carbon:nitrogen ratio

The ratio of the weight of carbon to the weight of nitrogen in a substance. All organic matter contains these two elements, but in markedly different ratios. The optimum ratio for decomposers is around 30:1. Wood, with a ratio at least ten times greater, is very deficient in nitrogen (used by living things to make protein), which is one of the reasons it is slow to decay.

This definition is abridged from A – Z of tree terms: A companion to British arboriculture.
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