Using canopy heights from digital aerial photogrammetry to enable spatial transfer of forest attribute models: a case study in central Europe

This paper describes a workflow utilizing detailed canopy height information derived from digital airphotos combined with ground inventory information gathered in state-owned forests and regression modelling techniques to quantify forest-growing stocks in private woodlands, for which little information is generally available. Random forest models were trained to predict three different variables at the plot level: quadratic mean diameter of the 100 largest trees (d₁₀₀), basal area weighted mean height of the 100 largest trees (h₁₀₀), and gross volume (V). Two separate models were created – one for a spruce- and one for a beech-dominated test site. We examined the spatial portability of the models by using them to predict the aforementioned variables at actual inventory plots in nearby forests, in which simultaneous ground sampling took place. When data from the full set of available plots were used for training, the predictions for d₁₀₀, h₁₀₀, and V achieved out-of-bag model accuracies (scaled RMSEs) of 15.1%, 10.1%, and 35.3% for the spruce- and 15.9%, 9.7%, and 32.1% for the beech-dominated forest, respectively. The corresponding independent RMSEs for the nearby forests were 15.2%, 10.5%, and 33.6% for the spruce- and 15.5%, 8.9%, and 33.7% for the beech-dominated test site, respectively.     

立体视觉技术应用于林木个体分布格局测定研究

详细介绍了应用立体视觉技术由立体像对测定林木个体分布空间格局的方法、步骤，探索了适合林业环境下的立体视觉实现的技术路线。摄像机标定采用基于非线性度量误差模型的摄像机标定方案；图像匹配采用外极线和Canny算子检测出的树干边缘约束下的人机交互式的相关匹配。最后通过实验对文中算法、策略进行了验证。结果表明，在实验条件下，应用立体视觉测定林木个体分布格局可以达到精度要求。     

Forest stand age classification using time series of photogrammetrically derived digital surface models

In this research, we developed and tested a remote sensing-based approach for stand age estimation. The approach is based on changes in the forest canopy height measured from a time series of photo-based digital surface models that were normalized to canopy height models using an airborne laser scanning derived digital terrain model (DTM). Representing the Karelian countryside, Finland, CHMs from 1944, 1959, 1965, 1977, 1983, 1991, 2003, and 2012 were generated and allow for characterization of forest structure over a 68-year period. To validate our method, we measured stand age from 90 plots (1256?m²) in 2014, whereby producer's accuracy ranged from 25.0% to 100.0% and user's accuracy from 16.7% to 100.0%. The wide range of accuracy found is largely attributable to the quality and characteristics of archival images and intrastand variation in stand age. The lowest classification accuracies were obtained for the images representing the earliest dates. For forest managers and agencies that have access to long-term photo archives and a detailed DTM, the estimation of stand age can be performed, improving the quality and completeness of forest inventory databases.     

Economic utility of 3D remote sensing data for estimation of site index in Nordic commercial forest inventories: a comparison of airborne laser scanning,digital aerial photogrammetry and conventional practices

ABSTRACT

Forest productivity is a crucial variable in forest planning, usually expressed as site index (SI). In Nordic commercial forest inventories, SI is commonly estimated by a combination of aerial image interpretation, field assessment and information obtained from previous inventories. Airborne laser scanning (ALS) and digital aerial photogrammetry (DAP) data can alternatively be used for SI estimation, however the economic utilities of the inventory methods have not been compared. We compared seven methods of SI estimation in a cost-plus-loss analysis, by which we added the expected economic losses due to sub-optimal treatment decisions to the inventory costs. The methods comprised direct and indirect estimation from combinations of ALS, DAP and stand register data, and manual interpretation from aerial imagery supported by field assessment and information from previous inventories (conventional practices). The choice of method had great impact on both the accuracy and the economic value of the produced estimates. Direct methods using bitemporal ALS and DAP data gave the best accuracy and the smallest total cost. DAP was a suitable and low-cost data source for SI estimation. Estimation from single-date ALS and DAP data and age obtained from the stand register provided practical alternatives when applied to even-aged stands.     

Comparing biophysical forest characteristics estimated from photogrammetric matching of aerial images and airborne laser scanning data

Recent development in aerial digital cameras and software facilitate the photogrammetric point cloud as a new data source in forest management planning. A total of 151 field training plots were distributed systematically within three predefined strata in a 852.6 ha study area located in the boreal forest in southeastern Norway. Stratum-specific regression models were fitted for six studied biophysical forest characteristics. The explanatory variables were various canopy height and canopy density metrics derived by means of photogrammetric matching of aerial images and small-footprint laser scanning. The ground sampling distance was 17 cm for the images and the airborne laser scanning (ALS) pulse density was 7.4 points m^–2. Resampled images were assessed to mimic acquisitions at higher flying altitudes. The digital terrain model derived from the ALS data was used to represent the ground surface. The results were evaluated using 63 independent test stands. When estimating height in young forest and mature forest on poor sites, the root mean square error (RMSE) values were slightly better using data from image matching compared to ALS. However, for all other combinations of biophysical forest characteristics and strata, better results were obtained using ALS data. In general, the best results were found using the highest image resolution.     

Calibration of laser-derived tree height estimates by means of photogrammetric techniques

Techniques based on laser point clouds and digital terrestrial images were demonstrated for the calibration of tree-height estimation. Individual tree heights can be roughly estimated from laser scanning data by using the approximated ground level and the highest hit of the treetop. However, laser-derived measurements often underestimate tree heights. This underestimation can arise from various error sources. Digital terrestrial images can be used to verify and understand the behaviour of laser point clouds. When laser data are backprojected in a close-range image, it is possible to show where each laser beam has reflected. This, however, requires a proper orientation of the images. In this study an interactive orientation method was used to derive image orientations, using one laser strip at a time as the reference data. Consequently, the backprojection of laser point clouds confirmed the height underestimations found by comparing the tacheometer reference measurements with the laser-derived tree heights. In addition, by using the described procedure the cause of underestimating tree heights could be explained.     

Deciduous forest mapping using change detection of multi-temporal canopy height models from aerial images acquired at leaf-on and leaf-off conditions

Discrimination of deciduous trees using spectral information from aerial images has only been partly successfully due to the complexity of the reflectance at different view angles, times of acquisition, phenology of the trees and inter-tree radiance. Therefore, the objective was to evaluate the accuracy of estimating the proportion of deciduous stem volume (P) utilizing change detection between canopy height models (CHMs) generated by digital photogrammetry from leaf-on and leaf-off aerial images instead of using spectral information. The study was conducted at a hemi-boreal study area in Sweden. Using aerial images from three seasons, CHMs with a resolution of approximately 0.5?m were generated using semi-global matching. For training plots, metrics describing the change between leaf-on and leaf-off conditions were calculated and used to model the continuous variable P, using the Random Forest approach. Validated at sub-stands, the estimation accuracy of P in terms of root mean square error and bias was found to be 18% and ?6%, respectively. The overall classification accuracy, using four equally wide classes, was 83% with a kappa value of 0.68. The validation plots in classes of high proportion of coniferous or deciduous stem volume were well classified, whereas the mixed forest classes showed lower classification accuracies.     

角尺度在林分空间结构调整中的应用

给出了应用角尺度调整林分空间结构的方法。角尺度是一种优秀的格局分析方法,不用测距也不用准确度量角度,既可用均值也可用单个值的分布来表达结果,对空间结构有很强的解析能力。根据进展演替的一般规律,顶级群落的水平分布格局应为随机分布,因此格局调整的目标是将所经营林分从非随机分布向随机型转变,也就是应将左右不对称的林分角尺度分布调整为左右基本对称。     

文峪河上游华北落叶松天然林立木空间分布模式研究

应用G re ig-Sm ith的等级方差分析方法,结合野外样带调查法,在山西文峪河流域的庞泉沟自然保护区设置了5条典型样带,对华北落叶松林三个群落类型的优势树种立木空间分布格局进行了数量化分析。研究结果表明,等级方差分析法可较方便地分析林木的空间分布格局,确定格局规模尺度,定性地比较分析聚集强度;样带宽度影响分析结果,实际研究中需进行必要的试验,以便确定适当的宽度;研究地区的三个华北落叶松林类型在16 m和64 m两个尺度上,都表现为明显的聚集分布格局,三者的差异反映了局部小尺度干扰和资源环境异质性分布的影响控制作用;研究地区三个类型的华北落叶松林中,在64 m斑块尺度上的聚集强度,灌木落叶松林>云杉落叶松林>苔草落叶松林;在16 m尺度上的聚集强度云杉落叶松林>灌木落叶松林>苔草落叶松林。     

0.5M分辨率航摄数字影像数据在森林资源规划设计调查中的应用

以0.5 M分辨率航摄数字影像数据为基础,结合以往调查设计及经营资料,对森林资源规划设计调查小班的部分因子进行判读,探讨高分辨率航摄数字影像数据在森林资源规划设计调查中的应用,结果表明:利用0.5M分辨率航摄数字影像数据进行小班因子判读,可以作为小班因子调查的辅助手段,并可显著提高小班调查质量及效率。     

福建南平林业产业布局模式研究

结合福建省区域经济发展的空间结构,对南平市林业产业布局现状进行了总结、分析;提出服从全局、整体最优、符合区域发展阶段和注重区域特征等区域空间结构优化的基本原则。在借鉴区域经济发展的相关模式的基础上,提出了南平林业产业布局的"十"字型和网络结构的2个阶段模式,为南平以及闽西北地区林业产业的空间结构优化提供参考。     

Community ecology and spatial distribution of trees in a tropical wet evergreen forest in Kaptai national park in Chittagong Hill Tracts,Bangladesh

We investigated the floristic composition, woody species diversity and spatial distribution of trees in a tropical wet evergreen forest in Kaptai national park in Chittagong Hill Tracks, Bangladesh. We recorded 25 families, 37 genera, 40 species and 1771 woody individuals in a 0.09 ha plot. Euphorbiaceae and Moraceae were the most speciesrich families, and Castanopsis, Ficus and Terminalia were the most species-rich genera. Bursera serrata Wall. ex Colebr. was the dominant species in terms of highest importance value(13%). Trema orientalis(L.)Bl was typically a light demanding species as it appeared in the top canopy with only one individual having the seventh highest IV, but had no regeneration. The expected maximum number of species(Smax) was 140,indicating that many species may invade the forest as the Smax is greater than the recorded total number of species. The nature of the disappearance and appearance of species in the present forest reflects instability of floristic composition. The values of Shannon's index H ′ and Pielou's index J ′(evenness) were 3.36 bit and 0.63, respectively. These values show moderately high species diversity as compared to other subtropical forests in the tropics. In addition, a sample area of 200 m2 in this forest would be sufficient for measuring the diversity indices H ′ and J ′,whereas the trend of J ′may indicate the rate of equality of individuals among the different species decreased with increasing area. The distribution pattern for the total stand was completely random. However, the dominant species showed aggregate distribution for small areas, but random distribution for large areas. The spatial association between species showed that the strongest positive interspecific association occurred between Streblus asper Lour. and Castanea indica Roxb.(ω =0.51). As a whole, most species were weakly associated with each other,of which 58% species associations were completely negative. The result of cluster analysis showed that species pairs were spatially independent at all or most small clusters; stands of species from all clusters are mosaics of complete habitat and pioneer habitat. All patches in this forest community have similar habitat and regeneration niches, which could be a phenomenon for a young growth forest. Thus, the existence of habitat and regeneration niches may be an important factor in the maintenance of diversity in this forest.     

青冈栎次生林主要树种空间分布格局及其关联性研究

青冈栎次生林作为亚热带地区次生林的典型代表之一,研究其林分内主要树种的空间分布格局及关联性,可以更好地开展次生林经营指导工作。通过对9块青冈栎次生林样地的调查,运用空间点格局分析方法对其林分内主要树种的空间分布格局及种间关联性进行研究。结果表明:1)以完全空间随机模型为零假设时,林分整体的空间分布格局在0~12m尺度上呈聚集分布,在12~25m尺度呈随机分布,大于25m尺度趋于均匀分布态势;以异质泊松模型为零假设时,林分整体的空间分布格局总体上呈随机分布;2)样地内青冈栎、杜鹃和拟赤杨在小尺度上呈聚集分布,随尺度增加呈随机分布或均匀分布;甜槠、杉木和檵木基本在所有尺度呈随机分布。3)样地内建群种青冈栎与杉木在所有尺度呈负相关,与其它主要树种在小尺度呈负相关,随着尺度增加变为不相关;所有伴生树种的种间关联性在0~2m为负相关,在其它尺度上不相关为主。青冈栎次生林的空间分布格局受生境异质性的影响,且空间分布格局和主要树种间的关联性随空间尺度的不同而变化。     

绿盲蝽蟓在树冠内的空间分布及第1代若虫对枣股的危害规律

为有效控制绿盲蝽蟓Lygus lucorum Meyer-Dür的危害,在河北沧州金丝小枣产区对绿盲蝽蟓在树冠内的空间分布及第1代若虫对不同年龄枣股的危害规律进行了研究。结果表明:第1代若虫主要危害枣股,8~15 a生枣树的多年生枣股受害占受害枣股的40%以上。绿盲蝽蟓在树冠不同高度层对枣果造成的危害没有显著差异。在不同管理方式下绿盲蝽蟓对枣果造成的危害差异极显著,精细管理、粗放管理和对照的枣果受害率分别为13.96%,23.25%和41.68%。     

Detection of individual trees and estimation of tree height using LiDAR data

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.     

混交林树种空间隔离程度表达方式的研究

混交度表明了任意一个树的最近相邻木为非同种的概率。以参照树及其相邻最近4株树组成的最小空间结构单元较“结构4组法”更能恰当地进行林分空间结构分析。当借助整个林分的混交度分布或均值来分析树种空间隔离程度时最好附加说明混交林分的树种组成及其比例。这一点对精确分析树种空间分布及其结构重建意义十分重大。     

松材线虫病致死松树上的松褐天牛季节性分布规律

连续两年定期监测、调查采样和鉴定证明：每年６～１０月出现的松材线虫病Ｂｕｒｓａｐｈｅｌｅｎｃｈｕｓｘｙｌｏｐｈｉｌｕｓ致死松树上，松褐天牛Ｍｏｎｏｃｈａｍｕｓａｌｔｅｒｎａｔｕｓ虫株率为１００％，而１１月至次年５月间出现的病死株上，虫株率为零。对前者应集中砍除，并加以严格的除害处理；后者可经剥皮处理后在疫情发生区内加工利用，部分可留在林间作为天牛产卵的饵木     

行道树树种结构及健康评价的研究

采用实地观测方法,研究了长春市主城区(环城路内)78条主要道路行道树的树种结构特征与健康状况,结果表明:垂柳、新疆杨和糖槭是研究区内行道树的主要树种,分别占研究区树木总株数5 897株的12.79%、10.99%和10.53%;平均密度为276株·hm-2,平均胸径、平均树高、平均活枝下高和平均冠幅分别为11.7 cm、742 cm、201 cm和347 cm。环城路以内行道树43.96%的植株处于亚健康等级;健康和不健康植株分别占17.49%和10.99%;中等健康植株占27.66%。     

细柄阿丁枫天然林种群空间分布格局

采用频次分布法、聚集度指标法和回归分析法对周宁县细柄阿丁枫天然林种群分布格局进行研究。结果表明这种树种空间分布型均符合Neyman分布(聚集分布)。     

抚育间伐对栓皮栎人工林直径和树高分布的影响

[目的]以河南登封林场栓皮栎人工林为研究对象,研究抚育间伐对林分不同生长阶段林木株数、林木直径分布和树高分布的影响,为制定科学合理的抚育经营措施奠定理论和技术基础.[方法]在株数强度为31.55％的间伐林分和条件基本一致的未间伐林分内,分别设置1个1 hm2样地,间伐作业2 a后获取每木检尺数据,分别利用Normal分...