Herbaceous plants of the Amazon floodplain near Manaus: Species diversity and adaptations to the flood pulse

In the floodplain of the Amazon river near Manaus, 388 herbaceous plant species, excepting epiphytes, were collected belonging to 64 families and 182 genera. 330 species are considered terrestrial, 34 aquatic, the others have an intermediate status. Most of the species occur in relatively small numbers. Only 17 species formed large monospecific stands. The largest number of species (273) was found during the dry phase in disturbed areas on the levees, as for instance in abandoned fields, because of a reduced impact of the flood and high light intensity. Low numbers were recorded during low water period from the floor of floodplain forest (25) because of insufficient light conditions and from low lying lake beds (26), which were dominated by a few highly adapted species. The following attributes were found to favour the occurrence of herbaceous plants in the Amazon floodplain: resistance of seeds and spores to flooding and dessication; short reproductive cycles; high reproduction rates; high primary production; tolerance of adult plants to flooding and drought; adaptations to waterlevel fluctuations (for example a floating way of life). Short life cycles and high reproduction rates allow the quick colonization of disturbed habitats and the substitution of population losses (r-strategy). This strategy is supported by the elevated nutrient status of the Amazon river floodplain in comparison with the floodplain of the Negro River, where herbaceous plants are scarce. The number of ruderal species and weeds including a rising number of neophytes is large. The great species diversity is related to great habitat diversity, fertility of sediments and water, predictability of the floodpulse and the reduction of interspecifìc competition due to the annual set back of the populations by the flooding and drought. The observations are in concordance with the predictions of the floodpulse concept

Simulated climate variability in the region of Rapa Nui during the last millennium

Rapa Nui, an isolated island in the Southeast Pacific, was settled by the Polynesians most likely around 1200 AD and was discovered by the Europeans in 1722 AD. While the Polynesians presumably found a profuse palm woodland on Rapa Nui, the Europeans faced a landscape dominated by grassland. Scientists have examined potential anthropogenic, biological and climatic induced vegetation changes on Rapa Nui. Here, we analyse observational climate data for the last decades and climate model results for the period 800-1750 AD to explore the potential for a climatic-induced vegetation change. A direct influence of the ENSO phenomenon on the climatic parameters of Rapa Nui could not be found in the model simulations. Furthermore, strong climatic trends from a warm Medieval Period to a Little Ice Age or rapid climatic fluctuations due to large volcanic eruptions were not verifiable for the Rapa Nui region, although they are detectable in the simulations for many regions world wide. Hence, we tentatively conclude that large-scale climate changes in the oceanic region around Rapa Nui might be too small to explain strong vegetation changes on the island over the last millennium

Is there a first mover advantage in lobbying? A comparative analysis of how the timing of mobilization affects the influence of interest organizations in 10 polities

The first mover advantage is a critical factor for the productivity of firms that enter new markets. Surprisingly, however, the importance of timing is rarely explored in studies of interest groups and their influence on new policy agendas. In this article, we therefore develop a theory of first mover advantages in lobbying. We argue that especially more resourceful and more highly affected organizations should be able to benefit from early lobbying. Using granular survey data on the timing of lobby efforts by interest groups on Covid-19 related policies in 10 European democracies, we test this novel theory. Our results show that timing is an important predictor of lobbying influence, but that interest groups which are hardly affected by a new policy cannot benefit from early mover advantages in the same way as affected organizations. Moreover, we give evidence for differences in first mover advantages depending on organizational staff resources

The effect of flooding on the exchange of the volatile C₂-compounds ethanol, acetaldehyde and acetic acid between leaves of Amazonian floodplain tree species and the atmosphere

The effect of root inundation on the leaf emissions of ethanol, acetaldehyde and acetic acid in relation to assimilation and transpiration was investigated with 2–3 years old tree seedlings of four Amazonian floodplain species by applying dynamic cuvette systems under greenhouse conditions. Emissions were monitored over a period of several days of inundation using a combination of Proton Transfer Reaction Mass Spectrometry (PTR-MS) and conventional techniques (HPLC, ion chromatography). Under non-flooded conditions, none of the species exhibited measurable emissions of any of the compounds, but rather low deposition of acetaldehyde and acetic acid was observed instead. Tree species specific variations in deposition velocities were largely due to variations in stomatal conductance. Flooding of the roots resulted in leaf emissions of ethanol and acetaldehyde by all species, while emissions of acetic acid were only observed from the species exhibiting the highest ethanol and acetaldehyde emission rates. All three compounds showed a similar diurnal emission profile, each displaying an emission burst in the morning, followed by a decline in the evening. This concurrent behavior supports the conclusion, that all three compounds emitted by the leaves are derived from ethanol produced in the roots by alcoholic fermentation, transported to the leaves with the transpiration stream and finally partly converted to acetaldehyde and acetic acid by enzymatic processes. Co-emissions and peaking in the early morning suggest that root ethanol, after transportation with the transpiration stream to the leaves and enzymatic oxidation to acetaldehyde and acetate, is the metabolic precursor for all compounds emitted, though we can not totally exclude other production pathways. Emission rates substantially varied among tree species, with maxima differing by up to two orders of magnitude (25–1700 nmol m−2 min−1 for ethanol and 5–500 nmol m−2 min−1 for acetaldehyde). Acetic acid emissions reached 12 nmol m−2 min−1. The observed differences in emission rates between the tree species are discussed with respect to their root adaptive strategies to tolerate long term flooding, providing an indirect line of evidence that the root ethanol production is a major factor determining the foliar emissions. Species which develop morphological root structures allowing for enhanced root aeration produced less ethanol and showed much lower emissions compared to species which lack gas transporting systems, and respond to flooding with substantially enhanced fermentation rates and a non-trivial loss of carbon to the atmosphere. The pronounced differences in the relative emissions of ethanol to acetaldehyde and acetic acid between the tree species indicate that not only the ethanol production in the roots but also the metabolic conversion in the leaf is an important factor determining the release of these compounds to the atmosphere

Long-term solar UV radiation reconstructed by Artificial Neural Networks (ANN)

International audienceArtificial Neural Networks (ANN) are efficient tools to derive solar UV radiation from measured meteorological parameters such as global radiation, aerosol optical depths and atmospheric column ozone. The ANN model has been tested with different combinations of data from the two sites Potsdam and Lindenberg, and used to reconstruct solar UV radiation at eight European sites by more than 100 years into the past. Annual totals of UV radiation derived from reconstructed daily UV values reflect interannual variations and long-term patterns that are compatible with variabilities and changes of measured input data, in particular global dimming by about 1980?1990, subsequent global brightening, volcanic eruption effects such as that of Mt. Pinatubo, and the long-term ozone decline since the 1970s. Patterns of annual erythemal UV radiation are very similar at sites located at latitudes close to each other, but different patterns occur between UV radiation at sites in different latitude regions

The trophic status of the fish fauna in Lago Camaleão, a macrophyte dominated floodplain lake in the middle Amazon

Food offer and consumption by the fish fauna were studied at medium and high waterlevels in a macrophyte dominated and strongly hypoxic floodplain lake of the middle Amazon. Detritus was shown to be the main food item, followed by terrestrial invertebrates and periphyton. Low aquatic macrophyte consumption is related to its low nutrient value in comparison with other abundant foods and its seasonal availability

High-sensitivity tracing of stable isotope labeled Ag nanoparticles in environmental samples using MC-ICP-MS

Silver nanoparticles (Ag NPs) are among the most widely used engineered nanomaterials and this warrants further investigation of their behaviour and fate in the environment. To support such work, we developed new techniques for efficient tracing of Ag NPs that are produced from, and hence labelled with, enriched 109 28 Ag (Ag-En). The methods encompass a one-step anion exchange separation of Ag from the sample matrix and precise determination of 109Ag/107Ag ratios and 109Ag abundances by multiple-collector ICP-MS. The sample preparation procedure has an Ag yield of 104 ± 13% (1 SD) and a procedural Ag blank of less than 7 pg, enabling analysis of samples with only trace Ag contents. Analyses of Ag solutions and realistic samples show that careful correction of memory effects is paramount for ensuring data quality. Using appropriate procedures, the 109Ag/107Ag ratios of samples containing Ag-En can be determined to a precision and trueness of better than about 0.5%, when more than 0.5 ng Ag are available for analysis. Even if Ag is only present at 50 pg or less, the Ag isotope ratios and Ag-En concentrations of samples can be measured to better than 5 to 10%. The methods are therefore able to resolve the presence of 1 pg of Ag-En in samples that contain as little as 10 pg and to up to 1 ng of natural Ag. As such, the techniques allow robust detection and quantification of Ag-En in environmental samples even when highly variable quantities of Ag-En and natural Ag are present. The new methodology thus enables the use of stable isotope tracing to investigate the fate of Ag NPs in complex environmental systems at dosing concentrations similar to the predicted environmental concentrations and for very small samples, whilst also providing high sample throughput