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由于山体滑坡的原因,导致森林资源连续清查中的固定样地变形,造成周界样木的错测、漏侧、多测,影响调查精度.据此提出了一种称之为特殊角规点抽样的样地创新调查方案,并对此进行了分析和评估. 相似文献
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森林资源二类调查系统抽样2种样地调查方法的比较与分析 总被引：2，自引：1，他引：1
《林业资源管理》2016,(3)
以贵州省锦屏县第四次森林资源二类调查系统抽样为例,对角规点抽样的标准表法和圆形样地每木检尺的二元立木材积表法进行了比较和分析。结果表明:角规样地与圆形样地对总体蓄积抽样精度分别为90.28%,90.38%,均达到规定的精度要求(≥90%),总体蓄积估计值仅相差1.63%;角规样地检尺样木株数较少,外业工作量相当于圆形样地的40%左右,抽样效率较高;角规样地对大部分林分公顷株数、公顷断面积、公顷蓄积的抽样估计偏低。小班蓄积采用角规辅助调查的标准表法,总体蓄积采用圆形样地每木检尺的二元立木材积表法进行抽样控制的方法是可行的。 相似文献
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固定样地是森林资源清查体系最基本的抽样单元，通过对所有固定样地多期的调查监测，最终得出各地区森林资源的现状及动态变化情况，所以固定样地的准确复位便成为森林资源清查体系的核心工作。目前，我国森林资源连续清查主要依靠人工设置一些固定样地标志，以保持样地位置的固定，并保证样地在以后的调查监测工作中不再发生位置和形状的改变。 相似文献
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《林业资源管理》2017,(2):40-45
利用110块临时方形样地(900 m~2)每木检尺调查和角规绕测调查资料及1 830块固定方形样地(667 m~2)每木检尺调查和角规控制检尺调查资料,以方形样地调查结果为参考,分析角规测树的断面积(G)、林分平均高(H)和每公顷蓄积量(M)的偏差并作配对t检验分析。结果表明:角规绕测G,H,M的平均偏差分别为-15.88%,5.27%和-12.16%;角规绕测G的偏差服从正态分布,但H和M的偏差不服从正态分布;角规绕测的G,H,M与方形样地每木检尺调查结果均存在显著性差异(可靠性为95%);角规控制检尺G的平均偏差为-4.59%;角规控制检尺G的偏差不服从正态分布,并与方形样地调查结果也存在着显著性差异(可靠性为95%)。角规测树偏差主要是操作不够规范、欠认真细致造成的。在森林资源调查中,需要研究和发展先进、可靠、可行的新技术新方法,如机载激光雷达。 相似文献
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角规测树在森林资源抽样调查中应用的研究 总被引：1，自引：0，他引：1
根据角规测树与抽样调查原理,在大田县桃源林场森林资源二类调查中,采用角规可变样圆测树调查与方形样地每木检尺调查,进行抽样调查试验比较,以探索角规测树方法应用于森林资源抽样调查的可行性。 相似文献
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1984年省决定在韶关市十二个县开展森林资源二类调查。根据《广东省森林资源二类调查操作细则》规定,在进行小班调查的同时,对蓄积量在200万m~3以上的县进行群状抽样控制,并把样点,样木固定下来,建立县级连续清查体系。群状抽样调查适用于林地小块、分散的粤北集体林区,采用这种方法,缩短了外业调查时间,节省了调查经费,并达到了精度要求。1984年采用群状抽样调查,全市总蓄积量为5081万m~3,同1983年省级连续清查体系采用方形样地调查的结果4965万m~3比较,相差2.3%,各县的 相似文献
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叙述森林资源连续清查成果的作用及有关样地数量的问题,详细论述确保连清成果无偏、提高样地样木复位率、提高调查工作的效率与精度、保证调查质量、使调查成果满足多方面需要及成果分析等森林资源连续清查体系的巩固、完善、提高方面的问题。 相似文献
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为了对比定株样园与方形样地的精度和效率,探索在森林资源清查中应用定株样园抽样,代替方形样地测树的可能性。在森林资源连续清查中,结合固定样地的测设,我们随机抽取了部分样点,进行定株样园与方形样地两种测树方法的对比试验,情况如下: 相似文献
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《Southern Forests》2013,75(3):137-143
The main issue in forest inventory is the reliability of data collected, which depends on the shape and size of inventoried plots. There is also a need for harmonisation of inventoried plot patterns in West Africa. This study focused on the impact of plot patterns on the quantitative analysis of two vegetation types of West Africa based on case studies from Benin. Twenty and fifteen plots of 1 ha each were demarcated in dense forest and woodland, respectively. Each 1 ha plot was divided into 100 quadrats of 100 m2 each and diameter at breast height (dbh) of trees was recorded in each quadrat. The required time to measuring trees diameter in each 1 ha plot was also recorded to compute the mean inventory effort. From the 100 quadrats in each 1 ha plot, 14 subplots of different shapes and sizes were considered by grouping together adjacent quadrats. The basal area of each subplot was computed and the relationship between estimation bias of the basal area and the size of subplots was modeled using Smith's Law (Smith 1938). The mean absolute error of the shape parameter c of Weibull distribution was computed for each of the subplot shape, size and direction. The direction and shape of subplots did not influence significantly (P > 0.05) the precision of the quantitative analysis of vegetation. However, square subplots were suitable in practice. On the contrary, plot size was significantly (P < 0.05) and inversely correlated to estimation efficiency. The optimal plot size for quantitative analysis of vegetation was 1 800 and 2 000 m2 with an inventory effort of 0.51 and 0.85 man-days per subplot in woodland and dense forest, respectively. It is concluded that use of standard sample sizes will help to harmonise a forestry database and to carry out comparisons at regional level. 相似文献
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《Scandinavian Journal of Forest Research》2012,27(1-4):121-126
The aim of the study was to develop methods for estimating the taper curves for trees tallied in a forest inventory. The average stem form in a stand was described by the principal components of the stand effects in the stem dimensions measured in the polar coordinate system. Measurements of diameter at breast height, diameter at a height of 6 meters, and height taken from trees on the sample tree plots were used for determining the first four principal components. Regression models were derived to predict the principal components from the site and growing stock variables. These models were used to estimate the taper curves of the tallied trees. Use of the principal components estimated by the regression models gave less reliable results than use of the principal component estimates based on measurement of the height of one randomly chosen tree on the sample plot. The best result was found with combined use of the principal component estimates and one height measurement per sample plot. 相似文献
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国家级森林资源监测体系中的地面样地设计 总被引：4，自引：1，他引：3
本文基于抽样原理, 在分析世界上国家级森林清查体系中样地设计特点的同时, 根据我国森林资源的特点, 对我国森林资源连续清查中采用的各种地面样地设计加以讨论, 并对新体系的地面样地设计提出了建议。 相似文献
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《Journal of Sustainable Forestry》2013,32(1):77-96
Abstract A total of 11 sample-based estimators of tree species richness (S) are evaluated in terms of accuracy and precision in a Monte Carlo simulated simple random sampling from 39,779 forest inventory plots with 7.8 million trees belonging to 85 species. The plots represent a 108 million hectare forested region in central and eastern Canada. Sample sizes varied from 50 to 800. A weighted index combining estimates of accuracy and precision identified Chao's first estimator (CHAO1) as overall best with an estimator based on the assumption of a gamma mixed Poisson distribution of species occurrence as a close runner-up. The observed sample species richness was almost always the most negatively biased estimate. A sample size of 400-700 conventional fixed area forest inventory plots are needed to produce results with bias <20%. 相似文献
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基于连清体系的森林生物多样性监测网络构建研究——以湖南省为例 总被引：1，自引：1，他引：0
以南方重点林区湖南省为例,在明确影响森林生物多样性主要环境因素的基础上,通过空间平衡抽样、改进的Whittaker样地设计,构建省级尺度上森林生物多样性监测网络。研究表明:1)与简单随机抽样、系统抽样相比,空间平衡抽样在降低样本点空间关联性、提高抽样效率和抽样精度方面具有明显的优势;2)改进的Whittaker样方设计可以帮助人们更好地分析物种丰富度、平均覆盖度、物种多样性空间分布规律;3)依托于现有的连清体系,采用空间平衡抽样方法进行森林生物多样监测样本构建,采用改进的Whittaker样方设计进行生物多样性调查,可以为省级尺度上的森林生物多样性监测网络的构建探索出一条具有统计学基础且经济适用的途径。 相似文献
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《林业研究》2021,32(4)
Monitoring sample plots is important for the sustainable management of forest ecosystems.Acquiring resource data in the field is labor-intensive,time-consuming and expensive.With the rapid development of hardware technology and photogrammetry,forest researchers have turned two-dimensional images into three-dimensional point clouds to obtain resource information.This paper presents a method of sample plot analysis using two charge-coupled device(CCD) cameras based on video photography.A handheld CCD camera was used to shoot the sample plot by surrounding a central tree.Video-based point clouds were used to detect and model individual tree trunks in the sample plots and the DBH of each was estimated.The experimental results were compared with field measurement data.The results show that the relative root mean squared error(rRMSE) of the DBH estimates of individual trees was 2.1-5.7%,acceptable for practical applications in traditional forest inventories.The rRMSE of height estimates was2.7-36.3%.Average DBH and heights,and tree density and volume were calculated.Video-based methods require compact observation instruments,involve low costs during field investigations,acquire data with high efficiency,and point cloud data can be processed automatically.Furthermore,this method can directly extract information on the relative position of trees,which is important to show distribution visually and provides a basis for researchers to regulate stand density.Additionally,video photography with its unique advantages is a technology warranting future attention for forest inventories and ecological construction. 相似文献
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西藏自治区森林碳密度及分布规律研究 总被引：1，自引：0，他引：1
利用森林资源连续清查实测样地及样木数据,结合相对树高曲线,构建生物量-蓄积量模型,解决了模型与各类森林资源调查数据的衔接问题,可应用于西藏自治区森林资源连续清查的目测与遥感样地生物量估算及森林资源规划设计调查小班生物量估算等。根据计算的森林资源连续清查各样地生物量密度,结合树种面积数据及含碳率,估算全区森林碳密度,并初步探讨了森林碳库地带性分布规律。 相似文献