The role of carbon-based plant secondary metabolites in decomposition in terrestrial ecosystems

Abstract

Among organic components, lignin is the primary controlling factor of decomposition rates of surface litter during the later phase of decomposition in most habitats and during the initial phase in warm, moist habitats (those with a high actual evapotranspiration, AET). In habitats with moderate AETs, the decreased control by lignin over annual decomposition rates of surface litter is due in part to a significant periodic or seasonal influence of other carbon-based plant secondary metabolites over rates in the initial phase of decomposition. The influence of other secondary metabolites over decomposition rates should be a function of other correlates of AET: phytochemical composition of the community and persistence of various secondary metabolites in litter. As AET decreases from the highest extreme, one expects more, but perhaps short-term seasonal, influence of monomeric phenolics and tannins. In warm, dry environments with still-lower AETs, one expects some control by terpenes. On an annual basis, the relative influence of components other than lignin should therefore increase with decreasing AET, and the influence of lignin content alone on decomposition rates of surface litter should be reduced proportionately. Effects of these various classes of compounds should exhibit different temporal patterns in litter and soil. Complexity is added to this model by the multifarious effects of stress on the production of specific secondary metabolites, changes that occur in secondary-metabolite composition during senescence of tissues, and differential effects of specific secondary metabolites on decomposition. -from Authors