The present book gives a modernized and comprehensive overview of the degradation of major litter components as well as the sum of processes when forest plant litter decomposes, releases nutrients and turns into humus. Covering mainly boreal and temperate forests, the book gives a synthesis of the different sub-processes on the basis that decomposition is microbially mediated and develops a system in the decomposition processes leading to chemical changes in litter. Further, it introduces a conceptual model for litter transformations from litter fall until the decomposing litter accumulates as humus. The effects of substrate quality, climate, and their interactions on decomposition are presented as well as examples of litter types that break the basic pattern. A system is suggested for humus accumulation rates among forest systems, a system that may be a starting point for estimates of carbon sequestration in forest systems.
