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Ecosystem management policies increasingly emphasize provision of multiple, as opposed to single, ecosystem services. Management for such "multifunctionality" has stimulated research into the role that biodiversity plays in providing desired rates of multiple ecosystem processes. Positive effects of biodiversity on indices of multifunctionality are consistently found, primarily because species that are redundant for one ecosystem process under a given set of environmental conditions play a distinct role under different conditions or in the provision of another ecosystem process. Here we show that the positive effects of diversity (specifically community composition) on multifunctionality indices can also arise from a statistical fallacy analogous to Simpson's paradox (where aggregating data obscures causal relationships). We manipulated soil faunal community composition in combination with nitrogen fertilization of model grassland ecosystems and repeatedly measured five ecosystem processes related to plant productivity, carbon storage, and nutrient turnover. We calculated three common multi-functionality indices based on these processes and found that the functional complexity of the soil communities had a consistent positive effect on the indices. However, only two of the five ecosystem processes also responded positively to increasing complexity, whereas the other three responded neutrally or negatively. Furthermore, none of the individual processes responded to both the complexity and the nitrogen manipulations in a manner consistent with the indices. Our data show that multifunctionality indices can obscure relationships that exist between communities and key ecosystem processes, leading us to question their use in advancing theoretical understanding-and in management decisions-about how biodiversity is related to the provision of multiple ecosystem services. [ABSTRACT FROM AUTHOR]

Stable isotope mass spectrometric approaches are proving to be valuable tools in unravelling biotic interactions in complex ecosystems, yielding information on trophic preferences and functional roles of individual species. Gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) provides considerable opportunities to assist in studies concerned with ecosystem processes mediated by soil invertebrates and microorganisms by determination of δ13C values of individual compounds, for example, Upids, amino acids etc. However, techniques conventionally adopted for "wet" chemical extractions and de 'nvatizations necessary for compound-specific stable isotope determinations restrict the size of soil organism that can be studied and can limit investigations of individuals or even parts of individuals. We demonstrate here that individual soil mesofauna can be probed directly for their fatty acid stable isotope signatures by pyrolysis-GC/C/IRMS. A thermally assisted hydrolysis and methylation (THM) reaction is described for the determination of δ13C fatty acid values using trimethylsulfonium hydroxide (TMSH). Authentic fatty acids, acyl lipids, and individual Collembola (Folsomia candida) raised on C[SUB3] and C[SUB4] isotopically labeled yeast were analyzed initially by py-GC/ MS with TMSH and then by py-GC/C/IRMS. A kinetic isotope effect (KIE) observed with the THM reaction prevents direct calculation of the fatty acid δl3C values by simple mass balance equations. However, the KIE is shown to be both reproducible and robust and can therefore be accounted for by the use of correction factors. The fatty acid methyl ester compositions of individual F. candida and their respective δ13C values were determined and shown to agree with those obtained by conventional "wet" chemical procedures applied to much larger numbers of Collembola, thus enhancing the scope to which stable isotopes can be applied to the study of invertebrates in complex food webs in any environment. [ABSTRACT FROM AUTHOR]

Forests have a key role as carbon sinks, which could potentially mitigate the continuing increase in atmospheric carbon dioxide concentration and associated climate change. We show that carbon dioxide enrichment, although causing short-term growth stimulation in a range of European tree species, also leads to an increase in soil microbial respiration and a marked decline in sequestration of root-derived carbon in the soil. These findings indicate that, should similar processes operate in forest ecosystems, the size of the annual terrestrial carbon sink may be substantially reduced, resulting in a positive feedback on the rate of increase in atmospheric carbon dioxide concentration. [ABSTRACT FROM AUTHOR]