Abstract. Studies on ecological successions have a long tradition and have strongly contributed to the understanding of community assembly, niche theory, and ecosystem structure and functionality. Reports on ecological successions are however mostly restricted to one or two taxonomic groups, neglecting the mutual influences and dependencies between multiple taxonomic groups that are the building blocks of diverse communities. We introduce the Alpine research platform Ödenwinkel to promote observational and experimental research on the emergence of multidiversity and ecosystem complexity. We established n= 140 permanent plots along the successional gradient of the forefield of the Ödenwinkelkees glacier at the end of the Stubachtal valley in the Hohe Tauern range (Hohe Tauern National Park, Land Salzburg, Austria). In summer 2019 we completed a first full inventory of biotic and abiotic characteristics of these plots covering the diversity and composition of vascular plants, bryophytes, arthropods, and other animals, bacteria and fungi as well as some geomorphologic properties. In this paper we introduce the design of the research platform and show first results. While focusing on the diversity and composition of vascular plants along the successional gradient, we also provide data on the diversity of animals, bacteria, and fungi. The Ödenwinkel platform will be available as a long-term ecological research site where researchers from various disciplines can contribute to the accumulation of knowledge on ecological successions and on how interactions between various taxonomic groups structure ecological complexity in this Alpine environment.

BackgroundFull scent profiles emitted by living tissues can be screened by using total ion chromatograms generated in full scan mode and gas chromatography–mass spectrometry technique using Headspace Sorptive Extraction. This allows the identification of specific compounds and their absolute quantification or relative abundance. Quantifications ideally should be based on calibration curves using standards for each compound. However, the unpredictable composition of Volatile Organic Compounds (VOCs) and lack of standards make this approach difficult. Researchers studying scent profiles therefore concentrate on identifying specific scent footprints i.e. relative abundance rather than absolute quantities. We compared several semi-quantitative methods: external calibration curves generated in the sampling system and by liquid addition of standards to stir bars, total integrated peak area per fresh weight (FW), normalized peak area per FW, semi-quantification based on internal standard abundance, semi-quantification based on the nearest n-alkane and percentage of emission. Furthermore, we explored the usage of nearest components and single calibrators for semi-quantifications.ResultsAny of the semi-quantification methods based on a standard produced similar or even identical results compared to quantification by a true-standard for a compound, except for the method based on standard addition. Each method beholds advantages and disadvantages regarding level of accuracy, experimental variability, acceptance and retrieved quantities.ConclusionsOur data shows that, except for the method of standard addition to the biological sample, the rest of the semi-quantification methods studied give highly similar statistical results. Any of the methodologies presented here can therefore be considered as valid for scent profiling. Regarding relative proportions of VOCs, the generation of calibration curves for each compound analysed is not necessary.Electronic supplementary materialThe online version of this article (10.1186/s13007-018-0335-2) contains supplementary material, which is available to authorized users.

The genus Antirrhinum comprises about 28 species with a center of origin in the Iberian Peninsula. They show an important diversity of growing niches. We have performed a comprehensive analysis of scent profiles in eight wild species, Antirrhinum linkianum, A. tortuosum, A. cirrigherum, A. latifolium, A. meonanthum, A. braun-blanquetii, A. barrelieri, and A. graniticum. We used also two laboratory inbred lines A. majus, 165E and Sippe50. We identified 63 volatile organic compounds (VOCs) belonging to phenylpropanoids, benzenoids, mono- and sesquiterpenes, nitrogen-containing compounds, and aliphatic alcohols previously described in plants. Twenty-four VOCs were produced at levels higher than 2% of total VOC emission, while other VOCs were emitted in trace amounts. The absolute scent emission varied during flower maturation and species. The lowest emitting was A. meonanthum while A. tortuosum had the largest emissions. Species were clustered according to their scent profiles and the resulting dendrogram matched the current species phylogeny. However, two accessions, A. majus Sippe 50 and A. braun-blanquetii, showed development-specific changes in their VOC composition, suggesting a precise control and fine tuning of scent profiles. Cluster analysis of the different scent components failed to identify a specific synthesis pathway, indicating a key role of scent profiles as blends. There is considerable degree of chemodiversity in scent profiles in Antirrhinum. The specific developmental stage plays an important role in scent quantitative emissions. The relative robustness of the bouquets could be an adaptation to local pollinators.

Research on successions and community assembly both address the same processes such as dispersal, species sorting, and biotic interactions but lack unifying concepts. Recent theoretical advances integrated both research lines proposing a sequence of stochastic and deterministic processes along successional gradients. Shifts in ecosystem states along successional gradients are predicted to occur abruptly once abiotic and biotic factors dominate over dispersal as main driver. Considering the multidiversity composed of five organismal groups including plants, animals, and microbes, our results imply that stochastic, likely dispersal-dominated, processes are replaced by rather deterministic processes such as environmental filtering and biotic interactions after around 60 years of succession in a glacier forefield. The niche-based character of later successional processes is further supported by a decline in multi-beta-diversity. Our results may update concepts of community assembly by considering multiple taxa, help to bridge the gap between research on successions and community assembly, and provide insights into the emergence of multidiverse and complex ecosystems.

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