2014. január 28., kedd

Kelemen et al. (2014) Biodiversity and Conservation

András Kelemen, Péter Török, Orsolya Valkó, Balázs Deák, Tamás Miglécz, Katalin Tóth, Tamás Ölvedi & Béla Tóthmérész (2014): Sustaining recovered grasslands is not likely without proper management: vegetation changes after cessation of mowing. Biodiversity and Conservation, in press. DOI: 10.1007/s10531-014-0631-8

Grasslands recovered by sowing low diversity seed mixtures of local provenance are usually managed by mowing. Besides restoration success only a few studies have focused on the direct effects of post-restoration mowing on recovered grassland vegetation. In this study we followed vegetation changes in 13 successfully recovered grasslands in 5 × 5-m-sized sites with continuous and ceased mowing at Hortobágy National Park, East-Hungary. We asked the following questions: (i) What are the effects of cessation of mowing on the vegetation structure and diversity of recovered grasslands? (ii) What are the effects of cessation of mowing on the abundance of sown grasses, target and undesirable species? (iii) Is yearly mowing an appropriate management tool for the maintenance of recovered grasslands? Our results showed that the cessation of mowing caused litter accumulation, while diversity, total vegetation cover and the cover of sown grasses decreased compared to the mown sites. The cover of undesirable perennial species was significantly higher in unmown sites than in mown ones. The species composition of mown sites remained more similar to near-natural grasslands than the unmown ones. Our results suggest that without regular post-restoration mowing the favourable status of recovered grasslands can rapidly decline due to litter accumulation and by the expansion of undesirable species, even in the short-run. We also stress that while yearly mowing is enough to maintain grasslands recovered by low-diversity seed sowing, it cannot be considered to be enough to recover target vegetation composition.

Grassland restoration, Seed sowing, Abandonment, Post-restoration management, Biodiversity, Cirsium arvense

2014. január 16., csütörtök

Dengler et al. (2014) Agriculture, Ecosystems & Environment

Jürgen Dengler, Monika Janišová, Péter Török, Camilla Wellstein (2014): Biodiversity of Palaearctic grasslands: a synthesis. Agriculture, Ecosystems & Environment, in press, DOI: dx.doi.org/10.1016/j.agee.2013.12.015

This article introduces a Special Issue on biodiversity of Palaearctic grasslands and provides a synthesis of the current knowledge on this topic. Four major categories of grasslands can be distinguished in the Palaearctic biogeographic realm: (a) zonal steppes (in areas too dry for forests), (b) arctic-alpine grasslands (in areas too cold for forests), (c) azonal and extrazonal grasslands (where hydrology, soil conditions, relief or natural disturbances within the forest biomes prevent tree growth locally) and (d) secondary grasslands (which replace natural forests in consequence of human land use). We summarize the present knowledge about species richness patterns (mainly of vascular plants) along abiotic and land use gradients. Further, we highlight the usefulness of diversity measures not based on species richness, namely functional diversity, phylogenetic diversity and within-species diversity. The strong differences observed for diversity patterns according to analyzed biodiversity parameter, spatial scale or taxonomic group call for comparative studies and caution when generalizing results. A particular challenge are the extreme plot-scale species richness values found in grasslands of a few European regions. We propose a conceptual model that explains the findings by an interplay of various factors acting at different levels: (i) The largest species pool is expected for habitats under conditions that prevailed over the last few million years, with a slight shift towards intermediate positions, i.e. for the Palaearctic in open, semi-dry, base-rich situations. (ii) The landscape-level species pool is increased by continuity of a grassland patch in space and time and heterogeneity of the surrounding landscape. (iii) The coexistence of regionally available species at a plot scale is due to reduced competitive exclusion according to Intermediate Disturbance Hypothesis, mowing once a year without fertilization being particularly effective. Ecosystem functions and services of Palaearctic grasslands are often positively connected to their biodiversity. At the same time, these communities and their biota are nowadays highly endangered. The semi-natural (High Nature Value) grasslands of Europe are mainly threatened by agricultural intensification or abandonment on low-productive sites in remote areas, while the natural steppes of the Palaearctic have largely been destroyed by conversion into arable land. Finally, we present some promising conservation and management approaches and call for a strong and comprehensive Convention on Grassland Conservation.

•The paper deals with natural, semi-natural and improved Palaearctic grasslands.
•High species richness at plot-scale occurs in semi-dry basiphilous grasslands.
•Palaearctic grasslands have a big species pool including many threatened biota.
•Semi-natural grasslands are threatened by intensification and abandonment.
•Natural steppes have largely been converted to arable land.

Conservation, Disturbance, Land use, Semi-natural, Species richness, Steppe

2014. január 13., hétfő

Erdős et al. (2014) Ecological Complexity

L. Erdős, Cs. Tölgyesi, M. Horzse, D. Tolnay, Á. Hurton, N. Schulcz, L. Körmöczi, A. Lengyel, Z. Bátori: Habitat complexity of the Pannonian forest-steppe zone and its nature conservation implications. Ecological Complexity, in press, DOI: http://dx.doi.org/10.1016/j.ecocom.2013.11.004

Eurasian forest-steppes are among the most complex ecosystems in the northern temperate zone. Alternating forest and grassland patches form a mosaic-like landscape, stretching in a stripe from eastern Europe almost to the Pacific coast. Although the edges (contact zones between woody and herbaceous vegetation) may play an important ecological role, their study has been neglected in the forest-steppes. In this study, we aimed to perform a comprehensive analysis on the components of a sandy forest-steppe in the Pannonian ecoregion (Hungary), with special regard to the edges. 2 m × 1 m coenological relevés were made in forest interiors, in edges and in grassland interiors. We carried out microclimate measurements in each habitat type. Compositional and structural characteristics of the forests, edges and grasslands were compared, including species number, Shannon diversity, summarized cover, life-form and geoelement spectra. Diagnostic species for each habitat type were identified, and the role of the habitats in harbouring protected and endemic species was also assessed. Based on the frequencies and cover values of tree seedlings and saplings in the three habitat types, we formulated tentative assumptions on vegetation dynamics. We found that edges possessed their own distinct species composition, having a considerably higher species number, Shannon diversity and vegetation cover than habitat interiors. Edges hosted relatively large numbers of edge-related species, and proved to be highly different from habitat interiors with regard to life-form and geoelement spectra. It seemed that the spatial interaction of two neighbouring communities resulted in the emergence of a third, unique community, the edge. The microclimate of the forests and the grasslands differed strikingly, whereas that of the edges fell between them. Except Populus alba, trees had very few seedlings and no saplings, which may have serious consequences if the current warming and drying trend continues. We conclude that in the study area, intermediate microclimate of the edges supports a community that is not intermediate compositionally and structurally: the edge should be recognized as a distinct community, although strongly connected to the neighbouring communities. As a consequence, forest-steppes have three integral components: forest, grassland and edge. Our results emphasize the conservation importance of all components. The conservation value of the sandy grasslands has long been recognized, but the contribution of edges and forest patches to species and habitat diversity should not be neglected either. Conservation activities should focus on maintaining the complexity of the forest-steppe ecosystem, with all of its integral components.

Diversity, Edge, Endemic plants, Microclimate