Net N mineralization in subalpine grasslands: effect of aboveground vertebrate and invertebrate herbivores

Aboveground herbivores have strong effects on grassland nitrogen (N) cycling. They can accelerate or slow down soil net N mineralization depending on ecosystem productivity and grazing intensity. We assessed how a diverse herbivore community affects net N mineralization in subalpine grasslands. By using size-selective fences, we progressively excluded large, medium, and small mammals, as well as invertebrates from two vegetation types, and assessed how the exclosure types (ET) affected net N mineralization. The two vegetation types differed in long-term management (centuries), forage quality, and grazing history and intensity. To gain a more mechanistic understanding of how herbivores affect net N mineralization, we linked mineralization to soil abiotic (temperature; moisture; NO3, NH4, and total inorganic N concentrations/pools; C, N, P concentrations; pH; bulk density), soil biotic (microbial biomass; abundance of collembolans, mites, and nematodes) and plant (shoot and root biomass; consumption; plant C, N, and fiber content; plant N pool) properties. Net N mineralization differed between ET, but not between vegetation types. Thus, shortterm changes in herbivore community composition and, therefore, in grazing intensity had a stronger effect on net N mineralization than long-term management and grazing history. We found highest N mineralization values when only invertebrates were present, suggesting that mammals had a negative effect on net N mineralization. Of the variables included in our analyses, only mite abundance and aboveground plant biomass explained variation in net N mineralization among ET. Abundances of both mites and leaf-sucking invertebrates were positively correlated with aboveground plant biomass, and biomass increased with progressive exclusion. The negative impact of mammals on net N mineralization may be related partially to (1) differences in the amount of plant material (litter) returned to the belowground subsystem, which induced a positive bottom-up effect on mite abundance, and (2) alterations in the amount and/or distribution of dung, urine, and food waste. Thus, our results clearly show that short-term alterations of the aboveground herbivore community, can strongly impact nutrient cycling within ecosystems independent of long-term management and grazing history

Exploratory topic modeling with distributional semantics

As we continue to collect and store textual data in a multitude of domains, we are regularly confronted with material whose largely unknown thematic structure we want to uncover. With unsupervised, exploratory analysis, no prior knowledge about the content is required and highly open-ended tasks can be supported. In the past few years, probabilistic topic modeling has emerged as a popular approach to this problem. Nevertheless, the representation of the latent topics as aggregations of semi-coherent terms limits their interpretability and level of detail. This paper presents an alternative approach to topic modeling that maps topics as a network for exploration, based on distributional semantics using learned word vectors. From the granular level of terms and their semantic similarity relations global topic structures emerge as clustered regions and gradients of concepts. Moreover, the paper discusses the visual interactive representation of the topic map, which plays an important role in supporting its exploration.Comment: Conference: The Fourteenth International Symposium on Intelligent Data Analysis (IDA 2015

Manganese Dissolution in alkaline medium with and without concurrent oxygen evolution in LiMn2_2O4_4

Manganese dissolution during the oxygen evolution reaction (OER) has been a persistent challenge that impedes the practical implementation of Mn-based electrocatalysts including the LiMn$_x$O$_4$ system in aqueous alkaline electrolyte. The investigated LiMn$_2$O$_4$ particles exhibit two distinct Mn dissolution processes; one independent of OER and the other associated to OER. Combining the bulk sensitive X-ray absorption spectroscopy, surface sensitive X-ray photoelectron spectroscopy and electrochemical detection of Mn dissolution using rotating ring-disk electrode, we explore the less understood Mn dissolution mechanism during OER. We correlate near-surface oxidation with the charge attributed to dissolved Mn, which demonstrates increasing Mn dissolution with the formation of surface Mn4+ species under anodic potential. The observed stronger dissolution during the OER is attributed to the formation of additional Mn$^{4+}$ from Mn$^{3+}$ during OER. We show that control over the amount of Mn4+ in Li$_x$Mn2O$_4$ before the onset of the OER can partially mitigate the OER-triggered dissolution. Overall, our atomistic insights into the Mn dissolution processes are crucial for knowledge-guided mitigation of electrocatalyst degradation, which can be broadly extended to manganese-based oxide systems

Perch-type Characteristics of Overwintering Red-tailed Hawks (Buteo jamaicensis) and American Kestrels (Falco sparverius)

Red-tailed Hawks (Buteo jamaicensis) and American Kestrels (Falco sparverius) are primarily sitand-wait predators that rely on perches to forage most efficiently. Overwintering Red-tailed Hawks and American Kestrels use available perches (e.g., utility poles and wires, trees, fences, gates, etc.) to hunt for prey items in agricultural fields in northeast Arkansas. Observations were made from December 2011-March 2012 and November 2012-March 2013 in three representative cover-types (short rice stubble, soybean stubble, and fallow areas including roadsides) to determine which perch-types were used by Red-tailed Hawks and American Kestrels. Utility pole crossbeams at an average height of 6.3 m were the main perchtypes used by Red-tailed Hawks, demonstrating the use of man-made structures’. These perches were generally in or near fallow areas or short rice stubble fields. Conversely, American Kestrels usually perched on wires at an average height of 4.9 m, over fallow roadsides’. Fallow areas had high prey density and vegetation cover. Niche separation via differential use of perches may be one factor that allows these raptors to avoid inter-specific competition

Seasonality of the pelagic ichthyofauna in the Lazarev Sea

The Southern Ocean is characterised by an extreme seasonality which is best observed by the huge variation in sea ice extent. It expands from a minimum extent of 4 million square kilometres in February to a maximum of 19 million square kilometres in September and influences the physics and chemistry of the surface layers and the corresponding life histories of organisms. Reduced light condition and sea ice cover have a pronounced impact on primary production and predation risk in the pelagic zone. Here we present comparison of the distribution of fish in the Lazarev Sea correlated to biotic an abiotic features. Samples were collected in the framework of three LAKRIS (Lazarev Krill Study) campaigns onboard RV Polarstern during summer, fall and winter. The main focus was on factors affecting krill distribution. As such a wide variety of biotic and abiotic measures were made. Fish and fish larvae were collected from trawls from the upper 200m during both seasons. Both during summer and winter larval composition was dominated by pre-metamorphic Electrona antarctica and Notolepis coatsi. Post-metamorphic E. antarctica showed a pronounced seasonal difference in occurrence

Do changes in health reveal the possibility of undiagnosed pancreatic cancer? Development of a risk-prediction model based on healthcare claims data.

Background and objectiveEarly detection methods for pancreatic cancer are lacking. We aimed to develop a prediction model for pancreatic cancer based on changes in health captured by healthcare claims data.MethodsWe conducted a case-control study on 29,646 Medicare-enrolled patients aged 68 years and above with pancreatic ductal adenocarcinoma (PDAC) reported to the Surveillance Epidemiology an End Results (SEER) tumor registries program in 2004-2011 and 88,938 age and sex-matched controls. We developed a prediction model using multivariable logistic regression on Medicare claims for 16 risk factors and pre-diagnostic symptoms of PDAC present within 15 months prior to PDAC diagnosis. Claims within 3 months of PDAC diagnosis were excluded in sensitivity analyses. We evaluated the discriminatory power of the model with the area under the receiver operating curve (AUC) and performed cross-validation by bootstrapping.ResultsThe prediction model on all cases and controls reached AUC of 0.68. Excluding the final 3 months of claims lowered the AUC to 0.58. Among new-onset diabetes patients, the prediction model reached AUC of 0.73, which decreased to 0.63 when claims from the final 3 months were excluded. Performance measures of the prediction models was confirmed by internal validation using the bootstrap method.ConclusionModels based on healthcare claims for clinical risk factors, symptoms and signs of pancreatic cancer are limited in classifying those who go on to diagnosis of pancreatic cancer and those who do not, especially when excluding claims that immediately precede the diagnosis of PDAC

Reconciling specific and unspecific risk factors: the interplay between theory and data

Contains fulltext : 89487.pdf (publisher's version ) (Closed access)1 juni 201

Principles for the post-GWAS functional characterisation of risk loci

Several challenges lie ahead in assigning functionality to susceptibility SNPs. For example, most effect sizes are small relative to effects seen in monogenic diseases, with per allele odds ratios usually ranging from 1.15 to 1.3. It is unclear whether current molecular biology methods have enough resolution to differentiate such small effects. Our objective here is therefore to provide a set of recommendations to optimize the allocation of effort and resources in order maximize the chances of elucidating the functional contribution of specific loci to the disease phenotype. It has been estimated that 88% of currently identified disease-associated SNP are intronic or intergenic. Thus, in this paper we will focus our attention on the analysis of non-coding variants and outline a hierarchical approach for post-GWAS functional studies