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Plant growth is affected by light availability, light capture, and the efficiency of light energy utilisation within the photosynthetic uptake processes. The radiation use efficiency (RUE) of four even-aged, fully stocked mature Norway spruce stands along a temperature, precipitation, and altitudinal gradient of the Czech Republic was investigated. A new straightforward, methodological approach involving an analysis of digital hemispherical photographs for RUE estimation was applied. The highest annual RUE value (0.72 g MJ−1) was observed in the stand characterised by the lowest mean annual air temperature, the highest annual amount of precipitation, located at the highest altitude, and with the lowest site index reflecting site fertility. From the viewpoint of global climate change mitigation, this stand fixed 4.14 Mg ha−1 and 13.93 Mg ha−1 of carbon units and CO2 molecules into above-ground biomass, respectively. The lowest RUE value (0.21 g MJ−1) within the studied growing season was found in the stand located at the lowest altitude representing the site with the highest mean air temperature and the lowest amount of precipitation where 1.27 Mg ha−1 and 4.28 Mg ha−1 of carbon units and CO2 molecules, respectively, were fixed. From the tested meteorological variables (mean air temperature, the monthly sums of temperature, precipitation, and air humidity), RUE was only significantly dependent on air temperature. Therefore, global warming can lead to diminishing RUE and carbon sequestration in Norway spruce stands, especially at low altitudes. [ABSTRACT FROM AUTHOR]

We prove that the crossing number of a graph decays in a 'continuous fashion' in the following sense. For any ε > 0 there is a δ > 0 such that for a sufficiently large n, every graph G with n vertices and m ≥ n edges, has a subgraph G′ of at most (1 − δ) m edges and crossing number at least (1 − ε)CR( G). This generalizes the result of J. Fox and Cs. Tóth. [ABSTRACT FROM AUTHOR]

Abstract: Let be a set of points in general position in the plane. General position means that no three points lie on a line and no two points have the same -coordinate. is a cup (resp. cap) if the points of lie on the graph of a convex (resp. concave) function. Denote the points of by according to the increasing -coordinate. The set is open in if there is no point of above the polygonal line . Valtr [P. Valtr, Open caps and cups in planar point sets, DCG (in press)] showed that for every two positive integers and there exists a positive integer such that any -point set in the plane in general position contains an open -cup or an open -cap. This is a generalization of the Erdős–Szekeres theorem on cups and caps. We show a simple proof for this theorem and we also show better recurrences for . This theorem implies results on empty polygons in -convex sets proved by Károlyi et al. [Gy. Károlyi, J. Pach, G. Tóth, A modular version of the Erdős–Szekeres theorem, Studia Sci. Math. Hungar. 38 (2001) 245–259], Kun and Lippner [G. Kun, G. Lippner, Large convex empty polygons in -convex sets, Period. Math. Hungar. 46 (2003) 81–88] and Valtr [P. Valtr, A sufficient condition for the existence of large empty convex polygons, Discrete Comput. Geom. 28 (2002) 671–682; P. Valtr, Open caps and cups in planar point sets, DCG (in press)]. A set of points is -convex if it determines no triangle with more than points inside. [Copyright &y& Elsevier]

Abstract: A geometric graph is a graph embedded in the plane in such a way that vertices correspond to points in general position and edges correspond to segments connecting the appropriate points. A noncrossing Hamiltonian path in a geometric graph is a Hamiltonian path which does not contain any intersecting pair of edges. In the paper, we study a problem asked by Micha Perles: determine the largest number such that when we remove any set of edges from any complete geometric graph on n vertices, the resulting graph still has a noncrossing Hamiltonian path. We prove that . We also establish several results related to special classes of geometric graphs. Let denote the largest number such that when we remove edges of an arbitrary complete subgraph of size at most from a complete geometric graph on n vertices the resulting graph still has a noncrossing Hamiltonian path. We prove that . Let denote the largest number such that when we remove an arbitrary star with at most edges from a complete geometric graph on n vertices the resulting graph still has a noncrossing Hamiltonian path. We show that . Further we prove that when we remove any matching from a complete geometric graph the resulting graph will have a noncrossing Hamiltonian path. [Copyright &y& Elsevier]

Summary: Preliminary results of an investigation of the thinning effect on Norway spruce tree growth in terms of xylogenesis and phloemogenesis are presented. Three plots were selected where the stand densities were reduced by pre-commercial thinning to 1800 trees/ha (plot A; mild thinning) and 1300 trees/ha (plot C; heavy thinning) in February 2020. Plot B had no silvicultural intervention and represented a control variant (4500 trees/ha). Three dominant 14-year-old Norway spruce trees were sampled (micro-cored) for studying the xylem and phloem formation in the 2020 growing season. The total differentiation duration was determined to be around 169.7 ± 12.7–179.3 ± 4.0 days. The average number of xylem cells formed in control plot B was only 140 mature cells, plots C and A were determined to have 175 and 200 mature cells, respectively. Plot A had the fastest growth rate of all the plots studied. In all three plots (A, B, C), the beginning of the early phloem, late phloem sieve cells, and axial parenchyma cells coincided. Nonetheless, in terms of total phloem cell increase, plot C displayed the fastest growth rate among the three plots studied. The first results showed that the rate of total increment in both xylem and phloem cells, as well as the total number of produced tracheids and sieve cells, seem to be positively affected after the thinning application. [ABSTRACT FROM AUTHOR]

The objective of this study was to assess the influence of European beech (Fagus sylvatica L.) and Norway spruce (Picea abies (L.) H. Karst.) on the vertical distribution of Cd, Cu, Pb and Zn in forest soil. Soil samples were taken from six beech- and six spruce-dominated mature (80–100-year-old) forest stands. In total, 420 composite soil samples were collected from the organic horizons, and at depths of 0–2, 2–10, 10–20 and 20–30 cm in the mineral soil, of 84 plots in a hexagonal sampling design. A direct influence of forest type was confirmed for Zn, which showed increased soil accumulation under beech. In spruce stand soils, Zn is likely to have leached more due to lower pH levels. While a minor influence of tree species on the vertical distribution of Cd, Cu and Pb was also confirmed, particularly as regards accumulation in the F + H layer of spruce stands, the results suggest a more dominant effect of other site-specific conditions at the scale studied, such as topography and atmospheric deposition, despite homogenous forest stand conditions. Furthermore, the C:N ratio had a significant impact on both Cd and Cu content, regardless of forest type, highlighting the importance of specific site conditions for driving decomposition of organic matter, a primary factor affecting Cd and Cu mobility in soil. [ABSTRACT FROM AUTHOR]

One of the main ideas of non-native tree species introduction into forest stands is to replace declining native species. The same is also valid for industry; the wood of native species should be replaced by a wood of the same or even better quality. Douglas-fir is often compared to other coniferous tree species based on its production. This study compared Douglas-fir wood properties with European commercial species, namely Norway spruce, Scots pine, and European larch. Trees representing different sites and ages were tested for wood density, shrinkage, and compression strength. In all cases, Douglas-fir outclassed spruce and pine in density and strength. The difference was striking, especially for spruce, where the density was surpassed by Douglas-fir by more than 100 kg.m−3 (above 25%). In the case of compression, the strength of Douglas-fir was up to 12.3 MPa higher (above 33%) compared to spruce. The only species that obtained higher figures was larch. Wood shrinkage was comparable to European softwoods. Therefore, Douglas-fir wood can be regarded as an excellent and promising substitute for the European processing industry. • Douglas-fir represents promising non-native species for Europe. • It should be a substitute, especially for Norway spruce in industry. • We tested some of the properties important for applications. • In contrast to previous studies, tested species grew together in the same stand. • Douglas-fir exceeded not only spruce but also Scots pine. [ABSTRACT FROM AUTHOR]

Aim To provide an overview of gambling and associated problems in the Czech Republic, including an overview of the historical context, legislation, prevalence, treatment and research base and agenda. Methods A review of literature and relevant sources. Results The trajectory of gambling patterns in the territory of the Czech Republic in the 20th century reflected broad socio-political changes. Those included significant expansion between the wars, strict state control and bans on some gambling activities during the communist regime and finally dynamic development characterized by a boom in electronic gaming machines (EGMs) and increasing accessibility of gambling facilities after 1989, which aggravated gambling-related problems. Many municipalities have banned EGMs, which has created conflict in regulation at state and municipal levels. The draft gambling law prepared in 2014 aims to clarify the regulatory framework. Before 2012 there was only sporadic research interest in gambling, but in 2012 the first complex research on gaming and problem gambling in the Czech population took place. The estimated prevalence of problem gambling is currently 2% in the population aged 15-64 years. Preventive measures, counselling and treatment services for problem gamblers are limited. Conclusions Weak and ineffective regulation of the gambling market in the Czech Republic during the past 20 years, despite the large growth in gambling, has led to inadequate prevention and response to problem gambling which has become a considerable public health, social and political issue. [ABSTRACT FROM AUTHOR]

Strategic resource control poses a trade-off to attackers and defenders. Actions that reclaim control of a resource pose costs, but control of a resource by an adversary also poses costs. Thus, strategy is required to maximize outcomes. Research on the Dark Triad of personality has suggested that Machiavellianism is associated with a strategic orientation, whereas psychopathy and narcissism are associated with direct aggression and overconfidence (respectively). Thus, individuals high in Machiavellianism should outperform those high in psychopathy and narcissism in a strategic resource control game. We tested this hypothesis using a modified version of the "Flipit" game. Using this type of behavioral extension of an Extensive Form Game (EFG) we found that Machiavellian individuals were more successful in their performance than were those high in narcissism and psychopathy. Further, poor performance in psychopathy was partially driven by non-attention to costs. Findings have implications for defending against Dark Triad attackers in cybersecurity settings. • Strategic games of resource control are relevant to the Dark Triad. • Participants were attackers in an extensive form version of flipit with full or partial information. • Attackers played against two defenders: random and a game-theoretic algorithm. • High Machiavellianism increased performance, high in narcissism and psychopathy decreased it. • Findings have implications for strategies in defending against different cyberattacker profiles. [ABSTRACT FROM AUTHOR]