Species strategy and N fluxes in grassland soil

The presence of a growing stand increased the N mineralisation rate of the root litter. Both the type of root litter and that of the rhizosphere significantly affected the N fluxes. A greater N harvest was recorded in the Dactylis stand and on the Lolium litter; while greater N loss by leaching occurred under the Lolium stand and from the Lolium litter. Lolium induced a greater N turnover in SOM, while Dactylis caused a faster decay rate of litter N. Dactylis favoured the “short” N cycle between stand and root litter, while Lolium favoured the “complete” N cycle between stand and SOM. The chemical composition of the root litter was similar, but the species effects on the N cycles could be accounted for by differences in morphological root traits. A set of functional root processes is proposed that differentiates species strategies towards the nitrogen cycle. Dynamic consequences for a mixture of the two species are discussed.