Boda et al. (2015) Journal of Insect Conservation

Réka Boda, Csaba Bereczki, Adrienne Ortmann-Ajkai, Péter Mauchart, Bálint Pernecker, Zoltán Csabai (2015): Emergence behaviour of the red listed Balkan Goldenring (Cordulegaster heros Theischinger, 1979) in Hungarian upstreams: vegetation structure affects the last steps of the larvae. Journal of Insect Conservation 19(3): 547-557.

Abstract
In odonates, the emergence behaviour and finding suitable substrates for successful molting may influence the next generation and ultimately can determine the survival of the entire population. Understanding emergence behavior of endangered species and those granted special conservation status is particularly important. Despite this, little is known about the life history and emergence behaviour of Cordulegaster heros, a characteristic inhabitant of headwater streams. We hypothesised that the taxonomic composition and structure of the vegetation significantly affect the travel distance to the emergence site and the substrate choice. Two stream sections with different riparian zone vegetation were surveyed for exuviae in the emergence periods in two consecutive years, supported with detailed vegetation mapping. Significant differences were found between the vegetation characteristics at the two sites and differences were also found between emergences in edge zones within a site, indicating that the importance of vegetation structure operates within the scale of sites as well as between sites. At the site with more diverse vegetation, smaller horizontal but higher vertical travel distances and more varied emergence substrate choice were found. Habitat composition and complexity appears to determine the emergence behaviour of C. heros, so for the successful conservation of this species we recommend choosing appropriate forest management regimes and even maintaining riparian forests in near-pristine condition.

Keywords
Odonata, Exuviae, Travel distances, Emergence-site selection and preference, Vegetation grid mapping

Boda et al. (2015) Hydrobiologia

Réka Boda, Csaba Bereczki, Bálint Pernecker, Péter Mauchart, Zoltán Csabai (2015): Life history and multiscale habitat preferences of the red-listed Balkan Goldenring, Cordulegaster heros Theischinger, 1979 (Insecta, Odonata), in South-Hungarian headwaters: does the species have mesohabitat-mediated microdistribution? Hydrobiologia, DOI: 10.1007/s10750-015-2317-y

Abstract
Life cycle and microdistribution patterns of Cordulegaster heros, a charismatic species for nature conservation, are poorly known. Life history characteristics and multiscale habitat preferences of the larvae were followed for one year in monthly intervals by systematic samplings in eight headwaters, which resulted in data on 2562 individuals. We hypothesized that meso- and microhabitat complexity play an important role in forming the population structure and microdistribution of the species. Based on the distribution of the consecutive larval instars, duration of later stages and time of molt and emergence, the larval development of C. heros in the Mecsek Mountains lasts for at least three, but with a maximum of four years. All three levels of the multi-habitat structure [habitat (sites), and meso- (riffle/pool sequence) and microhabitats (biotic and different particle-sized abiotic types)] have significant effects on the spatial distribution of the larvae. Densities and population structures vary among the sites, but mesohabitat type and microhabitat diversity (heterogeneity within a pool or riffle) govern the microdistribution. C. heros prefers pools with small or medium microhabitat heterogeneity and higher proportion of small particle-sized substrates, especially in younger stages. Older larvae are less sensitive for these effects.

Keywords
Odonata, Larvae, Life cycle, Spatial microdistribution, Meso- and microhabitat preference

Deák et al. (2015) Basic and Applied Ecology

Balázs Deák, Orsolya Valkó, Péter Török, András Kelemen, Tamás Miglécz, Szilárd Szabó, Gergely Szabó, Béla Tóthmérész (2015): Micro-topographic heterogeneity increases plant diversity in old stages of restored grasslands. Basic and Applied Ecology, in press. doi:10.1016/j.baae.2015.02.008

Abstract

It is a truism in ecology that environmental heterogeneity increases diversity. Supporting field studies are mostly concerned with a large-scale topographic heterogeneity, ranging from a couple of meters to landscape-scale gradients. To test the role of fine-scale micro-topography on plant diversity, we studied the initial vegetation of recently filled (1-year-old), and established vegetation on old (7-year-old) soil-filled channels in an alkali landscape, East-Hungary. We hypothesised that (i) recently filled channels are characterised by a high cover of ruderal species and high species diversity and (ii) high micro-topographic heterogeneity increases the diversity of species and plant strategy types (mixed C-S-R categories) in early stages but later on this effect diminishes. We found that diversity of species and plant strategy types was higher in recently filled channels compared to old filled channels. Micro-topographic heterogeneity had no effect on the studied vegetation parameters in recently filled channels. Conversely, in old filled channels higher micro-topographic heterogeneity resulted in higher diversity and lower cover of the dominant grass Festuca pseudovina. Higher micro-topographic heterogeneity resulted in increased ruderality and decreased stress-tolerance, but it did not increase the diversity of plant strategy types. In contrast with former studies, we found that a couple of centimeters of micro-topographic heterogeneity had no effect on vegetation in recently filled channels, but supported a high diversity in old filled channels. An important practical implication of our study is that in grassland restoration projects, micro-topographic heterogeneity has a crucial role in sustaining biodiversity.

Keywords

Alkali landscape, C-S-R strategies, Elevation, Functional diversity, Grassland restoration, Plant trait, Soil disturbance, Succession, Topography

Deák et al. (2014) Flora

Deák, B.; Valkó, O.; Alexander, C.; Mücke, W.; Kania, A.; Tamás, J.; Heilmeier, H. (2014): Fine-scale vertical position as an indicator of vegetation in alkali grasslands - case study based on remotely sensed data. FLORA 209: 693-697.

 

Highlights

• Small-scale elevation gradients affect salt and water balance in alkali landscapes.•
• Elevation–vegetation correlations have not been studied in inland alkali landscapes.•
• We linked elevation data with vegetation patterns using remote sensing techniques.•
• Main vegetation categories can be separated by their small-scale vertical positions.•
• Remote sensing based vegetation mapping is an ideal tool in such complex landscapes.

Abstract
Vertical position is an important driver of vegetation zonation at multiple scales, via determining abiotic environmental parameters, such as climate, soil properties and water balance. In inland alkali landscapes, elevation is a key factor for understanding patterns of salt accumulation and water table which is therefore considered a good indicator of alkali vegetation types. Remote sensing techniques offer viable solutions for linking elevation data to vegetation patterns by providing an elevation model of extended areas. Our goal was to test the relationships between fine-scale differences in vertical position and vegetation patterns in inland alkali landscapes by vegetation data collected in the field and elevation data generated using airborne laser scanning (ALS). We studied whether vertical position influences vegetation patterns at the level of main vegetation groups (based on alliances) or even at the level of associations. Our study sites were situated in a lowland alkali landscape in Hortobágy National Park (East-Hungary). We grouped the associations into four main vegetation groups: loess grasslands, alkali steppes, open alkali swards and alkali meadows. Even though we detected a very limited range (121 cm) in the vertical position of the main vegetation groups, they were well separated by their vertical positions. At the level of associations, a more detailed elevation-based distinction was also possible in many cases. The revealed elevation–vegetation correlations show that high-resolution mapping based on ALS remote sensing techniques is an ideal solution in complex lowland areas, such as alkali landscapes. Our findings suggest that in other types of lowland landscapes, characterised by elevation differences, the applied method might hold a great potential as a supporting tool for vegetation mapping.


Keywords
Vegetation zonation, Airborne laser scanning, Saline grassland, Festucion pseudovinae, Natura 2000, Digital terrain model

Burai et al. (2015) Remote Sensing

Burai, P., Deák, B., Valkó, O., Tomor, T (2015): Classification of herbaceous vegetation using airborne hyperspectral imagery. Remote Sensing 7: 2046-2066.


Abstract
Alkali landscapes hold an extremely fine-scale mosaic of several vegetation types, thus it seems challenging to separate these classes by remote sensing. Our aim was to test the applicability of different image classification methods of hyperspectral data in this complex situation. To reach the highest classification accuracy, we tested traditional image classifiers (maximum likelihood classifier—MLC), machine learning algorithms (support vector machine—SVM, random forest—RF) and feature extraction (minimum noise fraction (MNF)-transformation) on training datasets of different sizes. Digital images were acquired from an AISA EAGLE II hyperspectral sensor of 128 contiguous bands (400–1000 nm), a spectral sampling of 5 nm bandwidth and a ground pixel size of 1 m. For the classification, we established twenty vegetation classes based on the dominant species, canopy height, and total vegetation cover. Image classification was applied to the original and MNF (minimum noise fraction) transformed dataset with various training sample sizes between 10 and 30 pixels. In order to select the optimal number of the transformed features, we applied SVM, RF and MLC classification to 2–15 MNF transformed bands. In the case of the original bands, SVM and RF classifiers provided high accuracy irrespective of the number of the training pixels. We found that SVM and RF produced the best accuracy when using the first nine MNF transformed bands; involving further features did not increase classification accuracy. SVM and RF provided high accuracies with the transformed bands, especially in the case of the aggregated groups. Even MLC provided high accuracy with 30 training pixels (80.78%), but the use of a smaller training dataset (10 training pixels) significantly reduced the accuracy of classification (52.56%). Our results suggest that in alkali landscapes, the application of SVM is a feasible solution, as it provided the highest accuracies compared to RF and MLC. SVM was not sensitive in the training sample size, which makes it an adequate tool when only a limited number of training pixels are available for some classes.


Keywords
grassland, habitat mapping, hyperspectral, maximum likelihood classifier, minimum noise fraction, nature conservation, open landscape, random forest, support vector machine

Lengyel & Podani (2015) Journal of Vegetation Science

Lengyel, A. & Podani, J. (2015): Assessing the relative importance of methodological decisions in classifications of vegetation data. Journal of Vegetation Science. doi: 10.1111/jvs.12268

Abstract
Questions: What is the relative importance of our methodological decisions concerning sampling (plot size) and data analysis (data transformation, resemblance coefficient, hierarchical clustering strategy and number of clusters) in vegetation classification? Are there differences between the conclusions when the full range or only a more practical narrow range of methodological choices is tested? What is the difference between results for actual and random data?
Location: Rock grassland in Hungary.
Methods: The full procedure of vegetation classification was simulated using actual and random data. Variation in classification results was partitioned using distance-based redundancy analysis. The RDA models were subjected to variation partitioning to determine the relative importance of methodological decisions.
Results: RDA models explained more variation in classifications of random than in real data. Classification algorithm, cluster level, data transformation and mean plot size were always included among the most significant variables, however, the other variables also had a considerable effect in certain situations.
Conclusions: As adjusted R2 values suggest, the overall effect of methodological decisions on classifications is larger for randomly structured than actual data, due possibly to a stronger clustering tendency in the latter. The clustering algorithm, cluster level, data transformation and plot size should be chosen most carefully before classification analyses, but any of the examined decisions can significantly affect the result. In addition to the mean, the range of plot sizes should also be carefully delimited during relevé selection for classification studies. The main decision about the classification algorithm is whether a chain-forming or group-forming method is used. The data transformation had a more significant effect on real data than on simulations with random variation, thus supporting the ability of the application of different abundance scales in revealing different facets of biologically relevant patterns in community composition. The resemblance measure had a relatively weak effect, suggesting that it is not as influential as previously thought.


Keywords
Data transformation, Flexible clustering, Model selection, Multivariate analysis, Plot size, Resemblance measure

Kelemen et al. (2015) Ecological Complexity

András Kelemen, Péter Török, Orsolya Valkó, Balázs Deák, Katalin Tóth, Béla Tóthmérész (2015): Both facilitation and limiting similarity shape the species coexistence in dry alkali grasslands. Ecological Complexity 21: 34–38. doi:10.1016/j.ecocom.2014.11.004

Abstract
Facilitation is an important driver of community assembly, and often overwhelms the effect of competition in stressed habitats. Thus, net effect of biotic interactions is often positive in stressed grasslands, where dominant species and litter can protect the subordinate species. Besides facilitation, niche partitioning can also support species coexistence leading to limiting similarity between subordinate species. Our aim was to provide a detailed analysis of fine-scale biotic interactions in stressed alkali grasslands. We supposed, that there are positive relationships between the main biomass fractions and species richness. We expected the expansion of trait ranges and the increase of trait dissimilarity with increasing biomass scores (total litter, green biomass of dominant species) and species richness. We studied the relationships between main biomass fractions, species richness, functional diversity and functional trait indices (ranges, weighted means and Rao indices). We used fine-scale biomass sampling in nine stands of dry alkali grasslands dominated by Festuca pseudovina. The detected relationships were always positive between the main biomass fractions (green biomass of dominant species, total litter and green biomass of subordinate species) and species richness. We found that the green biomass of dominant species and total litter increased ranges and dissimilarity of functional traits. Our results suggest that in dry alkali grasslands facilitation is crucial in shaping vegetation composition. The green biomass of dominant species and total litter increased the biomass production of subordinate species leading to overyielding. We found that mechanisms of facilitation and limiting similarity were jointly shaping the species coexistence in stressed grasslands, such as alkali grasslands.

Highlights

• We proposed a model of fine-scale biotic interactions in stressed alkali grasslands.
• Trait-based analyses are used to reflect fine-scale species co-existence patterns.
• Diversity and biomass of subordinate species increased by Festuca biomass and litter.
• Festuca increased the ranges and dissimilarity of functional traits.
• Facilitation and limiting similarity jointly shape species coexistence.

Keywords
Abiotic stress, Biomass, Competition, Functional diversity, Plant traits, Trait dissimilarity