森林地上生物量的极化相干层析估计方法   总被引：2，自引：1，他引：1  

罗环敏  陈尔学  李增元  曹春香 《遥感学报》2011,15(6):1147-1162

基于微波的后向散射系数估计森林地上生物量(AGB)易受后向散射系数饱和的影响,而利用森林高度,根据生长方程估计AGB,却没有考虑和AGB密切相关的林分密度、树种组成、林层垂直分布等空间结构特征的作用,针对这些问题,提出一种基于极化相干层析(Polarization Coherence Tomography,PCT)技术的AGB估计方法。基于德国宇航局(DLR)机载SAR系统(ESAR)获取的特劳斯坦(Traunstein)试验区L-波段极化干涉SAR(PolInSAR)数据,通过对具有不同AGB水平的典型林分的相对反射率函数曲线的分析,定义了9个与AGB具有相关性的特征参数。然后基于20个林分的实测AGB数据,以林分尺度上这9个特征参数的平均值为自变量,以实测林分平均AGB为因变量,采用逐步回归分析法构建了AGB估测模型,并对该模型进行评价,对影响模型估计精度的因素进行分析,结果表明,由PCT提取的相对反射率函数特征参数对AGB很敏感,充分利用相对反射率函数信息可提高AGB估计精度。  相似文献   

利用组件GIS和构件技术建立林业GIS系统     

王佳  易正晖  冯仲科 《测绘科学》2011,36(5):141-143,149

随着计算机技术的进步,以林业GIS系统为代表的林业信息化进程得到前所未有的发展,但也存在着工程重复建设的问题,没有按统一的标准、规范和要求进行,特别是林业专业模型的实现一直进展缓慢.本文将软件复用的思想引入到林业GIS系统专业模型的构件设计与开发上,通过组件GIS技术与构件技术相结合的方法实现林业GIS系统功能的复用,...  相似文献   

利用遥感数据对单株木和森林场景进行建模     

郭俊  牛铮 《武汉大学学报(信息科学版)》2011,(2):181-184,198

针对遥感在三维可视化方面的不足,提出了用SRTM(航天飞机雷达地形测图任务)和TM(陆地资源卫星专题绘图仪)数据建立森林场景的方法。利用L系统语言和L-studio软件,通过提取的分枝规则建立了针叶树和不同叶面积指数(LAI)落叶树的几何模型,并将其作为森林场景内树木的纹理贴图。实验区的三维地形用四叉树结构建立,综合应用数据分块、动态载入、双缓存数组等措施提高大范围场景的漫游速度。从TM影像获取目视判读的遥感分类图和LAI反演图,结合控制树木的栽种位置和纹理选择,建立了单幅TM影像大小的森林场景。实验为其他遥感数据的三维显示提供了通用的建模方法。  相似文献   

利用动态阈值的森林草原火灾火点检测算法   总被引：2，自引：0，他引：2  

刘良明  魏然  周正 《武汉大学学报(信息科学版)》2011,36(12):1434-1437

针对传统固定阈值的森林和草原火灾火点遥感检测算法因时空环境变化而导致的火点漏检和误检问题,提出了一种综合季节、地理位置和土地覆盖类型等影响因素的时空动态阈值火点检测算法。实验结果表明,时空动态阈值火点检测算法能有效改善火点检测结果,具有时空自适应性。  相似文献   

基于GIS和RS的森林火灾管理系统的设计与实现     

王中 《测绘与空间地理信息》2011,34(5):16-19

介绍了组件式GIS开发技术的概念和特点,分析了GIS和RS技术在森林防火中的应用前景。针对森林防火管理的特点,将GIS和RS技术结合设计和开发出森林火灾管理系统,该系统实现了对火灾高发区及火场的定位、预测、监控和分析等功能,促进了森林防火信息化管理。利用组件式开发技术,森林火灾管理系统可以实现对林区的基本空间分析功能,并且可以对林区火场实现3维漫游,以辅助决策指挥。  相似文献   

Synergistic Effects of Nitrogen Amendments and Ethylene on Atmospheric Methane Uptake under a Temperate Old-growth Forest     

XU Xingkai  HAN Lin  LUO Xianbao  HAN Shijie 《大气科学进展》2011,28(4):843-854

An increase in atmospheric nitrogen (N) deposition can promote soil acidification, which may increase the release of ethylene (C2H4) under forest floors. Unfortunately, knowledge of whether increasing N deposition and C2H4 releases have synergistic effects on soil methane (CH4) uptake is limited and certainly deserves to be examined. We conducted some field measurements and laboratory experiments to examine this issue. The addition of (NH4)2SO4 or NH4Cl at a rate of 45 kg N ha-1 yr-1 reduced the soil CH4 uptake under a temperate old-growth forest in northeast China, and there were synergistic effects of N amendments in the presence of C2H4 concentrations equal to atmospheric CH4 concentration on the soil CH4 uptake, particularly in the NH4Cl-treated plots. Effective concentrations of added C2H4 on the soil CH4 uptake were smaller in NH+4 -treated plots than in KNO3-treated plots. The concentration of ca 0.3 μl C2H4 L-1 in the headspace gases reduced by 20% soil atmospheric CH4 uptake in the NH4Cl-treated plots, and this concentration was easily produced in temperate forest topsoils under short-term anoxic conditions. Together with short-term stimulating effects of N amendments and soil acidification on C2H4 production from forest soils, our observations suggest that knowledge of synergistic effects of NH+4 , rather than NO3- , amendments and C2H4 on the in situ soil CH4 uptake is critical for understanding the role of atmospheric N deposition and cycling of C2H4 under forest floors in reducing global atmospheric CH4 uptake by forests. Synergistic functions of NH4+ -N deposition and C2H4 release due to soil acidification in reducing atmospheric CH4 uptake by forests are discussed.  相似文献   

大兴安岭林区地闪放电特征的观测与分析   总被引：4，自引：2，他引：2  

王东方  宣越健  刘继明 《大气科学》2011,35(1):147-156

利用2009年夏季在大兴安岭林区开展的雷暴及闪电的多站GPS同步观测资料,详细分析了该地区的地闪放电特征.通过对464次地闪资料的分析,发现具有单次回击的地闪所占的比例高达69,且正地闪比例较高,达到了22%.对连续电流的统计表明,约有27%的地闪伴随有连续电流过程且长连续电流过程主要出现在具有单次回击的负地闪中,其平...  相似文献   

Can we improve the spatial predictions of seabed sediments? A case study of spatial interpolation of mud content across the southwest Australian margin     

Jin Li  Andrew D. HeapAnna Potter  Zhi HuangJames J. Daniell 《Continental Shelf Research》2011,31(13):1365-1376

Spatially continuous data of environmental variables is often required for marine conservation and management. However, information for environmental variables is usually collected by point sampling, particularly for the marine region. Thus, methods generating such spatially continuous data by using point samples to estimate values for unknown locations become essential tools. Such methods are, however, often data- or even variable-specific and it is difficult to select an appropriate method for any given dataset. In this study, 14 methods (37 sub-methods) are compared using samples of mud content with five levels of sample density across the southwest Australian margin. Bathymetry, distance-to-coast, slope and geomorphic province were used as secondary variables. Ten-fold cross validation with relative mean absolute error (RMAE) and visual examination were used to assess the performance of these methods. A total of 1850 prediction datasets are produced and used to assess the performance of the methods and the effects of other factors considered. Considering both the accuracy and the visual examination, we found that a combined method (i.e., random forest and ordinary kriging: RKrf) is the most robust method. This method is novel, with a RMAE up to 17% less than that of the control. No threshold in sample density was detected in relation to prediction accuracy. No consistent patterns are observed between the performance of the methods and data variation. The RMAE of three most accurate methods is about 30% lower than that of the best methods in previous publications, highlighting the robustness of the methods selected in this study. The implications and limitations of this study are discussed and a number of suggestions are provided for further studies.  相似文献   

Use of magnetic measures to assess soil redistribution following deforestation in hilly region   总被引：1，自引：0，他引：1  

Parisa Mokhtari Karchegani  Shamsollah Ayoubi  Sheng Gao Lu  Naser Honarju 《Journal of Applied Geophysics》2011,75(2):227-236

Limited information is available about the use of magnetic susceptibility property to determine soil redistribution in hilly areas of the semi-arid regions. This study was conducted to evaluate the use of magnetic properties to determine soil redistribution along a hill slope following deforestation. The study area is located in the Quaternary hilly region of Lordegan district in west Iran. Ten transects were established in two land uses that included natural Querqus forested and cultivated lands. Soil samples were collected at different positions along the slope and magnetic properties (χlf, χhf, SIRM, ARM, and χfd) and selected physico-chemical properties were determined. The results (based on the χfd, SIRM/ARM) showed that the magnetic susceptibly in the calcareous materials is pre-dominantly derived during the pedogenic processes and the superparamagnetic particles which were transported to lower positions of hill slope following deforestation. The results confirmed that this methodology could be applied for monitoring soil redistribution along the slope in calcareous hilly areas in the semi-arid regions.  相似文献   

“I Still Have the Old Tradition”: The co-production of sweetgrass basketry and coastal development     

Brian Grabbatin  Patrick T. Hurley  Angela Halfacre 《Geoforum》2011,42(6):638-649

Scholars working around the world have drawn attention to the physical and social changes associated with rural gentrification. Case studies from the United States have focused on how these patterns lead to the cultural displacement and replacement of land-based livelihoods, including non-timber forest product (NTFP) practices. Scholars have also documented the persistence of culturally and economically important NTFP practices in urban and suburban areas. We reconcile these disparate outcomes, displacement on the one hand and persistence on the other, by focusing on the social relationships that co-produce land use and livelihood change. Our case investigates how African American sweetgrass basketmakers in Mount Pleasant South Carolina negotiate the complex terrain of a rapidly urbanizing and gentrifying landscape.Analysis of interviews with basketmakers and participant observation at public meetings suggests that gathering materials and selling baskets occur across spaces not typically considered important for NTFP practices. Access to these sites depends upon continually reinforced and negotiated social relationships between a variety of actors. Findings illustrate that, by themselves, development and gentrification are insufficient for explaining livelihood and land use patterns that emerge in places experiencing intensive development. Using a co-production framework, we acknowledge the wide variety of complex trajectories and local power dynamics shaping land use and livelihoods. Findings also have implications for connecting global research on housing, employment, and demographic transitions associated with rural gentrification, to international NTFP research, which is increasingly turning to rural–urban interfaces for insights on how livelihoods are linked to land development and migration.  相似文献