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用对数正态分布模型分析绵阳官司河流域防护林乔木层的种多度关系，用多种公式计算防护林各层次的物种多样性，并与我国暖温带落叶阔叶林的物种多样性相比较，得出以下结论：①该流域防护林乔木层的种多度关系符合对数正态分布模型，说明个体数量最多的乔木仅限于少数几种树木；②主要群落内乔木层、灌木层和草本层的丰富度、均匀度和总多样性指数都比较低，甚至低于我国暖温带落叶阔叶林相对应的指数．这说明防护林尚属于恢复初期，发展不成熟，受人为干扰较大，造林时树种选择存在着片面性；③因此，物种多样性应是评价长江中上游防护林综合效益的重要指标之一．
The logarithm normal distribution model was used to analyze the species-abundance relationship of shelterbelts in Mianyanghe watershed in Mianyang, and the species diversity of shelterbelts was calculated by various formulas. Compared with the species diversity of temperate deciduous broad-leaved forests in China, The conclusions are as follows: ①The species abundance relationship of shelterbelts in this basin complied with the logarithm normal distribution model, indicating that the individuals with the most individuals were only limited to a few kinds of trees; ②The arbors, shrubs and herbs in the main community The indices of richness, evenness and total diversity are relatively low, even lower than the corresponding index of deciduous broad-leaved forest in warm temperate China. Therefore, species diversity should be one of the most important indicators to evaluate the comprehensive benefits of shelterbelts in the middle and upper reaches of the Yangtze River.