The population density decreases with the increase of diameter class.

种群密度随径级增大而减小。

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Tree density in the forest decreased with the increases of height class and diameter class, whereas species abundance did not increase.

栎类次生林乔木的密度随高度级、径级的增加而递减，但树种丰富度却不随树木的密度增加而增加。

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Both the Numbers of tree species and tree density decreased as height class or diameter class increased, fitting both negative exponential and negative power equations.

树种数和树木的密度都随高度级、径级的增加而呈负指数或负幂函数递减。

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