EFFECTS OF WATER AND NUTRIENT SUPPLY ON AMOUNT AND ON NUTRIENT CONCENTRATION OF LITTERFALL AND FOREST FLOOR LITTER IN EUCALYPTUS-GLOBULUS PLANTATIONS

A field experiment was initiated in March 1986 in central Portugal to evaluate the influence of water and nutrient supply on the productivit y of E. globulus. The treatments applied were, irrigation plus fertili ser, irrigation and the application of fertilisers in rainfed plots. T he control received neither fertilisers nor irrigation. The annual pat tern litterfall was measured over a period of 5 years and the litter l ayer was quantified 6 years after planting. The amount of litterfall v aried with the treatments. Simultaneous water and nutrient supply incr eased significantly litterfall, in respect to control. In rainfed cond itions the timing of the maximum of litterfall was anticipated relativ e to the irrigated plots. However, the time of maximum litterfall did not coincide with the dry season but rather with period of maximum gro wth in each treatment. The N and P concentration was higher in the lit terfall of the two fertilised treatments than in the others. The lowes t concentrations of N and P in the leaf litter were coincident with th e summer period in all treatments. The withdrawal of N and P ranged be tween 32 and 65% according to treatment and season. The deliverance of nutrients through litterfall was strongly increased by simultaneous w ater and nutrient supply. The supply of fertilisers in rainfed conditi ons promoted higher deliverance of nutrients than in the plots irrigat ed only. The mass of the litter layer was significantly increased by s imultaneous water and nutrient supply. Application of fertilisers indu ced an increase in N and P concentration and a decrease in C/N ratio o f the litter layer. Treatments and C/N values did not influence appare ntly the proportion of carbon, N and P released through mineralization from the litter layer. The non-fertilized treatments showed a more ef ficient N cycling than the others.