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Long and high-resolution proxy records are still sparse in the southeastern Tibetan Plateau (TP), hampering our understanding of past climatic variability from a long-term perspective. In this study, we developed a regional maximum latewood density (MXD) chronology of Larix speciosa stretching up to 523 years based on 72 tree-ring cores (44 trees) collected from three sites close to the tree line in the Gaoligong Mountains, southeastern TP. This chronology responded well to temperatures during August through September and was thus used to reconstruct late summer (August-September) temperature over the period A.D. 1690-2008. The reconstruction explains 40.9% of the total temperature variance during the calibration phase. Cold conditions prevailed during the periods 1695-1702, 1806-1821, the 1850s, 1882-1889, the 1900s and the 1960s. Warm phases occurred in 1734-1745, the 1770s, 1824-1840, the 1890s, 1927-1936, the 1940s-1950s and 2002-2008. Spatial correlation with the gridded temperature data set showed that our reconstruction captures large-scale regional temperature variations for the southeastern and southern TP. Comparison with other tree-ring inferred temperature time series in the surrounding areas, glacier fluctuations and historical documental records imply a high degree of confidence for our reconstruction. (C) 2015 Elsevier B.V. All rights reserved.

To solve the nanoparticles (NPs) agglomeration phenomena of nanometer calcium carbonate (nano-CaCO3) modified asphalt binder, in this paper, solvent-free CaCO3 nanofluids (NFs) were prepared based on surface-functionalized CaCO3 NPs to study the effect on asphalt. Microscopic structures, compositions, and thermal stability were characterized by Fourier transform infrared spectrometer (FTIR), X-ray diffractometer (XRD), transmission electron microscope (TEM), and thermogravimetric analyzer (TGA), respectively. Results showed that perfect CaCO3 NFs were successfully prepared, and were good enough for asphalt mixing due to their excellent thermal stability. Scanning electron microscopy (SEM), conventional tests, dynamic shear rheometry (DSR), and bending beam rheometry (BBR) were conducted to investigate the modifying effect. The SEM results indicated that CaCO3 NFs had better compatibility with asphalt binder than original CaCO3 NPs. Conventional and DSR test results demonstrated that CaCO3 NFs had slight negative effects on high-temperature performance while improving the low-temperature performance of the asphalt binder. The BBR test results confirmed that the modifier addition effectively enhanced asphalt binders&rsquo, low-temperature crack resistance performance.

Nonisothermal, confined pyrolysis was applied to a mature shale sample from the Ordovician Salgan Formation in Tarim Basin, northwest China. Experiments were conducted using gold-tubes with added water at a very slow heating rate (2 °C/h) and end temperatures between 336 and 600 °C. To investigate the influence of inorganically bound sulfur on the generation of gases and to consider the geological occurrence of sulfur-containing minerals, such as prevalent pyrite in shales, the experiments were carried out with and without admixtures of MgSO4, CaSO4, and pyrite. High amounts of methane along with lower amounts of wet gases were formed from highly mature shale without minerals added, demonstrating a huge late gas generation potential at post peak-oil window maturities. In the experiments with added sulfates and pyrite, all organic gases were consumed in varying proportions, resulting in different chemical and stable carbon isotopic compositions. Pyrite treatment affects wet gas (C2–C5) evolution directly, ...

Pyrolysis of Kukersite kerogen was conducted in gold capsules, with the yield and stable carbon isotopic (d

With the ongoing crisis of biodiversity loss and limited resources for conservation, the concept of biodiversity hotspots has been useful in determining conservation priority areas. However, there has been limited research into how temporal variability in biodiversity may influence conservation area prioritization. To address this information gap, we present an approach to evaluate the temporal consistency of biodiversity hotspots in large marine ecosystems. Using a large scale, public monitoring dataset collected over an eight year period off the US Pacific Coast, we developed a methodological approach for avoiding biases associated with hotspot delineation. We aggregated benthic fish species data from research trawls and calculated mean hotspot thresholds for fish species richness and Shannon’s diversity indices over the eight year dataset. We used a spatial frequency distribution method to assign hotspot designations to the grid cells annually. We found no areas containing consistently high biodiversity through the entire study period based on the mean thresholds, and no grid cell was designated as a hotspot for greater than 50% of the time-series. To test if our approach was sensitive to sampling effort and the geographic extent of the survey, we followed a similar routine for the northern region of the survey area. Our finding of low consistency in benthic fish biodiversity hotspots over time was upheld, regardless of biodiversity metric used, whether thresholds were calculated per year or across all years, or the spatial extent for which we calculated thresholds and identified hotspots. Our results suggest that static measures of benthic fish biodiversity off the US West Coast are insufficient for identification of hotspots and that long-term data are required to appropriately identify patterns of high temporal variability in biodiversity for these highly mobile taxa. Given that ecological communities are responding to a changing climate and other environmental perturbations, our work highlights the need for scientists and conservation managers to consider both spatial and temporal dynamics when designating biodiversity hotspots.

Author(s): Hughes, Brent B; Beas-Luna, Rodrigo; Barner, Allison K; Brewitt, Kimberly; Brumbaugh, Daniel R; Cerny-Chipman, Elizabeth B; Close, Sarah L; Coblentz, Kyle E; De Nesnera, Kristin L; Drobnitch, Sarah T; Figurski, Jared D; Focht, Becky; Friedman, Maya; Freiwald, Jan; Heady, Kristen K; Heady, Walter N; Hettinger, Annaliese; Johnson, Angela; Karr, Kendra A; Mahoney, Brenna; Moritsch, Monica M; Osterback, Ann-Marie K; Reimer, Jessica; Robinson, Jonathan; Rohrer, Tully; Rose, Jeremy M; Sabal, Megan; Segui, Leah M; Shen, Chenchen; Sullivan, Jenna; Zuercher, Rachel; Raimondi, Peter T; Menge, Bruce A; Grorud-Colvert, Kirsten; Novak, Mark; Carr, Mark H

Allometric models of internodes are an important component of Functional-Structural Plant Models (FSPMs), which represent the shape of internodes in tree architecture and help our understanding of resource allocation in organisms. Constant allometry is always assumed in these models. In this paper, multilevel nonlinear mixed-effect models were used to characterize the variability of internode allometry, describing the relationship between the last internode length and biomass of Pinus tabulaeformis Carr. trees within the GreenLab framework. We demonstrated that there is significant variability in allometric relationships at the tree and different-order branch levels, and the variability decreases among levels from trees to first-order branches and, subsequently, to second-order branches. The variability was partially explained by the random effects of site characteristics, stand age, density, and topological position of the internode. Tree- and branch-level-specific allometric models are recommended because they produce unbiased and accurate internode length estimates. The model and method developed in this study are useful for understanding and describing the structure and functioning of trees.

Inorganic phosphorus (SRP) concentrations in the subtropical North Atlantic are some of the lowest in the global ocean and have been hypothesized to constrain primary production. Based upon data from several transect cruises in this region, it has been hypothesized that dissolved organic phosphorus (DOP) supports a significant fraction of primary production in the subtropical North Atlantic. In this study, a time-series of phosphorus biogeochemistry is presented for the Bermuda Atlantic Time-series Study site, including rates of phosphorus export. Most parameters have a seasonal pattern, although year-over-year variability in the seasonal pattern is substantial, likely due to differences in external forcing. Suspended particulate phosphorus exhibits a seasonal maximum during the spring bloom, despite the absence of a seasonal peak in SRP. However, DOP concentrations are at an annual maximum prior to the winter/spring bloom and decline over the course of the spring bloom while whole community alkaline phosphatase activities are highest. As a result of DOP bioavailability, the growth of particles during the spring bloom occurs in Redfield proportions, though particles exported from the euphotic zone show rapid and significant remineralization of phosphorus within the first 50 m below the euphotic zone. Based upon DOP data from transect cruises in this region, the southward cross gyral flux of DOP is estimated to support ~25% of annual primary production and ~100% of phosphorus export. These estimates are consistent with other research in the subtropical North Atlantic and reinforce the hypothesis that while the subtropics may be phosphorus stressed (a physiological response to low inorganic phosphorus), utilization of the DOP pool allows production and accumulation of microbial biomass at Redfield proportions.