of focus, gyration diameter, sférická aberace, hloubka ostrosti, and gyrační průměr
Language:
Czech
Description:
The paper deals with the analysis of the influence of spherical aberration on the depth of focus of symmetrical optical system for imaging of axial points. Analytical formulas for the calculation of beam's caustics are derived with the use of ray equations in the image plane and with the use of longitude aberrations as well. Concurrently, the influence of aberration coefficients on the extremes of such a curve is presented. Afterwards, the conditions for aberration coefficients are derived if the Strehl definition should be the same in two symmetrically placed planes with respect to the paraxial image plane. Such conditions for optical systems with large aberrations are derived with the use of geometric-optical approximation where the gyration diameter of the beam in given planes of the optical system is evaluated. Therefore, one can calculate aberration coefficients in such a way that the optical system generates a beam of rays which has the gyration radius in given interval smaller than defined limit value. Moreover, one can calculate the maximal depth of focus of the optical system respecting the aforementioned conditions. and Práce se zabývá analýzou vlivu sférické aberace na hloubku fokusu rotačně symetrické optické soustavy při zobrazení osových bodů. Jsou odvozeny analytické vztahy pro výpočet kaustiky paprskového svazku pomocí rovnic paprsku v obrazové rovině a pomocí podélné sférické aberace. Je ukázán vliv aberačních koeficientů na extrémy této obálky svazku. Dále jsou odvozeny požadavky na aberační koeficienty optické soustavy, má-li být Strehlova definice stejná ve dvou rovinách symetricky položených vzhledem k paraxiální obrazové rovině. Pro soustavy s velkými aberacemi jsou tyto požadavky odvozeny s použitím geometricko-optické aproximace, kde je hodnocen gyrační průměr svazku v daných rovinách. Aberační koeficienty sférické aberace lze tedy určit tak, aby optická soustava generovala paprskový svazek, který má v zadaném intervalu gyrační poloměr menší než jeho předem zadaná limitní hodnota. Lze také předem určit maximální dosažitelnou hloubku ostrosti optické soustavy, která splňuje výše uvedené podmínky.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public