While several diffusivity models have been developed for mineral soils, there are few data for the forest humus layers that overlie, and are distinct from, the mineral soil. We measured soil gas diffusivity of the organic layer of spruce and beech stands. Total pore space and relative soil gas diffusivity were much higher in the humus layer than in mineral soil. An exponential diffusivity function was used to describe relative soil gas diffusivity in the humus layer of all spruce sites using one parameter set. The best-fit parameters exceeded the range recommended for mineral soil, indicating the distinctness in pore structure of mineral soil and the organic layer. Different model parameter sets were required to describe the different types of humus at the beech sites. As a consequence, traditional predictive models developed for mineral soil should not be used to derive diffusivity values to interpret the aeration status of the forest humus layer. Specific parameter sets should be used for calculating soil gas fluxes through these layers using the gradient flux approach.

中文翻译：

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森林腐殖质层中的气体扩散率

虽然已经为矿质土壤开发了几种扩散率模型，但关于覆盖在矿质土壤上且与矿质土壤不同的森林腐殖质层的数据很少。我们测量了云杉和山毛榉林有机层的土壤气体扩散率。腐殖质层的总孔隙空间和相对土壤气体扩散率远高于矿质土壤。指数扩散率函数用于使用一个参数集描述所有云杉林地腐殖质层中的相对土壤气体扩散率。最佳拟合参数超出了矿质土壤的推荐范围，表明矿质土壤孔隙结构与有机层的区别。需要不同的模型参数集来描述山毛榉遗址不同类型的腐殖质。作为结果，不应使用为矿质土壤开发的传统预测模型来推导扩散率值来解释森林腐殖质层的通气状况。应该使用特定的参数集来使用梯度通量方法计算通过这些层的土壤气体通量。