ELSEVIER Applied Soil Ecology 4 (1996) 1-3 Applied Soil Ecology Viewpoint Decomposition: driven by nature or nurture? Meine van Noordwijk lCRAF-S.E. Asia. P.O. Box 161, Bogor, Indonesia Accepted 23 February 1996 Although the carbon flow involved in decomposi- tion is approximately equal to that in primary pro- duction, the amount of research is far less. A recent symposium under the title "Driven by Nature" re- viewed the role of plant litter quality in determining decomposition in terrestrial ecosystems, both in the tropics and in the temperate region (Cadisch and Giller, 1996). In as far as decomposition of plant residues is indeed fully 'driven by their nature', i.e. determined by the physical, chemical and biological qualities of the organic residue, a fairly small re- search attention might be justified. In practice, how- ever, the biotic and abiotic environment in which decomposition takes place (the 'nurture') has a con- siderable modifying effect both on the rate at which decomposition occurs and on the end-products formed (CO 2, CH 4, humus, charcoal). The role of cell and tissue structure as well as 'secondary' metabolites during the life of the plant can now be connected to their effects during decomposition after death of the plant (or its parts). There has been a lot of progress in the past 2 decades in understanding the principles and varia- tions on the theme of decomposition (Swift et ai., 1979; Woomer and Swift, 1994; Palm, 1995). Yet, the practical application of this knowledge falls short of expectations and the soil ecological research com- munity may not have responded to all the current challenges. Such applied research may start with the questions: what's wrong with the way decomposition processes work: are they too fast or too slow? Do they yield the wrong end-products? If there is noth- ing wrong with decomposition, it is not a priority area for research. Decomposition research must shed its 'undertaker' image: dealing with the fate of dead plants and animals can lead to lively debates. In my view, decomposition studies can contribute to solving some of the major issues of this time: sustainability and environmental side-effects of agri- cultural production, climate change (greenhouse gas emissions and C sequestration of today's and tomor- row's soils and vegetation) and the maintenance of biodiversity, especially where below-ground organ- isms (a considerable share of the total number of living species) are concerned. Sustainability issues concentrate on the need for, and mechanisms of maintaining, adequate amounts of soil organic matter in pools with an intermediate turnover time, as well as on the time pattern of N mineralization in relation to uptake demands by plants. Several new soil fractionation techniques have been developed and tested, often based on a physical fractionation of the soil by size (aggregation) and physical density (degree of organo-mineral linkage) as the first step, followed by chemical characteriza- tion of the fractions. Considerable progress has been achieved in obtaining 'indicators' of the various dynamic pools hypothesized in current models of soil organic matter dynamics (Hassink, 1995), but actual measurements of the pool size have proven difficult to achieve as yet. The search for an 'active' soil organic matter resembles the search for the Holy Grail, or at least that of the Cheshire cat: the be- haviour of soil organic matter in soils is determined 0929-1393/96/$15.00 Copyright © 1996 Elsevier Science B.V. All rights reserved. PH S0929- 1393(96)00103-5