Classifying tree species in a northern mixed forest using high-resolution IKONOS data

The high-spatial-resolution IKONOS satellite is now operating as a resource and disaster monitor, after a successful launch in September 1999. The ground resolution of the IKONOS panchromatic band is about 1m, the greatest of any satellite. The objectives of this study were to verify the extent to which high-resolution IKONOS data can be used to classify tree species. A field survey and image analysis study used IKONOS imagery to classify 21 species in mixed stands of deciduous and conifer species with the following results: (1) The panchromatic and multi-spectral bands 4, 3, and 2 were useful for classifying tree species owing to the great difference in the reflectance values between tree species. (2) Some groups, for which there were significant differences among species, were identified using Tukeys multiple comparison test; conifers and some broadleaved trees were identified correctly more often than other species. (3) A random selection of validation pixels showed that the overall classification accuracy was 62%. The classification accuracy of broadleaved trees was a little low, ranging from 40% to 63%, while that of conifers exceeded 70%. (4) The overall accuracy of the classification at the genus level improved by 4% more than the species level. The misclassification of broadleaved trees was due to the similar spectral characteristics of species in the same genus.     

耐大气污染树种表现划分——以珠三角地区为例

对30种树种在典型大气污染区、重度污染区和清洁区3类不同环境下的叶面积、株高、基径、冠幅等表观指标进行测定分析,结果表明：绝大部分植株生长表观指标均受到大气污染物的影响,对大气污染物敏感性顺序为冠幅〉株高〉基径〉叶面积。植物对大气污染的耐受性有一个阈值。而且得到综合生长比值的计算公式GRC=0．46×RCA＋0．37×RH＋O．17×RBD。根据此比值和冠幅生长量增减比值,作为划分树种耐受性等级的基准数据,结合植物在典型大气污染区中的生长形态表观（叶、枝、梢、花、果的长势和受害状况）确定了植物对大气污染耐受性等级划分的方法。     

全国立木生物量建模总体划分与样本构成研究

结合全国生态地理区域和行政区域,并兼顾立木材积表的建模总体划分,提出了全国立木生物量建模总体划分方案,将全部树种分为34个树种组,全国分为6大地理区域,共划分70个建模总体;通过对已有立木生物量数据进行建模分析,将立木生物量模型的预估精度确定为95%以上,同时根据变动系数分析结果提出合适的建模样本单元数应该在150以上,且要按划定的10个径阶均匀分配,保证每个径阶的样本单元数不少于15个;以第七次全国森林资源清查数据为基础,确定了每一个建模总体的样本结构,将样本单元数全部落实到了各省和各级径阶。研究成果可为推进全国森林生物量调查建模工作提供参考依据。     

闽浙乡村行道树种结构特征的比较

随着新农村建设政策的稳步推进,乡村道路建设的不断改善,乡村行道树的建设逐渐受到重视.道路绿化具有生态保护、交通辅助、景观组织和文化隐喻等功能[1].当前,全国正开展新农村绿色家园建设,乡村行道树作为绿化的重要内容,在村庄内部,村庄与村庄之间,形成一个完整的绿化系统,合理选用乡村行道树对改善农村生态环境、提高乡村道路质量、美化乡村景观以及提高经济效益都有重要作用;然而,目前有关行道树的研究主要集中在城市[2-5],在一定区域尺度,有关乡村道路绿化树种选择、树种组成、树种特征、生长要素等等方面,目前尚无人涉及研究~[6-8],难以为新农村绿色家园建设提供技术支撑.     

Genetic fingerprinting using AFLP cannot distinguish traditionally classified baobab morphotypes

Baobab (Adansonia digitata L.) is one of the predominant tree species in West African agroforestry systems. A local morphological classification system is used by farmers, identifying trees with desired or undesired combinations of traits. This study evaluates the genetic significance of these morphotypes by comparing local identification with AFLP marker information. Eight morphotypes were recognized by seven ethnic groups from Benin, Ghana and Senegal, among 182 sampled baobab trees. Five primer pairs were used for DNA fingerprinting, resulting in a total of 254 scored bands, of which between 94.1% and 100% was polymorphic within morphotypes. Generally, genetic fingerprinting did not correlate with the traditional morphological identification of Adansonia digitata. Probably, AFLP markers are not directly linked to the differences in phenotype or the traits used for the traditional classification are largely dependent on environmental factors. Since no genetic differentiation is found between the morphotypes, a morphotype-based approach in the collection of genetic variation for conservation programs is not advisable. A. E. Assogbadjo and T. Kyndt equally contributed to this work.     

Biomass determination of fuelwood trees and bushes of Botswana, Southern Africa

In order to establish a relation between tree fresh biomass and tree dimensions, samples of 14 tree species indigenous to Botswana were measured, cut and weighed. The relation best suited to the indirect estimation of total tree fresh weight was the regression between tree fresh weight and stem basal area at ankle height (5–10 cm above ground level). The regression curves of the 14 tree species overlay in a narrow band. On the basis of the measured data points of all 14 tree species a single regression curve is calculated: the combi-line. The combi-line satisfactorily describes the relation between stem basal area and fresh weight for most trees. A comparison of the combi-line with some tree species from elsewhere in Africa, India and Europe shows that the combi-line also describes, to a large extent, the basal area-fresh weight relation for those trees.     

Temporal Trends in Twig Growth of Fagus sylvatica L. and their Relationships with Environmental Factors

Dendrochronology and twig growth studies provide useful historicalinformation about tree growth and permit analyses of the effectsof measured environmental parameters on such growth. Recentgrowth histories of currently healthy and unhealthy beech {Fagussylvatica L.) trees were reconstructed for a number of sitesin southern England, by measuring annual twig extension growthback to 1960. The relationships between twig growth and a numberof climatic (and one pollution) variables were then determined,using multiple regression analyses. A substantial reduction in twig growth was found in 1976 and1977 for all trees, indicating the dramatic effect of the severedrought that was experienced throughout much of southern Englandduring 1976. After this time, healthy trees at all sites quicklyregained their pre-1976 growth rates. In contrast, unhealthytrees at two sites failed to recover and still show greatlyreduced rates of growth. At two additional sites, while theeffect of the 1976 drought is clear, the growth rates of unhealthytrees have been significantly lower than their healthy neighbourssince before 1960. Soil type and tree age failed to providean adequate explanation for the lower than expected growth ratesof unhealthy trees seen at almost all sites. At most sites, a significant proportion of the variance in twiggrowth is explained by combinations of climatic variables. Inmost such cases, growth rates decreased as the variable concernedincreased. Ozone was included in the best fit model for unhealthytrees at two sites. However, since this pollutant accountedfor only a small amount of the model variance and the ozonedata were of poor spatial resolution, care must be taken overthe interpretation of this result.     

Relationships between reflectance and absorbance chlorophyll indices with RGB (Red,Green, Blue) image components in seedlings of tropical tree species at nursery stage

Methods based on RGB (Red, Green, Blue) image segmentation may emerge as a new and low-cost method for estimation the quality of tree seedlings. However, the vast number of indexes based on the use of the RGB image segmentation and the lack of references in the literature still hinder the widespread use of this technology. Thus, we conducted a study aiming to test the relationships between methods based on absorbance and reflectance, widely used for the estimation of chlorophyll contents and physiological status of trees, and ten indexes based on RGB component analysis. We used leaves of five tropical tree species, belonging to different botanical families. Leaf absorbance was measured using the handheld chlorophyll meter SPAD-502, reflectance was measured using a spectrometer and the RGB indices were obtained from digitalized images of the leaves using a flatbed scanner. Modified linear regression models including all five species were used to relate RGB indices to absorbance and reflectance indices. Data collected from leaves of seedlings of five tropical tree species indicated that digital image processing technology can be a useful and rapid nondestructive method for assessment of physiological status of tree seedlings at nursery stage. Among the RGB indexes tested in this study the R, 2R*(G???B)/(G?+?B) and 2G*(G???B)/(G?+?B) are the most promising for analysis the tropical seedlings physiological status and quality.

     

扬州市城区道路绿地植物结构调查与分析

对扬州市城区多条道路的绿化带进行了实地调查和分析，结果显示：扬州市道路绿地系统常用的乔木树种有18科，27属，32种；灌木18科，21属，24种，出现频度最高的乔木、灌木分别为香樟40％，石楠65％。常绿、落叶树种的数量配比为17：33，其中乔木的常绿、落叶树种数量配比为13：50。乔木与灌木种类配比为4：3。同时还总结出扬州市城区道路绿化带中绿化树种较少，没有形成特色道路景观，没有充分考虑行车视线以及灌木高矮差别较大等不足之处，并针对性地提出解决办法。     

Evaluating the potential of sentinel-2, landsat-8, and irs satellite images in tree species classification of hyrcanian forest of iran using random forest

ABSTRACT

Spatially explicit information on tree species composition of any forest provides valuable information to forest managers as well as to nature conservationists. In this study, the potential of three spaceborne sensors: (1) Landsat-8, (2) Sentinel-2, and (3) IRS-Pansharpened were compared by applying Random Forest (RF) classification algorithms to classify the three most common tree species: Pinus taeda, Alnus spp., and Populus spp., in Hyrcanian forest of Iran. Three RF models with optimized parameters of mtry and ntree were used for the classification of trees species. Based on our Overall Accuracy (OA) and Kappa Coefficient (KC) analysis, IRS-Pansharpened data showed the highest accuracy (OA = 84.9% and KC = 79.7%), followed by Landsat-8 (OA = 78.2% and KC = 70.6%), and Sentinel-2 (OA = 77% and KC = 70%). According to the Mean Decrease in Accuracy (MDA) criterion delivered as an output of RF, the near-IR spectral band was found on the top rank (high variable importance) as compared to all other spectral bands for tree species classification. The findings of this study can be used by the researcher, forest managers, economists and policy and decision makers in the context of sustainable forest management of Hyrcanian forest resources.     

An assessment of Hawaiian dry forest condition with fine resolution remote sensing

Remote sensing offers the potential to spatially map forest cover quickly and reliably for inventory purposes. We developed a new image analysis approach using an integrated methodology of “object-based” image classification techniques and field-based measurements to quantify forest cover in a degraded dry forest ecosystem on the leeward side of the Island of Hawaii. This new approach explicitly recognized the transitional areas between tree crowns and tree shades (tree shadows) as a unique class and fully utilized them for the quantification of canopy cover. Object-oriented classification of Ikonos-2 satellite images allowed delineation of tree shades and crowns and the transitional areas between them from objects with similar reflectance and size that were surrounding the trees. These included patches of fountain (Pennisetum setaceum) and kikuyu (Pennisetum clandestinum) grass, lava outcrops and lava–grass mixtures. Crown-shade transitions were clearly differentiated in spite of their wide range of spectral values and reflectance similarities with areas of lava–grass mixture. Segments representing tree shades and dark lava outcrops were also classified into their respective classes even if they were contiguous. The image estimates of canopy cover using the tree shade plus transition classes were linearly related with field estimates of canopy cover (R² = 0.86 and slope = 0.976). Based on this relationship, dry forest cover throughout the 2627-ha area was estimated at 7.7 ± 1.9%. An immediate application of this new approach is to select and delineate areas with higher canopy cover in order to concentrate ecological restoration and conservation efforts.     

LIDAR技术在林业调查中的应用研究

以LIDAR测量树高为研究内容,利用全站仪对研究区选定的37株样木的树高和材积进行精准测量,获取训练样本实测数据。通过BP神经网络分析,建立了LIDAR测量树高与实测树高、材积的拟合函数方程,实现了用LIDAR树高数据计算单木材积的过程。从拟合的结果来看,树高相关系数R为0.993 2,平均残差平方和为0.086 312。材积相关系数R为0.974 7,平均残差平方和为0.000 310 5,达到了林业调查精度的要求,在林业数表的编制方面是一个比较好的范例。     

Applied 3D texture features in ALS-based forest inventory

Airborne laser scanning (ALS) data are not usually considered to be very informative with respect to tree species, and this information is often obtained by combining such data with spectral image material. The aim was to test the ability of height, density, intensity and applied 2D and 3D texture variables derived solely from a very high-density ALS point cloud to describe the crown shape and structure characteristics required for tree species discrimination. Linear discriminant analysis was used to find optimal combinations of variables within the predictor groups, and classifications based on variables from different groups were compared. The third power of the tree diameter was used as a stem volume approximate, and rather than examining species alone, the classification was evaluated with respect to the volume approximates assigned to the predicted species. The sensitivity of pulse density to the methodology presented here was determined by simulating thinned data sets by reducing the initial pulse density. The reliability of the estimates was analysed both with functions generated using the original data and with new functions for each thinning level. Alpha shape metrics developed for describing tree crowns constructed from the 3D point clouds proved capable of discriminating between all three species groups evaluated, and several height distribution and textural variables were found to discriminate between the coniferous tree species. The results demonstrate the importance of species interpretation in forest inventories based on allometric modelling, but then indicate that species-specific estimation could be carried out using ALS-derived variables alone.     

A non-destructive method for estimating above-ground forest biomass in threatened woodlands

Current techniques for calculation of biomass in agroforestry require felling of many trees. Such methods are not well suited to the natural environment, especially if the environment is subject to anthropic degradation and if the wood supply to local populations is at stake. The method we describe here was used in a socioeconomic and ecological study of the biomass of a thuriferous juniper woodland (Juniperus thurifera L.) in the High Central Atlas mountains (Morocco). This computerized method reconstructs the different component volumes of a tree from two orthogonal-view photographs. Then, using the volume and the density of each component, it estimates the biomass of the tree. Regression curves were established between dendrometric parameters for 102 trees (tree height × crown projection area) and their estimated biomass by this computer method. A second-order polynomial equation gave the best regressions with a high coefficient of determination (R² = 0.96). To validate the method, the biomass of seven trees (cut in a previous study) was compared with those obtained from our regression equations, while in a second study, the biomass of three trees, estimated from photographs using the computer program, was compared with values obtained after felling and weighing the same trees.

The results show that the method is reliable with a mean error percentage varying between 2.5 and 7.5 per tree. For young trees, the accuracy of the biomass could be improved, for example, by using a tree morphology classification.     

Hollows in jarrah (Eucalyptus marginata) and marri (Corymbia calophylla) trees: I. Hollow sizes, tree attributes and ages

One hundred and fifty-four jarrah (Eucalyptus marginata) and 85 marri (Corymbia calophylla) trees were measured and assessed, and the numbers and sizes of hollows in these trees were determined by destructive sampling; 665 hollows were located and measured. The relationship between tree diameter and tree age was determined from counts of annual growth rings on 162 of these trees. Large trees and trees with moderately senescent crowns individually bear the most hollows. Although the number of hollows found in individual trees increased with tree diameter, the distribution of tree diameters in the forest is skewed and the large number of small trees with diameters between 40 and 80 cm contribute approximately 50% of all hollows in the jarrah forest. The distributions of entry size, and of hollow depth, are highly skewed, with small hollows occurring more frequently than large hollows. Although jarrah trees bear more hollows than marri trees and the distribution of entry sizes is similar for both tree species, the hollows in jarrah are significantly smaller than the hollows in marri. Most hollows are cylindrical in shape, vertically oriented and occur in dead wood in the tree crown. Relatively few hollows (14%) occur in the tree bole or at crown break. Counts of hollows made from ground level are inaccurate as estimates of the actual number of hollows in trees.     

Anchorage of mature conifers: resistive turning moment, root-soil plate geometry and root growth orientation

Eighty-four mature Norway spruce (Picea abies L. Karst), silver fir (Abies alba Mill) and Scots pine (Pinus sylvestris L.) trees were winched over to determine the maximum resistive turning moment (M(a)) of the root-soil system, the root-soil plate geometry, the azimuthal orientation of root growth, and the occurrence of root rot. The calculation of M(a), based on digital image tracking of stem deflection, accounted not only for the force application and its changing geometry, but also for the weight of the overhanging tree, representing up to 42% of M(a). Root rot reduced M(a) significantly and was detected in 25% of the Norway spruce and 5% of the silver fir trees. Excluding trees with root rot, differences in M(a) between species were small and insignificant. About 75% of the variance in M(a) could be explained by one of the four variables--tree mass, stem mass, stem diameter at breast height squared times tree height, and stem diameter at breast height squared. Among the seven allometric variables assessed above ground, stem diameter at breast height best described the root-soil plate dimensions, but the correlations were weak and the differences between species were insignificant. The shape of the root-soil plate was well described by a depth-dependent taper model with an elliptical cross section. Roots displayed a preferred azimuthal orientation of growth in the axis of prevailing winds, and the direction of frequent weak winds matched the orientation of growth better than that of rare strong winds. The lack of difference in anchorage parameters among species probably reflects the similar belowground growth conditions of the mature trees.     

Nutrient supply at the local tree level in mixed forests of sessile oak and beech

In mixed-species forests, tree species composition can affect nutrient return through litter fall. This in turn is expected to have an effect on soil available nutrients, which could influence the nutrient status at the local tree level. Using ion-exchange resins, we estimated resin available soil nutrients at two depths beneath target trees of sessile oak and beech in the Belgian Ardennes. First we tested whether resin available nutrients were related to tree nutrition, using foliar nutrient concentrations as a proxy. In a second step, we tested whether local litter fall, through total nutrient return or litter species composition, affected resin available nutrients. In a final stage, we tested the impacts of local stand composition, as an integrated proxy of above- and belowground processes, and compared them to those of litter composition. With the exception of P for oak, nutrient supply was only poorly related to foliar nutrient concentrations for both target species. The effects of litter fall on nutrient supply were driven by litter species composition and not by total nutrient inputs. Litter composition and local stand composition effects were in close agreement. Our results show that nutrient supply to target trees in mixed-species stands is affected by local neighbourhoods, yet to a limited extent. Direct translation of resin available nutrients into foliar concentrations is probably hampered by complex capture patterns.     

Time series diagnosis of tree hydraulic characteristics

An in vivo method for diagnosing hydraulic characteristics of branches and whole trees is described. The method imposes short-lived perturbations of transpiration and traces the propagation of the hydraulic response through trees. The water uptake response contains the integrated signature of hydraulic resistance and capacitance within trees. The method produces large signal to noise ratios for analysis, but does not cause damage or destruction to tree stems or branches. Based on results with two conifer tree species, we show that the method allows for the simple parameterization of bulk hydraulic resistance and capacitance of trees. Bulk tree parameterization of resistance and capacitance predicted the overall diel shape of water uptake, but did not predict the overshoot water uptake response in trees to shorter-term variations in transpiration, created by step changes in transpiration rate. Stomatal dynamics likely complicated the use of simple resistance-capacitance models of tree water transport on these short time scales. The results provide insight into dominant hydraulic and physiological factors controlling tree water flux on varying time scales, and allow for the practical assessment of necessary tree hydraulic model complexity in relation to the time step of soil- vegetation-atmosphere transport models.     

绿化树种接种VA菌根真菌的生长效应研究

试验结果表明,VA菌根真菌对10个参试的绿化树种均有不同程度的增效。对苗高和基径均有增效的占参试树种的80%,其中对苗高有增效的占80%,对基径有增效的占100%。但接种效应差异性程度各有不同,处理与对照苗高、基径生长均达到极显著差异的树种有黑金刚、花金刚、巴西榕,差异显著的有竹节树,其余树种接种后虽有增效作用,但没有达到显著水平。综合来看,VA菌根真菌对黑金刚、花金刚、红关公、巴西榕和竹节树的增效效应最为明显,对扭纹铁、红桂木的增效效应较好,而对石楠、红楣和伞花木则稍差。