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1.
Using political ecology as its conceptual framework, this paper focuses on the changes in forest utilisation and management of South Kyrgyzstan's walnut-fruit forests over the last century The aim of this study on human-environment interactions is to investigate the relationship between actors on the one side, their interests and demands, and the forests and forested lands on the other. Forest resource utilisation and management - and even the recognition of different forest products as resources - are connected with political and socioeconomic conditions that change with time. The walnut-fruit forests of South Kyrgyzstan are unique, characterised by high biodiversity and a multiplicity of usable products; and they have been utilised for a long time. Centralised and formal management of the forests started with the Russian occupation and was strengthened under Soviet rule, when the region became a part of the USSR. During this era, a state forest administration that was structured from Moscow all the way down to the local level drew up detailed plans and developed procedures for utilising the different forest products. Since the collapse of the Soviet Union, the socio-political and economic frame conditions have changed significantly, which has brought not only the sweeping changes in the managing institutions, but also the access rights and interests in the forest resources. At present, the region is suffering from a high unemployment rate, which has resulted in the forests' gaining considerable importance in the livelihood strategies of the local population. Political and economic liberalization, increased communication and transregional exchange relations have opened the door for international companies and agents interested in the valuable forest products. Today, walnut wood and burls, walnuts, wild apples and mushrooms are all exported to various countries in the world. Scientists and members of various international organisations stress the ecological value of the forests and are trying to establish nature conservation areas. Nevertheless, it is to fear that a multiplicity of interrelated factors - the present transformation and globalization processes, the appearance of new actors, the local population's insecure economic situation and the erosion of managing institutions - are all leading to an intensified and unregulated exploitation of the forests, resulting in their degradation.  相似文献   
2.
山东半岛东部诸岛水域叶绿素—a含量和初级生产力   总被引:1,自引:0,他引:1  
据1990.11-1991年8月期间,山东半岛东部诸岛水域调查资料,分析了该水域叶绿素-a含量的时空分布和初级生产力的分布与变化,此分布与该水域的温度和营养盐水含量密切相关。叶绿素-a含量的季节变化分三种类型,年变幅为0.11-12.81mg/m^3,年平均值为1.17mg/m^3。初级生产力夏季〉春季〉秋季〉冬季,年变幅为23.00-791.60mg.c/m^2.d年平均为152.0mg.c/m  相似文献   
3.
北京云蒙山地区花岗岩穹隆及伸展构造的探讨   总被引:9,自引:0,他引:9  
张建新  曾令森 《地质论评》1997,43(3):232-240
北京云蒙山花岗岩为一中生代侵入的花岗岩穹隆,花岗岩穹隆的叶理普遍发育,叶理轨迹基本平行于穹隆的外部边界,并显示出从核部到边部逐渐增强,东南侧明显强于西北侧的特点。变形构造研究显示,花岗岩穹隆的边部及围岩中普遍存在不同层次及不同运动方向的伸展构造。东南侧以具河防口-水峪伸展型韧性剪切带为特征,剪切运动标志显示为从NW-SE的正剪切运动,有限应变分析估算其剪切位移量在10km以上,剪切带上部被河防口正  相似文献   
4.
黄海北部长山群岛海洋农牧化分区探讨   总被引:7,自引:0,他引:7  
张耀光 《地理学报》1991,46(1):47-56
本文采用主成分-聚类分析等定量方法,并通过对长山群岛海域的资源、环境、生产条件等的相似性和差异性分析,将其划分为三个海洋农牧化区域,为海水养殖业的合理布局提供科学依据。  相似文献   
5.
The Milos volcanic field includes a well-exposed volcaniclastic succession which records a long history of submarine explosive volcanism. The Bombarda volcano, a rhyolitic monogenetic center, erupted ∼1.7 Ma at a depth <200 m below sea level. The aphyric products are represented by a volcaniclastic apron (up to 50 m thick) and a lava dome. The apron is composed of pale gray juvenile fragments and accessory lithic clasts ranging from ash to blocks. The juvenile clasts are highly vesicular to non-vesicular; the vesicles are dominantly tube vesicles. The volcaniclastic apron is made up of three fades: massive to normally graded pumice-lithic breccia, stratified pumice-lithic breccia, and laminated ash with pumice blocks. We interpret the apron beds to be the result of water-supported, volcaniclastic mass-How emplacement, derived directly from the collapse of a small-volume, subaqueous eruption column and from syn-eruptive, down-slope resedimentation of volcaniclastic debris. During this eruptive phase, the activity could have involved a complex combination of phreatomagmatic explosions and minor submarine effusion. The lava dome, emplaced later in the source area, is made up of flow-banded lava and separated from the apron by an obsidian carapace a few meters thick. The near-vertical orientation of the carapace suggests that the dome was intruded within the apron. Remobilization of pyroclastic debris could have been triggered by seismic activity and the lava dome emplacement. Published online: 30 January 2003 Editorial responsibility: J. McPhie  相似文献   
6.
施雅风 《冰川冻土》1996,18(4):289-295
黄汲清院士是在多方面作出重大贡献的地质学大师,也是第四纪冰川研究的先驱者。他于1932 ̄1935年在瑞士完成博士论文期间,受到良好的冰川地质学训练。于1943 ̄1944年与合作者对天山南麓台兰河谷中游地质调查中,对冰碛与非冰碛沉积物进行仔细的正确的调查和精美的地质制图,撰写出高水平的论文,由此对中国第四纪冰川研究作出了重要贡献。他关注中国东部第四纪冰川研究的进展,指出忽视古气候研究是工作中的重要缺  相似文献   
7.
毛洋头铀(银,钼)矿床同位素地球化学研究   总被引:1,自引:0,他引:1  
毛洋头铀矿床的(H、O)同位素特征表明:早期矿化热液主要为岩浆水,而晚期矿化热液则主要为大气降水。铅同位素组成反映该矿床中铅为不同来源的混合铅。C、S同位素组成变化范围小,且与火成岩的C、S同位素组成相当,说明矿床中的碳和硫主要淋取于火成围岩或源于地壳深部。  相似文献   
8.
New structural and petrological data unveil a very complicated ductile deformation history of the Xiongdian-Suhe HP metamorphic unit, north-western Dabie Shun, central China. The finegrained symplectic amphibolite-facies assemblage and coronal structure enveloping eclogite-facies garnet,omphacite and phengite etc., representing strain-free decompression and retrogressive metamorphism,are considered as the main criteria to distinguish between the early-stage deformation under HP metamorphic conditions related to the continental deep subduction and collision, and the late-stage deformation under amphibolite to greenschist-facies conditions occurred in the post-eclogite exhumation processes.Two late-stages of widely developed, sequential ductile deformations D3 and D4, are recognized on the basis of penetrative fabrics and mineral aggregates in the Xiongdian-Suhe HP metamorphic unit, which shows clear, regionally, consistent overprinting relationships. D3 fabrics are best preserved in the Suhe tract of low post-D3 deformation intensity and characterized by steeply dipping layered mylonitic amphibolites associated with doubly vergent folds. They are attributed to a phase of tectonism linked to the initial exhumation of the HP rocks and involved crustal shortening with the development of upright structures and the widespread emplacement of garnet-bearing granites and felsic dikes. D4 structures are attributed to the main episode of ductile extension (D^24) with a gently dipping foliation to the north and common intrafolial, recumbent folds in the Xiongdian tract, followed by normal sense top-to-the northductile shearing (D^24) along an important tectonic boundary, the so-called Majiawa-Hexiwan fault (MHF), the westward continuation of the Balifan-Mozitan-Xiaotian fault (BMXF) of the northern Dabie Shan. It is indicated that the two stages of ductile deformation observed in the Xiongdian-Suhe HP metamorphic unit, reflecting the post-eclogite compressional or extrusion wedge formation, the subhorizontal ductile extension and crustal thinning as well as the top-to-the north shearing along the high-angle ductile shear zones responsible for exhumation of the HP unit as a coherent slab, are consistent with those recognized in the Dabie-Sulu UHP and HP metamorphic belts, suggesting that they were closely associated in time and space. The Xiongdian-Suhe HP metamorphic unit thus forms part of the Triassic(250-230 Ma) collision orogenic belt, and can not connect with the South Altun-North Qaidam-North Qinline UHP metamorphic belt formed durin~ the Early Paleozoic (500-400Ma).  相似文献   
9.
从土地利用转移类型、空间格局变化定量分析、动态变化预测模型等方面分析近20年都安土地利用变化,进而对其生态环境质量变化进行定量分析,得出结论:都安各乡(镇)生态环境质量改善与恶化在很大程度取决于裸岩地扩展与收缩,土地利用时空变化与区域生态环境质量的区域差异有很大相关性。  相似文献   
10.
Staurolite–cordierite assemblages are common in mica schists of the Aston and Hospitalet gneiss domes of the central Axial Zone, Pyrenees (France, Andorra). Within a 200 m wide zone, staurolite, cordierite and andalusite porphyroblasts contain inclusion trails that preserve the same stage of development of a crenulation cleavage, strongly suggesting that all three phases are contemporaneous. Their syntectonic growth occurred during a short period at the beginning of the formation of the dominant schistosity (S2) of the domes. Staurolite and cordierite touching each other further indicates an equilibrium relationship. Whole‐rock analyses show that some staurolite–cordierite schists are depleted in K2O compared to post‐Archean shales (PAAS) and amphibolite facies pelites. Analysis of the st‐crd paragenesis in K‐poor schists without muscovite using KFMASH and MnNCKFMASH petrogentic grids, pseudosections and AFM compatibility diagrams predicts stable conditions at pressures of ~3.5 kbar at 575 °C. For metapelites with intermediate XMg values (0.7 >  XMg >0.48) a ‘muscovite‐out window’ exists from 550–650 °C at 3.5 kbar in the KFMASH system. Conventional thermobarometry (GB‐GASP, AvT‐AvP) and petrogenetic grids show an isobaric P–T path to peak temperatures of ~650 °C, supported by the presence of sillimanite‐K‐feldspar gneiss and migmatites. LP‐HT metamorphism in the Aston dome is related to early Carboniferous (c. 339 Ma) granitic intrusions into the dome core. As metamorphism is directly linked with the formation of the main S2 schistosity, the temporal relations demonstrated in this study conflict with previous studies which constrained LP‐HT metamorphism and the development of flat‐lying schistosity to the late Carboniferous (315–305 Ma) – at least in the eastern Axial Zone.  相似文献   
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