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61.
随机森林模型预测岩溶区酸性煤矿井水锰污染 总被引:1,自引:0,他引:1
酸性煤矿井水严重威胁地下水的水质。如何更有效对受影响区域的地下水源进行动态监测是当前的一个关键问题。采用随机森林中的回归模型,利用自变量(采空区水位、岩溶水位、pH值、泉水流量、电导率)和因变量(污染离子浓度)的相关性,建立回归模型;使用测试数据进行误差分析,结果证明模型准度较高,所得预测值具有参考价值;得出各自变量对因变量影响的重要程度,分析结果与实际情况相符合。试验表明,随机森林回归模型在酸性煤矿井水污染预测方面具有适用性,可作为辅助手段监测水质污染情况,对今后工作有一定的指导意义和经济价值。 相似文献
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面向对象的极高海拔区水体及冰川信息提取——以珠穆朗玛峰国家级自然保护区核心区为例 总被引:2,自引:0,他引:2
极高海拔地区多为河流发源、冰川发育地,由于地形起伏强烈,且野外考察验证工作困难,传统的遥感信息提取方法很难保证该地区水体及冰川的提取精度。本文基于ASTER影像,运用面向对象的图像信息自动分析方法,对珠穆朗玛峰国家级自然保护区核心区的水体及冰川信息进行了提取研究。为保证信息提取的准确度,将数字高程模型(DEM)及其衍生数据(坡度、坡向),归一化植被指数(NDVI)数据,及有助于区分水体、冰川与其他地物的相关指数(冰雪指数NDSII)及波段运算结果(b1-b3)、(b3/b4)等,分别作为一个波段叠加到原始图像中,使之成为对目标地物光谱特征的有益补充。并对不同类型的水体及冰川进行多级、多尺度分割,以满足其对分割尺度的不同要求。分割完成后,综合考虑目标地物的光谱特征、纹理特征、空间结构特征,根据各特征指数的直方图信息,设定合适的阈值,建立了各水体及冰川类型信息提取的知识规则,并结合实地调查对信息提取的精度进行验证,改进了ASTER遥感影像自动快速提取极高海拔区水体及冰川信息的实用模型。 相似文献
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Kesang WANGCHUK András DARABANT Prem Bahadur RAI Maria WURZINGER Werner ZOLLITSCH Georg GRATZER 《山地科学学报》2014,11(5):1182-1191
We investigated whether species richness, diversity and density of understory herbaceous plants differed along logging(gap) and grazing(primarily by cattle) disturbance gradients, and sought to identify drivers of richness, diversity and density of understory vegetation of logged sites. A factorial experiment was conducted in the mixed conifer forest of Gidakom in Western Bhutan. Levels of the logging treatment included small(0.15 – 0.24 ha), medium(0.25 – 0.35 ha) and large(0.36 – 1.31 ha) gaps. The grazing treatment included grazed(primarily by cattle) and ungrazed(where herbivores were excluded by a fence) plots nested within each gap. Data were collected from 12 gaps(4 replicates at each level of logging) using the point intercept method. Shannon Weaver Diversity and Margalef's indices were used to estimate species diversity and describe species richness, respectively. Soil samples were analyzed for pH and nutrients. The interaction effect of logging and grazing was significant(p≤0.001) only on species diversity. Relative to ungrazed areas, species diversity was significantly higher(0.01≤p≤0.05) in medium grazed gaps. Under grazed conditions, soil P was negatively correlated with gap size and species diversity. While species diversity was positivelycorrelated(0.01≤p≤0.05) with soil N in grazed plots species richness was positively correlated(0.001≤p≤0.01) with soil N in ungrazed plots. Relative density of Yushania microphylla and Carex nubigena were higher under ungrazed conditions. Our study suggests that the combined effect of cattle grazing and logging results in higher species diversity of understory vegetation in medium and grazed gaps in mixed conifer forests of Bhutan,whereas increase or decrease in relative density of major species is determined primarily by the independent effects of grazing and logging. From management perspective, forest managers must refrain from creating large gaps to avoid loss of nutrients(mainly P and N), which may eventually affect tree regeneration. Managers intending to maintain understory vegetation diversity must consider the combined effects of grazing and logging, ensuring low to moderate grazing pressure. 相似文献
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Ana Moreno Blas L. Valero‐Garcés Montserrat Jiménez‐Sánchez María José Domínguez‐Cuesta M. Pilar Mata Ana Navas Penélope González‐Sampériz Heather Stoll Pedro Farias Mario Morellón J. Pablo Corella Mayte Rico 《第四纪科学杂志》2010,25(7):1076-1091
A sedimentological and geochemical study of the Lago Enol sequence (Cantabrian Mountains, northern Spain), together with detailed geomorphological mapping, provides a first record of glacier evolution and climate change over the last 40 ka in the Picos de Europa National Park. The Enol glacier retreated from its maximum extent prior to 40 ka BP as demonstrated by the onset of proglacial lacustrine sedimentation in two glaciated depressions: the Comella hollow to the north (before 40 ka BP) and the Lago Enol (before 38 ka BP). These results support previous evidence that the maximum extent of southern European glaciers occurred earlier than in northern Europe. Alternation of homogeneous and laminated proglacial sediments during the glacier retreat illustrate a dynamic glacial evolution during the Marine Isotope Stage (MIS) 3 (40–26 ka BP). A slight warming is detected at 26 ka ago with the change from proglacial sediments (in a lake located in contact to the glacier) to glaciolacustrine sedimentation (in a non‐contact or distal lake). Finally, the onset of organic‐rich sediments took place at 18 ka ago. This last transition occurred in two phases, similarly to the North Atlantic Last Termination, suggesting a link between North Atlantic Deep Water formation oscillations and palaeohydrological variability in the Cantabrian Mountains. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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本文从探空史、气象学史、气候学史、物侯学史、军事地理学史、数理地理学史以及科学家评介、自然科学史理论等几个侧面,较为系统地论述了竺可桢教授在地理学史方面的贡献.以此纪念竺可桢教授逝世二十周年. 相似文献
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The karst landscape in the interior of the Philippines' Bohol Province represents one of the world's premier kegelkarst (cone karst) environments. Government efforts to protect some of this karst, exemplified by the establishment of the Rajah Sikatuna National Park and the Chocolate Hills Natural Monument, have proven to be significant catalysts of social conflict. In Bohol there is a long history of traditional land tenure, which has recently been supplanted by a Westernized model. Protected area establishment is a response to deforestation, agricultural exploitation and uncontrolled quarrying. However, the imposition of protective legislation to prevent further degradation has disenfranchized and marginalized many local farmers and residents. The conflict between the obligation of the State to ensure environmental protection and the perceived property rights of landowners and farmers has provoked an escalation in civil unrest and armed conflict. 相似文献