Comparison of UAV and WorldView-2 imagery for mapping leaf area index of mangrove forest

Unmanned Aerial Vehicle (UAV) remote sensing has opened the door to new sources of data to effectively characterize vegetation metrics at very high spatial resolution and at flexible revisit frequencies. Successful estimation of the leaf area index (LAI) in precision agriculture with a UAV image has been reported in several studies. However, in most forests, the challenges associated with the interference from a complex background and a variety of vegetation species have hindered research using UAV images. To the best of our knowledge, very few studies have mapped the forest LAI with a UAV image. In addition, the drawbacks and advantages of estimating the forest LAI with UAV and satellite images at high spatial resolution remain a knowledge gap in existing literature. Therefore, this paper aims to map LAI in a mangrove forest with a complex background and a variety of vegetation species using a UAV image and compare it with a WorldView-2 image (WV2).In this study, three representative NDVIs, average NDVI (AvNDVI), vegetated specific NDVI (VsNDVI), and scaled NDVI (ScNDVI), were acquired with UAV and WV2 to predict the plot level (10 × 10 m) LAI. The results showed that AvNDVI achieved the highest accuracy for WV2 (R² = 0.778, RMSE = 0.424), whereas ScNDVI obtained the optimal accuracy for UAV (R² = 0.817, RMSE = 0.423). In addition, an overall comparison results of the WV2 and UAV derived LAIs indicated that UAV obtained a better accuracy than WV2 in the plots that were covered with homogeneous mangrove species or in the low LAI plots, which was because UAV can effectively eliminate the influence from the background and the vegetation species owing to its high spatial resolution. However, WV2 obtained a slightly higher accuracy than UAV in the plots covered with a variety of mangrove species, which was because the UAV sensor provides a negative spectral response function(SRF) than WV2 in terms of the mangrove LAI estimation.     

变化发展中的中国人文与经济地理学

学科方向与研究领域的确定是学科发展的灵魂。人文与经济地理学是研究领域乃至研究方向均处于变化中的学科,重新认识人文与经济地理学的研究领域与学科方向至关重要。通过梳理几十年来中国人文与经济地理学主要分支学科发展阶段,总结了人文与经济地理学对转型发展社会背景的响应,一方面要坚持学科交叉的性质,以“人-地系统”为理论方向和走理论与实践相结合的道路,另一方面人文与经济地理学者要以新的心态、新的视野,来思考未来发展的重点领域、发展理念以及理论与方法的创新。对长期以来学科涉及到的主要问题,战略性、咨询性、预测性甚至总结经验性（成果表现为发展学科理论）的工作将会逐渐增加,重要性将逐渐显现。阐述了信息化与社会空间经济组织、区域经济新格局与新型城镇化等重要研究领域的发展变化趋势,就“国际热点”与“国际前沿”、理论研究及理论与实践的关系等重要问题的研究理念以提出了新设想,并提出将“人文地理学”改称为“人文与经济地理学”的建议。     

中国县域小城镇就业岗位对人口集聚的影响研究——基于分位数回归的实证检验

利用中国县域建制镇数据,研究了中国小城镇常住人口与就业岗位的空间分布特征,采用分位数回归实证检验了就业岗位对小城镇人口集聚的影响。主要结论是：① 中国县域小城镇常住人口主要集中在胡焕庸线以东地区,尤其是哈大沿线、成渝地区、长江中下游和东南沿海省份。2009~2014年,中国小城镇常住人口密度普遍上升,中国小城镇常住人口比重在胡焕庸线两侧基本保持着稳定状态。② 中国县域小城镇非农就业岗位分布与常住人口分布大致吻合,且集聚程度更高。③ 中国县域小城镇就业岗位促进常住人口的集聚。随着县域小城镇人口规模的增加,就业岗位对小城镇常住人口集聚的影响逐渐降低,且第三产业就业岗位数量对人口集聚的影响将超过第二产业。④ 分区域看,县域小城镇就业岗位的人口促进作用对东部地区最为显著,中部次之,西部最低。     

从神话、传说与文字记录中探索中国活火山喷发的信息

火山喷发文字记录资料的考证可以给出历史上火山喷发的最为准确的时间限定，对喷发过程、灾害效应也都可给出极为详细、准确的措施。长白山天池火山喷发的满语资料是除了汉语、朝语之处另一种极为重要的资料来源，目前已从有关满语神话传说中得到了若干有重要意义的火山与火山学信息。本文列出了3类、14条天池火山喷发的神话与传说，从中可以得知数千年以来天池火山发生过多次猛烈的与温和的周期性的喷发。天池火山喷发与火山泥石流、喷发后洪水泛滥有密切关系，泛滥物波及到距离天池火山460km以过的嫩江流域及珲春一带。在中国近代史上还有若干次火山喷发记录，经考察较为确定的1951年昆仑山西部于田县卡尔达西火山喷发是一次地下岩浆上侵、地表汽爆炸与喷发的火山喷发事件。     

大陆桥江苏沿线地区旅游资源评价与旅游业发展战略研究

在深入分析大陆桥江苏沿线地区的徐州、连云港两市旅游资源、旅游动力和旅游市场的基础上，概括出其旅游业发展的总体思路，并就旅游经济运行机制、系统开发、形象驱动等基本战略提出了对策。     

Hydrogeologic delineation of habitats for endangered species: the Comal Springs/River System

 We delineate 18 distinct habitats for the endangered fountain darter in the Comal Springs/River system based upon a combination of vegetative, geologic, and hydrologic criteria. Comal Springs are the largest natural discharge from the Edwards aquifer of central Texas; they issue along faults which penetrate the confined portion of the aquifer. The springs are the head of the Comal River which is an important economic and recreational resource to the local community. The spring/river system is the home of the fountain darter, a federally listed endangered species. Previous studies of this system were on a large scale and lacked detail necessary for characterization. The fountain darter and other fauna in the Comal Springs/River system are threatened by the possibility of diminished flows and the concomitant habitat change. The 18 habitats are defined by the dominant species of vegetation, the substrate, and the flow conditions. Human alterations and spring discharge control the morphology of the river and the substrates. Stream velocities determined substrate conditions and, thus indirectly, the distribution of vegetation and habitats. In this system, hydrochemical parameters were uniform as were the soils adjacent to the stream; these factors were not important to the habitat delineation. The range of stream velocities necessary to maintain the habitats can be estimated with the Hjulstrom diagram. The darters were associated with a number of these habitats. We surmise that significant alteration of the system's habitats will occur if discharge conditions change. Received: 22 January 1996 · Accepted: 4 March 1996     

The pulse of citizenship: reflections on Griffith Taylor and ‘nation‐planning‘

This exercise in a type of applied historiography begins by annotating aspects of reform in Western education from the 1880s to the 1930s, an interval which exhibits the responses of ‘new’ subjects to political and social demands for improved civics education, and encompasses the inauguration of a recognisably ‘academic’ geography in Australia. Designedly, since the nominated period also incorporates the early life and career of pioneering geographer Griffith Taylor, the discussion probes beneath the strata of obfuscatory generalisation to relate one individual's engagement with the vortex of change. More specifically, it extracts a few lessons from Taylor's approach to ‘Nation‐Planning’ to suggest an appropriate orientation to current reformism in Australian education. It is argued that, while this trend questions the civic utility of established disciplines, it has been badly served by a disturbing ignorance of the social and intellectual heritage of the subjects under challenge.     

论徐连经济带建设

通过对徐连经济带在全省，淮海经济区中经济地位的分析，与省内宁镇扬，苏锡常两区的比较，找出本带经济中存在的问题及原因，提出加快其经济发展所拥有的优势区位，优越的自然条件和重要意义，并就点轴开理论本带建设布局中的应用进行了探讨。     

Spatial Variation in Diameter Structures of Forests in Lassen Volcanic National Park,California*

Variation in seedling/sapling densities and stand diameter forms for six coniferous tree species is related to stand structural development and to elevation and topography in Lassen Volcanic National Park, California. Understory density patterns reflect differences in species tolerance; densities decrease with stand development for shade intolerant pines, but increase for shade tolerant firs and mountain hemlock. Pine species exhibit reverse-J diamter structures on recently disturbed sites, and decreaser and random forms elsewhere. More tolerant fir species show topographically mediated patterns of diameter structure, with reverse-J form common on northerly exposures and upland sites, but with decreaser and random forms on more xeric slopes. Interaction among species tolerance, environmental setting, and disturbance history yields a complex mosaic of stand diameter structures in the Lassen landscape.     

地震预测研究中引入系统科学的几个问题的讨论

随着对复杂事物认识的不断深入，系统科学被引入地震科学研究中。本文 郑重讨论了浑沌论、协同学、耗散结构理论和突变论等理论在研究地震问题中的相互关系，并从认识论的角度探讨了一些问题，以期有益于有关研究。