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 carb on flows have been performed. However, analysis of long-term effects of fau nal 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 humific ation ratio (the fraction of litter that eventually becomes humus). Results from published soil fauna experiments (measurements made in presence versu s 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), w hich is used for projections of soil C pools and fluxes during a 30-year pe riod. Model outputs indicate that changes in humification ratio and old material ("humus") decomposition rates have much greater influence than changes in y oung 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 mode l projections. (C) 2001 Elsevier Science B.V. All rights reserved.