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Long term vegetation monitoring provides valuable information on spatio-temporal patterns in plant communities that could be analysed to detect spatial relationship changes among species and to interpret dynamic tendencies and assembly rules in non-equilibrium phytocoenoses. In studies of this kind, one should take into account recent ecological theories emphasizing the scale dependence of vegetation; in particular, fine-scale spatial patterns of vegetation are important constraints in the genesis and maintenance of diversity. The information theory models of Juhász-Nagy offer an appropriate tool for describing the relationship between diversity and multispecies spatial dependence in vegetation. Diversity (florula diversity) and spatial dependence (associatum) are calculated for a series of increasing plot sizes (spatial scaling). The plot sizes at which the two coenostate descriptors reach the maximum information represent the characteristic scales that should be considered as optimal plot sizes in monitoring data collection. Moreover, this methodology enables us to study non-equilibrium dynamics and assembly rules in a more effective way. Diversity and spatial dependence are related, but the power and direction of this relationship change according to environmental characteristics, vegetation type and successional context. The demonstrated correspondence between dominant pattern-generating mechanisms and the related trajectories in abstract coenostate spaces (florula diversity and associatum maximum values), obtained by exploratory simulation studies, can improve interpretation of dynamic state and vegetation tendencies and can support a better inference about the relative role of different background mechanisms. We present some results obtained using this methodology with field data from the forest of Bialowieza National Park (Poland). In particular, we compared the herb layer spatial patterns of dynamically contiguous regeneration phases of the same phytocoenosis. Sampling was performed by recording the presence of plant species in 10 cm x 10cm contiguous microquadrats arranged in 150 m long circular transects. Field data were analysed with the same information theory methods as the ones applied to simulated data. Results show that assemblages of plant individuals are less diverse and more associated in primary than in regenerating stands, suggesting, in both situations, competitive dominance and disturbance as the main ecological mechanisms. Thus, the method was proven effective in distinguishing slightly different dynamical processes.

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Abstract  

Snow layers in lasting snow fields in High Tatras are effectively isolated from each other by ice crust. Every layer has a specific amount of fallout particles, pH, concentration of dissolved ions. Plutonium oxidation state (VI), from the adsorption behaviour of the isotopes of U, Th, Ra, Sr and Mn in six independent layers was elucidated. Behaviour of plutonium was similar to that of226Ra and90Sr. Isotopes of Th showed quite different dependence in snow layers. Concentration of Th and Mn in snow has similar extreme, which imply higher oxidation state of Mn than Mn(II). Behaviour of uranium may be explained by a mixture of U(VI) and U(IV) oxidation states because of their dependence in successive snow layers is a superposition of the same dependences of226Ra (or90Sr) and thorium isotopes.

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Gábor Fekete academician respectfully but affectionately called ‘Master’ (“Tanár Úr” in Hungarian, a version of ‘Professor’ that we used with a specific meaning of being not only a Tutor but Father and Master as well) by generations of vegetation scientists passed away on the 29th November 2016. His death deprived us of an experienced and didactic teacher who was loved by all. This warm regard was expressed in many commemorating writings published since his death. The present paper mainly concentrates on his scholarly work and the importance of his scientific findings also showing how particular publications signify stages in his scientific career.

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Abstract  

Rhyolite-rhyodacite tuff samples were analysed by X-ray powder diffraction, ICP-OES and thermogravimetric (TG) methods to determine mineral and major element composition as well as different types of bound water, respectively. Similarly to CIA values, some TG parameters (H2O[I] — water released up to ca. 200–220°C; H2O[III] — water loss above 500–550°C and H2O[I+III]) show positive correlation to the amount of secondary minerals. Moreover, these parameters are in close positive correlation to CIA values. Our results suggest that TG determination of different types of bound water may serve as a useful tool for estimation and characterisation of alteration degree of rocks.

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Studies addressing the question of how communities develop reported contrasting temporal patterns of species associations during succession. Several hypotheses were formulated about succession, but a general explanation of community assembly is missing. We analysed trends of species associations during old-field succession in two contrasting habitats: the first with chernozemic brown forest soil and temperate climate, and the second with sand soil and dryer climate. Significant pair-wise associations were calculated across a range of spatial scales. Comparing the two succession seres, one under harsh and the other under favourable environment, we attempted to make generalisations about species relation patterns. We found no trend but fluctuation in the level of community organization during succession. None of the existing succession models explained our results about changes in spatial structure of grassland communities during succession. Fluctuation in the number of significant associations was more intense and took longer under less favourable environmental conditions. Our results suggest that the stressed habitat type posed stronger constraints on species coexistence during succession than the favourable habitat did, but validating this hypothesis needs further investigations.

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Conservation treatments often take place at the scale of vegetation stands and affect within-stand heterogeneity and coexistence patterns of species first. Therefore, it is important to capture changes in these characteristics of vegetation to assess response to treatments early. We propose a method based on Juhász-Nagy’s information theory models, which is capable of describing fine-scale spatial structure of plant communities and characterizes temporal processes as a function of spatial pattern. The proposed multiscale approach handles structural complexity and its dependence on spatial scales with the help of a few coenological descriptors and helps to reveal how fine-scale vegetation pattern affects dynamics. The information statistical functions used in our study (species combination diversity, FD and associatum, As ) characterize the scale-dependent variability of multispecies coexistence (structural complexity) and multispecies spatial dependence (the degree of spatial organization). The maxima of these functions and the related characteristic areas (plot sizes) can be used to construct an abstract coenostate space, where spatiotemporal processes (degradation, regeneration) can be followed. We demonstrate the usefulness of the proposed methods for detecting degradation and monitoring vegetation changes in different stands (18 seminatural and 13 slightly degraded stands) of Brachypodium pinnatum dominated wooded steppe meadows in Hungary. The information theory measures captured changes of fine-scale vegetation patterns that remained unexplored by species richness and Shannon diversity. The maximum values of information statistical measures and the related characteristic areas detected differences between seminatural and slightly degraded stands. In the coenostate space, seminatural stands appeared to be less variable compared to degraded ones. Seminatural stands from various geographic locations were less dispersed in this space, i.e., less heterogeneous than degraded ones. The two regions of the coenostate-space defined by the set of seminatural and degraded stands were significantly different. Furthermore, we conclude that the region containing seminatural stands can be regarded as a reference region in this abstract space. Temporal variation of seminatural and degraded stands was also clearly different. Therefore, we recommend the approach for exploring the actual dynamic states of vegetation stands to be treated and for following consequences of treatments in order to determine effectiveness of the conservation action.

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Community Ecology
Authors: S. Bartha, G. Campetella, E. Ruprecht, A. Kun, J. Házi, A. Horváth, K. Virágh, and Zs. Molnár

Decreasing diversity and plant cover, as well as increasing variability of these characteristics with increasing aridity are expected in grasslands due to climate change. These predictions were tested in perennial sand grasslands in Hungary. Two sites were chosen in different positions on an aridity gradient and two stands in each site were monitored for 9 years. Presence of plant species were recorded along 52 m long circular belt transects of 1040 units of 5 cm × 5 cm contiguous microquadrats. This sampling procedure — a version of line-intercept methods — enabled us to monitor diversity and total abundance in a sensitive, precise and non-destructive way. We found no trend but fluctuation in most community level attributes and in species composition. Contrary to fluctuations, between-site differences in diversity did not change and diversity remained lower in the more arid site during our 9-year-study. Compositional diversity performed better than species diversity because allowed us to detect vegetation changes that would have remained hidden if monitoring would be based only on the species richness. Comparing the magnitudes of fluctuations, five times higher relative interannual variability (CV%) was found for compositional diversity at the more arid site, while the relative temporal variability of total abundance and species richness did not show consistent patterns. We conclude that a 9 year-long study was too short to identify trends caused by the changing climate. However, the larger temporal variability of species combinations found in the more arid site suggests larger vulnerability and highlights the importance of non-linear dynamics during climate changes.

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Remnants of the former semiarid forest-steppe vegetation of Hungary are suspected to undergo degradation processes because of recent land-use changes. Secondary succession towards closing of the vegetation starts with shrub invasion, mainly with species of the shrub layer of loess steppe oak forest. Soil respiration (SR) activity of the intercanopy loess grassland community was followed occasionally along of six years period, as well as the spatial patterns of SR and soil water content (SWC) with three direct measuring campaigns. Dependence of SR on SWC-soil temperature was statistically significant for the six years period, but the rest of the variance should be explained by other factors, as found for normalized difference vegetation index. In the spatial analysis, significant differences were found in the ranges of semivariograms according to the seasonal variation of soil moisture content. Larger scale patches were found under summer water stress (4 m for SR, 2.6 m for SWC) and autumn senescence (3.8 m for SR, 1.3 m for SWC) periods than under well-watered, peak performance summer circumstances (0.8 m for SR, 0.6 m for SWC). This suggests that homogeneity of patterns is typical at good water supply, while coarse-grained patches prevail under drought stress.

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Cereal Research Communications
Authors: Sz. Fóti, Sz. Czóbel, J. Balogh, J. Nagy, A. Juhász, Z. Nagy, S. Bartha, and Z. Tuba
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