Sodium demand of microorganisms in the phyllosphere and the organic layer of a tropical montane forest in south Ecuador

Recent studies raise the hypothesis that Na shortage restricts decomposition and affects the carbon cycle in tropical forests. When Na concentrations in soils are low and the stands are far off-coast, they do not receive substantial Na inputs from the atmosphere. Since terrestrial plants have low concentrations of Na, which is not considered as an essential element, the demand of soil fauna may not be covered. Yet, in contrast to animals, little is known of Na demands of fungi and phyllosphere microorganisms. We present results from a study on Na limitation in a montane forest ecosystem in South Ecuador, which is located on the eastern cordillera of the Andes. We tested the hypotheses that (1) the study area is characterized by low Na concentrations because of low deposition rates with incident precipitation (wind directions mainly from the Amazonian Basin), (2) decomposition processes are limited by fauna and fungal Na restrictions and (3) Na is retained in the canopy because of Na limitation of microorganisms in phyllosphere. Since 1998, we measure Na fluxes in rainfall, throughfall, stemflow, litter leachate, litterfall and organic layer in a microcatchment under an undisturbed lower montane rainforest. Results reveal comparatively low Na concentrations in the ecosystem and similar Na concentrations in throughfall and stemflow. Since Na fluxes are lower with throughfall than with incident rainfall, we conclude that Na is retained in the canopy. To explore the role of the phyllosphere in Na retention we sampled leaves covered by phyllosphere microorganisms and leaves without phyllosphere cover from several tree species, which were sprayed with a NaCl solution containing 0.5 mg L-1 Na, corresponding to the Na concentration in incident rainfall in our study area. Additionally, responses of litter decomposition to Na additions and the involved interaction of soil fungi and fauna were tested in a litterbag experiment at two sites (1000 and 2000 m a.s.l.). Results revealed enhanced decomposition rates following Na additions, though only in the presence of soil fauna. These results might have future ecosystem implications, since our time series showed that total Na deposition decreased within the past 15 years from ca. 40 kg ha-1 a-1 to 10 kg ha-1 a-1, suggesting a potential role of Na in regulating ecosystem processes

15N tracing to elucidate links between biodiversity and nitrogen cycling in a grassland experiment

Nitrogen (N) cycling is a fundamental ecosystem function of high complexity because N undergoes many transformations in soil and vegetation. The effect of biodiversity loss on ecosystem functions in general, and on N cycling in particular, was studied in several manipulative field experiments. To generate a comprehensive view of the influence of species richness on all major N transformations, we conducted laboratory incubations, in which we added 15N-labeled ammonium and nitrate to soil samples of the “Jena Experiment”, a manipulative large scale, long-term biodiversity experiment in grassland. The experimental site is located in Jena, Germany. The design consists of 4 blocks and 82 plots with 1-60 species and 1-4 functional groups (grasses, legumes, small herbs, tall herbs). Approx. 400 g of field-fresh soil was sampled from each plot of one of the 4 blocks and divided into three aliquots of 100 g each. In order to trace N turnover, we amended the incubations (in triplicate) either with 15N-labelled (98 at%) ammonium, nitrate, or with a mixture of both. The samples were incubated for two months at 20°C. Soil solution was extracted 1, 2, 4, 9 and 16 days after 15N application by percolating 100 mL of nutrient solution through each vessel. Concentrations of NH4-N, NO3-N and total N in the extracts were determined with colorimetric methods. The N-isotopic composition in nitrate was analyzed by isotope ratio mass spectrometry (IRMS) using the denitrifier method. Ammonium N isotope ratios were determined using the “hypobromite oxidation” method, in which ammonium-N is converted to nitrite followed by azide reaction to nitrous oxide and IRMS analysis. The results will be comprehensively evaluated in a quantitative context using the modelling approach of Müller et al. (2007) to determine the size of six N pools and the rates of nine N transformations. Links between N transformation rates, N-pool size and plant species richness will be verified with the help of ANOVA

End-to-End Learning on Multimodal Knowledge Graphs

Knowledge graphs enable data scientists to learn end-to-end on heterogeneous knowledge. However, most end-to-end models solely learn from the relational information encoded in graphs' structure: raw values, encoded as literal nodes, are either omitted completely or treated as regular nodes without consideration for their values. In either case we lose potentially relevant information which could have otherwise been exploited by our learning methods. We propose a multimodal message passing network which not only learns end-to-end from the structure of graphs, but also from their possibly divers set of multimodal node features. Our model uses dedicated (neural) encoders to naturally learn embeddings for node features belonging to five different types of modalities, including numbers, texts, dates, images and geometries, which are projected into a joint representation space together with their relational information. We implement and demonstrate our model on node classification and link prediction for artificial and real-worlds datasets, and evaluate the effect that each modality has on the overall performance in an inverse ablation study. Our results indicate that end-to-end multimodal learning from any arbitrary knowledge graph is indeed possible, and that including multimodal information can significantly affect performance, but that much depends on the characteristics of the data.Comment: Under submission. arXiv admin note: substantial text overlap with arXiv:2003.1238

Tree species driving functional properties of mobile organic matter in throughfall and forest floor solutions of beech, spruce and pine forests

The chemical nature of mobile organic matter is a prerequisite for advancing our understanding of the C and nutrient cycling and other forest ecosystem processes. Tree species differ in leaf composition (e.g. nutrient, polyphenol content) and leaf litter quality, which in turn affects a variety of ecosystem processes. However, the composition of OM derived from living plant material via throughfall (TF) and its compositional fate traversing the forest floor (FF) is insufficiently understood. Are there tree-species specific differences in functional properties (e.g. aromaticity) of OM in TF and FF solutions collected from pine, spruce and different beech stands? And if yes- how do functional properties change with tree species and ecosystem compartment (throughfall vs. forest floor)? We addressed these questions by applying solid-state C-13 NMR spectroscopy to TF and FF solutions from European beech forests of the three DFG “Biodiversity Exploratories”, from Norway spruce sites of the Hainich-Dün-Exploratory and Scots pine stands in East-Thuringia. C-13 NMR spectroscopy revealed a homogeneous composition of TF-DOM under beech between the three Exploratories and exhibited remarkable tree-species related differences in DOM composition: Compared to spruce and pine, TF-DOM under beech showed higher intensities of aromatic and phenolic C (beech > pine > spruce) and lower ones of alkyl-C (pine ≈ spruce > beech). Consequently, beech TF exhibited higher aromaticity values and lower alkyl/O-alkyl ratios (i.e. extent of decomposition) in comparison to coniferous TF-DOM. FF-DOM under beech was very similar between the three “Biodiversity Exploratories” and surprisingly analog to FF-DOM under spruce, while under pine higher intensities of aromatic and phenolic C and alkyl-C (pine > beech ≈ spruce) and lower O-alkyl-C signals were observed. Thus, pine FF-DOM exhibited the highest values for both aromaticity (28%) and decomposition (0.87). In essence, tree-species effects became most notable for the composition and functionality of DOM in TF exhibiting consistently the highest aromatic and phenolic C signals for the beech sites. In view of the allelopathic effectiveness of phenolic compounds, the results might point to an increased allelopathic potential of beech TF, which successfully impairs competing plants and organisms and hence alter ecosystem processes and functioning. In the end, the ecological functions of DOM in ecosystems are still imperfectly understood

15N-Fraktionierung in NO3- während der Passage von Wasser durch einen Bergregenwald in Ecuador

Natürliche Stickstoffisotopenfraktionierungen können Einblicke in N-Umsetzungsprozesse geben. Wir untersuchten die Veränderung von delta15N-Werten in Nitrat während des gelösten Transports durch einen tropischen Bergregenwald, um N-Transformationen zu bestimmen. Abnehmende delta15N-Werte in Nitrat und zunehmende Nitrat-Konzentrationen bei der Wasserpassage des Kronenraums und der organischen Auflage belegten Nitrifikation in diesen Kompartimenten. Abnehmende Konzentrationen und 15N-Anreicherung in Nitrat während der Auswaschung durch den Mineralboden ließen sich als Rayleigh-Fraktionierung beschreiben und belegten somit Denitrifikation. Während Nitrifikation in der organischen Auflage und Denitrifikation im Mineralboden ganzjährig auftraten, wurde die Nitrifikation im Kronenraum kurzzeitig durch Nitrat-Aufnahme unterbrochen, die wahrscheinlich durch die Deposition co-limitierender Spurenelemente induziert war. Somit ließen sich anhand von N-Isotopenfraktionierungen in Nitrat Transformationen und gasförmige Emissionen von N nachweisen. Unsere Ergebnisse widersprechen der Annahme, dass tropische Bergregenwälder durch einen geschlossenen Kreislauf von N charakterisiert sind

Altered fMRI restingâ state connectivity in individuals with fibromyalgia on acute pain stimulation

BackgroundFibromyalgia is a chronic widespread pain condition, with patients commonly reporting other symptoms such as sleep difficulties, memory complaints and fatigue. The use of magnetic resonance imaging (MRI) in fibromyalgia has allowed for the detection of neural abnormalities, with alterations in brain activation elicited by experimental pain and alterations in resting state connectivity related to clinical pain.MethodsIn this study, we sought to monitor state changes in resting brain connectivity following experimental pressure pain in fibromyalgia patients and healthy controls. Twelve fibromyalgia patients and 15 healthy controls were studied by applying discrete pressure stimuli to the thumbnail bed during MRI. Restingâ state functional MRI scanning was performed before and immediately following experimental pressure pain. We investigated changes in functional connectivity to the thalamus and the insular cortex.ResultsAcute pressure pain increased insula connectivity to the anterior cingulate and the hippocampus. Additionally, we observed increased thalamic connectivity to the precuneus/posterior cingulate cortex, a known part of the default mode network, in patients but not in controls. This connectivity was correlated with changes in clinical pain.ConclusionsThese data reporting changes in restingâ state brain activity following a noxious stimulus suggest that the acute painful stimuli may contribute to the alteration of the neural signature of chronic pain.What does this study/add?In this study acute pain application shows an echo in functional connectivity and clinical pain changes in chronic pain.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/122449/1/ejp832_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/122449/2/ejp832.pd

Resting state connectivity correlates with drug and placebo response in fibromyalgia patients

AbstractFibromyalgia is a chronic pain syndrome characterized by widespread pain, fatigue, and memory and mood disturbances. Despite advances in our understanding of the underlying pathophysiology, treatment is often challenging. New research indicates that changes in functional connectivity between brain regions, as can be measured by magnetic resonance imaging (fcMRI) of the resting state, may underlie the pathogenesis of this and other chronic pain states. As such, this parameter may be able to be used to monitor changes in brain function associated with pharmacological treatment, and might also be able to predict treatment response.We performed a resting state fcMRI trial using a randomized, placebo-controlled, cross-over design to investigate mechanisms of action of milnacipran (MLN), a selective serotonin and norepinephrine reuptake inhibitor (SNRI), in fibromyalgia patients. Our aim was to identify functional connectivity patterns at baseline that would differentially predict treatment response to MLN as compared to placebo. Since preclinical studies of MLN suggest that this medication works by augmenting antinociceptive processes, we specifically investigated brain regions known to be involved in pain inhibition.15 fibromyalgia patients completed the study, consisting of 6 weeks of drug and placebo intake (order counterbalanced) with an interspersed 2 week wash out period. As a main finding we report that reductions in clinical pain scores during MLN were associated with decreased functional connectivity between pro-nociceptive regions and antinociceptive pain regions at baseline, specifically between the rostral part of the anterior cingulate cortex (ACC) and the insular cortex (IC), as well as between the periaqueductal gray (PAG) and the IC: patients with lower preexisting functional connectivity had the greatest reduction in clinical pain. This pattern was not observed for the placebo period. However a more robust placebo response was associated with lower baseline functional connectivity between the ACC and the dorsolateral prefrontal cortex.This study indicates that ACC–IC connectivity might play a role in the mechanism of action of MLN, and perhaps more importantly fcMRI might be a useful tool to predict pharmacological treatment response

Relationships between ecosystem functions vary among years and plots and are driven by plant species richness

Ecosystem management aims at providing many ecosystem services simultaneously. Such ecosystem service multifunctionality can be limited by tradeoffs and increased by synergies among the underlying ecosystem functions (EF), which need to be understood to develop targeted management. Previous studies found differences in the correlation between EFs. We hypothesised that correlations between EFs are variable even under the controlled conditions of a field experiment and that seasonal and annual variation, plant species richness, and plot identity (identity effects of plots, such as the presence and proportion of functional groups) are drivers of these correlations. We used data on 31 EFs related to plants, consumers, and physical soil properties that were measured over 5 to 19 years, up to three times per year, in a temperate grassland experiment with 80 different plots, constituting six sown plant species richness levels (1, 2, 4, 8, 16, 60 species). We found that correlations between pairs of EFs were variable, and correlations between two particular EFs could range from weak to strong or negative to positive correlations among the repeated measurements. To determine the drivers of pairwise EF correlations, the covariance between EFs was partitioned into contributions from species richness, plot identity, and time (including years and seasons). We found that most of the covariance for synergies was explained by species richness (26.5%), whereas for tradeoffs, most covariance was explained by plot identity (29.5%). Additionally, some EF pairs were more affected by differences among years and seasons, showing a higher temporal variation. Therefore, correlations between two EFs from single measurements are insufficient to draw conclusions on tradeoffs and synergies. Consequently, pairs of EFs need to be measured repeatedly under different conditions to describe their relationships with more certainty and be able to derive recommendations for the management of grasslands