A most widespread technique in vegetation boundary detection is the Moving Split Window analysis. It is effective in single edge cases provided that the attributes are highly correlated. In dry grasslands with mosaic structure, boundary zones are frequent, they are rather close to one another, causing some uncertainty in edge detection. Artificial community patterns were used to reveal the response of dissimilarity/distance functions to the number and distance of edges and to window sizes. Dissimilarity functions are sensitive to the compositional difference of the adjacent patches, and the dissimilarity increases with window size. The usual significance test highly depends on the patch size and edge frequency, therefore additional analyses must be applied or other randomization methods should be found that can ignore the effect of patch size.
We investigated the pattern of boundary types in alkaline grassland communities in Hungary. We used moving split window boundary analysis with dissimilarity functions, usually applied to detect ecotones and landscape boundaries at a coarse scale. The results were compared with those of correspondence analysis and clustering methods for the same data set, as well as with the local frequency distributions of populations along the studied transects. The MSW technique, usually applied in boundary and transition zone detection, was effective at a fine scale as well. The visible boundaries and transition zones were detectable with this method in most cases, but only sharp and narrow boundaries were verified with ordination and classification. If the changes are gradual in microtopography, then it is possible to detect transition zones between the vegetation patches. These types of transition zones can be considered as ecoclines. Despite the gentle microtopographical gradient, a marked border was detected between the Artemisio-Festucetum pseudovinae and the Achilleo-Festucetum pseudovinae communities. However, neither MSW did indicate boundary zone nor multivariate methods could distinguish sharply between these two communities. The small patches of the Artemisio-Festucetum pseudovinae association appear transitional between the adjacent communities in species composition along both transects. These patches cannot be considered as representing a distinct community type, and thus should be considered as ecotones.
The influence of elevation and vegetation characteristics on the spatial pattern of an epigeic true bug assemblage was investigated along a transect in a sandy grassland of Kiskunság. A 55 m long transect through wind grooves and dune tops, perpendicular to the vegetation borders was established. Both the moving split window technique and the ordination method revealed that dune top habitat has a distinct Heteroptera assemblage. This sand dune habitat was characterized by the most abundant Heteroptera species. We did not observe a distinct true bug assemblage in the wind groove habitat. Canonical correspondence analysis and multiple linear regressions showed that the relative altitude had a greater effect on the distribution of true bugs than vegetation cover and plant species richness.
Climate change and other local factors in Central Hungary resulted in a severe water table drawdown during the last few decades. Several studies with different methodical approaches have already been conducted in the region to examine the reaction of the vegetation to the new conditions. In this paper we report the results of a unique, long-term vegetation study of a permanent site, which was also suffering from the loss of its original water supply. The site consisted of a drier section with sandy steppe communities and a wetter one located in an interdune depression. By using diversity measures, relative ecological indicators, flora element classifications, Raunkiaer’s life-form categories and Borhidi’s social behaviour types we could show that both sections were influenced by the water table drawdown, though most shifts were more prominent in the wet section. According to the results the vegetation of the wet section was in a drying phase, it was getting more thermophilous and its continental character was getting stronger. We found that the vegetation of both sections had undergone a transitional degradation before the study was started and during the study it was in a regeneration phase towards a new natural state. This fortunate process proves that these communities have a potential to adapt to drier conditions, but beside the decrease of the overall habitat diversity we could also detect an obvious negative trend in the productivity, which we consider a severe general trend for the entire region.
Authors:Cs. Tölgyesi, L. Erdős, L. Körmöczi, and Z. Bátori
Ecotones between plant communities have received considerable attention among ecologists in the context of fragmentation, climate change and the management of heterogeneous landscapes. However, the predictability of ecotone dynamics is low and the processes taking place within ecotones are still poorly understood. In this study we aimed to characterize the positional and structural dynamics of thirteen ecotones in an ecotone-rich steppe–wetland landscape of Hungary in relation to the inter-annual fluctuations of water regime and the gradients of elevation and of soil composition. According to our results, the ecotones between steppe and wetland communities were sharp and their positions coincided with those places in the landscape where the rate of change in elevation was the highest, confirming that microtopography is a major determinant of ecotone position. Soil boundaries were also detected, mostly downhill to the ecotones. Interestingly, the fluctuations of the water supply had no effect on the position of the ecotones but significantly influenced a structural ecotone parameter, the compositional contrast bridged by the ecotones. High water supply caused high contrast, while low supply went along with low contrast. We explain these changes by asymmetric sensitivities to edge effects. When the water supply was low, the wetland edges became similar to the steppe edges due to the decrease of wetland specialists and to the increase of steppe specialists, but steppe edges did not exhibit an opposite change in wet years, suggesting that steppe communities dominated over wetland communities. The asymmetry in the interaction between the two communities may have pushed the soil boundaries downhill to the ecotones but the currently steppe-like soil of wetland edges could also make wetland edges more sensitive to edge effects; thus, the cause-effect relationship is difficult to disentangle.
Authors:L. Erdős, R. Gallé, L. Körmöczi, and Z. Bátori
Habitat boundaries in general and forest edges in particular belong to the central issues in ecology. Theories about community and environmental edge-responses are diverse, but there is a lack of sufficient supporting field evidence: no consensus exists about distinctness and diversity of edges, and the existence of edge-related species. Moreover, as most studies focus on man-made edges, natural forest edges are less understood. We studied xeric forest edges in a wooded-steppe area. Twelve forest patches were selected, and plots were set up within the edges, the forest interiors and the grasslands. Species composition, species richness and Shannon diversity were compared between the three habitat types as well as between differently oriented edges. We identified diagnostic species for all habitats. Local habitat preferences of the edge-related species were compared to their regional preferences. Environmental factors of the different habitats were assessed by using ecological indicator values. Forest edges differed both from forest interiors and grasslands, forming a narrow but distinct habitat type between them. Species composition of the edges was not simply a mixture of forest and grassland species, but there were several edge-related species, most of which are regionally regarded as typical of closed steppe grasslands. Neither shady conditions of the forests, nor dry conditions of the grasslands are tolerated by these species; this is why they are confined to edges. Species richness and Shannon-diversity were higher within edges than in either of the habitat interiors. Ecological indicator values suggested that light intensity and temperature were higher in the edges than in the forests, but were lower than in the grasslands. In contrast, soil moisture was lower in the edges than in the forests but was higher than in the grasslands. There were slight differences between differently exposed edges concerning species composition, species richness and Shannon diversity. We conclude that edges should be considered an integral part of wooded-steppes. Their high diversity may have nature conservation implications. Our study emphasizes that edge species may be confined to edges only locally, but may have a broader distributional range in other areas. These species may be referred to as local edge species. Our results also point out that the very same edge can be interactive and non-interactive at the same time, depending on the characteristics considered.
Authors:L. Erdős, C. Tölgyesi, V. Cseh, D. Tolnay, D. Cserhalmi, L. Körmöczi, K. Gellény, and Z. Bátori
Pannonian forest-steppes host a high number of endemic species and contribute to landscape-scale heterogeneity. Alterations in the proportion of forests and grasslands due to changes in land-use practice and climatic parameters can have serious nature conservation consequences. Hypotheses about forest-steppe dynamics have rarely been verified by detailed analyses, especially for the sandy forest-steppes. We integrated historical analysis, aerial photo interpretation and field investigation to determine how vegetation of a sandy forest-steppe has changed, how current dynamical processes operate and how native and exotic tree species regenerate under present conditions. The vegetation of the study area before the onset of major anthropogenic environmental transformations in the Carpathian Basin may have been a mosaic of forested and unforested patches. However, there is strong evidence that after heavy deforestation, the region was almost completely treeless between the 15th and the 19th centuries. Forest cover was able to recover by the 1800s but the lack of forested areas in the region for centuries explains why forest patches are still poor in species. Grasslands, which existed continuously, are more diverse, supporting several rare and endemic species. From 1953 till 2013, 72.45% of the area proved to be stable, but 27.55% showed clear dynamical character, changing either from forest to grassland, or vice versa. Thus, cyclic dynamics can occur in sandy forest-steppes. We found that forest patches of different size, differently exposed edges and grasslands provide different habitats for the tree species. Exotic species were present in large numbers, probably due to the small size of the reserve and the lack of a buffer zone.