This fully revised and updated 2nd edition of Plant Litter focuses on decomposition processes in natural terrestrial systems such as boreal and temperate forests. The availability of several long-term studies from these forest types allows a more in-depth approach to the later stages of decomposition as well as to humus formation. It further briefly explores how processes are modified due to anthropogenic influences. Earlier findings are re-evaluated in light of recent research and with relevance to current areas of investigation. New concepts that modify or go beyond those already presented are covered and a new chapter on patterns of decomposition and accumulation on a regional scale was introduced.