Leaf water δ 18/O, δ2H and d-excess isoscapes for Australia using region-specific plant parameters and non-equilibrium vapour

Oxygen (δ18O) and hydrogen (δ2H) isotope ratios, and their relationship to one another (d-excess) are altered as water travels from the atmosphere to the land surface, into soils and plants and back to the atmosphere. Plants return water to the atmosphere through transpiration (evaporation through the stomata), which causes isotopic fractionation concentrating the heavier isotopes (18O and 2H) in the water that remains behind in the leaves. The degree of isotopic fractionation during transpiration is controlled largely by climate, and as a result can be predicted using process-based models and climate data. The modelled transpirational isotopic fractionation can be applied to plant source water isotopic values to predict leaf water isotope ratios and generate maps of isotopic composition, or isoscapes. This approach of mechanistic modelling has been well demonstrated in the first generation of global leaf water isoscapes (PLoS One, 3(6), e2447, 2008). However, use of leaf water isoscapes in fields such as hydrology, ecology, and forensics requires a new generation of updated region-specific isoscapes. Here, we generate leaf water isoscapes of δ18O, δ2H and d-excess for Australia, the driest vegetated continent on Earth, where leaf water represents a critical water resource for ecosystems. These isoscapes represent an improvement over previous global isoscapes due to their higher resolution, region-specific, empirically derived plant parameters, and non-equilibrium corrections for water vapour isotopic composition. The new isoscapes for leaf water are evaluated relative to observed isotope ratios of leaf cellulose and cherry juice. The model predictions for annual average leaf water isotope ratios showed strong correlations with these plant tissues that integrate over time. Moreover, inclusion of region-specific leaf temperature estimates and non-equilibirum vapour corrections improved prediction accuracy. Regionally based isoscapes provide improved characterisations of average leaf water isotope ratios needed to support research in hydrology, plant ecophysiology, atmospheric science, ecology, and geographic provenancing of biological materials

Methane production and oxidation potentials along a fen-bog gradient from southern boreal to subarctic peatlands in Finland

Methane (CH4) emissions from northern peatlands are projected to increase due to climate change, primarily because of projected increases in soil temperature. Yet, the rates and temperature responses of the two CH4 emission-related microbial processes (CH4 production by methanogens and oxidation by methanotrophs) are poorly known. Further, peatland sites within a fen-bog gradient are known to differ in the variables that regulate these two mechanisms, yet the interaction between peatland type and temperature lacks quantitative understanding. Here, we investigated potential CH4 production and oxidation rates for 14 peatlands in Finland located between c. 60 and 70 degrees N latitude, representing bogs, poor fens, and rich fens. Potentials were measured at three different temperatures (5, 17.5, and 30celcius) using the laboratory incubation method. We linked CH4 production and oxidation patterns to their methanogen and methanotroph abundance, peat properties, and plant functional types. We found that the rich fen-bog gradient-related nutrient availability and methanogen abundance increased the temperature response of CH4 production, with rich fens exhibiting the greatest production potentials. Oxidation potential showed a steeper temperature response than production, which was explained by aerenchymous plant cover, peat water holding capacity, peat nitrogen, and sulfate content. The steeper temperature response of oxidation suggests that, at higher temperatures, CH4 oxidation might balance increased CH4 production. Predicting net CH4 fluxes as an outcome of the two mechanisms is complicated due to their different controls and temperature responses. The lack of correlation between field CH4 fluxes and production/oxidation potentials, and the positive correlation with aerenchymous plants points toward the essential role of CH4 transport for emissions. The scenario of drying peatlands under climate change, which is likely to promote Sphagnum establishment over brown mosses in many places, will potentially reduce the predicted warming-related increase in CH4 emissions by shifting rich fens to Sphagnum-dominated systems.Peer reviewe

Safeguarding sandalwood: A review of current and emerging tools to support sustainable and legal forestry

Societal Impact Statement: Sandalwood and other high value tree species are under significant threat from illegal harvest. Illegal logging is an increasing problem contributing to deforestation, biodiversity loss, human rights abuses and funding transnational crime. Successful prosecution of illegal logging is hindered by a lack of methods to provide evidence of the origin of timber. New analytical techniques have been developed to trace timber back to its source. These methods, together with the establishment of sustainable sources of forest resources, can help protect vulnerable species by providing evidence to prosecute illegal harvest and ensure that commercially available forest products come from sustainable sources. Summary: Sandalwood is highly valued for its fragrant oil and has a long history of cultural and economic importance in many regions of the world. Historical overharvest and poor management have depleted natural populations of sandalwood, which are slow to regenerate. The increasing establishment of plantation sandalwood creates an alternative resource for the sandalwood industry while potentially relieving harvesting pressure on natural stands. Due to the high demand for sandalwood, remaining wild populations are still under threat from illegal logging and methods to identify the source of harvested sandalwood are needed. Laws and regulations aimed at preventing illegal harvest and possession of sandalwood have been put in place but cannot be enforced without the forensic tools to independently verify claimed origin or product quality. The high value of sandalwood combined with the difficulties in enforcing illegal logging laws makes these species particularly vulnerable to poaching. There is an immediate need to develop tools that can identify illegally sourced and adulterated sandalwood products. This paper reviews the current and developing scientific tools that can help identify and control illegal activity in sandalwood supply chains and provides recommendations for future research. Topics include isotope and DNA analysis for tracing illegally harvested sandalwood, chemical profiling for quality control of sandalwood oils, network and policy development to establish a framework for future regulation of the sandalwood trade

Clinical Utility of Circulating Tumour Cell Androgen Receptor Splice Variant-7 Status in Metastatic Castration-resistant Prostate Cancer.

Abstract Background Detection of androgen receptor splice variant-7 (AR-V7) mRNA in circulating tumour cells (CTCs) is associated with worse outcome in metastatic castration-resistant prostate cancer (mCRPC). However, studies rarely report comparisons with CTC counts and biopsy AR-V7 protein expression. Objective To determine the reproducibility of AdnaTest CTC AR-V7 testing, and associations with clinical characteristics, CellSearch CTC counts, tumour biopsy AR-V7 protein expression and overall survival (OS). Design, setting, and participants CTC AR-V7 status was determined for 227 peripheral blood samples, from 181 mCRPC patients with CTC counts (202 samples; 136 patients) and matched mCRPC biopsies (65 samples; 58 patients). Outcome measurements and statistical analysis CTC AR-V7 status was associated with clinical characteristics, CTC counts, and tissue biopsy AR-V7 protein expression. The association of CTC AR-V7 status and other baseline variables with OS was determined. Results and limitations Of the samples, 35% were CTC+/AR-V7+. CTC+/AR-V7+ samples had higher CellSearch CTC counts (median CTC; interquartile range [IQR]: 60, 19–184 vs 9, 2–64; Mann-Whitney test p Conclusions Studies reporting the prognostic relevance of CTC AR-V7 status must account for CTC counts. Discordant CTC AR-V7 results and AR-V7 protein expression in matched, same-patient biopsies are reported. Patient summary Liquid biopsies that determine circulating tumour cell androgen receptor splice variant-7 status have the potential to impact treatment decisions in metastatic castration-resistant prostate cancer patients. Robust clinical qualification of these assays is required before their routine use

Global patterns of nitrate isotope composition in rivers and adjacent aquifers reveal reactive nitrogen cascading

Remediation of nitrate pollution of Earth’s rivers and aquifers is hampered by cumulative biogeochemical processes and nitrogen sources. Isotopes (δ15N, δ18O) help unravel spatiotemporal nitrogen(N)-cycling of aquatic nitrate (NO3−). We synthesized nitrate isotope data (n = ~5200) for global rivers and shallow aquifers for common patterns and processes. Rivers had lower median NO3− (0.3 ± 0.2 mg L−1, n = 2902) compared to aquifers (5.5 ± 5.1 mg L−1, n = 2291) and slightly lower δ15N values (+7.1 ± 3.8‰, n = 2902 vs +7.7 ± 4.5‰, n = 2291), but were indistinguishable in δ18O (+2.3 ± 6.2‰, n = 2790 vs +2.3 ± 5.4‰, n = 2235). The isotope composition of NO3− was correlated with water temperature revealing enhanced N-cascading in warmer climates. Seasonal analyses revealed higher δ15N and δ18O values in wintertime, suggesting waste-related N-source signals are better preserved in the cold seasons. Isotopic assays of nitrate biogeochemical transformations are key to understanding nitrate pollution and to inform beneficial agricultural and land management strategies

Stickstoffkreisläufe in renaturierten und degradierte Auen von Flüssen

Steigender Nutzungsdruck auf Flusslandschaften führte zur Einengung aktiver Auen, was wiederum zum Verlust von Ökosystemleistungen dieser natürlichen Übergangsbereiche führte. Die bisherigen Bemühungen zur Reaktivierung dieser Gebiete beschränkten sich überwiegend auf die hydrologische Wiederanbindung dieser Flächen an die Hauptläufe von Flüssen. Die aus der Wiederanbindung resultierenden, biogeochemischen Veränderungen wurden jedoch meist wenig bis gar nicht beachtet. Aus diesem Grund befasst sich diese Arbeit mit den Auswirkungen von groß angelegten Renaturierungsprojekten auf die biogeochemischen Kreisläufe in zwei Überschwemmungsgebieten entlang der Donau bei Wien. Das wichtigste Ergebnis dieses Projekts war der Beweis, dass Renaturierung und Wiederanbindung von Auen den Stickstoffkreislauf beeinflusst und wichtige Faktoren für den Umsatz sowie das Verhältnis von produziertem N2O zu N2 verändert. Es konnte bewiesen werden, dass Renaturierung durch Erhöhung der Überschwemmungsfrequenz die Effizienz der biogeochemischen Kreisläufe steigert. Die N2O Emissionen verringern sich dadurch im Vergleich zu nicht angebundenen Überschwemmungsgebieten. Durch ein im Rahmen dieses Projekts entwickeltes Modell konnte Aktivitäten auf Landschaftsebene prognostiziert werden, die Bereiche hoher Aktivität in häufig von der Donau überfluteten Bereichen identifizieren konnte. In einer Serie von Laborexperimenten konnten die spezifischen Bedingungen, welche zur Reduktion der N2O Ausgasung führen, identifiziert werden. Abschließend lässt sich feststellen, dass dieses Projekt das Verständnis für Managementmaßnahmen von Überschwemmungsgebieten maßgeblich verbessert hat. Es konnten darüber hinaus Vorschläge für Restaurierungsmaßnahmen gemacht werden, welche in Bezug auf die Umwandlung von Nährstoffen in Auen deutlich effizienter sind und das Potential haben, den Nährstofftransport auf Einzugsgebietsebene zu beeinflussen.Increasing pressure on rivers results in the decoupling of the naturally occurring floodplains, resulting in a loss of the ecosystem services provided by these transition zones. Efforts to restore floodplains by reconnecting them to their source rivers have primarily focused on reestablishing the unique habitats found in floodplains (i.e. fish spawning sites). However, the resulting biogeochemical changes are not well documented. The purpose of this study was to understand the effects of this large-scale change to the biogeochemical cycling of two floodplain systems in the Danube River Basin. Nitrogen cycling was chosen due to the capacity of floodplains to remove nitrate from the river and to produce nitrous oxide, a harmful greenhouse gas. The most important finding of this project demonstrated how floodplain restoration alters the nitrate removal pathways and ultimately N2O and N2 emission. I have shown that restoration, by increasing the frequency of inundation, improves biogeochemical cycling efficiency and reduce N2O emissions from denitrification compared to decoupled floodplains. Generally, this project improved understanding of the function of different subsystems within the floodplain landscape as well as the role of overall transformation capacity and biogeochemical interplay within floodplain systems. Using the produced modeling tool, patterns of high activity in areas which were frequently inundated by the Danube River were identified. A series of laboratory experiments elucidated the specific changes which resulting in a reduction of N2O production. Overall, this project furthered the understanding of nitrogen cycling in floodplains and suggested restoration efforts which are more effective at transforming nutrients within the riverine landscape which affects the nutrient transport at the catchment scale.Nina Diana WeltiZsfassung in engl. SpracheWien, Univ. für Bodenkultur, Diss., 2012OeBB(VLID)193017

Limitations of stream restoration for nitrogen retention in agricultural headwater streams

High nutrient loading and channelization reduce the nutrient retention capacity of agricultural streams and lead to increases in nutrient downstream transport. The aim of the current study was to study the effects of channel reconfiguration and riparian reforestation on the nitrogen retention capacity of eutrophic agricultural headwater streams. In addition, we investigated the role of stream sediments as a nitrogen sink or source for the stream ecosystem.We compared two restored reaches with two morphologically pristine and four channelized reaches in an agricultural catchment in the north-east of Austria regarding in-stream ammonium uptake, whole-reach retention of dissolved inorganic nitrogen, potential denitrification enzyme activity, and sedimentary ammonium release.Restored and pristine reaches exhibited significantly shorter ammonium uptake lengths (330m) and larger mass transfer coefficients (2.7×10-5ms-1) than channelized reaches (2500m and 1.1×10-5ms-1, respectively). Increased ammonium uptake was positively correlated with increased transient storage in restored and pristine reaches. Total DIN retention was slightly, though not significantly higher in restored sections (average rates 0.06g DINm-2h-1) and showed signs of temporal nitrogen saturation in all reaches. In general, sediments were characterized by small grain sizes (0.04-0.31mm), high ammonium (60-215μgg-1 DW), and low nitrate concentrations (0.4-5.7μgg-1 DW). Ammonium was released from sediments of all reaches below concentrations of 100μg NH4 +-NL-1 in the overlying water column which shows the high potential of nutrient-rich sediments to act as an internal ammonium source for the stream ecosystem. Potential denitrification was lowest in sediments of restored reaches and significantly increased after nitrate amendment to 3-26mgNm-2h-1.The study reveals that stream sediments, which are loaded with nutrient-rich soil from the agricultural catchment, may limit the effects of stream restoration in agricultural streams. In order to improve the nutrient retention capacity of agricultural streams, reach-scale restoration measures have to be combined with measures in the catchment which reduce nutrient and soil inputs to streams

Seasonal nitrous oxide and methane emissions across a subtropical estuarine salinity gradient

Currently, there is a lack of knowledge about GHG emissions, specifically NO and CH, in subtropical coastal freshwater wetland and mangroves in the southern hemisphere. In this study, we quantified the gas fluxes and substrate availability in a subtropical coastal wetland off the coast of southeast Queensland, Australia over a complete wet-dry seasonal cycle. Sites were selected along a salinity gradient ranging from marine (34\ua0psu) in a mangrove forest to freshwater (0.05\ua0psu) wetland, encompassing the range of tidal influence. Fluxes were quantified for CH (range −0.4–483\ua0mg C–CH\ua0h\ua0m) and NO (−5.5–126.4\ua0μg N–NO\ua0h\ua0m), with the system acting as an overall source for CH and NO (mean NO and CH fluxes: 52.8\ua0μg N–NO\ua0h\ua0m and 48.7\ua0mg C–CH\ua0h\ua0m, respectively). Significantly higher NO fluxes were measured during the summer months (summer mean 64.2\ua0±\ua022.2\ua0μg N–NO\ua0h\ua0m; winter mean 33.1\ua0±\ua024.4\ua0µg N–NO\ua0h\ua0m) but not CH fluxes (summer mean 30.2\ua0±\ua081.1\ua0mg C–CH\ua0h\ua0m; winter mean\ua037.4\ua0±\ua079.6\ua0mg C–CH\ua0h\ua0m). The changes with season are primarily driven by temperature and precipitation controls on the dissolved inorganic nitrogen (DIN) concentration. A significant spatial pattern was observed based on location within the study site, with highest fluxes observed in the freshwater tidal wetland and decreasing through the mangrove forest. The dissolved organic carbon (DOC) varied throughout the landscape and was correlated with higher CH fluxes, but this was a nonlinear trend. DIN availability was dominated by N–NH and correlated to changes in NO fluxes throughout the landscape. Overall, we did not observe linear relationships between CH and NO fluxes and salinity, oxygen or substrate availability along the fresh-marine continuum, suggesting that this ecosystem is a mosaic of processes and responses to environmental changes

Nitrogen dynamics in complex Danube River floodplain systems: effects of restoration

International audienceWe used a hydromorphological model to assess areas of potential high denitrification rates and nitrous oxide release in a frequently and an infrequently connected fl oodplain system of the Danube River under different river discharge conditions. Based on the model’s projections, the decoupled floodplain was predicted to have more areas of high potential denitrification during mean and elevated discharge, but with more sites dominated by incomplete denitrification, resulting in higher N2O emission. In the restored floodplain, frequently inundated, the model predicted that lower rates of denitrification would occur at lower river discharge levels, dominated by complete denitrification, resulting in N2rather than N2O production. During an annual flood (5300 m3s–1), flooding both floodplains, the restored floodplain was predicted to have more areas of high potential denitrification activity than the decoupled floodplain. The model outputs suggest that floodplains subject to frequent inundations can effectively and efficiently use nitrate input from the main river channel, resulting in complete denitrification. Restoration measures should attempt to promote frequent inundation periods in order to fully realize the high denitrification potential of floodplain systems