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基于立地与密度效应的湖南栎类天然林平均木胸径生长模型 被引量:5
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作者 何静 朱光玉 +3 位作者 张学余 王忠诚 刘洪娜 屠维亚 《中南林业科技大学学报》 CAS CSCD 北大核心 2021年第10期75-82,共8页
【目的】天然林生长模型一直是国内外林业研究的难点,单木生长模型是林木生长与收获模型的重要组成部分,林分平均木生长过程模拟是单木生长模型乃至林分生长模型的研究基础,密度和立地是影响其生长的重要因素。因此,探讨与构建反应密度... 【目的】天然林生长模型一直是国内外林业研究的难点,单木生长模型是林木生长与收获模型的重要组成部分,林分平均木生长过程模拟是单木生长模型乃至林分生长模型的研究基础,密度和立地是影响其生长的重要因素。因此,探讨与构建反应密度和立地差异的栎类天然林胸径生长模型,能客观地反应其生长规律,为林分预估和提高林分质量提供理论支持。【方法】以湖南栎类天然林样地数据为基础,以林分平均木胸径为研究对象,基于树木理论生长方程,利用数量化方法Ⅰ和非线性混合效应回归建模方法,构建含林分密度和立地效应的栎类林分平均木胸径生长模型。【结果】1)利用评价指标(确定系数R^(2)、平均绝对误差MAE及均方根误差RMSE),从4个基础模型中选定Logistic为林分胸径生长的最优基础模型,确定系数R^(2)为0.33897;2)采用数量化方法Ⅰ筛选出海拔、坡度、坡向和株数密度是对林分胸径生长影响显著的因子;3)将海拔、坡度、坡向分级并组成基本立地类型组合,将株数密度和立地类型组合作为混合效应加入到基础模型中构成非线性混合效应模型,模型确定系数由0.33897提升到了0.93016。【结论】胸径的生长既受林分密度的影响,又与立地条件有关,不同的株数密度和立地条件对林分平均木胸径生长的影响很大。林分的密度与胸径呈现负相关,密度越小,林分平均木胸径越大;林分的立地条件越好,林分平均木的胸径越大。考虑株数密度和立地类型效应的生长模型可以有效解决栎类天然林林分密度和立地类型差异对胸径预估的影响。 展开更多
关键词 栎类 平均木胸径生长模型 数量化方法Ⅰ 非线性混合效应
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Application of the Attenuation Correction Technology in C-band Radar Precipitation Estimation
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作者 WANG Nan 《Meteorological and Environmental Research》 2012年第1期51-54,共4页
[ Objective] The research aimed to study application of the attenuation correction technology in C-band radar precipitation estimation. [ Method~ Based on CINRAD-CB radar data in Shaanxi, we conducted the attenuation ... [ Objective] The research aimed to study application of the attenuation correction technology in C-band radar precipitation estimation. [ Method~ Based on CINRAD-CB radar data in Shaanxi, we conducted the attenuation correction experiment by using iteration method and Kufa method respectively. Moreover, we conducted application expedment of the Kufa attenuation correction method in the quantitative precipitation esti- mation. [ Result~ Attenuation correction technology could compensate for attenuation problem of the echo at the distant range. Calculation result of the iteration method finally tended to that of the Kufa method. Moreover, iteration method spent more time. Therefore, Kufa attenuation correction technology was more suitable for business operation. When strong echo was near radar, generated attenuation was more obvious, and application value of the attenuation correction was bigger. Attenuation correction technology was used for quantitative precipitation estimation, which was favor- able for improving accuracy of the precipitation estimation. But we should conduct detailed planning on calculation scheme of the precipitation esti- mation because that different calculation schemes had great influences on accuracy of the quantitative precipitation estimation. [ Cendusien] This research provided a basis for improving accuracy of the quantitative precipitation estimation in Shaanxi. Key words Attenuation correction 展开更多
关键词 Attenuation correction K-ufa methyl iteration method i quantitative precipitation estimation China
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