The influence of millipedes on selected soil elements: a microcosm study on three species occurring on coastal sand dunes

1, The effect of mechanical breakdown of detritus by the millipedes Centrob olus fulgidus, Centrobolus richardii and Spinotarsus sp. on selected soil e lements was investigated in the laboratory. 2. Microcosms containing soils, detritus and millipedes from areas undergoi ng vegetation regeneration were set up in a climate chamber. Short-term cha nges in soil concentrations of ammonia (NH4+), nitrates (NO3-), phosphorus (P), calcium (Ca), potassium (K), magnesium (Mg), nitrogen (N) and carbon ( C) in the presence and absence of millipedes were determined. 3, Soil concentrations of the elements investigated were higher in microcos ms subjected to millipede activity than in controls. Microcosms containing Spinotarsus sp. and C. richardii were found to have the highest concentrati ons of Mg, K, N and C. 4, The results further illustrated no major sex-specific differences for in dividual species. 5. For most elements, rates of change were not affected by milipede biomass . However, the largest effect was in rate of change of Mg and K measured at 5-15 g of millipedes per microcosm. 6, Compositional effects (species present) were recorded for rates of chang e in K concentrations. 7, Influence of species richness on rates of change was only recorded for K and N, with rates for both increasing as the number of species increased. The predictability of rate of change diminished for K with an increase in t he number of species. 8. It is concluded that millipedes influence concentrations of soil element s through species-specific differential effects. Patterns related to compos ition and species richness only reflect species-specific differences. Never theless, the rate at which these soil elements increase in the microcosms s uggests that millipede activity may accelerate the release of elements in a reas undergoing vegetation development on coastal dune forests.