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This stored carbon is found mostly in the forests' humus layer, which contains decomposed leaves and other organic matter.

The last, completely rotted layer is built up of a thick and dark organic matter called humus, a type of soil that provides the ideal environment in which plants grow and thrive.

Temperatures in the piles decrease and the compost matures into a dark and crumby humus, resembling rich organic soil in both look and smell, the zoo said.

Chernozem is richer than other soils in nutrients such as humus, phosphorus and nitrogen and extends deep into the ground, as much as 1.5 metres.

Most home landscapes are a mix of trees, shrubs and perennials, conditions most like a woodland, where coarse materials, like fallen leaves and twigs, gradually decompose into a fine-textured, biologically rich layer of humus soil.