基于距离相关系数和KNN回归模型的森林蓄积量估测研究

【目的】探究Landsat8 OLI数据和KNN算法在森林蓄积量估测中的潜力。【方法】以湖南省湘潭县为研究区,采用Landsat8 OLI数据和同时期的二类调查数据,通过距离相关系数筛选特征,分别采用线性回归模型(MLR)、K-近邻模型(KNN)、距离加权KNN模型(DW-KNN)和优化欧式KNN模型(FW-KNN)对森林蓄积量进行估测。使用十折交叉方法进行精度检验,对检验结果进行对比分析。【结果】3种KNN模型的估测结果均高于传统的线性模型,并且在3种KNN模型中,FW-KNN算法效果最好,决定系数达到0.69,为3种模型中最高;3种KNN模型中,本研究优化欧氏距离KNN模型的估测精度最高,其均方根误差为30.3%,相比于传统KNN模型的均方根误差降低了5.1%,相比于DW-KNN模型降低了3.3%。【结论】采用DW-KNN蓄积量估测结果明显优于其他两种模型,说明通过特征与蓄积量的相关性优化样本间的距离是一种可行的KNN优化方法。     

落叶松人工林林分径级结构的研究

本文描述了落叶松人工林抚育后径级结构特征。试验表明，抚育后的林分在一定密度条件下，其密度遵从Ｗｅｉｂｕｌｌ分布，并能保持相当长的时间不变；其密度较大，Ｗｅｉｂｕｌｌ参数值在２～３间变动，ｂ值在６～８间变动；稀疏时不能用Ｗｅｉｂｕｌｌ分布模拟。     

根据盗伐、滥伐林木现场树坑作相应林木材积估测

介绍了在盗伐、滥伐林木现场仅有树坑的情况下，利用相应小班森林资源规划设计调查资料或相近林分调查资料对被盗伐、滥伐林木作材积估测的方法，并举例说明。     

进口木地板坯料应注意的问题

本文提出了进口木地板坯料时应考虑南北气候差异及木材密度等材性差异来确定留有不同的加工余量，并建议海关按照国际惯例制定以净尺寸材积作为计税材积的标准，避免各港口实行不同征税标准，给企业进口地板坯料带来诸多困难。该建议已引起海关总署重视，并委托国家林业局起草单耗标准。     

Application of acoustic Doppler current profiler combined with a scientific echo sounder for krill Euphausia pacifica density estimation

ABSTRACT:   An application of the acoustic Doppler current profiler (ADCP, 153.6 kHz) in combination with a scientific echo sounder (EK60, 38 and 200 kHz) was investigated to estimate the density of krill Euphausia pacifica . The acoustic backscattering strength from sound scattering layers was compared with biomass estimates from midwater trawls. Euphausia pacifica was targeted among mixed species populations in the sound scattering layer in the offshore Funka Bay area of Hokkaido, Japan. The frequency characteristics of acoustic backscattering by krill were calculated using a distorted wave Born approximation scattering model at three frequencies. Krill aggregations identified from the EK60 data were extracted as the mean volume backscattering strength difference between two frequencies. They were then used to identify similar aggregations in the ADCP data by matching observation times and depths for the two methods, which were applied simultaneously. Results from the comparison of the mean volume backscattering strength and the density calculated from the ADCP and EK60 showed that ADCP can be used to measure density and spatial–temporal distribution of krill aggregations. Current speed and direction at the study site were found to be 16.1 cm/s and 187.0°, respectively, and krill speed and direction (including the current component) were found to be 19.8 cm/s and 172.2°, respectively. Based on the ADCP data, the net speed and direction of the krill aggregations were found to be 5.9 cm/s and 128.0°, respectively.     

Analysis of the Impact of Alfalfa Forage Production under Summer Water-Limiting Circumstances on Productivity, Agricultural and Growers Returns and Plant Stand

The trade-off between summer water conservation from alfalfa production and the effects on plant growth, agricultural crop value, and grower returns in the low desert area (Imperial, Palo Verde, Parker and Yuma Valleys of California and Arizona) was analysed using an experimental plot in the Palo Verde Valley. The purpose was to provide a basis for evaluating water conservation decisions and policies. Four summer dry-down periods (withdrawing water for a predetermined period) of 0 days (control), 35 days, 70 days, and 105 days were analysed. Our results show that whereas the various dry-down periods would provide water conservation ranging from 254 to 944 million m³, the region would experience agricultural income decline by US $16 to US $73 million. For growers, benefits of dry-down would be effective only if the water price exceeds US $0.045 m⁻³ in California and US $0.036 m⁻³ in Arizona. Also dry-down would have possible adverse effects in the following areas including declines in plant stand density, long-term productivity, service industry sales, employment and biological benefits of soil fertility and organic matter that is attributed by the alfalfa plant in which case agriculture's and growers monetary losses could increase.     

毛竹笋用林梅前开山施肥试验初报

通过2年的梅前开山，施肥和大量挖掘鞭笋，增挖冬笋的试验，笋产量及产值分别比原来增长49．62％，57．95％，纯收入增加75．82％，每工值增加43．53％，投入产出比1：3．37。     

阔叶次生林抚育改造初探

安远县国营林场根据生态学原理,对阔叶次生林进行改造,把天然更新和人工改造更新有机的结合起来。通过改造可很快的形成多树种的混交林,林木材积生长提高115％～219％,土壤物理性比杉木纯林好,土壤贮水量比杉木纯林提高57％～92％,有良好的生态经济效益。实践证明,次生林改造是次生林经营的重要措施,是加速培育森林资源的好途径。     

天山云杉人工幼林树冠结构及其在林分间伐中的应用研究

本文对天山云杉人工幼林树冠结构以及树冠结构与林木之间的关系进行了研究，并基于生物学原理，在确定有效树冠的法础上，通过决定林木能力的树冠特征对其人林分间伐中的应用进行了初步研究。