Mulga, a major tropical dry open forest of Australia: Recent insights to carbon and water fluxes

© 2016 IOP Publishing Ltd. Mulga, comprised of a complex of closely related Acacia spp., grades from a low open forest to tall shrublands in tropical and sub-tropical arid and semi-arid regions of Australia and experiences warm-to-hot annual temperatures and a pronounced dry season. This short synthesis of current knowledge briefly outlines the causes of the extreme variability in rainfall characteristic of much of central Australia, and then discusses the patterns and drivers of variability in carbon and water fluxes of a central Australian low open Mulga forest. Variation in phenology and the impact of differences in the amount and timing of precipitation on vegetation function are then discussed. We use field observations, with particular emphasis on eddy covariance data, coupled with modelling and remote sensing products to interpret inter-seasonal and inter-annual patterns in the behaviour of this ecosystem. We show that Mulga can vary between periods of near carbon neutrality to periods of being a significant sink or source for carbon, depending on both the amount and timing of rainfall. Further, we demonstrate that Mulga contributed significantly to the 2011 global land sink anomaly, a result ascribed to the exceptional rainfall of 2010/2011. Finally, we compare and contrast the hydraulic traits of three tree species growing close to the Mulga and show how each species uses different combinations of trait strategies (for example, sapwood density, xylem vessel implosion resistance, phenological guild, access to groundwater and Huber value) to co-exist in this semi-arid environment. Understanding the inter-annual variability in functional behaviour of this important arid-zone biome and mechanisms underlying species co-existence will increase our ability to predict trajectories of carbon and water balances for future changing climates

Optimizing fluid management in patients with acute decompensated heart failure (ADHF): the emerging role of combined measurement of body hydration status and brain natriuretic peptide (BNP) levels

The study tests the hypothesis that in patients admitted with acutely decompensated heart failure (ADHF), achievement of adequate body hydration status with intensive medical therapy, modulated by combined bioelectrical vectorial impedance analysis (BIVA) and B-type natriuretic peptide (BNP) measurement, may contribute to optimize the timing of patient’s discharge and to improve clinical outcomes. Three hundred patients admitted for ADHF underwent serial BIVA and BNP measurement. Therapy was titrated to reach a BNP value of <250 pg/ml, whenever possible. Patients were categorized as early responders (rapid BNP fall below 250 pg/ml); late responders (slow BNP fall below 250 pg/ml, after aggressive therapy); and non-responders (BNP persistently >250 pg/ml). Worsening of renal function (WRF) was evaluated during hospitalization. Death and rehospitalization were monitored with a 6-month follow-up. BNP value on discharge of ≤250 pg/ml led to a 25% event rate within 6 months (Group A: 17.4%; Group B: 21%, Chi2; n.s.), whereas a value >250 pg/ml (Group C) was associated with a far higher percentage (37%). At discharge, body hydration was 73.8 ± 3.2% in the total population and 73.2 ± 2.1, 73.5 ± 2.8, 74.1 ± 3.6% in the three groups, respectively. WRF was observed in 22.3% of the total. WRF occurred in 22% in Group A, 32% in Group B, and 20% in Group C (P = n.s.). Our study confirms the hypothesis that combined BNP/BIVA sequential measurements help to achieve adequate fluid balance status in patients with ADHF and can be used to drive a “tailored therapy,” allowing clinicians to identify high-risk patients and possibly to reduce the incidence of complications secondary to fluid management strategies

Comparison of frying performance of olive oil, bi-fractionated palm oil and sunflower oil

Fatty acid composition of a frying oil is very important in order to limit the reactions of oxidation, hydrolysis and polymerization which may occur during cooking operations. The objective of this study was to evaluate the thermal stability of olive oil, super palm olein and sunflower oil during frying of frozen French fries. Termo-oxidized oil, frying oil and oil extracted from potatoes were subjected to the following analysis: free fatty acids (AGL), peroxide value (NP), total polar compounds (CPT) and analysis of the methyl esters fatty acids (EMAG). In addition, each sample has been characterized by analysis of the dynamic headspace coupled to gas chromatography -mass detection (DHS / GC-MS). In thermo-oxidized olive oil 2,4-E, E-decadienal, 2,4-E, E-nonadienal and acids showed a good correlation with the CPT as well as the 2E-non-enal and n-butyl pyrrole in thermo-oxidized sunflower oil. The fat extracted from potatoes fried with palm olein was found to contain styrene which seems to arise not only from a phenomenon of migration from packaging material but from a mechanism of neo-formation. Alkylbenzenes and pyrazines were detected in the fat extracted from potatoes fried with sunflower oil and olive oil

Xylem hydraulic properties in subtropical coniferous trees influence radial patterns of sap flow: implications for whole tree transpiration estimates using sap flow sensors

Key message: A high spatial resolution dataset of sap flux density in subtropical conifers is used to assess the minimum number and location of sap flow sensors required to monitor tree transpiration accurately. Abstract: Tree transpiration is commonly estimated by methods based on in situ sap flux density (SFD) measurements, where the upscaling of SFD from point measurements to the individual tree has been identified as the main source of error. The literature indicates that the variation in SFD with radial position across a tree stem section can exhibit a wide range of patterns. Adequate capture of the SFD profile may require a large number of point measurements, which is likely to be prohibited. Thus, it is of value to develop protocols, which rationalize the number of point measurements, while retaining a satisfactory precision in the tree SFD estimates. This study investigates cross-sectional SFD variability within a tree and successively for six individual trees within a stand of Pinus elliottii var. elliottii\ua0×\ua0caribaea var. hondurensis (PEE\ua0×\ua0PCH). The stand is part of a plantation in subtropical coastal Australia. SFD is estimated using the Heat Field Deformation method simultaneously for four cardinal directions with measurements at six depths from the cambium. This yields a reference value of single tree SFD based on the twenty-four point measurements. Large variability of SFD is observed with measurement depth, cardinal direction and selected tree. We suggest that this is linked to the occurrence of successive narrow early and latewood rings with contrasting-specific hydraulic conductivities and wood water contents. Thus, an accurate placement of sensors within each ring is difficult to achieve in the field with the sensor footprint covering several rings of both early and latewood. Based on the reference dataset, we identified both an “ideal” setup and an “optimal” setup in terms of cost effectiveness and accuracy. Our study shows the need of using a systematic protocol to optimize the number of sensors to be used as a trade-off between precision and cost. It includes a preliminary assessment of the SFD variability at a high spatial resolution, and only then based on this, an appropriate placement of sensors for the long-term monitoring

Relationship between wood density and distance from pith and wood density and time in <i>Avicennia marina</i>.

<p>Relationship between A) wood density and distance from pith, slopes between stems were significantly different (<i>p<0.0001</i>), the regression equations were: Wood density (<i>stem 1</i>)  = −4.3×10⁻² distance from pith +1.01, <i>r²</i> = 0.78, <i>n</i> = 57; wood density (<i>stem 2</i>)  = −4.8×10⁻² distance from pith +0.95, <i>r²</i> = 0.83, <i>n</i> = 47; wood density (<i>stem 3</i>)  = −5.5×10⁻² distance from pith +0.86, <i>r²</i> = 0.78, <i>n</i> = 41; wood density (<i>stem 4</i>)  = −5.7×10⁻² distance from pith +0.95, <i>r²</i> = 0.94, <i>n</i> = 51; <i>p</i><0.0001 for all stems (<i>stem 1</i> – <i>stem 4</i>), vertical lines  = 1<b>σ</b>. Relationship between B) wood density and time, slopes between stems were significantly different (<i>p<0.0001</i>), the regression equations were: Wood density (<i>stem 1</i>)  = −5.07×10⁻² time +10.9, <i>r²</i> = 0.78, <i>n</i> = 48; wood density (<i>stem 2</i>)  = −3.1×10⁻² time +7.04, <i>r²</i> = 0.81, <i>n</i> = 72; wood density (<i>stem 3</i>)  = −2.5×10⁻³ time +5.75, <i>r²</i> = 0.76, <i>n</i> = 89; wood density (<i>stem 4</i>)  = −4.7×10⁻³ time +9.93, <i>r²</i> = 0.94, <i>n</i> = 63; <i>p</i><0.0001 for all stems (<i>stem 1</i> – <i>stem 4</i>), vertical lines  = 1<b>σ</b>. C) Detrended wood density and distance from pith, vertical lines  = 1<b>σ</b> and D) Detrended wood density and time, vertical lines  = 1<b>σ</b>.</p

Relationship between annual rainfall and the Pacific Decadal Oscillation Index.

<p>Relationship between A) annual rainfall (dashed line) and the Pacific Decadal Oscillation Index (PDO, solid line) in the Exmouth Gulf, Western Australia between 1966 and 2008. B) The line represents the linear regression where Rainfall  = −63.2 PDO +255, <i>r²</i> = 0.16, <i>p</i> = 0.006, <i>n</i> = 44.</p