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

Abstract
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.

Highlights
•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.

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

Lengyel et al. (2012) Applied Vegetation Science

Szabolcs Lengyel, Katalin Varga, Beatrix Kosztyi, László Lontay, Eszter Déri, Péter Török, Béla Tóthmérész (2012): Grassland restoration to conserve landscape-level biodiversity: a synthesis of early results from a large-scale project. Applied Vegetation Science 15(2): 264-276.



Abstract
Question: European landscapes have long been influenced by intensifying use by humans. Although habitat restoration can reverse this process, it is often limited in scope by socioeconomic constraints. Here we present a grassland restoration project that is exceptional in spatial scale in Europe.
Location: A total area of 760 ha of arable land was restored in the Egyek-Pusztakócs unit (50 km2) of Hortobágy National Park, east Hungary, between 2005 and 2008.

Methods: Restoration targeted alkali steppes and loess grasslands by sowing seeds of either two (alkali) or three (loess) foundation grass species. In 2009, we surveyed the vegetation in restored and target grasslands and quantified the factors influencing restoration success in a space-for-time substitution design.
Results: We recorded 100 species of flowering plants, of which 37 species were non-weed, ‘target’ species. Annual weeds dominated 1-yr-old fields but had decreased dramatically by the third year due to a developing perennial grass cover. Former alfalfa fields had proportionally fewer weeds than former cereal and sunflower fields. The diversity of common species and the cover of target species increased from 1- to 4-yr-old restored fields. Alkali-restored fields had more heterogeneous vegetation and more species than loess-restored fields. Distance to the target vegetation did not directly affect vegetation variables. There was significant spatial variability in vegetation development, possibly suggesting several local pathways of succession.
Conclusions: Grassland restoration was generally successful in accelerating secondary succession towards alkali steppes and loess grasslands. However, further management is necessary to counter the homogenizing effects of litter accumulation, to reduce perennial weeds and to enhance the colonization of target species. Our project provides useful practical insights into grassland restoration and in applying restoration at a number of sites within a larger area to conserve biodiversity at the landscape scale.


Keywords
Conservation; Habitat diversity; Landscape ecology; Management; Mosaic habitat structure; Pannonic alkali steppe; Pannonic loess steppic grassland; Restoration success; Succession