Summary1 Ecological and agronomic research suggests that increased crop diversity in speciespoor intensive systems may improve their provision of ecosystem services. Such general predictions can have critical importance for worldwide food production and agricultural practice but are largely untested at higher levels of diversity. 2 We propose new methodology for the design and analysis of experiments to quantify diversity-function relationships. Our methodology can quantify the relative strength of inter-specific interactions that contribute to a functional response, and can disentangle the separate contributions of species richness and relative abundance. 3 Applying our methodology to data from a common experiment at 28 European sites, we show that the above-ground biomass of four-species mixtures (two legumes and two grasses) in intensive grassland systems was consistently greater than that expected from monoculture performance, even at high productivity levels. The magnitude of this effect generally resulted in transgressive overyielding. 4 A combined analysis of first-year results across sites showed that the additional performance of mixtures was driven by the number and strength of pairwise inter-specific interactions and the evenness of the community. In general, all pairwise interactions contributed equally to the additional performance of mixtures; the grass-grass and legume-legume interactions were as strong as those between grasses and legumes. 5 The combined analysis across geographical and temporal scales in our study provides a generality of interpretation of our results that would not have been possible from individual site analyses or experimentation at a single site. 6 Our four-species agricultural grassland communities have proved a simple yet relevant model system for experimentation and development of methodology in diversity-function research. Our study establishes that principles derived from biodiversity research in extensive, semi-natural grassland systems are applicable in intensively managed grasslands with agricultural plant species.

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a b s t r a c tBiomass dry matter partitioning and growth characteristics are important selection criteria for energy crops. The objective of the study was to examine the response of switchgrass (cv. Alamo) to irrigation (2 levels: rainfed and irrigated with 250 mm) and N-fertilization (4 levels: 0, 80, 160 and 240 kg N ha −1 ) under two different soil-climatic conditions for two growing seasons 2011 and 2012. The results demonstrated a significant effect (P < 0.05) of irrigation, fertilization and their interaction on crop growth and biomass productivity. Biomass yield ranged from 14 to 27 Mg ha −1 for the calcareous, clay loam to clay, fertile soil (Velestino; Greece) and for the deep, calcareous sandy loam to loam, semi-fertile soil (Palamas; Greece), respectively. In both sites, switchgrass accumulated a high amount of biomass in stems. Dry stem/total biomass ratio was stabilized in the 3rd growing year and it was rather constant throughout the growing period (range 68-71%). The maximum growth rates were similar for both sites with value of 390 kg ha −1 day −1 , whereas the highest leaf area index observed was 7.59, indicating that switchgrass has high growth rate independently of the site and its microclimate. Therefore switchgrass should be included in future cropping systems as an important energy crop for solid bio-fuel production.

CH 1 INTRODUCTION TO CARBON IN SENSITIVE EUROPEAN ECOSYSTEMSuse of soils has led to a strong decline of soil carbon worldwide (Lal, 2004). Marginal agricultural land in Europe is frequently being afforested, with strong implications on carbon fluxes and pools. The state-of-knowledge for land use change is covered and evidence given on how well the understanding of carbon processes is supported by real data. A particular challenge is the temporal extent of the soil carbon change. Consequently, the chapter also explores how knowledge on land use change can be reconciled with the time frame of reporting.Another chapter deals with disturbances. It is well understood that ecosystem disturbance changes the total carbon pool much quicker and sometimes with more severity than with the gradual evolution of an ecosystem (Körner, 2003). A series of natural and anthropogenic ecosystem disturbances are evaluated with hindsight to soil carbon pools, and it is demonstrated how management may affect the pools. The final chapter in the first part presents an overview on knowledge of soil carbon pools from a European perspective. This information is of crucial importance because it sets the limitations on an international soil carbon accounting scheme. It also addresses the highly important question of the baseline of soil carbon stocks that should be used when interpreting the current stock and stock changes of soil carbon.Part 2 of the book picks out several types of ecosystems of particular relevance. It is intended to find a niche for this text by focusing on soils that deserve more attention than they have received in the past. In a chapter on mountain and high latitude ecosystems, the topic of above-average warming as predicted by the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) (Fischlin et al., 2007) is covered. Nevertheless, the biological activity of soil microorganisms is constrained by low temperatures and a short growing season. In a warmer climate substantial quantities of carbon dioxide may be lost from soils. A second strong driver is land use change due to the abandonment of alpine pastures and the subsequent reforestation.A comprehensive treatment is given to 'Peatlands'. From the knowledge of processes and responses of upland (mineral) soils to global warming, only limited predictions can be deduced for peatlands. Even their delineation on soil maps is uncertain. However, peatlands are a heterogeneous group of soils with different emissions. Drainage and subsequent land use change can have a strong effect on carbon fluxes and GHG emissions. The fate of peatlands as a consequence of climate change calls for a rigorous evaluation.A separate chapter is devoted to Mediterranean ecosystems. Simulation models predict a low carbon sequestration potential for Mediterranean forest soils, mainly because the productivity of sites with a prolonged summer drought is low. More important than adapted forest management may be the effect of land use change (afforestation), because it may rever...

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