The abundance index of the tree layer was higher than the shrub layer.

郑州市不同类型公园绿地乔木物种丰富度稍大于灌木。

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The species component, density and index of crown cover in the tree layer effect on distribution of illumination and under plants in the plant community.

群落中光照的分布状况受乔木层的种类组成、密度与冠幅指数等因子的影响，且对下层植物分布有较大的作用。

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If you peel birch bark in the winter, we call it "the winter bark", another layer, a tougher inner layer of the tree adheres to the bark, producing a stronger material.

如果你在冬天剥桦树皮，我们称它为“冬树皮”，另外一层更加坚硬的紧贴树皮的树层就可以生产出更强更硬的材料。

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