Published online by Cambridge University Press: 11 May 2010
LITTER DECOMPOSITION CONCEPT
Litter decomposition is defined as the process through which dead organic material is broken down into particles of progressively smaller size, until the structure can no longer be recognized, and organic molecules are mineralized to their prime constituents: H2O, CO2 and mineral components. During the process, recalcitrant organic compounds are formed and dissolved organic carbon may be leached to the mineral soil. It is also universally recognized that there are three main processes through which decomposition occurs: (1) leaching of soluble compounds into the soil, (2) fragmentation of litter into smaller sizes and (3) catabolism by decomposer organisms (i.e. micro-organisms and fauna). Swift et al. (1979), presented the triangle (P–O–Q), representing individual and interacting factors influencing litter decomposition: i.e. P for the physical–chemical environment; O for decomposer organisms and Q for resource quality (Fig. 5.1).
This definition and understanding, so clearly stated, has guided research on litter decomposition for the past decades, which has been devoted mainly to:
quantify rates of litter decay
develop mathematical models that better represent decay dynamics
identify litter quality factors that control decay rates, and eventually the equation defining the relationship
determine dynamics of nutrients and carbon-based compounds during litter decay
identify climatic factors that control decay, and eventually the equation defining the relationship
identify the interdependence between litter quality and climate
evaluate the role of soil organisms.