Diversity and zonal distribution of arbuscular mycorrhizal fungi on the northern slopes of the Tianshan Mountains

The arbuscular mycorrhizal (AM) fungal status of the 20 most common plant species distributed in 4 vegetation types (meadow steppe, desert steppe, steppe desert and typical desert) on the northern slopes of the Tianshan Mountains was investigated. Samples of the plant species and their rhizosphere soils were collected from the 4 vegetation zones and examined to compare their mycorrhizal status, AM fungal spore densities, biovolumes, and community structures. 28 AM fungal species were isolated from the rhizosphere soils: of these, 5 belonged to Acaulospora, 1 to Archaeospora and 22 to Glomus. 5 AM fungi, Glomus aggregatum, G. claroideum, G. deserticola, G. etunicatum and G. sinuosum, were observed in all 4 zonal types. No significant differences were observed in mean proportion of root length colonized by AM fungi among the plant species within each zonal type. Comparing the 4 zonal types, Plantago minuta (84.5%) in steppe desert and Eremopyrum orientale (83.1%) in typical desert showed the highest root colonizatsion rates. AM fungal spore densities and biovolumes were significantly different in the different zonal types. AM fungal spore densities and biovolumes, species richness and diversity were highest in meadow steppe and lowest in typical desert.     

Comparative microstructures of natural and experimentally produced clay-bearing fault gouges

Fault rocks formed in phyllosilicate-bearing rocks formed over a wide range of environmental conditions within the Earth's crust are characterised by similar structural and microstructural features. The most striking of these are (a) P foliation, defined by the preferred alignment of phyllosilicates in a plane oblique to the direction of shear and (b) small-scale shear zones either parallel to the shear direction (Y shears) or oblique to the direction of shear but with the opposite sense of obliquity relative to the P foliation (Riedel shears, R₁). The minor shear zones have the same sense of displacement as the host shear zone.The occurrence of these and other structures in clay-rich fault gouges from exceptionally well-exposed fault zones in southeastern Spain is described. The pervasive development of these flow structures throughout large volumes of fault gouge permits fault-displacement vectors to be inferred. For the region studied the movement pictures is relatively simple and is superposed on a complex network of variably oriented fault zones.The naturally produced fault-gouge structures are compared with fault gouges produced experimentally by shearing kaolinite-quartz mixtures between intact blocks over a wide range of experimental conditions. Good correspondence between their respective microstructural features was observed.Finally, attention is drawn to the fact that natural clay-bearing fault gouges are the products of deformation accompanied by very low-grade retrogressive metamorphism, and that part of the micro-structure of these rocks may be ascribed to crystallization under stress. Microstructures are described that are from long-duration experimental runs, (5 months at high temperature and in the presence of water) which go some way towards simulating these effects.     

Subsolidus reactions in lunar pyroxenes: An electron petrographic study

Zoned lunar pyroxenes have been examined by high voltage (800–1000 kV) transmission electron microscopy and electron diffraction, with the particular aim of providing information on the cooling history of individual pyroxenes. Microstructures resulting from composition discontinuities occurring during continuous crystallization, exsolution lamellae of pigeonite and augite and the development of denuded zones, and anti-phase domains (APD's) in pigeonite have been studied with respect to their scale, morphology and micro-structural evolution. These features have been further interpreted with respect to a proposed pseudobinary phase diagram of constant En/Fs.Information found to be the most useful for determining cooling rates in pyroxenes are: for quickly cooled rocks; microstructural evolution and APD size for moderately cooled rocks; and denuded zone widths and APD morphology for slowly cooled rocks.Now at U.S. Geological Survey, 959 National Center, Reston, Virginia 22092.     

Long term monitoring of photosystem II herbicides--correlation with remotely sensed freshwater extent to monitor changes in the quality of water entering the Great Barrier Reef, Australia

Photosystem II (PSII) herbicides are used in large quantities on agricultural lands adjoining the Great Barrier Reef (GBR). Routine monitoring at 14 sites in inshore waters of the GBR using passive sampling techniques detected diuron (32-94% of sampling periods) at maximum concentrations of 1.7-430ng L(-1) in the relatively pristine Cape York Region to the Mackay Whitsunday Region, respectively. A PSII herbicide equivalent (PSII-HEq) index developed as an indicator for reporting was dominated by diuron (average contribution 89%) and typically increased during the wet season. The maximum PSII-HEq indicates the potential for photosynthetic inhibition of diatoms, seagrass and coral-symbionts. PSII herbicides were significantly positively correlated with remotely sensed coloured dissolved organic matter, a proxy for freshwater extent. Combining these methods provides for the first time the potential to cost-effectively monitor improvements in water quality entering the GBR with respect to exposure to PSII herbicides.     

Ecological monitoring strategy with special reference to a rocky subtidal programme

Excluding the most polluted areas, a general problem to handle in an ecological monitoring context is the recognition of pollution-induced changes as opposed to natural variations always occurring in marine communities. In the search for solutions to this problem, a combination of different methods is suggested. The use of basic ecological community studies, comparison of common patterns on a broad geographical scale, and making predictions from short and long term trend models are the methods that have been tried and discussed. Ecological knowledge and comparison of common patterns are here suggested as the most fruitful tools in an ecological monitoring programme.     

Population MCMC methods for history matching and uncertainty quantification

This paper presents the application of a population Markov Chain Monte Carlo (MCMC) technique to generate history-matched models. The technique has been developed and successfully adopted in challenging domains such as computational biology but has not yet seen application in reservoir modelling. In population MCMC, multiple Markov chains are run on a set of response surfaces that form a bridge from the prior to posterior. These response surfaces are formed from the product of the prior with the likelihood raised to a varying power less than one. The chains exchange positions, with the probability of a swap being governed by a standard Metropolis accept/reject step, which allows for large steps to be taken with high probability. We show results of Population MCMC on the IC Fault Model—a simple three-parameter model that is known to have a highly irregular misfit surface and hence be difficult to match. Our results show that population MCMC is able to generate samples from the complex, multi-modal posterior probability distribution of the IC Fault model very effectively. By comparison, previous results from stochastic sampling algorithms often focus on only part of the region of high posterior probability depending on algorithm settings and starting points.     

The thermal and deformational history of apollo 15418, A partly shock-melted lunar breccia

A thermal and mechanical history of lunar gabbroic anorthosite 15418 (1140g) has been deduced from petrographic examination of both exterior and interior thin sections and electron microprobe analysis and transmission electron microscopy of interior thin sections. We suggest that the rock underwent two major shock events - an early brecciation and annealing that produced a recrystallized breccia, followed by a second shock event that melted the surface of the rock, vitrified the interior plagioclase and heavily deformed the mafic phases. This latter shock even was also followed by annealing which crystallized the shock-produced glass and promoted recovery and recrystallization of the deformed crystalline phases. The complex mechanical and thermal history of 15418 compared with other ANT suite rocks at Spur Crater suggests that it had a different provenance.     

Nested gridding and streamline-based simulation for fast reservoir performance prediction

Detailed reservoir models routinely contain 10⁶–10⁸ grid blocks. These models often cannot be used directly in a reservoir simulation because of the time and memory required for solving the pressure grid on the fine grid. We propose a nested gridding technique that efficiently obtains an approximate solution for the pressure field. The domain is divided into a series of coarse blocks, each containing several fine cells. Effective mobilities are computed for each coarse grid block and the pressure is then found on the coarse scale. The pressure field within each coarse block is computed using flux boundary conditions obtained from the coarse pressure solution. Streamline-based simulation is used to move saturations forward in time. We test the method for a series of example waterflood problems and demonstrate that the method can give accurate estimates of oil production for large 3D models significantly faster than direct simulation using streamlines on the fine grid, making the method overall approximately up to 1,000 times faster than direct conventional simulation.     

The effects of water vapour and oxides of nitrogen on ozone and temperature structure of the stratosphere

Summary A steady-state mean meridional model of the stratosphere is used to investigate the effects of water vapour and nitrogen oxides on ozone and temperature distributions in the stratosphere. The Chapman classical photochemical scheme for ozone is extended to include the dominant reactions involving hydrogen compounds and nitrogen oxides. The ozone and temperature changes are studied under radiative-photochemical equilibrium conditions and in a model incorporating both transport and radiative-photochemical processes. It is found that both hydrogen and nitrogen reactions contribute to substantial decreases in ozone and temperature under photochemical equilibrium conditions, but the computed distribution do not resemble those observed. The effect of transport processes is to reduce the deviations in the ozone mixing ratio and temperature with the computed distributions having many features in common with the observations. It is found that the ozone and temperature respond more readily to the arbitrary increase of nitrogen oxides than to that of water vapour.     

Water‐quality response to a high‐elevation wildfire in the Colorado Front Range

Water quality of the Big Thompson River in the Front Range of Colorado was studied for 2 years following a high‐elevation wildfire that started in October 2012 and burned 15% of the watershed. A combination of fixed‐interval sampling and continuous water‐quality monitors was used to examine the timing and magnitude of water‐quality changes caused by the wildfire. Prefire water quality was well characterized because the site has been monitored at least monthly since the early 2000s. Major ions and nitrate showed the largest changes in concentrations; major ion increases were greatest in the first postfire snowmelt period, but nitrate increases were greatest in the second snowmelt period. The delay in nitrate release until the second snowmelt season likely reflected a combination of factors including fire timing, hydrologic regime, and rates of nitrogen transformations. Despite the small size of the fire, annual yields of dissolved constituents from the watershed increased 20–52% in the first 2 years following the fire. Turbidity data from the continuous sensor indicated high‐intensity summer rain storms had a much greater effect on sediment transport compared to snowmelt. High‐frequency sensor data also revealed that weekly sampling missed the concentration peak during snowmelt and short‐duration spikes during rain events, underscoring the challenge of characterizing postfire water‐quality response with fixed‐interval sampling. Copyright © 2015 John Wiley & Sons, Ltd.