复测角规样本估计蓄积生长量的新方法

角规是一种效率高的测树方法。但用常规角规方法测林分蓄积生长量,在前后两期计数木相同的情况下,断面积生长量为0;如前后期计数木不同,则每相差一株计数木,对单位面积断面积和蓄积的生长量影响颇大。这种跳跃式变化往往不符合林分生长实际,从而影响这一方法的推广采用。为此,曾提出过许多其他用角规测林分蓄积生长量的方法。这些方法可概括分为两类。一类是直接方法,其前后两期都计数的保留木对林分蓄积生长量贡献很小,其断面积生长量为0,蓄积生长仅是形高生长。保留木断面积生长量     

用点抽样和乘积估计值法测定林分蓄积量

用点抽样和乘积估计值法测定林分蓄积量宋新民关键词点抽样，乘积估计值，次级样本用角规点抽样，林分每公顷蓄积量为：Ｍ＝ＦＺ－Ｒ（式中，Ｆ为角规断面积因子，Ｚ为样点计数木株数，－Ｒ为林木平均形高）。为了获得－Ｒ值，必须采用角规控制检尺和一元立木材积表。目前...     

固定角规点上估测林分生长的期初特征值法

复测固定角规点时，令保留木和进界木的期初断面积分别为ｇ１和ｇ０，它们的期末断面积为ｇ２，若把断面积比（ｇ１／ｇ２）和（ｇ０／ｇ２）分别称为保留木和进界木期初断面积特征值δ１和δ０，而它们的期末特征值仍为δ＝１，则林分每公顷断面积生长量△Ｇ＝Ｆ（∑Ｚ２ｉ＝１δｉ－∑Ｚ１ｊ＝１δ１ｊ－∑Ｚ２－Ｚ１ｋ＝１δｏｋ）。当保留木和进界木的期初形高分别为ｈｆ１和ｈｆ０，它们的期末形高为ｈｆ２时，则林分每公顷的蓄积生长量△Ｍ＝Ｆ（∑Ｚ２ｉ＝１ｈｆ２ｉ－∑Ｚ１ｊ＝１（δ１ｈｆ１）ｊ－∑Ｚ２－Ｚ１ｋ＝１（δ０ｈｆ０）ｋ。期初特征值法的特点是，既能保持直接法的优点———与林分蓄积现状具有一致性，便于连续清查，又能避免其缺点———抽样效率低。能真实地反映林分生长的连续性、渐进性。模拟实验证明，期初特征值法的抽样精度为９５％左右，平均系统误差为±５％左右。抽样效率是直接法的１０—３０倍。     

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

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。     

几种常用森林蓄积量调查方法对比分析

在云南省澜沧县糯福乡面积为4.0 hm2的试验林分中,采用机械角规样地调查法、全林每木检尺法、带状样地调查法、样圆调查法和角规辅助典型选样调查法进行了林分蓄积量调查,对所得结果进行分析,认为不同精度要求条件下应采用适宜的调查方法.     

点抽样采用常数检尺是有偏的——热带雨林实例研究

一、前言在水平点抽样中,正确的方法是为林分、林层或森林选择一个合适的断面积系数(BAF),并在所有角规点都使用这个BAF。在每个角规点,改变BAF进行绕测,直到获得指定的最少树木株数(检尺木)的方法,就是“常数检尺规则”法,近     

测定林分蓄积的角规两维点抽样法

根据树干断面积和干长的量测误差对材积计算的影响，探讨了角规测树时胸高断面积和形高的测定误差对林分蓄积的影响，提出了角规两维点抽样法。特点是既能减少的工作量，又能取得满意的测树效果。计算机模拟实验证明了该方法的可靠性。     

长白落叶松人工林间伐林分的生长模拟

利用黑龙江省孟家岗林场长白落叶松人工林间伐标准地定位观测数据,其于间伐林分断面积与相同年龄、相同立地、相同保留木株数的未间伐林分面积,随时间趋于一致的假设,根据未间伐人工林林分断面积生长的一般预测模型导出了间伐林分的断面积生长预测模型,同时,结合抚育间伐技术批示的确定,进行和林分的动态模拟。     

华北落叶松间伐效应生长量分析

本文详细论述了如何用间伐效应生长量分析方法,将间伐林分断面积总生长量分解为基本生长量、效应生长量两部分进行考察,以及单独定量间伐效应生长量的基本理论及具体途径。 通过对华北落叶松人工林间伐固定标准地的研究分析表明:该树种间伐林分株数按径级分布符合韦布尔分布,林分在不同生长发育时期,其间伐最大效应生长量所对应的保留株数不同。     

湘潭市杉木林平均形高表的编制

本文利用湘潭市编制杉木材积表的样木，分别建立林分平均形高Ｈｆ与相应的林分平均树高Ｈ、林分平均形高Ｈｆ与相应林分平均胸径Ｄ的数学模型，编制数表，以提高角规测树在各种调查中的精度。     

Estimating the volume of forest growing stock using auxiliary information derived from relascope or ocular assessments

The aim of this study is to demonstrate the potential of integrating probabilistic sampling and estimation with the conventional technique referred to as forest inventory by compartments. The objective of this paper is to propose two strategies for the assessment of growing stock volume using two-phase sampling, namely: (i) relascope basal area estimation performed on first-phase sampling points followed by volume estimation performed on a sub-sample of points selected in the second phase; (ii) ocular evaluation of growing stock volume performed on first-phase sampling plots of fixed size followed by volume estimation performed on a sub-sample of plots selected in the second phase. The effectiveness of using the auxiliary information gathered in the first phase is assessed by comparing the double-expansion estimator of total volume which depends solely on the second-phase sample with the two-phase ratio estimator which instead calibrates the double-expansion estimator on the basis of first-phase information. Conservative estimators of sampling variances and confidence intervals are derived for both the estimators. As is usual in forest inventories, first-phase sampling is assumed to be performed on a systematic random grid while three different schemes are considered for drawing the second-phase sample: simple random sampling without replacement, stratified sampling and 3-P sampling. The performance of double-expansion and ratio estimators under the three schemes adopted in the second phase is empirically checked by means of a simulation study performed on a real compartment in a beech forest of Central Italy. Simulation results show that the use of auxiliary information generated in the first phase constitutes a very effective way of increasing the accuracy of volume estimation at the compartment level, with a moderate increase of fieldwork.     

杨树人工林林木蓄积量调查方法对比研究

采用全林每木检尺法、标准地调查法、样圆调查法、角规调查法对同一块杨树人工林林木蓄积量进行调查,比较了不同调查方法的调查精度与工作量大小.结果表明：四种调查方法调查所得林木蓄积量无明显差异.以全林每木检尺法调查的林木蓄积量为标准值,标准地调查法所测数据精度最高,其次为样圆调查法、角规调查法.从调查工作量上来看,全林每木检尺法工作量最大,样圆调查法与角规调查法操作容易,工作效率较高.     

Critical point relascope sampling for unbiased volume estimation of downed coarse woody debris

Critical point relascope sampling is developed and shown tobe design-unbiased for the estimation of log volume when usedwith point relascope sampling for downed coarse woody debris.The method is closely related to critical height sampling forstanding trees when trees are first sampled with a wedge prism.Three alternative protocols for determining the critical samplingpoints on a log are presented and simulations are employed tosuggest the most efficient protocol to use in practice.     

Efficiency of alternative forest inventory methods in partially harvested stands

Forest inventory is vital to all aspects of forest management and inventory methods can vary greatly in their accuracy, precision, efficiency and cost. In Maine, much of the forestland base has been managed using partial harvesting methods over the past two decades. These partial harvesting methods generally produce highly heterogeneous stand structures and composition. Consequently, it is currently unclear which inventory methods are best given the distinct spatial and structural heterogeneity that is created. We compared efficiency and stand-level inventory estimates using horizontal point, fixed area and horizontal line sampling measurement methods in 16 partially harvested stands across northern and central Maine. Some stand-level variables were sensitive to measurement method (e.g., volume, quadratic mean diameter and small stem density and basal area), while others were less sensitive (e.g., overall basal area and stem density). Efficiency, defined as a combination of precision of volume estimates and measurement time, varied among measurement methods at lower stand basal area values but was similar at higher basal area, with the exception of the fixed area method. Overall, horizontal line sampling proved to be a viable method in post-partial harvest stand conditions. Our results illustrate the trade-offs between precision and time costs involved in several measurement methods under a range of heterogeneous stand conditions.     

An improved technique for non-destructive measurement of the stem volume of standing wood

An improved technique, cheaper and less time-consuming, to measure standing wood volume by using an electronic theodolite was tested, by which greater information from the forest could be acquired accurately and non-destructively. This was achieved by recording the diameter at breast height and ground-level diameter of a tree as well as the included angle between the electronic theodolite and the left and right tangents of the stem at any point. The standing wood volume then was computed precisely by section. In addition, the factors that influence the precision of the method (observable distance and number of segments) were also analysed. In the study, 175 Larix gmelinii (Rupr.) Kuzen. trees and 190 Populus tomentosa Carrière trees chosen randomly for sampling were measured with the electronic theodolite, and then were cut down for measurement of the average cross-section volume. Based on the data acquired from 100 sample trees, a standard volume table was compiled, and then the data for the remaining random 10 sample trees in each group were selected for a comparison test. The results indicated that the optimal distance for indirect observation should be as high as the sample tree, and the optimal visual distinguished section was about 2?m. The correlation coefficient between the value measured non-destructively and the value of the felled trees of L. gmelinii was 0.97, with an average relative error of 1.62%. With regard to P. tomentosa, the correlation coefficient between the two values obtained by the two methods was 0.905 with an average relative error of 8.40%. It was concluded that the standard volume model based on the non-destructive measurement technique meets the requirements for precision in forest surveys. The precision of the standard volume model for L. gmelinii (a coniferous tree) was superior to that of the model for P. tomentosa (a broad-leaved tree). The electronic theodolite method provides an alternative technique for measuring trees without destructive sampling and is widely applicable for forest surveys.     

How much space does a seedling need?

A method is described to identify canopy trees which significantly affect regeneration at a given point, estimate the effect of these trees on the growth and survival of seedlings, and determine the maximum density of the canopy trees compatible with successful regeneration. All this information is obtained using point sampling done with several basal area factors from the same point. An example of the method's application is provided.     

Design-unbiased point-to-object sampling on lines,with applications to areal sampling

Sampling methods that depend on the distance between a sample point and a fixed number of objects, such as trees or downed logs, have often been proposed in the forestry and ecology literature. However, such methods have been biased when objects are not distributed with complete spatial randomness, have required difficult field procedures (such as measuring the position of out-of-sample objects), or both. Here a new approach based on measurement of the distance to objects along sample lines is proposed. The approach does not require measuring the position of out-of-sample objects, and its design-unbiased estimators require only simple arithmetic. Furthermore, because many useful sampling procedures can be related back to sampling on a line, the new method leads quickly to sampling procedures applicable when objects are distributed in a two-dimensional region. These include, among others, fixed-count approaches to line intersect sampling, a new approach to variable-area transect sampling, and a density-adapted variable sector sampling method.     

南方山地森林小班蓄积量调查方法的对比分析

以南方山地森林为研究对象,选取有代表性的4个小班,分别采用角规抽样调查法、中心样圆法、样圆群法、六株木法、垂直样带法、标准地法共6种方法对小班蓄积量进行测定,并从6种方法的调查精度、误差大小、工作量及工具和仪器的难易程度等方面对小班蓄积量进行了对比分析,认为角规抽样调查法是最适合南方山地森林小班蓄积量的调查方法。