吉林省西部沙化土地持续农业体系建立的实践

吉林省沙化土地的８７．９％分布在吉林省西部白城、松原半干旱地区，统属科尔沁和松嫩沙地，面积９２１６．５ｋｍ２，占吉林省西部总面积的１９．６％。８年（１９８６年～１９９３年）实践证明：针对沙地环境特点建立的“乔、灌、草”、“果、药、杂”、“田、林、草”为主体的三种持续农业体系效果明显。     

Unsiting Nuclear Power Plants: Decommissioning Risks and Their Land Use Context*

Nuclear power plant siting provided the first significant public opportunity to examine nuclear safety and to affect nuclear policy. These discussions were prompted and fueled by perceptions of nuclear risk. Now, as we begin the process of nuclear decommissioning, we are finding that power plant removal—unsiting–is also likely to attract public interest. This paper presents a preliminary survey of how we are likely to react to this emerging theme, applying these findings within a land use context to see if it is likely to produce issues salient to the public. In so doing it also examines how these issues could affect decommissioning timing and type. It suggests that the most likely prospect is that power plants will remain on the landscape long after they are closed.     

Modelling of soil temperature profiles using data from the pilot experiment at Anand

We present some preliminary results from a multi-layer soil temperature finite-difference model using the data set obtained during the pilot experiment on land surface processes at Anand. We hope that the present results will prove useful during the final field experiments scheduled for the coming monsoon season.     

Subduction,mega-shear systems and Late Palaeozoic basin development in the African segment of Gondwana

 Basins within the African sector of Gondwana contain a Late Palaeozoic to Early Mesozoic Gondwana sequence unconformably overlying Precambrian basement in the interior and mid-Palaeozoic strata along the palaeo-Pacific margin. Small sea-board Pacific basins form an exception in having a Carboniferous to Early Permian fill overlying Devonian metasediments and intrusives. The Late Palaeozoic geographic and tectonic changes in the region followed four well-defined consecutive events which can also be traced outside the study area. During the Late Devonian to Early Carboniferous period (up to 330 Ma) accretion of microplates along the Patagonian margin of Gondwana resulted in the evolution of the Pacific basins. Thermal uplift of the Gondwana crust and extensive erosion causing a break in the stratigraphic record characterised the period between 300 and 330 Ma. At the end of this period the Gondwana Ice Sheet was well established over the uplands. The period 260–300 Ma evidenced the release of the Gondwana heat and thermal subsidence caused widespread basin formation. Late Carboniferous transpressive strike-slip basins (e.g. Sierra Australes/Colorado, Karoo-Falklands, Ellsworth-Central Transantarctic Mountains) in which thick glacial deposits accumulated, formed inboard of the palaeo-Pacific margin. In the continental interior the formation of Zambesi-type rift and extensional strike-slip basins were controlled by large mega-shear systems, whereas rare intracratonic thermal subsidence basins formed locally. In the Late Permian the tectonic regime changed to compressional largely due to northwest-directed subduction along the palaeo-Pacific margin. The orogenic cycle between 240 and 260 Ma resulted in the formation of the Gondwana fold belt and overall north–south crustal shortening with strike-slip motions and regional uplift within the interior. The Gondwana fold belt developed along a probable weak crustal zone wedged in between the cratons and an overthickened marginal crustal belt subject to dextral transpressive motions. Associated with the orogenic cycle was the formation of mega-shear systems one of which (Falklands-East Africa-Tethys shear) split the supercontinent in the Permo-Triassic into a West and an East Gondwana. By a slight clockwise rotation of East Gondwana a supradetachment basin formed along the Tethyan margin and northward displacement of Madagascar, West Falkland and the Gondwana fold belt occurred relative to a southward motion of Africa. Received: 2 October 1995 / Accepted: 28 May 1996     

Causes of Land Subsidence in the Kingdom of Saudi Arabia

The occurrence of land subsidence in the Kingdom Saudi Arabia is either natural or man-made. Natural land subsidence occurs due to the development of subterranean voids by a solution of host rocks in carbonate and evaporite terrains, over many areas of Saudi Arabia. Man-induced land subsidence is either due to the removal of groundwater in the agricultural areas or to wetting of unstable soils. Therefore, earth fissures and a lowering of the ground surface in unconsolidated sediments took place in alluvial plains and volcanic vent terrains. Unstable soils include Sabkha soils and loess sediments. These types of soils occur in coastal plains, desert areas and volcanic terrains. When this soil is wetted either during agricultural activities, waste disposal or even during a rain storm, subsidence takes place due to either the removal of salts from the Sabkha soil or the rearrangement of soil particles in loess sediments.     

我国北方农牧交错带的环境演变

中国北方农牧交错带在１０～８．５ｋａＢ．Ｐ．经历了三次阶段性增暖后进入全新世暖期。８．５～８．０ｋａＢ．Ｐ．和４～３．５ｋａＢ．Ｐ．暖期的开始与结束事件中降水变化落后于温度变化３００～５００ａ；暖期盛期时的年均温较现代高２～３℃，降水多１００ｍｍ左右；暖期中存在多次短期寒冷事件，年均温最冷时较现代低３℃以上。３．５ｋａＢ．Ｐ．以来冷干趋势之上叠加着大致由３００ａ稳定与５００ａ波动构成的约８００ａ的周期性变化。全新世暖期原始农业文化的阶段性发展与暖期内环境波动相对应；暖期结束时发生了由农业向牧业文化转换的事件；暖期以后的冷干期为农牧交错文化时期，农业经济随冷干程度的变化而兴衰     

Simulation Experiments of Land Surface Physical Processes and Ecological Effect over Different Underlying Surface

Based on the existing Land Surface Physical Process Models(Deardorff, Dickinson, LIU, Noilhan, Seller, ZHAO), a Comprehensive Land Surface Physical Process Model (CLSPPM) is developed by considering the different physical processes of the earth‘s surface-vegetation-atmosphere system more completely. Compared with SiB and BATS, which are famous for their detailed parameterizations of physical variables, this simplified model is more convenient and saves much more computation time. Though simple, the feas...     

建设用地地质灾害危险性评估中几个问题的思考

结合工作实践，就建设用地地质灾害危险性评估及其成果审查工作中经常遇到的5个问题——评估灾害类型的确定原则，评估区环境条件分析深度的把握，现状、预测及综合地质灾害危险性评估内容的侧重点，土地适宜性评价的依据以及优秀评估成果的判定标准，提出了个人的理解和认识。供从事类似工作的同志参考。     

Method of high-density seismic imaging ex-ploration and application samples

Introduction Now, shallow seismic reflection wave technique has been used extensively in geological ex-plorations of bridge, dam, high building and so on. Since shallow seismic reflection wave tech-nique is often implemented in industrial zone or city with dense population, the background dis-turbance including industrial noise, life noise, etc is very serious. Furthermore, the disturbance of seismic source is also serious due to short array length and offset of the method. In general, shal-lo…