Carbon and water fluxes in a semiarid shrubland ecosystem located in the southeast of Spain (province of Almería) were measured continuously over one year using the eddy covariance technique. We examined the influence of environmental variables on daytime (photosynthetically active photons, FP >10 µmol m-2 s-1) ecosystem gas exchange and tested the ability of an empirical eco-physiological model based on FP to estimate carbon fluxes over the whole year. The daytime ecosystem fluxes showed strong seasonality. During two solstitial periods, summer with warm temperatures (>15 °C) and sufficient soil moisture (>10 % vol.) and winter with mild temperatures (>5 °C) and high soil moisture contents (>15 % vol.), the photosynthetic rate was higher than the daytime respiration rate and mean daytime CO2 fluxes were ca. -1.75 and -0.60 µmol m-2 s-1, respectively. Daytime evapotranspiration fluxes averaged ca. 2.20 and 0.24 mmol m-2 s-1, respectively. By contrast, in summer and early autumn with warm daytime temperatures (>10 °C) and dry soil (<10 % vol.), and also in mid-winter with near-freezing daytime temperatures the shrubland behaved as a net carbon source (mean daytime CO2 release of ca. 0.60 and 0.20 µmol m-2 s-1, respectively). Furthermore, the comparison of water and carbon fluxes over a week in June 2004 and June 2005 suggests that the timing-rather than amount-of spring rainfall may be crucial in determining growing season water and carbon exchange. Due to strongly limiting environmental variables other than FP, the model applied here failed to describe daytime carbon exchange only as a function of FP and could not be used over most of the year to fill gaps in the data. and P. Serrano-Ortiz ... [et al.].
In the previous paper called ''Aperture size influence on beam clipping of super-Gaussian beams with use of VirtualLab'' purely a power transmission issues were revealed to the reader. Influence of diffraction in the focal plane was not considered in the previous model. In the actual paper the study is extended by adding the investigation of diffraction effects in the focal plane and by the analysis of the apodization masks influence on these effects. Simultaneously the need to introduce new metrics, or at least strongly modify the old ones to assess the beam quality is demonstrated. To aid presented simulations Wyrowski VirtualLab Fusion is used. and Předchozí příspěvek nazvaný ''Vliv konečné apertury na přenos výkonu super-gaussovských svazků'' byl věnován numerické simulaci vlivu velikosti apertury optického systému na přenos výkonu gaussovských a super-gaussovských svazků. V aktuálním příspěvku je studovaná problematika rozšířena o difrakční jevy a je také ukázán vliv apodizačních masek na charakter stop v ohniskové rovině. Zároveň bude demonstrována nutnost zavést buď nové metriky pro charakterizaci kvality svazku, nebo přinejmenším ty stávající dostatečně upravit potřebám studia fokusace super-gaussovských svazků používaných pro přenosy vysokovýkonových laserových svazků. K simulacím je využito optického simulačního prostředí Wyrowski VirtualLab Fusion.