沙丘不同部位土壤呼吸对人工降水的响应

 利用LI-8100土壤呼吸测量仪,对古尔班通古特沙漠南缘阜康北部地区沙丘不同部位（坡底、坡中、坡顶）的土壤呼吸速率进行了测量,探讨了沙丘不同部位土壤呼吸速率对降雨的响应,分析了土壤水分和土壤温度对土壤呼吸速率的影响。结果表明:①沙丘不同部位土壤呼吸速率的日变化呈“双峰曲线”,而增雨处理后,土壤呼吸速率的日变化曲线大部分转变为“单峰曲线”。②增雨处理增加了沙丘不同部位土壤呼吸速率的变化幅度、平均值和极差,推后了土壤呼吸速率最大值到来的时间。③土壤呼吸速率与土壤温度的相关性对降雨表现出积极的响应,降雨改变了土壤温度的日变化曲线类型,提高了土壤温度与土壤呼吸速率的相关系数。④非增雨处理时,沙丘坡底、坡中和坡顶的土壤呼吸速率与土壤水分的相关性系数均较高,而增雨处理后,土壤呼吸速率与土壤水分的相关系数有所下降,仅坡中的相关系数通过了α=0.01的显著性检验。     

Understanding historical coastal spit evolution: A case study from Spurn,East Yorkshire,UK

Globally sandy coastlines are threatened by erosion driven by climatic changes and increased storminess. Understanding how they have responded to past storms is key to help manage future coastal changes. Coastal spits around the world are particularly dynamic and therefore potentially vulnerable coastal features. Therefore, how they have evolved over the last few centuries is of great importance. To illustrate this, this study focuses on the historical evolution of a spit at Spurn on the east coast of the UK, which currently provides critical protection to settlements within the Humber estuary. Through the combination of digitized historical mapping and luminescence dating, this study shows that Spurn has been a consistent coastal feature over at least the past 440 years. No significant westward migration was observed for the last 200 years. Results show a long-term extension of the spit and a decrease in its overall area, particularly in the last 50 years. Breaches of the neck cause temporary sediment pathway changes enabling westward extension of the head. Use of digitized historical maps in GIS combined with OSL dating has allowed a more complete understanding of long-term spit evolution and sediment transport modes at Spurn. In doing so it helps inform future possible changes linked to pressures, such as increases in storm events and sea-level rise. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd     

The soils on the calcareous sand dunes southeast of South Australia

 The properties of soils on previously dated sand dunes from Robe to Naracoorte in South Australia were examined. In these areas younger sand dunes are composed of fresh sand, but older sand dunes are composed of calcarenited sand. The soils on the sand dunes developed successionally by the age of sand dunes. The soil properties of these sand dunes differ depending on the ages of the sand dunes. The properties of sand particles in soils are as follows: (1) On the sand dunes of 4300 years B.P., A/C profile developed (Rendzina). On the sand dunes older than 125 000 years B.P. and on the plateau of Tertiary limestone, soil profiles of A₁/AB/B/C on the sand dunes of 83 000 years B.P. and A₁/A₃/B₁/B₂/C (Terra rossa) are well developed. (2) Within the sand of A/C horizons of the sand dunes with the age of 4300 year B.P., the calcite grain content is about 64%, and the quartz content is about 35%. Within the B horizons of soils on the dunes from 83 000 years B.P. to 347 000 years B.P., the calcite grain content is only 1–2%; however, the quartz grain content is about 92%. In the B₂ horizons of soils on the dune of 690 000 years B.P. and on the Tertiary plateau, there are some calcite grains but the quartz grain content is about 96%. (3) The average size of quartz grains in the soils on the sand dunes from 4300 B.P. to 347 000 years B.P. is generally smaller, but the average size of quartz on the sand dunes of 690 000 year B.P. becomes larger and the grains are well rounded. On the Tertiary limestone plateau, the average quartz size becomes again smaller, and the grains are more rounded. (4) Fe_t in B₂ horizon of the soil profiles increases clearly corresponding to the age. Iron activity expressed by Fe_o/Fe_d also shows a close relation to the chronological sequence. The B horizon of the soil profiles shows a drastic decrease of Fe_o/Fe_d according to the age. Iron crystalinity, (Fe_d-Fe_o)/Fe_t, has a tendency for a positive relation with increasing age. Received: 1 June 1995 · Accepted: 4 December 1995     

Stemflow and throughfall in a tropical dry forest

The rainfall received by a small plot of tropical deciduous forest on sand dunes in Veracruz, Mexico, was partitioned into stemflow and throughfall components to determine whether funnelling by stemflow could reduce soil leaching by transmitting large volumes of water through vertical soil pathways beneath each stem. Although soil infiltration capacities were high, only a very small proportion of incoming rainfall was funnelled by canopy stems. This is attributed to the widely-branched morphology of mature trees. Smaller trees and shrubs were more effective funnellers of rainfall, and a crude estimate of the magnitude of stemflow in the understorey stratum in one rain event suggested a contribution approximately ten times that of canopy stemflow. However, even if augmented by the understorey stratum in this way, total stemflow is unlikely to have exceeded 10 per cent of gross precipitation, implying that it does not represent an important leaching-avoidance mechanism in this forest.     

Runoff generation in a sandy area—the nizzana sands,Western Negev,Israel

This paper presents the results of sprinkling experiments conducted over the lower part of vegetated and crusted linear dunes as well as over flat playa surfaces that appear in the interdune corridors. Data obtained show that these two surface units respond quickly to rainstorms. Runoff generation can be expected for any storm exceeding 2-3 mm and runoff coefficients are high. When the topsoil algal crust, 1 to 2 mm thick, is removed from the surface of the dune, infiltration increases drastically and eliminates any possibility of runoff generation under present-day rainfall conditions. This data may be of great help in the understanding of the geomorphology and sedimentary sequence of the corridors separting linear dunes.     

高分辨率遥感影像制作方法创新

随着卫星遥感获取技术的发展,运用遥感技术获取的影像资源日益丰富,特别是高分辨率遥感影像被列入国家重大工程建设以来,其在制作正射影像、三维模型、对地观测系统等方面作用突出,能够真实地反映研究地区地表的各种地理信息特点。与此同时,高分辨率遥感影像能够在实时状态下获取地理信息,可满足未来信息化战争、非战争军事行动等对地理环境保障提出的新要求。本文结合工作实际,对高分辨率遥感影像制作方法,以及影像制作中方案的改进进行探讨,取得了事半功倍的效果。     

东山岛以东近岸海域水下沙丘及其环境

1990～1991年，我所对东山岛海域进行海底地形、底质调查、水文泥沙测验时发现：1）沿东山岛一古雷半岛的NNE、NE向断裂在海域呈现为落差可达20m左右“V”字型深糟；2）在东山岛东部10m等深线以东海域发育众多的水沙丘群，水深15m左右有一地形坡折线，水深20～25m海底为水下一级阶地。据底质粒度、石英电镜扫描、重矿物、地球化学指标等分析表明，水下沙丘群分布区的沉积为准残留沉积，水下一级阶地及水下沙丘为早期滨岸的准残留地貌作，又受到后期现代水动力的改造。     

Ecogeomorphic state variables and phase‐space construction for quantifying the evolution of vegetated aeolian landscapes

Cellular automaton modelling for the simulation of dune field formation and evolution has developed progressively in aeolian geomorphology in the last decade or so. A model that incorporates the effects of vegetation and its interactions with geomorphic landscape development – the Discrete Ecogeomorphic Aeolian Landscapes (DECAL) model – can replicate a number of important visual and qualitative aspects of the complex evolution of aeolian dune landscapes under the influence of vegetation dynamics in coastal environments. A key challenge in this research area is the analysis and comparison of both simulated and real‐world vegetated dune landscapes using objective and quantifiable principles. This study presents a methodological framework or protocol for numerically quantifying various ecogeomorphic attributes, using a suite of mathematically defined landscape metrics, to provide a rigorous and statistical evaluation of vegetated dune field evolution. Within this framework the model parameter space can be systematically explored and simulation outcomes can be methodically compared against real‐world landscapes. Based on a simplified scenario of parabolic dunes developing out of blow‐outs the resulting dune field realizations are investigated as a function of variable growth vigour of two simulated vegetation types (pioneer grass and successional woody shrub) by establishing a typological phase‐diagram of different landscape classes. The set of simulation outcomes furthermore defines a higher‐dimensional phase‐space, whose axes or dimensions can be interpreted by analysing how individual ecogeomorphic landscape metrics, or state variables, contribute to the data distribution. Principal component analysis can reduce this to a visual three‐dimensional (3D) phase‐space where landscape evolution can be plotted as time‐trajectories and where we can investigate the effects of changing environmental conditions partway through a simulation scenario. The use of landscape state variables and the construction of a 3D phase‐space presented here may provide a general template for quantifying many other eco‐geomorphic systems on the Earth's surface. Copyright © 2010 John Wiley & Sons, Ltd.     

遥感影像在最大极值范围的并行稳定匹配

针对目前立体影像匹配时普遍存在的配准稳定性与配准精度不能同时兼顾问题,该文采用金字塔和分块策略,首先在多尺度空间下进行粗匹配,获得大量的初始特征点集;然后通过限制金字塔影像的阶数对初始特征点进行坏点剔除和滤点均匀化来获得良好的初始特征点;最后通过进行分块影像并行化SIFT算法匹配来实现精确匹配,提高效率.实验结果证明,此遥感立体影像并行稳定匹配方法能够提高匹配的效率,对影像的旋转、缩放和视角变换具有更强的抵抗性,其配准精度较高,适用于大范围的遥感立体影像的匹配.     

基于大倾角的角锥体空间后方交会研究

在摄影测量中,当倾角变大时,由于三角函数的多值性和奇异性导致传统的共线条件方程线性化的空间后方交会方法已经不能稳定地求解出摄影瞬间影像的外方位元素。文中通过对传统空间后方交会、基于单位四元素的空间后方交会和文中所用到的基于简化的DLT线性方程求解线元素初值的角锥体法比较发现,在像片倾角逐渐变大,传统方法和四元素法不能正确求解出外方位元素的情况下,基于角锥体法的空间后方交会仍能稳定、准确地求解出像片的外方位元素。