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Fil: Loydi, Alejandro. Justus-Liebig University Giessen; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida(i); Argentina

Photo observations are a highly valuable but rarely used source of citizen science (CS) data. Recently, the number of publicly available photo observations has increased strongly, for example, due to the use of smartphone applications for species identification. This has enabled the raising of ecological insights in poorly studied subjects. One of the fields with the highest potential to benefit from the use of photo observations is phenology. We propose a workflow for iPhenology, the use of publicly available photo observations to track phenological events at large scales. The workflow comprises data acquisition, cleaning of observations, phenological classification and modelling spatiotemporal patterns of phenology. We explore the suitability of iPhenology to observe key phenological stages in the plant reproductive cycle of a model species and discuss limitations and future prospects of the approach using the example of an invasive species in Europe. We show that iPhenology is suitable to track key phenological events of widespread species. However, the number and quality of available observations may differ among species and phenological stages. Overall, publicly available CS photo observations are suitable to track key phenological events and can thus significantly advance the knowledge on the timing and drivers of plant phenology. In future, integrating the workflow with automated image processing and analysis may enable real‐time tracking of plant phenology. Fotobeobachtungen sind eine äußerst wertvolle, aber selten genutzte Quelle von Citizen Science Daten. In jüngster Zeit hat die Zahl der öffentlich verfügbaren Fotobeobachtungen stark zugenommen, unter anderem durch den Einsatz von Smartphone‐Apps zur Artbestimmung. Diese Entwicklung ermöglicht es, Erkenntnisse in wenig erforschten Gebieten der Ökologie zu gewinnen. Die Phänologie ist einer der Bereiche mit dem größten Potenzial, von der Nutzung von Fotobeobachtungen zu profitieren. Wir beschreiben einen Workflow für iPhenology, die Nutzung öffentlich zugänglicher Fotobeobachtungen zur Analyse phänologischer Ereignisse. Der Workflow umfasst Datenerfassung, Bereinigung der Beobachtungen, phänologische Klassifizierung und die Modellierung räumlich‐zeitlicher Muster. Wir untersuchen die Eignung von iPhenology zur Beobachtung unterschiedlicher phänologischer Ereignisse im pflanzlichen Reproduktionszyklus anhand einer Modellart und erörtern aktuelle Begrenzungen/Einschränkungen und zukünftige Anwendungsgebiete des Ansatzes. Wir zeigen, dass öffentlich verfügbare Fotobeobachtungen geeignet sind, phänologische Schlüsselereignisse wie die Blüte oder Fruchtreife weit verbreiteter Arten zu analysieren. Die Anzahl und Qualität der verfügbaren Beobachtungen kann sich jedoch je nach Art und phänologischer Phase stark voneinander unterscheiden. Fotobeobachtungen sind geeignet, um wichtige phänologische Ereignisse zu analysieren und können somit das Wissen über den zeitlichen Ablauf und die Einflussfaktoren der phänologischer Phasen erheblich erweitern. In Zukunft könnte die Integration des iPhenology‐Workflows mit Tools zur automatischen Bildverarbeitung und ‐analyse die Echtzeitbeobachtung phänologischer Ereignisse ermöglichen.

Numerous restoration campaigns focused on re-establishing species-rich floodplain meadows of Central Europe, whose species composition is essentially controlled by regular flooding. Climate change predictions expect strong alterations on the discharge regime of Europe's large rivers with little-known consequences on floodplain meadow plants. In this study, we aim to determine the effects of flooding on seedlings of different ages of four typical flood meadow species. To this end, we flooded seedlings of two familial pairs of flood meadow species of wetter and dryer microhabitats for 2 weeks each, starting 2, 4, 6, and 8 weeks after seedling germination, respectively. We show that a 2-week-flooding treatment had a negative effect on performance of seedlings younger than 6 weeks. Summer floods with high floodwater temperatures may have especially detrimental effects on seedlings, which is corroborated by previous findings. As expected, the plants from wet floodplain meadow microhabitats coped better with the flooding treatment than those from dryer microhabitats. In conclusion, our results suggest that restoration measures may perform more successfully if seedlings of restored species are older than the critical age of about 6 weeks before a spring flooding begins. Seasonal flow patterns may influence vegetation dynamics of floodplain meadows and should, therefore, be taken into account when timing future restoration campaigns.

Desiccation cracks are a natural phenomenon of clay-rich soils that form via soil shrinkage during dry conditions. Our aim was to test the seed trapping potential of such cracks and assess its impact on seed bank formation in a flood-meadow ecosystem. We documented crack patterns on permanent plots and analysed the soil seed content along and adjacent to cracks. Seed translocation via cracks was tested with a mark-recapture experiment, and post-entrapment seed fate was tested with a burial experiment. Most cracks re-opened in the same positions in consecutive dry periods. Along cracks, most seeds were found in 10-20 cm depth, whereas adjacent to cracks most seeds were found in 0-5 cm depth. The majority of seeds found in shallow depths adjacent to cracks belonged to species that were also present in the above-ground vegetation, whereas this rate was always under 50% along desiccation cracks. The mark-recapture experiment gave evidence for vertical seed translocation through desiccation cracks. Post-entrapment seed fate differed between species and burial depth, with a trend towards increasing survival with increasing depth. We conclude that desiccation cracks act as natural seed traps, foster seed bank formation and thus influence plant community dynamics in flood meadow systems.

Floodplain meadows along rivers are semi-natural habitats and depend on regular land use. When used non-intensively, they offer suitable habitats for many plant species including rare ones. Floodplains are hydrologically dynamic ecosystems with both periods of flooding and of dry conditions. In German floodplains, dry periods may increase due to reduced summer precipitation as projected by climate change scenarios. Against this background, the question arises, how the forage quantity and quality of these meadows might change in future. We report results of two field trials that investigated effects of experimentally reduced summer precipitation on hay quantity and quality of floodplain meadows at the Rhine River (2011-2012) and at two Elbe tributaries (2009-2011). We measured annual yield, the amount of hay biomass, and contents of crude protein, crude fibre, energy, fructan, nitrogen, phosphorus, and potassium. The annual yield decreased under precipitation reduction at the Rhine River. This was due to reduced productivity in the second cut hay at the Rhine River in which, interestingly, the contents of nitrogen and crude protein increased. The first cut at the Rhine River was unaffected by the treatments. At the Elbe tributaries, the annual yield and the hay quantity and quality of both cuts were only marginally affected by the treatments. We conclude that the yield of floodplain meadows may become less reliable in future since the annual yield decreased under precipitation reduction at the Rhine River. However, the first and agriculturally more important cut was almost unaffected by the precipitation reduction, which is probably due to sufficient soil moisture from winter/spring. As long as future water levels of the rivers will not decrease during spring, at least the use of the hay from the first cut of floodplain meadows appears reliable under climate change.

Plant invasions are among the key drivers of global biodiversity and ecosystem change. They often cause reductions in native species richness and overall biodiversity. Nitrogen-fixing plants are problematic as they affect soil nutrient availability and outcompete species of nutrient-poor sites. Here we assessed the impacts of the legume Lupinus polyphyllus on species and functional diversity of mountain meadow communities in the UNESCO Biosphere Reserve Rhön. We compared species diversity (richness, evenness and effective species number), functional diversity (functional richness, evenness, divergence and dispersion) and similarity of plots in three characteristic vegetation types (Nardus grassland, mesic and wet mountain hay meadows) between different lupine cover classes. We calculated community weighted means (CWMs) of single plant traits and plotted them against lupine cover classes. The invasion of L. polyphyllus homogenizes vegetation composition since the similarity among plots of the different vegetation types increased with increasing lupine cover. It significantly affected species diversity in terms of richness and effective species number and the functional divergence of the vegetation. The trait set of species occurring together with lupine was shifted towards more competitive trait values. We demonstrate strongly negative impacts of L. polyphyllus on different mountain meadow vegetation types since L. polyphyllus, fosters the growth of competitive species and leads to overall more productive plant communities.

Since inference concerning the relative effects of propagule pressure, biotic interactions, site conditions and species traits on the invasibility of plant communities is limited, we carried out a field experiment to study the role of these factors for absolute and relative seedling emergence in three resident and three non-resident confamilial herb species on a nutrient-poor temperate pasture. We set up a factorial field experiment with two levels each of the factors litter cover (0 and 400 g m(-2)), gap size (0.01 and 0.1 m(2)) and propagule pressure (5 and 50 seeds) and documented soil temperature, soil water content and relative light availability. Recruitment was recorded in spring and autumn 2010 and in spring 2011 to cover initial seedling emergence, establishment after summer drought and final establishment after the first winter. Litter alleviated temperature and moisture conditions and had positive effects on proportional and absolute seedling emergence during all phases of recruitment. Large gaps presented competition-free space with high light availability but showed higher temperature amplitudes and lower soil moisture. Proportional and absolute seedling recruitment was significantly higher in large than in small gaps. In contrast, propagule pressure facilitated absolute seedling emergence but had no effects on proportional emergence or the chance for successful colonisation. Despite significantly higher initial seedling emergence of resident than non-resident species, seed mass and other species-specific traits may be better predictors for idiosyncratic variation in seedling establishment than status. Our data support the fluctuating resource hypothesis and demonstrate that the reserve effect of seeds may facilitate seedling emergence. The direct comparison of propagule pressure with other environmental factors showed that propagule pressure affects absolute seedling abundance, which may be crucial for species that depend on other individuals for sexual reproduction. However, propagule batch size did not significantly affect the chance for successful colonisation of disturbed plots.

Most range shift predictions focus on the dispersal phase of the colonization process. Because moving populations experience increasingly dissimilar nonclimatic environmental conditions as they track climate warming, it is also critical to test how individuals originating from contrasting thermal environments can establish in nonlocal sites. We assess the intraspecific variation in growth responses to nonlocal soils by planting a widespread grass of deciduous forests (Milium effusum) into an experimental common garden using combinations of seeds and soil sampled in 22 sites across its distributional range, and reflecting movement scenarios of up to 1600 km. Furthermore, to determine temperature and forest‐structural effects, the plants and soils were experimentally warmed and shaded. We found significantly positive effects of the difference between the temperature of the sites of seed and soil collection on growth and seedling emergence rates. Migrant plants might thus encounter increasingly favourable soil conditions while tracking the isotherms towards currently ‘colder’ soils. These effects persisted under experimental warming. Rising temperatures and light availability generally enhanced plant performance. Our results suggest that abiotic and biotic soil characteristics can shape climate change‐driven plant movements by affecting growth of nonlocal migrants, a mechanism which should be integrated into predictions of future range shifts.

Community composition and ecosystem processes during succession may be driven partly by traits of plant species that attain dominance. Here, we addressed the hypothesis that Stipa pulcherrima, the dominant grass of abandoned continental grasslands, controls seedling recruitment of co-occurring species through chemical effects of its litter. Eight species with successful and unsuccessful recruitment under field conditions were selected (four familial pairs) to study experimentally the effects of leaf leachate under four temperature regimes. Since fungi developed in leachate-treated Petri dishes, in another experiment seeds were surface sterilized to remove confounding effects of fungi on recruitment. Leachate affected various stages of seedling recruitment: it significantly reduced seed germination (by 33–94%) and radicle elongation, and it delayed germination of seedlings of all species. In two families, species with unsuccessful field recruitment were more negatively affected than the successful ones. In a third family, the species with successful recruitment was more negatively affected, and in the fourth there were no differences. Similar germination responses after exclusion of fungi through seed-surface sterilization suggested that leachate was responsible for the observed effects on recruitment. Besides other traits and physical/microclimatic effects of accumulating litter, S. pulcherrima influences plant community dynamics and may potentially affect ecosystem processes through its secondary compounds.

Landscape composition and structure may strongly affect the spread of invasive species in landscapes. Landscape analysis provides a powerful toolset for assessing invasive species invasions over time and for planning control measures. We applied a combination of aerial mapping and landscape analysis to assess the invasion of the legume, Lupinus polyphyllus, in the Rhön UNESCO Biosphere Reserve. The Biosphere Reserve contains different types of large and well-connected grasslands threatened by lupine invasion. We assessed the changes in lupine distribution between 1998 and 2016 in a strictly protected part of the Biosphere Reserve by means of landscape structure analysis. The area invaded by L. polyphyllus doubled from 1998 to 2016. While the number of lupine stands decreased by 25%, stand size on average increased by 300%; stands also became less compact during that period. Furthermore, the degree of invasion of different grassland types changed. In 1998, all investigated grassland types were invaded to equal extents, whereas in 2016, large and well-connected mesic grasslands located close to roads were more heavily invaded than small and remote wet grasslands. Our results show that landscape composition plays an important role for the spread of lupine. Specifically, invasive stand characteristics, such as stand size, form, and connectivity, are crucial for driving the invasion of lupine. Therefore, in addition to landscape composition, invasive stand characteristics should be included in the planning of conservation measures. Overall, aerial mapping combined with landscape analysis provides a cost-effective and practical tool for landscape managers to prioritize invasive control measures.