Nutrient cycling in deciduous forest ecosystems of the Sierra de Gata mountains: nutrient supplies to the soil through both litter and throughfall

The present work fits into a general study on nutrient cycling in four Quer cus pyrenaica oak forests and one Castanea sativa chestnut coppice located in the Sierra de Gata mountains (Central System, western Spain). The work c onsists of an estimation of bioelement supplies to the soil by the litter o f these species and by throughfall from the canopy with a view to defining their role in the soil and, more generally, in ecosystem bioelement dynamic s. It is concluded that the greatest differences between the oak stands and the chestnut coppice lie in the fact that in the latter ecosystem potentia lly more N, P, K, Mg, Na and Mn return through the litter owing to greater production in the chestnut coppice (and/or root uptake). Additionally, the relative importance of some bioelements (N, P, K and Mn) in the chestnut co ppice is different from that of the oak forests. It is also possible to dif ferentiate three groups of bioelements: 1) those that potentially return al most exclusively through the litter (C and N); 2) those for which both litt er and throughfall must be taken into account to determine the potential re turn of bioelements (Ca, Mg, P, K, Fe and Mn); and 3) those that return alm ost exclusively through canopy leaching (Na, Cu and Zn). Despite this, on a ttempting to calculate the actual minimum annual returns, the three groups must be reduced to two: bioelements that almost exclusively return by throu ghfall (Na, Cu and Zn), and bioelements that return through litter decay an d canopy leaching. Exceptionally, Fe behaves in a special way in the sense that it tends to be immobilized by decaying leaf litter. (C) Inra/Elsevier, Paris.