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In this study our main objective was to quantify water interrill erosion in the sloping lands of Southeast Asia, one of the most bio‐geochemically active regions of the world. Investigations were performed on a typical hillslope of Northern Laos subjected to slash and burn agriculture practiced as shifting cultivation. Situations with different periods of the shifting cultivation cycle (secondary forest, upland rice cultivation following a four‐year fallow period and three‐year continuous upland rice cultivation) and soil orders (Ultisols, Alfisols, Inceptisols) were selected. One metre square micro‐plots were installed to quantify the soil material removed by either detachment of entire soil aggregate or aggregate destruction, and the detached material transported by thin sheet flow, the main mechanisms of interrill erosion. In addition, laboratory tests were carried out to quantify the aggregate destruction in the process of water erosion by slaking, dispersion and mechanical breakdown. The average runoff coefficient (R) evaluated throughout the 2002 rainy season was 30·1 per cent and the interrill erosion was 1413 g m?2 yr?1 for sediments and 68 g C m?2 yr?1 for soil organic carbon, which was relatively high. Among the mechanisms of interrill water erosion, aggregate destruction was low and mostly caused by mechanical breakdown due to raindrops, thus leading to the conclusion that detachment and further transport by the shallow runoff of macro‐aggregates predominates. R ranged from 23·1 to 35·8 per cent. It decreased with the proportion of mosses on the soil surface and soil surface coverage, and increased with increasing proportion of structural crust, thus confirming previous results. Water erosion varied from 621 to 2433 g m?2 yr?1 for sediments and from 31 to 146 g C m?2 yr?1 for soil organic carbon, and significantly increased with increasing clay content of the surface horizon, probably due to the formation of easily detachable and transportable sand‐size aggregates, and proportion of macro‐aggregates not embedded in the soil matrix and prone to transport. In addition, water erosion decreased with increasing proportion of structural crusts, probably due to their higher hardness, and when cultivation follows a fallow period rather than after a long period of cultivation due to the greater occurrence of algae on the soil surface, which affords physical protection and greater aggregate stability through binding and gluing. This study based on simultaneous field and laboratory investigations allowed successful identification and quantification of the main erosion mechanisms and controlling factors of interrill erosion, which will give arguments to further set up optimal strategies for sustainable use of the sloping lands of Southeast Asia. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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《Geoforum》2014
Political memories—which are crucial for establishing and maintaining ‘political capital’, based on individual and group positioning during past conflict and wars, but also in relation to presentday politics—are important when considering varied outcomes from negotiations and other interactions that occur in the Lao People’s Democratic Republic in relation to large-scale economic land concessions. This paper continues to expand on the idea of political memories of past conflicts and wars by considering the concept in relation to the theoretical framework proposed by Hall et al. (2011) in their book Powers of Exclusion, which stresses the importance of interactions between regulation, force, the market and legitimation for understanding different types of exclusionary processes, especially those linked to land access. I argue that political memories are particularly relevant when it comes to legitimation, but that expanding the concept so as to include political memories is important. In relation to large-scale plantation, mining and hydropower dam concessions, I also stress the importance of political memories in (re)shaping understandings of landscapes, thus creating particular varieties of memory laden political landscapes, which too are constituted by the past but are also politically mobilized in the present. 相似文献
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1∶5万水系沉积物测量显示,平然地区矿化异常是一个以Cu、Ni、Co异常为主,伴随有Cr、V、Ti等的多元素组合异常,体现了基性—超基性岩石的成矿专属性。对元素分布特征、单元素异常特征、异常元素组合特征进行了研究,得出该区异常主要受区域性NW向断裂构造和基性—超基性岩石控制。对平然地区水系沉积物测量数据聚类分析表明,15种元素可以分为三类:Ni、Cr、Cu、V、Co、Zn、Ti为一类,反映了与基性—超基性岩有关的元素分布、富集特征和相关矿化信息;As、Sb、Pb为一类,反映了与中低温热液作用有关的矿化信息;剩余元素的相关性差,归为一类。平然地区F1主因子可能代表了与基性—超基性有关的Cu、Ni、Co矿化。对平然地区3806个样品分别计算F1因子得分,得分大于2的607个样品分布特征与Cu、Ni、Co异常分布特征大致吻合。因此,Cu、Ni、Co异常区域及F1因子得分大于2的样品所在区域的重叠处应该是以Cu、Ni、Co为主的重点找矿区域。 相似文献
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帕奔金矿位于琅勃拉邦—黎府(泰国)成矿带的中部,矿床容矿围岩主要为灰岩,矿体严格受NNW—近SN向断裂控制。流体包裹体研究表明,含矿方解石中包裹体为液、气两相包裹体,以液相为主;成矿均一温度为164~252℃,平均盐度(w(NaCl,eq))为1.77%~7.64%,具中低温、低盐度特征;估算成矿压力为9.34×10~5~21.37×10~5 Pa,成矿深度为0.48~0.960km;矿石中方解石的碳同位素δ(~(13) C_(V-PDB))=-4.5×10~(-3)~-5.2×10~(-3),氧同位素δ(~(18) O_(V-SMOW))=20.3×10~(-3)~21.1×10~(-3),方解石为流体与二叠系海相碳酸盐岩相互作用的产物。综合分析认为帕奔金矿为浅成中低温热液型金矿床。 相似文献
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老挝班康姆某矿床位于老挝沙耶武里省巴莱县西南部,属于琅勃拉邦—黎府成矿带。前人已完成矿床铜、金资源量的预测,尚未对矿石工艺特性进行研究。本文利用化学分析、光学显微鉴定、X射线扫面电镜能谱分析、物相分析等方法,对该矿床铜金矿石的工艺特性进行了系统研究。研究确定矿石属原生硫化物型铜(伴生金)矿石,可选性好。选矿回收的目标元素为Cu、Au,品位分别为0.74%、0.94g/t。Cu主要以黄铜矿形式存在;Au主要以银金矿形式存在,以包裹金为主。黄铜矿为回收Cu、Au的目标矿物。当磨矿细度为-0.074mm占70%±之时,选矿试验得到Cu回收率90.8%、Au回收率63.5%,铜精矿产品达到国家二级标准。以上结果表明,矿石工艺矿物学研究对选矿试验具有良好的指导作用。 相似文献