International wood trade and forest change: A global analysis     

Thomas Kastner  Karl-Heinz ErbSanderine Nonhebel 《Global Environmental Change》2011,21(3):947-956

Throughout history, humans have transformed natural forests into agricultural land, settlement areas and managed forests. Studies on the dynamics of forest change are one of the mainstays in land change science. The forest transition theory offers a powerful tool to analyze changes in human interference with forests. At the national level, a range of factors have been found to influence a country's forest change. The role of international wood product trade has, however, rarely been studied based on empirical data. We offer a global assessment of how this trade helps shape observed forest change, by relating forest stock change to net trade of wood products for the period 1997-2007 and by localizing the origin of wood consumed in a given nation. For many nations, traded wood products have a relevant impact on the course of ongoing forest transitions. We develop a general typology of how wood product trade can influence forest change and place various nations within this framework. We find that many wealthy nations with returning forests seem to accelerate this return by importing wood products. These imports appear to be provided by two main types of wood exporters: (a) by wealthy countries with low population densities and stable forests and (b) by relatively poor countries with declining forests, employing increasing population and welfare levels. We discuss these findings in the light of general theories on land use transitions and forest change and conclude by highlighting implications for national forest policies and global environmental governance, aiming at reducing negative impacts of wood products and enhancing the positive role they can play in replacing more fossil fuel intensive products.  相似文献   

The Campanian Ignimbrite (Y5) tephra at Crvena Stijena Rockshelter, Montenegro     

Mike W. Morley  Jamie C. Woodward 《Quaternary Research》2011,75(3):683-696

Clearly defined distal tephras are rare in rockshelter sediment records. Crvena Stijena, a Palaeolithic site in Montenegro, contains one of the longest (> 20 m) rockshelter sediment records in Europe with deposits ranging in age from Middle Pleistocene to mid-Holocene. A distinctive tephra is clearly exposed within the well stratified record approximately 6.5 m below the present land surface. We present geochemical data to confirm that this tephra is a distal equivalent of the Campanian Ignimbrite deposits and a product of the largest Late Pleistocene eruption in Europe. Originating in the Campanian volcanic province of southwest Italy, this tephra has been independently dated to 39.3 ka. It is a highly significant chronostratigraphic marker for southern Europe. Macrostratigraphic and microstratigraphic observations, allied with detailed particle size data, show that the tephra layer is in a primary depositional context and was transported into the rockshelter by aeolian processes. This site is unique because the tephra forms an abrupt boundary between the Middle and Upper Palaeolithic records. Before they can be used as chronostratigraphic markers in rockshelter and cave-mouth environments, it is essential to establish the stratigraphic integrity of distal tephras and the mechanisms and pathways involved in their transport and deposition.  相似文献   

A new approach for phase transitions in miscible multi-phase flow in porous media   总被引：1，自引：0，他引：1  

A. Lauser  C. Hager 《Advances in water resources》2011,34(8):957-966

The tightly coupled, strongly nonlinear nature of non-isothermal multi-phase flow in porous media poses a tough challenge for numerical simulation. This trait is even more pronounced, if miscibility is also considered. A primary reason why inclusion of miscibility tends to be problematic are the difficulties stemming from phase transitions: on the one hand, phase transitions need to be included since the presence or absence of fluid phases has a major impact on the flow behavior; on the other hand, convergence of the nonlinear solver may be severely affected if they are not handled robustly.In this work, we present a mathematically sound approach to include phase transitions in the nonlinear system of equations: first, the transition conditions are formulated as a set of local inequality constraints, which are then directly integrated into the nonlinear solver using a nonlinear complementarity function. Under this scheme, Newton-Raphson solvers exhibit considerably more robust convergence behaviour compared to some previous approaches, which is then illustrated by several numerical examples.  相似文献   

岩浆到热液演化的包裹体记录——以骑田岭花岗岩体为例   总被引：3，自引：2，他引：1  

单强  廖思平  卢焕章  李建康  杨武斌  罗勇 《岩石学报》2011,27(5):1511-1520

骑田岭花岗岩是燕山期花岗岩早期多阶段侵入复式岩体,岩石化学的研究表明它是富碱的、高分异的A型花岗岩,形成于板内拉张的构造环境。在其第二阶段中细粒黑云母花岗岩内广泛发育着厘米级至米级似伟晶岩囊状体和石英晶洞, 它们是富挥发份岩浆固结的产物,代表岩石形成过程经历了明显的岩浆-热液过渡阶段。包裹体显微岩相学研究在骑田岭黑云母花岗岩的石英中发现熔体-流体包裹体和流体包裹体共存,这一结果进一步证实骑田岭中细粒黑云母花岗岩中的似伟晶岩囊状体和石英晶洞是花岗质熔体在岩浆-热液过渡阶段的产物。显微测温结果显示,熔体-流体包裹体的捕获温度大于530℃,说明岩浆热液过渡阶段的温度不低于该温度;闪锌矿中流体包裹体的均一温度在285~417℃之间,盐度为11.7% NaCleqv,代表了成矿流体的温度和盐度;流体包裹体的均一温度为172~454℃,代表热液阶段流体的温度。从中细粒黑云母花岗岩到似伟晶岩囊状体再到石英晶洞,岩浆-热液体系经历了富挥份熔体→熔体+高盐度流体→高盐度流体→低盐度流体的完整演化过程,形成了CaCl₂-NaCl-H₂O-CO₂体系的岩浆热液流体。包裹体岩相学及激光拉曼探针分析结果显示,在流体包裹体和多晶熔体-流体包裹体中含有长石、方解石、金红石及金属氧化物等子矿物,暗示其所捕获的流体具有较强的成矿能力。  相似文献   

陕西陈耳金矿床不同构造－岩相带微量元素地球化学特征及构造控矿机理   总被引：1，自引：1，他引：0       下载免费PDF全文

李建波蒋振频  鲁勇花郭 磊 史兴俊 曾 涛 《中国地质》2011,38(6):1551-1561

通过对陈耳金矿床两类不同构造-岩相带微量元素分布特征分析,发现元素特别是成矿元素Au的含量从片理化带→破碎蚀变带→石英脉逐渐增强。构造-岩相带内变形岩石的石英Rf/φ法有限应变测量表明,片理化带应变强度最大,破碎蚀变带应变强度小,应变集中在韧性剪切带边部的片理化带内。R型聚类分析表明Au与Ag、Cu、Pb及Zn的相关系数远大于Au与Ni、Co元素的相关系数,甚至接近于1。研究认为:破碎蚀变带内由于应变软化导致脆性裂隙大量发育,易于成矿流体的迁入与淀积而强富集;片理化带由于应变集中,造成成矿流体的迁出而弱富集。韧性剪切带脆-韧性变形转换不仅控制了矿体就位空间,同时也决定着元素迁移的方向。  相似文献   

热液矿床水相变控矿理论初探   总被引：2，自引：0，他引：2  

胡宝群  吕古贤  孙占学  李满根  廖玉婷  郭国林  白丽红 《地质通报》2011,30(4):565-572

在综合水物理化学性质、热液矿床、溶解度实验研究等资料的基础上,曾提出热液矿床水相变控矿理论框架.在此进一步完善该理论:①当水发生相变时可引起热容、水中矿质溶解度、压缩系数、膨胀系数等物理化学性质突变,特别是在临界点处二级相变时还出现"临界奇异性"、部分参数趋于无穷大,与水在非相变区物理化学性质的小幅度渐变区剐明显,必将...  相似文献   

http://www.sciencedirect.com/science/article/pii/S1674987110000149     

Xiang Wu  Shan Qin  Leonid Dubrovinsky 《地学前缘(英文版)》2011,2(1):107-114

The structural stability of manganese titanate MnTiO3 at high pressure was investigated by X-ray diffraction and Raman spectroscopy with diamond anvil cells. Ilmenite-type MnTiO3 is stable at least to 26.6 GPa, and lithium niobate type MnTiO3 reversibly transforms at room temperature to perovskite at 2.0 GPa. Bulk moduli (K300) of ilmenite, lithium niobate and perovskite are 174(4) GPa, 179(8) GPa, and 208(5) GPa, respectively (at fixed first pressure derivative K′ = 4). The Grüneisen parameter γ has been estimated to be 1.28 for ilmenite and 1.75 for perovskite. In ilmenite phase, TiO6 octahedra become more regular with increasing pressure. In perovskite phase structural distortion increases with pressure increase.  相似文献   

温度和光照对孔石莼光合作用的影响   总被引：1，自引：0，他引：1  

潘光华  高山  王广策  解修俊 《海洋科学》2011,35(9):14-17

采用叶绿素荧光分析技术对孔石莼（Ulva pertusa）在不同温度及光照强度影响下的光合作用活性进行研究。结果表明孔石莼在温度相对较低的10℃和20℃下光合活性较强,而在较高的30℃下,光合作用受到抑制,处于光抑制状态的藻体能够通过加强自身热耗散以及启动光系统间的状态转换来实现逆境下的光保护,孔石莼对光照依赖性较低,...  相似文献   

1005号热带气旋“乌鲁伊”移动路径分析     

魏新  王力群  曹洋  李海宁 《台湾海峡》2011,30(4):498-506

利用欧洲格点资料,应用天气学方法,从环流场演变、B效应、不对称结构等方面对1005号热带气旋“乌鲁伊”活动过程进行了分析,探讨了“乌鲁伊”不同阶段路径变化的原因．结果表明,澳大利亚大陆高压维持稳定以及热带气旋“托马斯”与“乌鲁伊”之间的相互作用是“乌鲁伊”西行北抬的根本原因．在“乌鲁伊”台风西行过程中,中高纬度环流场进行强烈调整是引起“乌鲁伊”移动路径南翘西折的关键,大陆高压在低纬向“乌鲁伊”北侧嵌入、以及地面气压场上从北指向南的气压梯度力突然增强,对热带气旋“乌鲁伊”移动路径南翘有直接影响．对西风指数的分析表明,“乌鲁伊”的南翘过程与西风指数从最低值484．4m。／s。向644．3m。／s。升高过程相对应,“乌鲁伊”移动路径西折与西风指数维持在644．3m。／s。以上有关．500hPa位势高度梯度场分析表明,热带气旋“乌鲁伊”从东向西、向南、向西南稳定移动过程中,东南侧和西北侧等梯度线中心数值的差值几乎为0,呈现出对称分布的特点;在热带气旋“乌鲁伊”南翘、西折时,东南侧与西北侧等梯度线数值发生显著变化,南翘时差值为一16．6m／s。,西折时差值则为12．0m／s。．500hPa位势高度梯度场的变化对“乌鲁伊”南翘西折路径具有很好的预示作用．  相似文献   

空间的文化解读与转型期中国的和谐发展     

孔翔  苗长松 《世界地理研究》2011,20(2):154-161

20世纪80年代以来,西方社会文化地理学的研究逐步由文化的空间研究转向空间的文化研究,以文化的视角解读空间成为新文化地理学的重要研究特色,并由此赋予了文化地理学以新的广阔研究空间。本文在解析新文化地理学“解读空间”特色的基础上,着重探索了解读空间对于中国社会文化地理学发展的借鉴意义,强调应该结合转型期中国的特殊语境进行文化空间的解读,以适应中国在工业化、城市化、国际化、现代化和生态化背景下谋求经济社会和谐发展的特殊要求。  相似文献