Preface Most of the Net Primary Production (annual gain of energy and matter by the plant sub-system) is not consumed by herbivores, but is returned to the environment as detritus which plays critical roles in organizing and sustaining ecosystems. In addition to its effects on trophic structure and dynamics, detritus physically alters habitats thereby facilitating some species and inhibiting others. It goes through a series of changes with time that are mediated by decomposers through the involvement of extracellular enzymes whose synthesis is affected by all the factors that affect microorganisms in soil, such as moisture, temperature, and available nutrients. After release, the activity of soil enzymes is regulated primarily by litter chemistry, substrate availability and temperature. Through their contribution to the recycling of essential chemical elements such as nitrogen and phosphorus (that are in limited supply for primary producers), decomposers play a key role in the primary productivity of ecosystems.

1.1. Characteristics and categories                  1.2. Litter     Patterns of accumulation     Successional trends     Seasonal variations     Fluctuations in accumulation 1.3. Dissolved organic matter     Sources of DOM     Fluxes of DOM 1.4. Woody detritus 1.5. Soil organic matter

2.1. The Physical environment     Light     Soil temperature     Water dynamics 2.2. Chemical environment     Production of phytotoxins 2.3. Biological environment     Trophic dynamics     Community structure     Biodiversity

3.1.Processes                          Leaching                         Fragmentation/Comminution     Catabolism                         Decomposition models                  3.2. Patterns                          Litter decomposition     Root decomposition                         Limit values for decomposition                 Decomposition pattern in ecosystems

4.1. Substrate quality     Litter quality     Soil organic matter (SOM) quality 4.2. Decomposer community     Soil animals     Soil microorganisms     Terrestrial fungi     Actinomycetes         Bacteria

5.1. Nature and role of soil enzymes     General account     Role in terrestrial ecosystems     Role in aquatic ecosystems 5.2. Environmental conditions and microbial enzyme activity