黄土高原沟壑区小流域不同地形下土壤性质分布特征

地形条件是影响黄土高原地区土壤性质分布的主要因素,研究不同地形条件下土壤性质的分布是合理评价黄土区土壤质量状况的重要前提。论文研究了黄土高原沟壑区小流域地形条件对土壤性质剖面分布的影响,结果表明土壤硝态氮、速效磷、碱性磷酸酶和蔗糖酶为高度变异的土壤性质;pH值和过氧化氢酶为小变异土壤性质。塬面和沟道土壤pH值和过氧化氢酶活性较低,阳离子交换量较高。土壤有机质、全氮、全磷、速效磷、碱性磷酸酶和蔗糖酶活性在土壤剖面随土层深度的增加逐渐降低,且均表现为塬面>梯田>坡地>沟道的趋势。不同地形条件下土壤pH值的变化由地形条件引起的土壤过程及硝态氮在土壤中的累积引起;阳离子交换量的变化由成土过程、pH值和有机质的差异引起;土壤有机质及氮、磷养分的差异由与地形条件对应的土地利用方式引起;土壤酶活性的差异则是有机质的差异引起的。

黄土高原森林水文生态效应和林草适宜覆盖指标

概述了黄土高原森林各层次的水文生态功能和水土保持效益。在此基础上 ,根据自然条件、地形地貌和国民经济发展要求 ,提出了为保护生态环境和协调经济发展的适宜林草覆盖指标

Modelling raindrop impact and splash erosion processes within a spatial cell: a stochastic approach

A new approach is proposed to simulate splash erosion on local soil surfaces. Without the effect of wind and other raindrops, the impact of free-falling raindrops was considered as an independent event from the stochastic viewpoint. The erosivity of a single raindrop depending on its kinetic energy was computed by an empirical relationship in which the kinetic energy was expressed as a power function of the equivalent diameter of the raindrop. An empirical linear function combining the kinetic energy and soil shear strength was used to estimate the impacted amount of soil particles by a single raindrop. Considering an ideal local soil surface with size of I m x I m, the expected number of received free-failing raindrops with different diameters per unit time was described by the combination of the raindrop size distribution function and the terminal velocity of raindrops. The total splash amount was seen as the sum of the impact amount by all raindrops in the rainfall event. The total splash amount per unit time was subdivided into three different components, including net splash amount, single impact amount and re-detachment amount. The re-detachment amount was obtained by a spatial geometric probability derived using the Poisson function in which overlapped impacted areas were considered. The net splash amount was defined as the mass of soil particles collected outside the splash dish. It was estimated by another spatial geometric probability in which the average splashed distance related to the median grain size of soil and effects of other impacted soil particles and other free-falling raindrops were considered. Splash experiments in artificial rainfall were carried out to validate the availability and accuracy of the model. Our simulated results suggested that the net splash amount and re-detachment amount were small parts of the total splash amount. Their proportions were 0.15% and 2.6%, respectively. The comparison of simulated data with measured data showed that this model could be applied to simulate the soil-splash process successfully and needed information of the rainfall intensity and original soil properties including initial bulk intensity, water content, median grain size and some empirical constants related to the soil surface shear strength, the raindrop size distribution function and the average splashed distance. Copyright (c) 2007 John Wiley & Sons, Ltd.

The characteristics of land cover and macroscopical ecology changes in the source region of three rivers in Qinghai-Tibet plateau during last 30 years

We obtained four phases of land cover spatial data sets by interpreting MSS images of middle and late 1970s and three phases of TM images of late 1980s, 2004 and 2008 based on field investigation in Three Rivers' Source Region. We analyzed the temporal and spatial characteristics of land cover and macro ecological changes in Three Rivers' Source Region in Qinghai-Tibet plateau since middle and late 1970s. Indicated by land cover condition index change rate and land cover change index, land cover and macroscopical ecological condition degenerated (7090 period Zc -0.63, LCCI -0.58)-obviously degenerated (9004 period, Zc -0.94, LCCI -1.76)-slightly meliorated (0408 period, Zc 0.06, LCCI 0.33). This course was jointly driven by climate change, grassland stocking pressure and implement of ecological construction project.

淤泥质潮滩地貌的遥感研究－以苏北辐射沙洲海岸为例

本文以具有典型特征的苏北淤泥质潮滩海岸作为研究区，利用1975-2003年间14景覆盖该地区的Landsat和SPOT卫星影像作为主要数据源，结合地面调查和验证工作，在遥感影像处理和地理信息系统分析技术的支持下，对区内潮滩、岸线、水边线和盐沼植被等进行遥感解译，分析苏北辐射沙脊群和沿岸地貌的空间分布特征和动态演变趋势。研究结果表明：苏北辐射沙脊群海域的潮汐水位过程的不同步现象普遍存在，限制了常规遥感数据在苏北潮滩地貌研究中的适用范围和解译精度；在人工判别的辅助下，多光谱遥感的非监督分类方法可以有效解译淤泥质潮滩的水边线；利用修改型土壤调整植被指数（MSAVI）可以较好地提取潮滩上的盐沼植被信息；苏北沿岸潮滩的快速淤长促进了盐沼植被带向海侧快速扩展，近年来持续的潮滩围垦工程则不断从陆侧侵占盐沼植被带，使盐沼植被带宽度减小乃至消失；在大规模人类活动和自然条件的共同影响下，苏北辐射沙脊群海岸的岸线发育趋于平直化，无序的潮滩围垦项目使得可垦滩地资源被过度消耗；1975～2002年间，研究区北部和南部沿岸的高潮滩整体上处于淤长状态，中部沿岸潮滩和离岸沙洲高潮滩则被大面积侵蚀；1999年以来，研究区内低潮滩部位开始形成有序排列的滩面地物，并表现出逐年大面积蔓延的趋势，可能是滩涂紫菜养殖区扩展的结果。

基于结构分析地震资料去噪方法研究

With the development of oil and gas exploration, the exploration of the continental oil and gas turns into the exploration of the subtle oil and gas reservoirs from the structural oil and gas reservoirs in China. The reserves of the found subtle oil and gas reservoirs account for more than 60 percent of the in the discovered oil and gas reserves. Exploration of the subtle oil and gas reservoirs is becoming more and more important and can be taken as the main orientation for the increase of the oil and gas reserves. The characteristics of the continental sedimentary facies determine the complexities of the lithological exploration. Most of the continental rift basins in East China have entered exploration stages of medium and high maturity. Although the quality of the seismic data is relatively good, this areas have the characteristics of the thin sand thickness, small faults, small range of the stratum. It requests that the seismic data have high resolution. It is a important task how to improve the signal/noise ratio of the high frequency of seismic data. In West China, there are the complex landforms, the deep embedding the targets of the prospecting, the complex geological constructs, many ruptures, small range of the traps, the low rock properties, many high pressure stratums and difficulties of boring well. Those represent low signal/noise ratio and complex kinds of noise in the seismic records. This needs to develop the method and technique of the noise attenuation in the data acquisition and processing. So that, oil and gas explorations need the high resolution technique of the geophysics in order to solve the implementation of the oil resources strategy for keep oil production and reserves stable in Ease China and developing the crude production and reserves in West China. High signal/noise ratio of seismic data is the basis. It is impossible to realize for the high resolution and high fidelity without the high signal/noise ratio. We play emphasis on many researches based on the structure analysis for improving signal/noise ratio of the complex areas. Several methods are put forward for noise attenuation to truly reflect the geological features. Those can reflect the geological structures, keep the edges of geological construction and improve the identifications of the oil and gas traps. The ideas of emphasize the foundation, give prominence to innovate, and pay attention to application runs through the paper. The dip-scanning method as the center of the scanned point inevitably blurs the edges of geological features, such as fault and fractures. We develop the new dip scanning method in the shap of end with two sides scanning to solve this problem. We bring forward the methods of signal estimation with the coherence, seismic wave characteristc with coherence, the most homogeneous dip-sanning for the noise attenuation using the new dip-scanning method. They can keep the geological characters, suppress the random noise and improve the s/n ratio and resolution. The rutine dip-scanning is in the time-space domain. Anew method of dip-scanning in the frequency-wavenumber domain for the noise attenuation is put forward. It use the quality of distinguishing between different dip events of the reflection in f-k domain. It can reduce the noise and gain the dip information. We describe a methodology for studying and developing filtering methods based on differential equations. It transforms the filtering equations in the frequency domain or the f-k domain into time or time-space domains, and uses a finite-difference algorithm to solve these equations. This method does not require that seismic data be stationary, so their parameters can vary at every temporal and spatial point. That enhances the adaptability of the filter. It is computationally efficient. We put forward a method of matching pursuits for the noise suppression. This method decomposes any signal into a linear expansion of waveforms that are selected from a redundant dictionary of functions. These waveforms are chosen in order to best match the signal structures. It can extract the effective signal from the noisy signal and reduce the noise. We introduce the beamforming filtering method for the noise elimination. Real seismic data processing shows that it is effective in attenuating multiples and internal multiples. The s/n ratio and resolution are improved. The effective signals have the high fidelity. Through calculating in the theoretic model and applying it to the real seismic data processing, it is proved that the methods in this paper can effectively suppress the random noise, eliminate the cohence noise, and improve the resolution of the seismic data. Their practicability is very better. And the effect is very obvious.

Quaternary palaeogeomorphologic evolution of the Wadi Faynan area, Southern Jordan

McLaren, S. Gilbertson, D. Grattan, J. Hunt, C. Duller, G. Barker, G. Quaternary palaeogeomorphologic evolution of the Wadi Faynan area, Southern Jordan. Palaeogeography, Palaeoclimatology, Palaeoecology. 2004. 205. pp 131-154

Volcanic rifting at Martian grabens

Cook, Anthony; Mege, D.; Garel, E.; Lagabrielle, Y., (2003) 'Volcanic rifting at Martian grabens', Journal of Geophysical Research 108(E5) pp. 1-33 RAE2008

Shore Shapers: Introducing children and the general public to biogeomorphological processes and geodiversity

Coastal processes and wildlife shape the coast into a variety of eye-catching and enticing landforms that attract people to marvel at, relax and enjoy coastal geomorphology. These landforms also influence biological communities by providing habitat and refuge. There are very few field guides to explain these processes to the general public and children. In contrast, there is a relative wealth of resources and organised activities introducing people to coastal wildlife, especially on rocky shores. These biological resources typically focus on the biology and climatic controls on their distribution, rather than how the biology interacts with its physical habitat. As an outcome of two recent rock coast biogeomorphology projects (detailed at: www.biogeomorph.org/coastal) a multi disciplinary team produced the first known guide to understanding how biogeomorphological processes help create coastal landforms. The ‘Shore Shapers’ guide (shoreshapers.org) is designed to: a. bring biotic geomorphic interactions (how animals, algae and microorganisms protect and shape rock) to life and b. introduce some of the geomorphological and geological controls on biogeomorphic processes and landform development. The guide provides scientific information in an accessible and interactive way – to help sustain children’s interest and extend their learning. We tested a draft version of the guide with children,the general public and volunteers on rocky shore rambles using social science techniques and present the findings, alongside initial results of an evaluation of a newer version of the guide and interactive workshops taking place throughout 2014.

A method for semi-automated objective quantification of linear bedforms from multi-scale Digital Elevation Models

The increasing availability of large, detailed digital representations of the Earth’s surface demands the application of objective and quantitative analyses. Given recent advances in the understanding of the mechanisms of formation of linear bedform features from a range of environments, objective measurement of their wavelength, orientation, crest and trough positions, height and asymmetry is highly desirable. These parameters are also of use when determining observation-based parameters for use in many applications such as numerical modelling, surface classification and sediment transport pathway analysis. Here, we (i) adapt and extend extant techniques to provide a suite of semi-automatic tools which calculate crest orientation, wavelength, height, asymmetry direction and asymmetry ratios of bedforms, and then (ii) undertake sensitivity tests on synthetic data, increasingly complex seabeds and a very large-scale (39 000km2) aeolian dune system. The automated results are compared with traditional, manually derived,measurements at each stage. This new approach successfully analyses different types of topographic data (from aeolian and marine environments) from a range of sources, with tens of millions of data points being processed in a semi-automated and objective manner within minutes rather than hours or days. The results from these analyses show there is significant variability in all measurable parameters in what might otherwise be considered uniform bedform fields. For example, the dunes of the Rub’ al Khali on the Arabian peninsula are shown to exhibit deviations in dimensions from global trends. Morphological and dune asymmetry analysis of the Rub’ al Khali suggests parts of the sand sea may be adjusting to a changed wind regime from that during their formation 100 to 10 ka BP.

Control estructural de agrietamientos poligonales en la Pedriza del Manzanares (Madrid)

Los agrietamientos poligonales representan una forma común de modelado granítico cuyo origen y evolución continúa en fase de estudio, no existiendo una sistematización de estas estructuras diversas. Algunos autores explican su origen por procesos geodinámicos internos, relacionándolo con movimientos de planos de fractura en estados tardíos de consolidación magmática. Otros autores atribuyen su formación y desarrollo a factores externos relacionados con el régimen climático. La gran variedad de agrietamientos poligonales requiere la utilización de un número mayor de variables para definir los distintos orígenes, y las posibles interrelaciones entre los factores externos e internos, así como para explicar la evolución de dichas estructuras y avanzar en la clasificación de los patrones concretos. Este trabajo pretende contribuir a sistematizar los mecanismos que intervienen en el desarrollo de agrietamientos poligonales. Para ello se estudian únicamente agrietamientos poligonales formados sobre planos de fractura verticales o subverticales. En particular se establecen relaciones entre la presencia de agrietamientos poligonales y la red de fracturación, la altura de aparición, la orientación e inclinación de la pared, la morfología de las placas y la profundidad de incisión de las grietas perimetrales. Por otra parte, establece relaciones entre procesos geodinámicos internos y procesos de meteorización externos.