Projecting soil fauna influence on long-term soil carbon balances from faunal exclusion experiments

In soil ecology, many investigations of faunal influence on, e.g. soil carbon flows have been performed. However, analysis of long-term effects of faunal activity on, e.g. long-term soil carbon pool changes are uncommon. We analyse possible effects on long-term soil carbon balances of soil fauna activity on humus and litter decomposition rates as well as litter humification ratio (the fraction of litter that eventually becomes humus). Results from published soil fauna experiments (measurements made in presence versus absence of organisms) Eire re-interpreted as parameter changes for a soil carbon model (ICBM, see http://www.mv.slu.se/vaxtnaring/olle/ICBM.html), which is used for projections of soil C pools and fluxes during a 30-year period. Model outputs indicate that changes in humification ratio and old material ("humus") decomposition rates have much greater influence than changes in young material ("litter"') decomposition rate on total soil carbon dynamics. We point out the risk of putting too much faith in model projections, and underline the need for long-term research data as a base for long-term model projections. (C) 2001 Elsevier Science B.V. All rights reserved.