Distribution patterns of SOC/TN content and their relationship with topography,vegetation and climatic factors in China’s north-south transitional zone

Journal of Geographical Sciences - The spatial distributions and variation mechanism of key soil indices in the Qinling-Daba Mountains are important indicators for the identification of the...     

云南省玉龙雪山表土花粉垂直散布与植被关系研究

对云南省玉龙雪山地区8个垂直植被带下采集的49个表土样品进行表土孢粉的垂直散布研究,同时选择43个受人类活动干扰较少的样品和20个主要木本花粉类型进行了降维对应分析(DCA)。结果表明,玉龙雪山地区不同垂直植被带的孢粉组合具有不同的代表性成分与变化特征,能够较好地反映相应的植被带类型。在植物稀疏、花粉产量低的高山杜鹃灌丛植被带中,孢粉组合以外来的松属、冷杉属、落叶松属、云杉属和铁杉属等为主;   冷杉林、落叶松林、云杉林和铁杉林等植被带孢粉组合的指示性成分分别是冷杉属、落叶松属、云杉属和铁杉属花粉,它们对应的峰值分别为13.6％,4.7％,39.4％和11.5％;   针阔混交林、中山湿性常绿阔叶林的孢粉组合分别以高含量的常绿栎类、栲/石栎属为特征,并都含有多种落叶阔叶乔木和灌木的花粉,但后者比前者所包含的阔叶乔木与灌木成分更多,且蕨类孢子的峰值也出现在中山湿性常绿阔叶林中;   云南松林的孢粉组合中除松属外很少有木本花粉出现。DCA排序结果较好地反映了现代植被与环境之间的相互关系,认为温度是决定不同植被带样点分布的最重要因素,这与垂直植被带随着海拔升高、温度逐渐降低而发生更替的规律是一致的。     

Estimation of soil compaction parameters by using statistical analyses and artificial neural networks

This study presents the application of different methods (simple–multiple analysis and artificial neural networks) for the estimation of the compaction parameters (maximum dry unit weight and optimum moisture content) from classification properties of the soils. Compaction parameters can only be defined experimentally by Proctor tests. The data collected from the dams in some areas of Nigde (Turkey) were used for the estimation of soil compaction parameters. Regression analysis and artificial neural network estimation indicated strong correlations (r ² = 0.70–0.95) between the compaction parameters and soil classification properties. It has been shown that the correlation equations obtained as a result of regression analyses are in satisfactory agreement with the test results. It is recommended that the proposed correlations will be useful for a preliminary design of a project where there is a financial limitation and limited time.     

Continuous simulation for computing design hydrographs for water structures

The contribution discusses the problems with modelling design floods for water structures. The statistical extrapolations of observed flood series of, for example, 80 years “only” to the annual exceedance probability AEP = 0.01 is difficult due to the large variability in extreme values. For large dams, however, the AEP = 0.001 or 0.0001 is required. Most of the uncertainties in hydrological modelling are epistemic (uncertainties in model structure, model parameters, inputs, calibration data, and in measurements) and moreover some measurements can be disinformative. With powerful computers, it is now possible to produce very long series (100 to100,000 years in hourly time step) using precipitation and temperatures computed with a weather model. Within the framework of the Generalised Likelihood Uncertainty Estimation (GLUE) many (thousands) of such continuous simulations are produced and compared to the observed historical data. According to Keith Beven's Manifesto for the equifinality thesis the differences between modelled and observed values should not be larger than some limits of acceptability based on what is known about errors in the input and output observations used for model evaluation (e.g., for flow the current metering data are used). The unacceptable realisations are rejected. We have been working with the frequency version of TOPMODEL in various versions according to the unique characteristics of each catchment. Design hydrographs for water structures are then extracted from the acceptable realisations. The continuous simulation with uncertainty estimation seems nowadays the most promising method of computing design hydrographs for important water structures, even if issues associated with epistemic uncertainty of model assumptions remain.     

Diagnostic evaluation of multiple hypotheses of hydrological behaviour in a limits‐of‐acceptability framework for 24 UK catchments

Testing competing conceptual model hypotheses in hydrology is complicated by uncertainties from a wide range of sources, which result in multiple simulations that explain catchment behaviour. In this study, the limits of acceptability uncertainty analysis approach used to discriminate between 78 competing hypotheses in the Framework for Understanding Structural Errors for 24 catchments in the UK. During model evaluation, we test the model's ability to represent observed catchment dynamics and processes by defining key hydrologic signatures and time step‐based metrics from the observed discharge time series. We explicitly account for uncertainty in the evaluation data by constructing uncertainty bounds from errors in the stage‐discharge rating curve relationship. Our study revealed large differences in model performance both between catchments and depending on the type of diagnostic used to constrain the simulations. Model performance varied with catchment characteristics and was best in wet catchments with a simple rainfall‐runoff relationship. The analysis showed that the value of different diagnostics in constraining catchment response and discriminating between competing conceptual hypotheses varies according to catchment characteristics. The information content held within water balance signatures was found to better capture catchment dynamics in chalk catchments, where catchment behaviour is predominantly controlled by seasonal and annual changes in rainfall, whereas the information content in the flow‐duration curve and time‐step performance metrics was able to better capture the dynamics of rainfall‐driven catchments. We also investigate the effect of model structure on model performance and demonstrate its (in)significance in reproducing catchment dynamics for different catchments. Copyright © 2013 John Wiley & Sons, Ltd.     

On the Stability of High Inclined L4 and L5Trojans

The orbits of real asteroids around the Lagrangian points L₄ and L ₅of Jupiter with large inclinations (i > 20°) were integrated for 50 Myrs. We investigated the stability with the aid of the Lyapunov characteristic exponents (LCE) but tested also two other methods: on one hand we integrated four neighbouring orbits for each asteroid and computed the maximum distance in every group, on the other hand we checked the variation of the Delaunay element H of the asteroid. In a second simulation – for a grid of initial eccentricity versus initial inclination – we examined the stability of the orbits around both Lagrangian points for 20° < i < 55° and 0.0 < e < 0.20. For the initial semimajor axes we have chosen the one ofJupiter(a = 5.202 AU). We determined the stability with the aid of the LCEs and also the maximum eccentricity of the orbits during the whole integration time. The region around L₄ turned out to be unstable for large inclinations and eccentricities (i > 55° and e > 0.12). The stable region shrinks for orbits around L₅: we found that they become unstable already for i > 45° and e > 0.10. We interpret it as a first hint why we observe more Trojans around the leading Lagrangian point. The results confirm the stability behaviour of the real Trojans which we computed in the first part of the paper.     

On new limits of the coefficient of gravitation shielding

New limits of the shielding coefficients in the supposed phenomenon of gravitation shielding have recently become available. The new values are briefly reviewed and discussed in order to update the state of art since some new limits for gravitation shielding are not necessarily the lowest ones which, instead, are those of interest when planning new experimental research or studying theoretically the possible effects of gravitation shielding.     

Limits to adaptation to interacting global change risks among smallholder rice farmers in Northwest Costa Rica

In this paper, we discuss the theoretical relationships among interacting global change risks, valued livelihood goals, and adaptation limits. We build from research on the impacts of multiple and interacting global change risks in lesser-developed countries and seek to understand household adaptation limits in agrarian communities. We ask: What are valued livelihood goals among smallholder farmers in Northwest Costa Rica? How do socio-economic determinants of adaptive capacities determine their ability to meet these goals in the face of the impacts of interacting global change risks? Our data were based on focus groups, interviews, survey responses from 94 smallholder farmers, government statistics, and published literature. We analyzed our data using qualitative content analysis and quantitative logistic regression models. Our analysis showed that farmers perceived rice production as an identity, and that they were being forced to consider limits to their abilities to adapt to maintain that identity. We found that farm size, cattle ownership, years spent farming, and household income variety were determinants of their abilities to remain in rice production while maintaining sufficient levels of livelihood security. We also showed that for those households most vulnerable to water scarcity, their ability to successfully adapt to meet valued livelihood goals is diminished because adaptation to water scarcity increases vulnerability to decreased rice-market access. In this way, they become trapped by the inability to reduce their vulnerability to risks of the interaction between global changes and therefore abandon valued identities and livelihoods.     

Engineering behavior of uplifted Smectite‐rich Cochin and Mangalore marine clays

Abstract

The present study aims to assess whether the smectite‐rich Cochin and Mangalore clays, which were deposited in a marine medium and subsequently uplifted, exhibit consistency limits response typical of expanding lattice or nonexpanding (fixed) lattice‐type clays on artificially changing the chemical environment. The chemical and engineering behaviors of Cochin and Mangalore marine clays are also compared with those of the smectite‐rich Ariake Bay marine clay from Japan. Although Cochin, Mangalore, and Ariake clays contain comparable amounts of smectite (32–45%), Ariake clay exhibits lower consistency limits and much higher ranges of liquidity indices than the Indian marine clays. The lower consistency limits of the Ariake clay are attributed to the absence of well‐developed, long‐range, interparticle forces associated with the clay. Also, Ariake clay exhibits a significantly large (48–714 times) decrease in undrained strength on remolding in comparison to Cochin and Mangalore clays (sensitivity ranges between 1 and 4). A preponderance of long‐range, interparticle forces reflected in the high consistency limits of Cochin and Mangalore clays (w_L range from 75 to 180%) combined with low natural water contents yield low liquidity indices (typically <1) and high, remolded, undrained strengths and are considered to be responsible for the low sensitivity of the Indian marine clays.     

Dissolved oxygen criteria for freshwater fish in New Zealand: a revised approach

Maintenance of suitable conditions in lowland rivers for both fish passage and resident species is crucial to ensuring the long-term sustainability of fish populations. The dissolved oxygen concentration of water is a key factor controlling habitat quality for fish and a critical measure of stream health. Continued land use intensification and greater exploitation of water resources has contributed towards increasing the frequency and duration of low dissolved oxygen events in lowland rivers and the associated risk of adverse effects on fish communities. Revised guidelines are therefore proposed to support setting of biologically relevant dissolved oxygen limits for the protection of New Zealand freshwater fish communities. These guidelines account for both event magnitude and duration, identify different protection levels based on the risk of negative impacts and are based on current scientific knowledge on the tolerances of New Zealand fish species.