László Demeter

The effect of fish and aquatic habitat complexity on amphibians

Fish introductions are considered one of the most widespread anthropogenic threats to aquatic ecosystems. Their negative impact on native amphibian communities has received increasing attention in recent years. We investigated the relationship between the introduced fish, emergent vegetation cover and native amphibians in man-made ponds generated by regulation and dam building along the Târnava Mare Valley (Romania) during the last 40 years. We inventoried amphibians and fish inhabiting 85 permanent ponds and estimated habitat complexity focusing on emergent vegetation cover. Four amphibian species were found to be negatively associated with the presence of predatory fish. Species richness of ponds without fish and ponds without predatory fish did not differ significantly, whereas ponds containing only predatory fish had significantly lower amphibian richness. A significant positive relationship was found between the emergent vegetation cover and pond occupancy of six amphibian species and amphibian species richness. As a management recommendation, we suggest the restriction of fish introductions to non predatory fish and the maintenance of high emergent vegetation cover in the ponds.

Pond and landscape characteristics — which is more important for common toads (Bufo bufo)? A case study from central Romania

The primary anthropogenic factor causing amphibian declines in Europe is habitat loss and fragmentation. Here we explore the effects of aquatic and landscape habitat variables on the adult counts of the Common Toad (Bufo bufo) in 43 ponds in central Romania surveyed between 2000 and 2005. Principal components analysis (PCA) identified two main factors, with which the adult counts can be related the first related to landscape variables (percentage of forest cover, presence/absence of roads and habitat corridors) and the second, to pond variables, in particular the presence/absence of fish, together accounting for 49% of the total variance. Analysis of variance (ANOVA) showed differences between ponds where toads were present or absent in factor loadings of both principal components, but only the landscape factor was significantly correlated with toad counts. These results highlight the role of landscape composition and configuration in maintaining toad populations in this area, and suggest a negative effect of landscape fragmentation. To efficiently protect amphibians in Romania, appropriate legislation and a close collaboration between landowners, landscape planners and herpetologists are needed.

Pond‐based survey of amphibians in a Saxon cultural landscape from Transylvania (Romania)

Habitat‐based inventories provide critical reference data that are essential to track changes in amphibian communities and their habitats. We present the results of a pond inventory in a cultural landscape from central Romania. The presence/absence of amphibians was assessed through multiple‐year surveys during the breeding season and larval development. Ten amphibian species and a species complex were identified: Triturus cristatus, T. vulgaris, Bombina variegata, Bufo bufo, B. viridis, Rana dalmatina, R. temporaria, R. arvalis, Hyla arborea, Pelobates fuscus and the R. esculenta complex. The species richness is larger in the permanent ponds than in the temporary ones. Rana dalmatina, B. bufo and the R. esculenta complex are the most frequent in the permanent ponds, while Bombina variegata and R. temporaria were the most common in temporary ponds. The scarcity of B. viridis and R. arvalis is explained by the lack of available habitats. Our data allow a more complex analysis of the spatial and temporal determinants of amphibian habitat use in this cultural landscape, and provide a consistent baseline for future surveys and monitoring programmes.

Declining Diversity in Abandoned Grasslands of the Carpathian Mountains: Do Dominant Species Matter?

Traditional haymaking has created exceptionally high levels of plant species diversity in semi-natural grasslands of the Carpathian Mountains (Romania), the maintenance of which is jeopardized by recent abandonment and subsequent vegetation succession. We tested the hypothesis that the different life history strategies of dominant grasses cause different patterns of diversity loss after abandonment of traditional haymaking in two types of meadow. Although diversity loss rate was not significantly different, the mechanism of loss depended on the life history of dominant species. In meadows co-dominated by competitive stress-tolerant ruderals, diversity loss occurred following the suppression of dominant grasses by tall forbs, whereas in meadows dominated by a stress-tolerant competitor, diversity loss resulted from increased abundance and biomass of the dominant grass. We conclude that management for species conservation in abandoned grasslands should manipulate the functional turnover in communities where the dominant species is a weaker competitor, and abundance and biomass of dominant species in communities where the dominant species is the stronger competitor.

Rural social–ecological systems navigating institutional transitions: case study from Transylvania (Romania)

Abstract Traditional rural social–ecological systems (SES) share many features which are crucial for sustainable development. Eastern European countries such as Romania, are still rich in traditional cultural landscapes. However, these landscapes are increasingly under internal (e.g., peoples aspirations toward western socioeconomic ideals) and external (institutional changes, globalization of the commodity market, connectivity with other cultures) pressures. Therefore, understanding the ways how traditional SES navigated past and more recent changes is of crucial importance in getting insights about the future trajectory of these systems. Here, we present the rural SES from the Saxon region of Transylvania through the lens of institutional transitions which happened in the past century in this region. We show that the rural SES went through episodic collapses and renewals, their cyclic dynamic being related to the episodic changes of the higher level formal institutions. These episodic collapses and renewals created a social–ecological momentum for the sustainability of these SES. While we recognize that policy effectiveness depends on institutional stability (and institutions are unstable and prone to collapses), maintaining those social–ecological system properties which can assure navigation of societies through the challenges imposed by global changes should be in the heart of every governance system. Such properties includes wide extent of native vegetation, fertile soils, wide range of provisioning ecosystem services, genuine links between people and landscapes and knowledge about the social–ecological systems. These features could provide important capitals and memory elements for the (re)emergence of social–ecological systems (old or new).