EFFECT OF A DENSE ALLIUM-URSINUM (L) GROUND COVER ON NUTRIENT DYNAMICS AND MESOFAUNA OF A FAGUS-SYLVATICA (L) WOODLAND

The aboveground biomass built up annually by Allium ursinum (L.) conta ins similar amounts of nutrients as the foliage of mature Fagus sylvat ica (L.) stands. The decomposition of the A. ursinum stand in early su mmer provides N rich forage for grazing mesofauna, especially favourin g collembolans and accelerating mineralization of soil organic matter. Short term decreases of soil pH had no negative effect on populations of collembolans. Synergistic effects from soil fauna and microbes may accelerate nitrogen release from decomposing leaf litter. A positive feed back may have emerged. High animal abundance and diverse mesofaun a populations are capable of high rates of litter fragmentation. Conse quently, favourable conditions for microorganisms are created and allo w high rates of mineralization and release of nutrients. Our data show that substantial amounts of nitrogen are lost from the system. Undist urbed forest ecosystems are considered to recycle mineralized nitrogen efficiently though. But temporal uncoupling of the N cycle due to mic robial activity and delayed or decreased N uptake of higher plants can cause enhanced leaching even from undisturbed systems. The tendency t o loose nutrients is apparent from high nitrate concentrations in the soil solution throughout the year. When nutrient losses from A. ursinu m subsystems are considered, lateral nutrient imports from adjacent pa rts of the ecosystem have to be taken into account. If lateral import does not counterbalance losses, maintenance of the soil nutrient statu s must occur by weathering or a decline is to be expected.