Land‐water interactions at Whatawhata,New Zealand: Introduction and synthesis     

John M. Quinn  A. Bryce Cooper 《新西兰海洋与淡水研究杂志》2013,47(5):569-577

  相似文献   

Microbial enzymatic response to catchment‐scale variations in supply of dissolved organic carbon     

Stuart Findlay  Christopher W. Hickey  John M. Quinn 《新西兰海洋与淡水研究杂志》2013,47(5):701-706

A suite of exoenzyme activities was assayed in three New Zealand streams draining pasture, native forest, and a pine catchment. There were differences among catchments in activity of three of the five enzymes assayed (cello‐biohydrolase, N‐acetylglucosaminidase, and dihydroxylphenylalanine oxidation). A principal components analysis (PCA) demonstrates that patterns of enzyme activity can be used to separate the three stream types. An experimental addition of algal‐leachate, leaf‐litter leachate, and high dissolved organic carbon (DOC) water from a small seep also resulted in marked shifts in epilithic enzyme activities 1 day after DOC additions. Oxidative enzymes showed a particularly strong response to additions of humic DOC. As for the field samples, a PCA showed large differences among treatments indicating that exoenzyme patterns can be used to examine which DOC sources predominate in different streams. Application of this approach to describing differences among streams will require detailed seasonal sampling together with longer‐term experiments.  相似文献   

Use of a traditional Maori harvesting method,the tau kōura,for monitoring kōura (freshwater crayfish,Paranephrops planifions) in Lake Rotoiti,North Island,New Zealand     

Ian A. Kusabs  John M. Quinn 《新西兰海洋与淡水研究杂志》2013,47(3):713-722

Sampling of kōura (freshwater crayfish Paranephrops planifrons) to assess population abundance and structure in lakes is often difficult or impractical because of the absence of representative methods. The tau kôura is a traditional Maori method used to catch kôura in central North Island lakes by placing whakaweku (bundles of bracken fern Pteridium esculentum) on the lake bed that kôura then colonise. It has advantages as a monitoring tool over conventional methods, such as baited traps and dive surveys, as it samples all kôura size classes, can be used in turbid waters and at a wide range of depths, and does not require expensive equipment or specialised expertise (e.g., SCUBA). We demonstrate its use to monitor kôura populations in Lake Rotoiti (mean depth 32 m), North Island, New Zealand. Application of the method allowed differences in population size structure to be distinguished between a shallow and a moderate depth site within Lake Rotoiti and to discern seasonal breeding patterns.  相似文献   

Feedback and the formation of dwarf galaxy stellar haloes     

G. S. Stinson  J. J. Dalcanton †  T. Quinn  S. M. Gogarten  T. Kaufmann  J. Wadsley 《Monthly notices of the Royal Astronomical Society》2009,395(3):1455-1466

Stellar population studies show that low-mass galaxies in all environments exhibit stellar haloes that are older and more spherically distributed than the main body of the galaxy. In some cases, there is a significant intermediate age component that extends beyond the young disc. We examine a suite of Smoothed Particle Hydrodynamic simulations and find that elevated early star formation activity combined with supernova feedback can produce an extended stellar distribution that resembles these haloes for model galaxies ranging from   v ₂₀₀= 15  to 35 km s⁻¹, without the need for accretion of subhaloes.  相似文献   

The inner structure of ΛCDM haloes – I. A numerical convergence study     

C. Power  J. F. Navarro †  A. Jenkins  C. S. Frenk  S. D. M. White  V. Springel  J. Stadel  T. Quinn 《Monthly notices of the Royal Astronomical Society》2003,338(1):14-34

  相似文献   

The in(a/tan/β) index: How to calculate it and how to use it within the topmodel framework     

P. F. Quinn  K. J. Beven  R. Lamb 《水文研究》1995,9(2):161-182

Topographic indices may be used to attempt to approximate the likely distribution of variable source areas within a catchment. One such index has been applied widely using the distribution function catchment model, TOPMODEL, of Beven and Kirkby (1979). Validation of the spatial predictions of TOPMODEL may be affected by the algorithm used to calculate the model's topographic index. A number of digital terrain analysis (DTA) methods are therefore described for use in calculating the TOPMODEL topographic index, In(a/tanβ) (a = upslope contributing area per unit contour; tanβ = local slope angle). The spatial pattern and statistical distribution of the index is shown to be substantially different for different calculation procedures and differing pixel resolutions. It is shown that an interaction between hillslope contributing area accumulation and the analytical definition of the channel network has a major influence on calculated In(a/tanβ) index patterns. A number of DTA tests were performed to explore this interaction. The tests suggested that an ‘optimum’ channel initiation threshold (CIT) may be identified for positioning river headwaters in a raster digital terrain model (DTM). This threshold was found to be dependent on DTM grid resolution. Grid resolution is also suggested to have implications for the validation of spatial model predictions, implying that ‘optimum’ TOPMODEL parameter sets may be unique to the grid scale used in their derivation. Combining existing DTA procedures with an identified CIT, a procedure is described to vary the directional diffusion of contributing area accumulation with distance from the channel network.  相似文献   

High-resolution simulations of the final assembly of Earth-like planets I. Terrestrial accretion and dynamics     

Sean N. Raymond  Thomas Quinn  Jonathan I. Lunine 《Icarus》2006,183(2):265-282

The final stage in the formation of terrestrial planets consists of the accumulation of ∼1000-km “planetary embryos” and a swarm of billions of 1-10 km “planetesimals.” During this process, water-rich material is accreted by the terrestrial planets via impacts of water-rich bodies from beyond roughly 2.5 AU. We present results from five high-resolution dynamical simulations. These start from 1000-2000 embryos and planetesimals, roughly 5-10 times more particles than in previous simulations. Each simulation formed 2-4 terrestrial planets with masses between 0.4 and 2.6 Earth masses. The eccentricities of most planets were ∼0.05, lower than in previous simulations, but still higher than for Venus, Earth and Mars. Each planet accreted at least the Earth's current water budget. We demonstrate several new aspects of the accretion process: (1) The feeding zones of terrestrial planets change in time, widening and moving outward. Even in the presence of Jupiter, water-rich material from beyond 2.5 AU is not accreted for several millions of years. (2) Even in the absence of secular resonances, the asteroid belt is cleared of >99% of its original mass by self-scattering of bodies into resonances with Jupiter. (3) If planetary embryos form relatively slowly, then the formation of embryos in the asteroid belt may have been stunted by the presence of Jupiter. (4) Self-interacting planetesimals feel dynamical friction from other small bodies, which has important effects on the eccentricity evolution and outcome of a simulation.  相似文献   

Forest Cover Change in the Toledo District,Belize from 1975 to 1999: A Remote Sensing Approach*     

Michael Emch  James W. Quinn  Marc Peterson  Mark Alexander 《The Professional geographer》2005,57(2):256-267

Measuring land‐cover change is an essential part of sustainable conservation planning. This project uses Landsat MSS and ETM+ data to document forest cover change in the Toledo District, Belize, from 1975 to 1999 and provides an initial assessment of why these changes took place. Supervised and subpixel classification methods were employed. The results showed an aggregate forest loss of almost 10 percent, which is approximately 36,000 ha. Deforestation expanded significantly in the most populous Mayan areas of central Toledo District and along the Guatemalan border. Subpixel classification results showed that in 1999 the most densely forested areas were in northern Toledo District in the Maya Mountains.  相似文献   

New constraints on metamorphism in the Rauer Group, Prydz Bay, east Antarctica   总被引：12，自引：0，他引：12  

D. E. Kelsey  R. W. White  R. Powell  C. J. L. Wilson  C. D. Quinn 《Journal of Metamorphic Geology》2003,21(8):739-759

Abstract Granulite facies metapelites of the Mather and Filla Paragneisses within the Rauer Group, east Antarctica, possess markedly different compositions. The metamorphic evolution of the two metapelite types has been interpreted as temporally distinct, with the Rauer Group preserving at least two distinct granulite facies tectonothermal episodes. Calculated P–T pseudosections and orthopyroxene Al content indicate the revised maximum‐preserved P–T conditions within the Mather Paragneiss to lie in the vicinity of 950–975 °C and 10–10.6 kbar, less extreme than previous estimates. The range of possible P–T paths for the Mather Paragneiss consistent with mineral textural relationships and pseudosections contoured for mineral proportion are significantly shallower (dP/dT) than previous estimates. A near‐isothermal decompression P–T path, and extreme peak metamorphic conditions, are not necessary to explain the development of preserved mineral reaction textures. The Filla Paragneiss contains pelitic assemblages less amenable to rigorous quantitative analysis. Nevertheless, possibilities for the shared or otherwise metamorphic evolution of the Mather and Filla Paragneisses may be postulated on the basis of calculated pseudosections in the context of existing geochronology for the Rauer Group and preserved microstructures. A shared evolution, most likely during Pan‐African granulite facies metamorphism, is plausible and consistent with mineral assemblage development, geochronology and microstructures. A revised interpretation of the Rauer Group's preserved metamorphic evolution may warrant the revision of existing tectonic models, applicable also to the remainder of Prydz Bay. More generally, the employed approach may incite a revision of peak P–T and P–T paths in other granulite facies terranes.  相似文献   

Aliphatic petroleum and biogenic hydrocarbons entering Narragansett Bay from tributaries under dry weather conditions     

James S. Latimer  James G. Quinn 《Estuaries and Coasts》1998,21(1):91-107

The temporal variability of hydrocarbon inputs from rivers discharging into Narragansett Bay under dry weather conditions, as well as the elucidation of the types and sources of hydrocarbons found in urban rivers, has been investigated. The rivers studied, the Blackstone, the Pawtuxet, the Moshassuck, and the Woonasquatucket, constitute the majority of river flow to the estuary. The unfiltered river water samples were extracted and analyzed for total aliphatic hydrocarbons, including natural and petroleum-derived species. The results of the year-long study revealed consistent oil pollution in all of the rivers sampled. Crankcase oil was ubiquitous, but the presence as well of fuel oils and, particularly in the Moshassuck River, gasoline (or kerosene), demonstrate that these rivers are subject to considerable oil pollution stress. The average concentration of hydrocarbons was ≈37 μg l^?1 which, according to some toxicologists, indicates that sensitive organisms may be under stress. In addition, most samples showed evidence of small amounts of terrigenous plant wax hydrocarbons. Hydrocarbon concentrations are comparable to those in other urban rivers but are higher than in rivers from rural areas; moreover, they did not vary in any systematic way with season. The mass transport of hydrocarbons in each of the rivers generally mimicked trends in river discharge, thereby emitting the lowest mass to the estuary in the summer and increasing throughout the remainder of the year. Moreover, due primarily to relative discharge differences, the Blackstone and Pawtuxet rivers constitute 90% of the total calculated flux of hydrocarbons from all four rivers. By combining the results from this investigation with those from previous studies, it was possible to obtain an estimate of the total annual inputs of these contaminants to Narragansett Bay. Total annual loads from rivers and wastewater treatment facilities were approximately 240 mt. When sources such as wet weather inputs were included, the total increased to 420 mt yr^?1. This value represents direct current inputs to the system and is considerably lower than previously published estimates. The current direct input estimate, while indicative of an improving situation, differs from previous estimates in that the latter were based upon calculations that approximated the long-term loadings from the watersheds, most of which are likely accumulating above the fall-lines of rivers throughout the watershed. Nevertheless, the current loadings represent a significant chronic flux of hydrocarbons to Narragansett Bay. For example, this estimate indicates that an amount equal to approximately 43% of the oil discharged into Narragansett Bay from the recent World Prodigy oil spill enters the estuary from chronic sources every year.  相似文献