The nitrogen cycle of tropical montane forest in Ecuador turns inorganic under environmental change

Water-bound nitrogen (N) cycling in temperate terrestrial ecosystems of the Northern Hemisphere is today mainly inorganic because of anthropogenic release of reactive N to the environment. In little-industrialized and remote areas, in contrast, a larger part of N cycling occurs as dissolved organic N (DON). In a north Andean tropical montane forest in Ecuador, the N cycle changed markedly during 1998–2010 along with increasing N deposition and reduced soil moisture. The DON concentrations and the fractional contribution of DON to total N significantly decreased in rainfall, throughfall, and soil solutions. This inorganic turn of the N cycle was most pronounced in rainfall and became weaker along the flow path of water through the system until it disappeared in stream water. Decreasing organic contributions to N cycling were caused not only by increasing inorganic N input but also by reduced DON production and/or enhanced DON decomposition. Accelerated DON decomposition might be attributable to less waterlogging and higher nutrient availability. Significantly increasing NO3-N concentrations and NO3-N/NH4-N concentration ratios in throughfall and litter leachate below the thick organic layers indicated increasing nitrification. In mineral soil solutions, in contrast, NH4-N concentrations increased and NO3-N/NH4-N concentration ratios decreased significantly, suggesting increasing net ammonification. Our results demonstrate that the remote tropical montane forests on the rim of the Amazon basin experienced a pronounced change of the N cycle in only one decade. This change likely parallels a similar change which followed industrialization in the temperate zone of the Northern Hemisphere more than a century ago.

Comparison of inorganic nitrogen uptake dynamics following snowmelt and at peak biomass in subalpine grasslands

Subalpine grasslands are highly seasonal environments and likely subject to strong variability in nitrogen (N) dynamics. Plants and microbes typically compete for N acquisition during the growing season and particularly at plant peak biomass. During snowmelt, plants could potentially benefit from a decrease in competition by microbes, leading to greater plant N uptake associated with active growth and freeze-thaw cycles restricting microbial growth. In managed subalpine grasslands, we expect these interactions to be influenced by recent changes in agricultural land use, and associated modifications in plant and microbial communities. At several subalpine grasslands in the French Alps, we added pulses of 15N to the soil at the end of snowmelt, allowing us to compare the dynamics of inorganic N uptake in plants and microbes during this period with that previously reported at the peak biomass in July. In all grasslands, while specific shoot N translocation (per g of biomass) of dissolved inorganic nitrogen (DIN) was two to five times greater at snowmelt than at peak biomass, specific microbial DIN uptakes were similar between the two sampling dates. On an area basis, plant communities took more DIN than microbial communities at the end of snowmelt when aboveground plant biomasses were at least two times lower than at peak biomass. Consequently, inorganic N partitioning after snowmelt switches in favor of plant communities, allowing them to support their growing capacities at this period of the year. Seasonal differences in microbial and plant inorganic N-related dynamics were also affected by past (terraced vs. unterraced) rather than current (mown vs. unmown) land use. In terraced grasslands, microbial biomass N remained similar across seasons, whereas in unterraced grasslands, microbial biomass N was higher and microbial C : N lower at the end of snowmelt as compared to peak biomass. Further investigations on microbial community composition and their organic N uptake dynamics are required to better understand the decrease in microbial DIN uptake.

Fourier transform infrared spectroscopy, a new method for rapid determination of total organic and inorganic carbon and biogenic silica concentration in lake sediments

Abstract We demonstrate the use of Fourier transform infrared spectroscopy (FTIRS) to make quantitative measures of total organic carbon (TOC), total inorganic carbon (TIC) and biogenic silica (BSi) concentrations in sediment. FTIRS is a fast and costeffective technique and only small sediment samples are needed (0.01 g). Statistically significant models were developed using sediment samples from northern Sweden and were applied to sediment records from Sweden, northeast Siberia and Macedonia. The correlation between FTIRS-inferred values and amounts of biogeochemical constituents assessed conventionally varied between r = 0.84–0.99 for TOC, r = 0.85– 0.99 for TIC, and r = 0.68–0.94 for BSi. Because FTIR spectra contain information on a large number of both inorganic and organic components, there is great potential for FTIRS to become an important tool in paleolimnology.

Thermal release rate studies of nuclear reaction products from polycrystalline metal matrices

The thermal release rate of nuclear reaction products was investigated in offline annealing experiments. This work was motivated by the search for a high melting catcher material for recoiling products from heavy ion induced nuclear fusion reactions. Polycrystalline refractory metal foils of Ni, Y, Zr, Nb, Mo, Hf, W, and Re were investigated as catcher metals. Diffusion data for various tracer/host combinations were deduced from the measured release rates. This work focuses on the diffusion and the release rate of volatile p-elements from row 5 and 6 of the periodic table as lighter homologues of the superheavy elements with Z ≥ 113 to be studied in future experiments. A massive radiation damage enhancement of the diffusion velocity was observed. Diffusion trends have been established along the groups and rows of the periodic table based on the dependence of diffusion velocity on atomic sizes.

PREDICTION OF DNA METHYLATION BASED ON GENOMIC ARCHITECTURE AND APPLICATIONS OF POSITIONAL WEIGHT MATRICES

Gene silencing due to epigenetic mechanisms shows evidence of significant contributions to cancer development. We hypothesis that the genetic architecture based on retrotransposon elements surrounding the transcription start site, plays an important role in the suppression and promotion of DNA methylation. In our investigation we found a high rate of SINE and LINEs retrotransposon elements near the transcription start site of unmethylated genes when compared to methylated genes. The presence of these elements were positively associated with promoter methylation, contrary to logical expectations, due to the malicious effects of retrotransposon elements which insert themselves randomly into the genome causing possible loss of gene function. In our genome wide analysis of human genes, results suggested that 22% of the genes in cancer were predicted to be methylation-prone; in cancer these genes are generally down-regulated and function in the development process. In summary, our investigation validated our hypothesis and showed that these widespread genomic elements in cancer are highly associated with promoter DNA methylation and may further participate in influencing epigenetic regulation.

Protein cross-linking mediated by tissue transglutaminase correlates with the maturation of extracellular matrices during lung development

At birth, the mammalian lung is still immature. The alveoli are not yet formed and the interairspace walls contain two capillary layers which are separated by an interstitial core. After alveolarization (first 2 postnatal weeks in rats) the alveolar septa mature: their capillary layers merge, the amount of connective tissue decreases, and the mature lung parenchyma is formed (second and third week). During the first 3 wk of life the role of tissue transglutaminase (tTG) was studied in rat lung by immunostaining of cryostat and paraffin sections, by Northern and Western blotting, and by a quantitative determination of gamma-glutamyl-epsilon-lysine. While enzyme activity and intracellular tTG were already present before term, the enzyme product (gamma-glutamyl-epsilon-lysine-crosslink) and extracellular tTG appeared between postnatal days 10 and 19 in the lung parenchyma. In large blood vessels and large airways, which mature earlier than the parenchyma, both the enzyme product and extracellular tTG had already appeared at the end of the first postnatal week. We conclude that tTG is expressed and externalized into the extracellular matrix of lung shortly before maturation of an organ area. Because tTG covalently and irreversibly crosslinks extracellular matrix proteins, we hypothesize that it may prevent or delay further remodeling of basement membranes and may stabilize other extracellular components, such as microfibrils.

Relationships between functional traits and inorganic nitrogen acquisition among eight contrasting European grass species

Backgrounds and Aims Leaf functional traits have been used as a basis to categoize plants across a range of resource-use specialization, from those that conserve available resources to those that exploit them. However, the extent to which the leaf functional traits used to define the resource-use strategies are related to root traits and are good indicators of the ability of the roots to take up nitrogen (N) are poorly known. This is an important question because interspecific differences in N uptake have been proposed as one mechanism by which species coexistence may be determined. This study therefore investigated the relationships between functional traits and N uptake ability for grass species across a range of conservative to exploitative resource-use strategies.Methods Root uptake of NH4+ and NO3-, and leaf and root functional traits were measured for eight grass species sampled at three grassland sites across Europe, in France, Austria and the UK. Species were grown in hydroponics to determine functional traits and kinetic uptake parameters (Imax and Km) under standardized conditions.Key Results Species with high specific leaf area (SLA) and shoot N content, and low leaf and root dry matter content (LDMC and RDMC, respectively), which are traits associated with the exploitative syndrome, had higher uptake and affinity for both N forms. No trade-off was observed in uptake between the two forms of N, and all species expressed a higher preference for NH4+.Conclusions The results support the use of leaf traits, and especially SLA and LDMC, as indicators of the N uptake ability across a broad range of grass species. The difficulties associated with assessing root properties are also highlighted, as root traits were only weakly correlated with leaf traits, and only RDMC and, to a lesser extent, root N content were related to leaf traits.

Promoting Pollinating Insects in Intensive Agricultural Matrices: Field-Scale Experimental Manipulation of Hay-Meadow Mowing Regimes and Its Effects on Bees

Bees are a key component of biodiversity as they ensure a crucial ecosystem service: pollination. This ecosystem service is nowadays threatened, because bees suffer from agricultural intensification. Yet, bees rarely benefit from the measures established to promote biodiversity in farmland, such as agri-environment schemes (AES). We experimentally tested if the spatio-temporal modification of mowing regimes within extensively managed hay meadows, a widespread AES, can promote bees. We applied a randomized block design, replicated 12 times across the Swiss lowlands, that consisted of three different mowing treatments: 1) first cut not before 15 June (conventional regime for meadows within Swiss AES); 2) first cut not before 15 June, as treatment 1 but with 15% of area left uncut serving as a refuge; 3) first cut not before 15 July. Bees were collected with pan traps, twice during the vegetation season (before and after mowing). Wild bee abundance and species richness significantly increased in meadows where uncut refuges were left, in comparison to meadows without refuges: there was both an immediate (within year) and cumulative (from one year to the following) positive effect of the uncut refuge treatment. An immediate positive effect of delayed mowing was also evidenced in both wild bees and honey bees. Conventional AES could easily accommodate such a simple management prescription that promotes farmland biodiversity and is likely to enhance pollination services.

An inter-regional assessment of concentrations and δ13C values of methane and dissolved inorganic carbon in small European lakes

Methane (CH4) and carbon dioxide emissions from lakes are relevant for assessing the greenhouse gas output of wetlands. However, only few standardized datasets describe concentrations of these gases in lakes across different geographical regions. We studied concentrations and stable carbon isotopic composition (δ13C) of CH4 and dissolved inorganic carbon (DIC) in 32 small lakes from Finland, Sweden, Germany, the Netherlands, and Switzerland in late summer. Higher concentrations and δ13C values of DIC were observed in calcareous lakes than in lakes on non-calcareous areas. In stratified lakes, δ13C values of DIC were generally lower in the hypolimnion due to the degradation of organic matter (OM). Unexpectedly, increased δ13C values of DIC were registered above the sediment in several lakes. This may reflect carbonate dissolution in calcareous lakes or methanogenesis in deepwater layers or in the sediments. Surface water CH4 concentrations were generally higher in western and central European lakes than in Fennoscandian lakes, possibly due to higher CH4 production in the littoral sediments and lateral transport, whereas CH4 concentrations in the hypolimnion did not differ significantly between the regions. The δ13C values of CH4 in the sediment suggest that δ13C values of biogenic CH4 are not necessarily linked to δ13C values of sedimentary OM but may be strongly influenced by OM quality and methanogenic pathway. Our study suggests that CH4 and DIC cycling in small lakes differ between geographical regions and that this should be taken into account when regional studies on greenhouse gas emissions are upscaled to inter-regional scales.

Twentieth Century Delta δC Variability in Surface Water Dissolved Inorganic Carbon Recorded by Coralline Algae in the Northern North Pacific Ocean and the Bering Sea

The oxygen isotopic composition and Mg/Ca ratios in the skeletons of long-lived coralline algae record ambient seawater temperature over time. Similarly, the carbon isotopic composition in the skeletons record delta(13)C values of ambient seawater dissolved inorganic carbon. Here, we measured delta(13)C in the coralline alga Clathromorphum nereostratum to test the feasibility of reconstructing the intrusion of anthropogenic CO(2) into the northern North Pacific Ocean and Bering Sea. The delta(13)C was measured in the high Mgcalcite skeleton of three C. nereostratum specimens from two islands 500 km apart in the Aleutian archipelago. In the records spanning 1887 to 2003, the average decadal rate of decline in delta(13)C values increased from 0.03% yr(-1) in the 1960s to 0.095% yr(-1) in the 1990s, which was higher than expected due to solely the delta(13)C-Suess effect. Deeper water in this region exhibits higher concentrations of CO(2) and low delta(13)C values. Transport of deeper water into surface water (i.e., upwelling) increases when the Aleutian Low is intensified. We hypothesized that the acceleration of the delta(13)C decline may result from increased upwelling from the 1960s to 1990s, which in turn was driven by increased intensity of the Aleutian Low. Detrended delta(13)C records also varied on 4-7 year and bidecadal timescales supporting an atmospheric teleconnection of tropical climate patterns to the northern North Pacific Ocean and Bering Sea manifested as changes in upwelling.

Pauli Spin Matrices

The Pauli Spin Matrix representation of Spin Operators in Quantum Mechanics are explicitly demonstrated and illustrated in detail for one and two spin systems.

An evaluation of the Cypress Creek watershed for inorganic chemical load as it flows into Lake Houston

Background. The Cypress Creek is one of the main tributaries of Lake Houston, which provides drinking water to 21.4 million customers. Furthermore, the watershed is being utilized for contact and non-contact recreation, such as canoeing, swimming, hiking trail, and picnics. Water along the creek is impacted by numerous wastewater outfalls from both point and non-point sources. As the creek flows into Lake Houston, it carries both organic and inorganic contaminants that may affect the drinking water quality of this important water source reservoir. Objective. This study was carried out to evaluate the inorganic chemical load of the water in Cypress Creek along its entire length, from the headwaters in Waller County and up to the drainage into Lake Houston. The purpose was to determine whether there are hazardous concentrations of metals in the water and what would be the likely sources. Method. Samples were collected at 29 sites along the creek and analyzed for 29 metals, 17 of which were on the Environmental Protection Agency priority pollution list. Public access sites primarily at bridges were used for sample collection. Samples were transported on ice to the University Of Texas School Of Public Health laboratory, spiked with 2 ml HNO3 kept overnight in the refrigerator, and the following day transported to the EPA laboratory for analysis. Analysis was done by EPA Method 200.7-ICP, Method 200.8ICP/MS and Method 245.1-CVAAS. Results. Metals were present above the detection limits at 65% of sites. Concentrations of aluminum, iron, sodium, potassium, magnesium, and calcium, were particularly high at all sites. Aluminum, sodium, and iron concentrations greatly exceeded the EPA secondary drinking water standards at all sites. ^ Conclusion. The recreational water along Cypress Creek is impacted by wastewater from both permitted and non-permitted outfalls, which deposit inorganic substances into the water. Although a number of inorganic contaminants were present in the water, toxic metals regulated by the EPA were mostly below the recommended limits. However, high concentrations of aluminum, sodium, and iron in the Cypress Creek bring forward the issue of unauthorized discharges of salt water from mining, as well as industrial and domestic wastewater.^