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Why are deciduous-forest soils often rich in organic matter?
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Temperate forest
Worldwide distribution of temperate forests.
Deciduous-forest soils are often rich in organic matter primarily due to the seasonal cycle of leaf shedding and subsequent decomposition. In autumn, declining temperatures and shorter days trigger trees to shed their leaves, which accumulate as a layer of litter on the forest floor.12
This organic material is then broken down by a community of fungi, bacteria, and invertebrates, such as earthworms, which incorporate the decaying matter into the mineral soil. This process creates a porous, nutrient-rich layer known as mull humus. Because this organic material is well-mixed with mineral soil near the surface, these soils are generally fertile and support a diverse ground flora.12