森林生态系统碳储量及碳通量遥感监测研究进展

在全球CO₂浓度持续增加导致气候变暖的背景下,森林生态系统碳储量及碳通量遥感大尺度监测成为关注热点。文中深入分析了当前国内外卫星遥感观测技术对森林碳循环评估的2种途径:1）基于遥感手段估算森林生物量并推算森林碳储量,通过碳储量变化确定森林生态系统的CO₂通量。归纳各类森林生物量遥感估算方法的原理及优缺点,系统评述各类方法在大区域森林碳储量估算中存在的不确定性。2）基于CO₂温室气体观测卫星遥感数据,定量监测森林生态系统与大气CO₂通量,基于交换的CO₂通量推算森林碳储量变化。归纳遥感手段观测森林生态系统与大气CO₂通量的主要数据、方法及优缺点,系统评述各类数据及方法在森林CO₂通量时空变化特征监测、森林碳储量估算等方面取得的进展,重点分析专用CO₂浓度监测卫星数据,尤其是我国自主碳卫星数据在CO₂柱浓度反演算法研究以及不同数据源之间的对比、验证和同化研究等方面取得的进展,总结专用温室气体遥感观测数据在森林碳储量及碳通量监测方面的优势。提出利用遥感手段进行森林生态系统碳循环定量监测的研究展望。     

林业部南方林业遙感试验场建场概况

林业部南方林业遥感场是1980年作为长期固定的遥感应用技术试验基地建立的。为此,就必须有一个相应的地面观测体系,配合遥感的需要,为现时及将来长期进行各种遥感试验定期提供地面实况数据,这是建立试验场地固定样地体系的出发点。建立试验场地固定样地体系的目的是为应用遥感手段进行多资源调查、资源动态监测等方面长期提供各种遥感技术所需的实况数据,并兼顾其它科学以及地方森林经营的需要。几年来,场部建成,多次进     

卫星遥感技术在政策性森林保险快速理赔中的应用——以内蒙古自治区为例

快速理赔是政策性森林保险健康快速发展的关键因素。介绍了森林灾害不确定性导致承保及投保两方面的不利影响,指出了快速、准确理赔对政策性森林保险发展的作用,分析了典型森林灾害遥感监测与评估的原理及主要技术手段,以内蒙古自治区东部主要林区为例开展了基于多源卫星遥感数据的森林灾害监测与评估。对卫星遥感技术在政策性森林保险快速理赔中的潜力、问题与前景进行了总结。     

卫星遥感监测技术在北京市森林防火中的应用

随着森林火灾造成的危害越来越大,防控的科学性和有效性已引起世界各国关注,遥感技术在监测和预警方面的应用已成为林火防控的发展方向之一。随着全国林草感知能力的全面推进,如何结合北京市森林防火实际,应用遥感卫星监测技术高效开展工作是北京市森林防火工作信息化的重点。本文通过利用H8、FY系列、NOAA、EOS、NPP等10颗静止、极轨遥感卫星数据,结合不同卫星传感器的优势,分析在森林火灾监测中综合应用多源遥感数据,及时开展火情监测预警、火场定位、发展趋势监测及灾后评估的应用成效,进而指导全市森林防火监测体系的科学发展,为精细化开展京津冀地区森林防火工作提供科技保障和建设经验。     

不同植被GPS定位精度影响因素分析及多路径效应

针对不同植被类型森林火灾的灾前预警、灾中扑救、灾后评估过程中需要精准确定火灾、水源位置和扑火路线的需求,利用Trimble Ag GPS132和Geo XT进行了草地(鸭趾草)、灌木丛(大叶黄杨)和树林(落羽杉)等不同植被类型时的GPS静态定位和动态定位试验,并观测记录了GPS卫星可见性和PDOP,对比分析其定位误差,进行不同截止高度角对能见卫星个数、PDOP和定位误差的影响,并分析其误差原因及改善方法,采用AUTO CAD结合速度过滤算法对不同植被类型时动态定位产生的多线进行简化。试验结果显示,根据卫星可见数和PDOP值,不同植被类型的GPS观测条件为草地灌木丛树林,定位误差的大小为草地灌木丛树林,灌木丛、树叶产生的多路径效应是在森林中定位误差的主要来源。得到了不同植被类型下测量次数与定位精度的回归拟合方程,定位精度与测量次数的对数成线性关系,静态定位时测量次数为200次比较合适。截止高度角太大,将导致观测失效、误差增大的现象,综合考虑根据卫星可见数、PDOP值、定位误差和减弱森林中的多路径效应等因素,截止高度角E在8°~20°比较合适。另外对于草地、灌木丛、树林不同植被类型进行动态定位时,速度过滤算法都能起到很好的修正误差、优化线型的作用。     

卫星遥感照片在森林调查中的应用

卫星遥感照片在林业方面主要用于森林资源调查、植被分类、土地利用调查、森林火灾、病虫害和森林动态监测。遥感图像主要采用中分辩率多谱段卫星遥感数据。遥感数据的获取应选择在植被生长季节，一般云量小于5%。在遥感图像成图时，一般要叠加10×15的经纬网;1km×1km网以及区划界线;并对以判读为主体的森林植被图像进行增强处理。 卫星遥感照片具有摄影范围大，迅速反映动态变化、资料收集方便、影像信息多和成图迅速、成本低等优点。因此，广泛应用于森林调查工作中。 1 利用卫星遥感照片，目视编制土地利用图 利用最新的卫片和相关资…     

基于CEBERS-WFI遥感数据的森林生物量估测方法研究

以中巴卫星CEBERS-WFI遥感数据为基础,结合东北三省的地理、气象因子及森林资源连续清查固定样地信息,构建BP人工神经网络森林生物量估测模型,对我国东北三省的森林生物量进行估测,并反演了森林生物量的空间分布图像。结果表明,基于CEBERS-WFI遥感数据的BP人工神经网络应用于森林生物量估测简单实用,是一种快捷、有效的估测方法。     

遥感影像分类技术在森林景观分类评价中的应用研究

以吉林省旺清林业局金沟岭林场为例,在地面调查数据和Landsat TM多光谱卫星遥感数据的基础上,以ERDAS遥感影像处理系统和MapInfo地理信息系统支持,利用基于二类调查数据取证遥感分类技术,对其森林景观进行分类和评价,得到金沟岭林场森林景观空间分布图及空间格局分析结果。本研究提出的一套实用技术方法可为宏观上快速提取森林景观要素及空间格局状态提供技术参考,结果可为进一步森林景观规划和设计提供依据。     

差分GPS定位精度研究

通过差分GPS(DGPS)定位实验数据的统计分析,获得DGPS在林分内外的定位精度及误差分布规律。在林分外定位的平均中误差为0.243m,集中分布在0~0.5m范围内,频率为92.1%,中误差小于1m的频率为98.4%。在郁闭度小于0.5林分中,平均中误差为0.502m,集中分布在0~0.7m范围内,频率为82.8%,中误差小于1m的频率为91.4%。分析结果表明:DGPS定位在林分外能够满足高分辨率遥感影像纠正对控制点的精度要求,可以应用DGPS进行QUIKBIRDI、KONOS等影像纠正控制点的采集,也可以在郁闭度小于0.5的林分中,进行如幼树、古树、标准地等定位调查。     

基于卫星遥感影像的森林病虫害监测研究进展

森林病虫害是森林的主要灾害,快速准确监测森林病虫害是开展病虫害防治的关键。利用卫星遥感影像监测森林病虫害是一种经济高效的手段。为进一步加强森林病虫害遥感监测的研究和实践,综合分析了国内外利用卫星遥感影像监测森林病虫害研究现状,系统总结了应用卫星遥感影像监测森林病虫害的主要技术方法,深入分析了存在的主要问题并进行研究展望。研究表明:森林病虫害遥感监测研究中主要存在3个问题:1)高空间分辨率影像的研究不足;2)影像纹理信息挖掘不充分;3)失叶遥感监测挑战大等问题。针对上述存在的主要问题,研究提出对策建议:1)多源遥感数据的综合应用;2)增强图像处理技术;3)加强病虫害生境因子的利用;4)构建病虫害遥感监测系统平台等。     

Comparing the precision and accuracy of GPS positioning in forested areas

The objective of this study is to clarify the performance of the Global Positioning System (GPS) in forested areas after selective availability (SA) was turned off. In this study, we conducted a field test on horizontal and vertical positional errors of GPS positioning at different points in forested areas. The precision and accuracy of GPS positioning at different points were then calculated and compared. Furthermore, the effect of differential GPS (DGPS) on precision and accuracy was analyzed using analysis of variance (ANOVA), and the necessity for DGPS after SA was turned off was discussed. As a result, the largest horizontal precision errors were found to be in the plantation forest, followed by the natural forest and forest road. On the other hand, precision errors were smallest at the landing, around which there were no obstacles. Horizontal accuracy errors were greatly improved by using the DGPS. Large vertical precision errors were produced in the plantation forest, on the forest road, and in the natural forest, while those at the landing were much smaller. Vertical accuracy errors were also relatively small at the landing. In conclusion, tree canopies greatly affected precision errors, and the DGPS improved not horizontal precision but horizontal accuracy. The autonomous GPS is sufficiently useful for purposes in which horizontal positional errors of a maximum of 10m are allowable. However, the DGPS should be used for surveying and mapping, for which higher accuracy is necessary.     

Estimation of GPS positional accuracy under different forest conditions using signal interruption probability

We proposed a signal interruption probability (SIP) value indicating the frequency of global positioning system (GPS) signal interruption or the fragmentation of GPS data, and used it to estimate the success probability of ambiguity resolution in carrier-phase differential GPS (DGPS) as well as the horizontal precision of code-phase DGPS under different forest conditions. In field tests, a rover was set up at four observation points, each representing a different condition within a forest. At each observation point, static surveying was conducted for four periods of 30 min, and data from the first 1, 5, 15, and 30 min from each observation point were extracted for analysis. The position of each point was calculated by baseline analysis using three types of GPS data, i.e., dual-frequency (L1 and L2), single-frequency (L1), and code-phase DGPS data. The results showed that ambiguity resolution was a key factor in determining the horizontal accuracy of carrier-phase DGPS, and that the success probability of ambiguity resolution differed greatly according to forest conditions, which were well explained not by the index of the canopy opening but by the SIP. Furthermore, estimation of the success probability of ambiguity resolution was made based on the SIP and the observation period using a logistic regression model. The horizontal precision of code-phase DGPS was also estimated based on the SIP and the observation period. In conclusion, the SIP was found to be an effective indicator of GPS positional accuracy under different forest conditions.     

基于双目立体视觉SLAM的林下实时定位

[目的]在林下环境中受到树木冠层的遮挡,易造成全球导航卫星系统卫星信号失锁,不能满足林下实时定位的需求.本研究引入双目立体视觉SLAM技术,在移动过程中根据周围环境中路标点的位置变化实时确定传感器的空间位置和姿态,以期在林下环境中达到实时定位的目的.[方法]实验过程中使用双目相机按照10 Hz的采集频率对3块边长为40...     

基于VRS技术的DGPS-PDA在森林资源连续清查中的应用研究

在介绍GPS、DGPS、RTK、VRS、PDA等技术的基础上,详细阐述了基于VRS技术的DGPS．PDA在森林资源连续清查中应用的工作流程及操作步骤。研究表明,定位平均精度可达0．5m左右,在信号较好的地方,精度可达0．3m左右,提高了样地定位精度和连清工作的连续可比性。利用PDA进行野外数据采集,提高了工作效率,可实现森林资源连续清查的无纸化。     

计划烧除引起水土流失的定量研究

首次在国内对计划烧除林地水土流失量进行了定位研究,结果显示计划烧除林地土壤侵蚀强度因坡度变陡而增加,坡度23的试验区为69．5t／(km·a),对照为52．6t／(km·a);坡度33“的试验区为104．7t／(km·a),对照为101．8t／(km·a)。计划烧除林地的土壤侵蚀量远远低干200t／(km·a)这个最低允许流失量标准。可以认为,在林内开展计划烧除所引起的水土流失量是很微弱的。周期性地开展计划烧除产生的生态负效应对环境质量的影响不显著。为了降低森林的燃烧性,大幅度减少森林火灾,积极开展计划烧除不仅必要,而且可行。     

Positioning precision and sampling number of DGPS under forest canopies

 Experimental results were studied to determine the relationships between positioning precision of a differential global positioning system (DGPS) and forest type, antenna height, and season, and to clarify the relationship between sampling number and the convergence of positioning precision. Observation was carried out for 24 h. Mean circular area probability (CEP₉₅) was 2.80 m for deciduous broadleaved trees, and 4.99 m for conifers. The mean CEP₉₅ taken at 7 m height (3.14 m) was higher than that at 1 m height (3.92 m) at all sites. The mean CEP₉₅ taken during the defoliation season (2.65 m) was slightly better than during the foliation season (2.96 m). There were significant differences between forest types (P < 0.001) and antenna heights (P < 0.05). Positioning precision was not noticeably improved if the sampling number was around ten or less. A sampling number of 100–1000 or more is required before substantial improvements can be expected. As long as high positioning precision is not required, it is acceptable to use 2D & 3D modes and relatively few samples to take measurements. Received: April 24, 2002 / Accepted: October 10, 2002 Correspondence to:I. Sawaguchi     

Soil depth and soil water regime in a catchment where tropical dry evergreen and deciduous forests coexist

In several areas in Northeast Thailand, evergreen and deciduous forests coexist under uniform climatic conditions. To identify the factors that determine the distribution of these different forest types, we compared soil depth and soil physical properties between evergreen and deciduous forests, and monitored soil moisture conditions for a year in both forest types at the Sakaerat Environmental Research Station. The soil was significantly deeper under the evergreen forests (mean 97 cm) than under the deciduous forest (mean 64 cm). The soil under the evergreen forests retained much more water throughout the year than the soil under the deciduous forest, and there was also a clear tendency for the evergreen forests to occur in ravine areas, regardless of soil depth. It is possible that the evergreen trees can maintain transpiration during the dry season on thicker soils or in ravine areas, whereas shallower soils cannot provide enough water for these trees to maintain their evapotranspiration during the dry period. From the present study, we showed that soil water availability could be a significant factor determining the distribution of the deciduous and evergreen forests in our catchments.     

基于DGPS的SPOT5遥感影像几何精校正研究

采用DGPS系统中的载波相位差分技术均匀地选取地面控制点,利用ERDAS IMAGINE9.1遥感影像处理软件,对天桥岭林业局太阳林场的SPOT5遥感影像进行了几何精校正。结果表明：采用3次多项式校正,相应面积控制点个数比在0.06～0.09（个.km-2）之间时校正精度最高,校正后误差为0.603个像元,即1.508 m。此方法不仅可以满足林业作业的精度要求,还可使外业工作量最小。