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1.
The k-nearest neighbors (kNN) method is widely employed in national forest inventory applications using remote sensing data. The objective of this study was to evaluate the kNN method for stand volume estimation by combining LANDSAT/ETM+ data with 622 field sample plots from the Japanese National Forest Inventory (NFI) in Kyushu, Japan. The root mean square error (RMSE) and relative RMSE of the volume estimates rapidly decreased as the number of nearest neighbors (k) increased up to five, and then it slightly declined. They were consistently smaller for the Euclidean distance than for the Mahalanobis distance. The estimation errors (RMSE and relative RMSE) were 169.2 m3/ha and 66.2%, respectively (k = 10). The relative RMSE was similar to the previous studies. The estimated values were more accurate towards the mean value of the total volume, with an overestimation of the low volumes and an underestimation of the high volumes. We found a significant linear relationship between the observed stand volumes and estimated errors, which suggests that systematic errors may be reduced using this linearity. This research concluded that the kNN method is suitable for estimating stand volumes in Kyushu.  相似文献   

2.

Information about the state of the forest is of vital importance in forest management planning. To enable high-precision modelling, many forest planning systems demand input data at the single-tree level. The conventional strategy for collecting such data is a plot-wise field inventory. This is expensive and, thus, cost-efficient alternatives are of interest. During recent years, the focus has been on remote sensing techniques. The k nearest neighbour (kNN) estimation method is a way to assign plot-wise data to all stands in a forest area, using remotely sensed data in connection with a sparse sample of field reference plots. Plot-wise aerial photograph interpretations combined with information from a stand register were used in this study. Nearness to a reference plot was decided upon using a regression transform distance. Standing stem volume was estimated with a relative root mean square error (RMSE) equal to 20% at the stand level, while age could be estimated with a RMSE equal to 15%. A cost-efficient data-capturing strategy could be to assign plot data with the presented kNN method to some types of forest, while using traditional field inventories in other, more valuable, stands.  相似文献   

3.
This article compares three methods for forest resource estimation based on remote sensing features extracted from Airborne laser scanning and CIR orthophotos. The estimation was made exemplarily for the total stem volume of trees for a given area, measured in cubic metres per hectare [m3 ha−1] (as one of the most important quantitative parameters to characterise a forest stand). The following methods were compared: Regression Analysis (RA), k-NN (nearest neighbour) method and a method that utilises regional yield tables, referred to as the yield table method (YT-method). The estimation of stem volume was examined in a mixed forest in Southern Germany using 300 circular inventory plots, each with a size of 452 m2. Remote sensing features relating to vegetation height and structures were extracted and used as input variables in the different approaches. The accuracy of the estimation was analysed using scatter plots and quantified using absolute and relative root mean square errors (RMSE). The comparison was made for all plots, as well as for averaged plot values located within forest stands that have the same age class. On “plot level” the RMSE yielded 79.79 m3 ha−1 (RA), 81.93 m3 ha−1 (k-NN) and 81.78 m3 ha−1 (YT-method) and for the averaged values 35.75 m3 ha−1 (RA), 35.06 m3 ha−1 (k-NN) and 42.98 m3 ha−1 (YT-method). Advantages and disadvantages, as well as requirements, of the methods are discussed.  相似文献   

4.
Abstract

The accuracy of forest stem volume estimation at stand level was investigated using multispectral optical satellite and tree height data in combination. The stem volumes for the investigated coniferous stands, located in southern Sweden, were in the range of 15–585 m3 ha?1 with an average stem volume of 266 m3 ha?1. The results from regression analysis showed a substantial improvement for the combined stem volume estimates compared with using satellite data only. The accuracy in terms of root mean square error (RMSE) was calculated to 11.2% of the average stem volume using SPOT-4 data and tree height data in combination compared with 23.9% using SPOT-4 data only. By replacing SPOT-4 data with Landsat TM data the RMSE was improved from 25.2% to 12.2%. In addition, a sensitivity analysis was performed on the combined stem volume estimates by adding random errors, normally distributed with zero expectations, with standard deviations of 1, 1.5 and 2 m to tree height data. The results showed that the RMSE increased with increasing random tree height error to 15.4%, 18.0% and 19.9% using SPOT-4 data and 16.3%, 19.2% and 21.2% using Landsat TM data. The results imply that multispectral optical satellite data in combination with accurate tree height data could be used for standwise stem volume estimation in forestry applications.  相似文献   

5.
One way of meeting the supply demands of the wood industry is through the reduction of waste in timber processing. It has been estimated in Ghana that for every tree felled, nearly 50% of the tree volume is left in the forest in the form of branches, crownwood, and stumps. In this study, the potential of utilizing branchwood as raw material from logging residues to help meet the timber demands of the downstream processing sector was analyzed experimentally. The sawing characteristics of the branchwood of Aningeria robusta and Terminalia ivorensis with diameters in the range 10–25 cm using live sawing and cant sawing methods were determined using a randomized complete block design, 2 × 4 factorial with three replications. Experimental results indicate that, the relative lumber value yields for first and second grade boards of A. robusta and T. ivorensis branches were 25 and 20%, respectively, while the green lumber volume yields were 40 and 32%, respectively. A high proportion of sapwood and the occurrence of washboarding in T. ivorensis contributed to that species’ relatively low lumber value and volume yield. The experimental results further indicate that the sawing technique used had no significant influence on lumber yields. However, at 5% level of significance, significant differences in lumber yield existed between some of the diameter classes.  相似文献   

6.
[目的]由于激光雷达技术已经能准确测定立木树高及相关树冠因子,应用该技术建立基于树高和树冠因子的立木材积模型,为激光技术在森林蓄积估计中提供技术支撑.[方法]利用云杉、冷杉、栎树、桦树4个树种组的3 010株实测样木数据,分析了立木材积与胸径、树高、树冠因子之间的相关关系;并通过对数回归方法构建了基于树高和树冠因子的立木材积模型,用确定系数R2和平均预估误差MPE等6项指标对模型进行评价.[结果]表明,立木材积与单一因子之间的相关,以胸径最为紧密,其次是树高,再次是冠长和冠幅.基于树高和树冠因子的立木材积模型中,以树高和冠幅作为解释变量的二元模型效果较好,再增加冠长因子的三元模型改进不大.云杉、冷杉、栎树、桦树4个树种组基于树高冠幅的立木材积模型,其R2分别为0.81、0.80、0.76和0.77,MPE分别为4.7%、5.3%、5.4%和5.3%,模型预估精度均能达到95%左右.[结论]本文对材积与林木因子之间相关关系的定量分析,建立了云杉、冷杉、栎树、桦树4个树种的立木材积模型,模型预估精度高.为激光雷达技术定量估测森林参数提供了依据.  相似文献   

7.
For estimation of tree parameters at the single-tree level using light detection and ranging (LiDAR), detection and delineation of individual trees is an important starting point. This paper presents an approach for delineating individual trees and estimating tree heights using LiDAR in coniferous (Pinus koraiensis, Larix leptolepis) and deciduous (Quercus spp.) forests in South Korea. To detect tree tops, the extended maxima transformation of morphological image-analysis methods was applied to the digital canopy model (DCM). In order to monitor spurious local maxima in the DCM, which cause false tree tops, different h values in the extended maxima transformation were explored. For delineation of individual trees, watershed segmentation was applied to the distance-transformed image from the detected tree tops. The tree heights were extracted using the maximum value within the segmented crown boundary. Thereafter, individual tree data estimated by LiDAR were compared to the field measurement data under five categories (correct delineation, satisfied delineation, merged tree, split tree, and not found). In our study, P. koraiensis, L. leptolepis, and Quercus spp. had the best detection accuracies of 68.1% at h = 0.18, 86.7% at h = 0.12, and 67.4% at h = 0.02, respectively. The coefficients of determination for tree height estimation were 0.77, 0.80, and 0.74 for P. koraiensis, L. leptolepis, and Quercus spp., respectively.  相似文献   

8.
This study assessed the sustainability of selection cutting in a community forest (CF) in Bhutan. The harvesting approach differed from cable crane logging operations in an adjacent commercially managed forest by creating much smaller canopy openings. This had many implications for natural regeneration of preferred species. The study was conducted in a late successional broadleaved CF containing 32 genera of tree species dominated by Quercus and Castanopsis and managed for timber, firewood, non-wood forest products and forest grazing. The study was based on a comparison of two forest inventories to assess forest structure and regeneration, a study of stumps to quantify harvesting intensities, and a household survey to quantify livestock holdings and grazing patterns. The study examined different intensities of selection cutting in three blocks of the CF and found that higher intensities of selection cutting did not have a negative impact on: (a) natural regeneration of seedlings and saplings of preferred timber species; (b) the diameter distribution of all species and use categories except for Quercus; (c) the diversity of tree genera; and (d) the percentage of remaining trees with favorable bole shape and form. These results contrasted with findings in the adjacent commercially managed forest. Community management of broadleaved forests with selection cutting appeared to be sustainable and avoid some of the unresolved silvicultural problems associated with commercially managed forests in Bhutan. However more research is needed on the sustainable management of Quercus spp.  相似文献   

9.
以马尾松人工林作为研究对象,用伐倒木样木数据,经干形分析和多指标精度比较,选定最佳的削度方程;通过树皮率方程和树高曲线方程进行计算机理论造材,依据各经济材种规格,编制出马尾松胸径树高二元经济材出材率表。经检验,以该方法编制的出材率表达到林业数表模型编制的精度要求。  相似文献   

10.
Sustainable forest management requires knowledge of forest structure and dynamics as well as an estimation of growing stock. The forest inventory provides the data for estimating stand variables. The measurement device MU2005-01738, patented by the Center for Forest Research (INIA-CIFOR), provides stereoscopic hemispherical images which can allow the 3D restoration of the stand around the sampling point. The aim of this study is to develop a methodology for forest stand mapping as well as tree diameter and height measurement along with volume estimation from the stereoscopic hemispherical images provided by the MU2005-01738. Using the MU2005-01738, Eucalyptus globulus Labill. plantations were sampled. Distance, diameter, height and volume were derived from the stereoscopic hemispherical images of 30 trees located at distances ranging from 0 to 15 m from the device. These variables were then compared with field measurements and the estimation errors analyzed. The (root-mean-squared error) RMSE was 0.23 m (8.95 %) for tree position and 1.51 cm (10.43 %) for diameter at breast height measurement at distances of less than 8 m. In the case of stem height and individual tree volume estimation, the RMSE was 2.59 m (23.05 %) and 0.025 m3 (17.94 %), respectively. The analysis of measurement errors indicated that the measurement precision decreases beyond 8 m from the device as well as for directions close to the baseline (the line between the optical centers of the two images), whereas the precision was highest for directions near to the line which is perpendicular to the base line. Future research should focus on improving measurement accuracy and possible applications in the field of forestry of the techniques presented in this study.  相似文献   

11.
The objective of forest management planning is often expressed as maximum sustainable economic yield. Methods used to collect information for forestry planning should, therefore, include variables significant for economic evaluations of management alternatives. It is important to be able to differentiate mature stands with respect to timber volumes and species mixture. In this study, digital high‐altitude aerial photographs are tested as a data source for planning. Circular plot data from a forest estate in northern Sweden were used as reference material. Global positioning system (GPS) measurements, with differential correction, were used to georeference the plots. Harvesting priorities were calculated for each plot using the Forest Management Planning Package. Volumes, species mixture and harvest priorities were estimated using regression analysis based on textural and spectral information from aerial photographs. The results show that the dependent variables could be estimated fairly well using only spectral information, e.g., R 2 = 0.44 when estimating timber volume at reference plot (10 m radius) level. Aggregated to stand level, the precision was comparable with customary field survey methods (e.g., RMSE= 13.4% for timber volume).  相似文献   

12.
We investigated conifer plantation management in Japan using high-resolution airborne data based on an individual tree crown (ITC) approach. This study is the first to apply this technique to Japanese forests. We found that forest resources can be measured at the level of a single tree. We also produced a tree-crown map for a test site with Chamaecyparis obtusa, Pinus densiflora, Larix kaempferi, Cryptomeria japonica, other conifers, and broadleaved trees, with a classification accuracy of 78%. Forest-stand polygons with tree-cover types were generated from this map, a tree-density map, and a crown-occupied-area map. Forest information for the stand polygons was extracted automatically and compared with detailed field-survey data. The error between our ITC estimates and the field-survey data ranged from 0.3 to 30.2%, depending on tree crown size, density, and other factors. Errors were highest for high-density stands with mixed compositions and tree crown diameters ≤5.0 m. However, the error for stands with crown diameters ≥6.2 m was 11.6% or less. Therefore, this technique is best suited to pure Japanese conifer plantations without multiple layers or high-density stands.  相似文献   

13.
Interferometric Synthetic Aperture Radar (InSAR) data from TerraSAR-X add-on for Digital Elevation Measurement (TanDEM-X) were used to estimate aboveground biomass (AGB) and tree height with linear regression models. These were compared to models based on airborne laser scanning (ALS) data at two Swedish boreal forest test sites, Krycklan (64°N19°E) and Remningstorp (58°N13°E). The predictions were validated using field data at the stand-level (0.5–26.1 ha) and at the plot-level (10 m radius). Additionally, the ALS metrics percentile 99 (p99) and vegetation ratio, commonly used to estimate AGB and tree height, were estimated in order to investigate the feasibility of replacing ALS data with TanDEM-X InSAR data. Both AGB and tree height could be estimated with about the same accuracy at the stand-level from both TanDEM-X- and ALS-based data. The AGB was estimated with 17.2% and 14.6% root mean square error (RMSE) and the tree height with 7.6% and 4.1% RMSE from TanDEM-X data at the stand-level at the two test sites Krycklan and Remningstorp. The Pearson correlation coefficients between the TanDEM-X height and the ALS height p99 were r?=?.98 and r?=?.95 at the two test sites. The TanDEM-X height contains information related to both tree height and forest density, which was validated from several estimation models.  相似文献   

14.
A field-based study was carried out to broaden our knowledge of fully mechanized cut-to-length harvesting productivity in naturally grown forests in the northern European part of Russia (NEPR). The recorded data comprised 38 midsized single-grip harvesters (JD 1270D) in clear-cutting operations in the Karelia, Komi, Vologda, Leningrad, Tver, and Kirov regions in NEPR, 4.3 million felled trees, and 1.4 million m3 u.b. (under bark) of processed timber. Harvesting operations were conducted in forest stands composed of spruce (48% on average), pine (19%), birch (22%), and aspen (11%), with an average stem volume 0.31 m3 u.b. The cut-to-length harvesters produced from 4.3 to 14.9 m3 u.b./productive machine hour (PMH) and 16.0–49.5 m3 u.b./stem processing machine hour (S proc MH). A machine evaluation analysis and a regression analysis were used to formulate models for predicting cutting productivity of modern single-grip harvester. The regression models were developed to estimate the productivity of the harvesters in the regions taking into account two significant factors influencing the productivity: the stem volume and tree species of the felled trees. Productivity/cubic meter u.b. of processed timber/PMH was calculated according to stem volume and tree species distributions in most forest-covered NEPR regions. Further research is suggested to improve the developed productivity models and to allow prediction of system performance over a broad range of stand and site conditions.  相似文献   

15.
To discover the site adaptability and density suitability of Larix principis-rupprechtii as a water conservation forest in Wutai Mountain, Shanxi Province, the growth process and diameter distribution characteristics of 10-year-old artificial L. principis-rupprechtii forests with density structures of 2600 trees/hm2 and 3500 trees/hm2 were studied using trunk analysis of a sample tree. The results showed that: 1) The tree height increment of the two kinds of forests were the same, and it was almost not affected by density. However, the growth process of the diameter and timber volume showed a great distinction. The growth status and density structure of the low density forest were superior to the high density forest. 2) The skewness (S k) of diameter distribution had great distinction. The S k (0.01) of the low density forest approached a normal distribution, which showed that the density structure was reasonable, while the S k (0.45) of the high density forest was partial to a normal distribution, which showed that the density structure was on the high side. The kurtosis (K) of the two forests (one was −0.64, the other was −0.74) had little distinction and the density factor had limited function to forest polarization. 3) The increment of diameter at breast height, timber volume and trunk stock of the low density forest increased yearly without the effect of density. However, the increment of high density forests had declined from the sixth year, which was restricted by high density. 4) The reasonable density of the 10-year-old L. principis-rupprechtii artificial forest was about 2600 trees/hm2, which is also the reasonable planting density if the utilization of double cutting is not considered. __________ Translated from Science of Soil and Water Conservation, 2007, 5(1): 1–6 [译自: 中国水土保持科学]  相似文献   

16.
Density estimators for k-tree distance sampling are sensitive to the amount of extra Poisson variance in distances to the kth tree. To lessen this sensitivity, we propose an adaptive composite estimator (COM). In simulated sampling from 16 test populations, a three-component composite density estimator (COM)–with weights determined by a multinomial logistic function of four readily available ancillary variables–was identified as superior in terms of average relative absolute bias. Results from a different set of nine validation populations–with widely different stem densities and spatial patterns of tree locations—confirmed that relative root mean squared errors (RRMSE) of COM were, on average, considerably lower than those obtained with the three-component k-tree density estimators. The RRMSE performance of COM improved with increasing values of k. With k = 6 and sample sizes of 10, 20, and 30, the average relative bias of COM was between −5 and 5% in seven validation populations but in an open low-density savanna-like population bias reached −12% (1979 data) and 7% (1996 data). For k = 6 and n = 10, the RRMSE of COM was, in six of the nine validation populations, within 3.3 percentage points of the RRMSE for sampling with fixed-area plots. Jackknife estimates of the precision of COM estimates of density were negatively biased, leading to under-coverage (7%) of computed 95% confidence intervals.  相似文献   

17.
Abstract

The Sierra Madre Occidental ecoregion accommodates some of the richest biodiversity anywhere in North America and contains about two-thirds of the standing timber biomass in Mexico. Worldwide forest trees provide an industrial output of about 363 million cubic meters, with the volume of bark accounting for an estimated 10% of total tree volume, so that bark is a very important nonwoody product. In this study, the proportion of bark volume (PBV) and its correlation with selected tree characteristics as well as the relationship between total tree volume and wood volume (WV) and total volume and bark volume (BV) were calculated for the first time for the 16 common and commercially most important tree species in the temperate pine-oak forest region of El Salto (Durango) on the Sierra Madre Occidental, Mexico. Measurements were made on 2,027 felled trees. The PBV in the species investigated ranges from 0.129 to 0.260 depending on the species and genus, with a mean value of 0.175. BV and WV can be accurately estimated. The approach used in this study is simple and effective, and very user-friendly. The method is recommended for researchers wishing to develop bark models for other tree species.  相似文献   

18.
Turvo Park in the Alto Uruguay River region of the State of Rio Grande do Sul is the last intact remnant of the Seasonally Deciduous Forest in southern Brazil. This forest once covered large parts of southern Brazil but it is now reduced to less than 3% of its original size due to intensive logging caused by its exceptional richness in tree species with commercial timber value. The current study presents results on the diversity of timber species inventored in Turvo Park and in a number of small and scattered forest remnants in its vicinity. All timber plants with DBH ≥5 cm were included in the forest inventory on 540 sampling points, established using the point-centred quarter method. On average, 313 plants ha−1 were recorded, belonging to 57 different species from 25 families. Timber species of commercial value represented 64% of all woody species and 36% of all woody plants. Nectandra megapotamica and Apuleia leiocarpa were the main dominant species. Twenty percent of all plants showed a DBH greater than 40 cm, representing 67% of the total log volume. Differences in species diversity and plant density among the forest remnants were detected. The few forest remnants represent an enormous richness of timber species, being the maintainers and propagule repository for all the biodiversity of that ecosystem. A knowledge-based forest management plan is therefore required to secure their vital role in forest enrichment programs or in projects aiming at recovering abandoned and degraded areas, and in breeding programs for the timber production improvement.  相似文献   

19.
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20.
以云南省宜良森林二类调查数据为样本,基于Google Earth Engine云平台Landsat 8 OLI影像,结合植被因子、纹理特征以及K-T变化为自变量,构建了多元线性回归和随机森林的建模方法,建立了森林蓄积量反演模型.以宜良县云南松为研究对象,运用Landsat8 OLI遥感影像数据结合地面角规控制样地调查数...  相似文献   

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