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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. 相似文献
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【目的】针对点云分类过程中多依据经验盲目构造特征的问题,本研究提出使用基于xgboost的特征选择弥补上述不足。【方法】本研究的数据为地面激光雷达扫描获得的蒙古栎人工林数据。本研究考虑构造适当的特征训练分类器将TLS点云快速分离为地面、树干与枝叶3个类别。在分类过程中,先在训练集中逐点搜索100个近邻构造19个特征,然后使用这些特征训练xgboost分类器,并依据控制分类器节点分裂的特征频率获得特征重要性。获得特征重要性之后将特征按重要性做降序排列,并依据该序列依次增加特征数量训练xgboost。因为构造了19个特征,所以在上述训练分类器的过程中可获得19个关于特征重要性的分类器模型。依次将上述模型应用于测试集的分类,在保证分类器性能的情况下,依据测试集的表现选择了前6个特征,从而实现了TLS点云分类的特征选择。【结果】使用基于特征选择获得的6个特征与依据经验构造的19个特征训练分类器的测试准确率分别为0.954 8与0.956 2。相较于使用19个特征,使用6个特征的分类器性能仅降低了0.001 4。在训练集与测试集中计算6个特征用时分别占计算19个特征用时的53.13%与54.33%。【结论】结果表明特征选择策略可有效提高特征计算效率,而且在保证分类器性能的前提下可以避免特征构造的盲目性。 相似文献
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以Landsat 8影像为数据源,在综合分析典型地物光谱、纹理和空间分布等特征的基础上,利用归一化湿度指数(NDMI)、纹理、地形等多源数据,构建了基于决策树规则的西双版纳森林覆盖信息提取模型。验证结果表明,该模型的总体精度达99.08%,与传统的监督分类相比(96.08%)提高了3个百分点。 相似文献
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Lance A. Vickers Thomas R. Fox David L. Loftis David A. Boucugnani 《Journal of Sustainable Forestry》2013,32(8):790-822
REGEN is an expert system designed by David Loftis to predict the future species composition of dominant and codominant stems in forest stands at the onset of stem exclusion following a proposed harvest. REGEN predictions are generated using competitive rankings for advance reproduction along with other existing stand conditions. These parameters are contained within modular REGEN knowledge bases (RKBs). To extend REGEN coverage into hardwood stands of the Central Appalachians, RKBs were developed for four site classes (xeric, subxeric, submesic, mesic) based on literature and expert opinion. Data were collected from 48 paired stands in Virginia and West Virginia to calibrate the initial RKBs. Paired stands consisted of one mature uncut hardwood stand adjacent to a regenerating clear-cut stand with similar site characteristics that was harvested within the previous 20 yr. Data from 17 additional paired stands was collected a year later to validate the performance of REGEN. Predicted values were within 4 percentage points of measured values on average, and model error was typically less than 20 percentage points for species groups. These results confirmed the suitability of REGEN to predict the future species composition of stands regenerated using the clear-cut method in the Central Appalachians of Virginia and West Virginia. 相似文献
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关于建立洮河自然保护区的必要性论证 总被引:1,自引:0,他引:1
位于甘南藏族自治州境内的洮河林区,总面积479534.6hm^2,森林覆盖率44.72%。区内动植物资源丰富,也是甘南重要的水源涵养林,目前保护形势严峻。论证了建立自然保护区的必要性,持续发挥“洮河天然水库”功能,涵养水源;保护恢复生态环境和野生动植物资源;促进区域社会经济可持续发展。 相似文献