Macronutrient inputs by litterfall as opposed to atmospheric deposition into two contrasting chestnut forest stands in southern Switzerland

The litterfall in two contrasting chestnut stands in Copera and Morbio, southern Switzerland, was collected between October 1994 and September 1995 and separated into the fractions leaves, branches, flowers, fruits and husks. The fractions were weighed and the concentrations of N, Ca, Mg, K, and C were measured. Wet deposition and throughfall of N, Ca, Mg, and K were measured and the corresponding dry deposition was estimated using multiple linear regression analysis. The total amount of litter in the two chestnut stands was 5.8 and 7.6 Mg ha(-1) a(-1) in Morbio and Copera, respectively. Leaves are the main constituents of the total litter, The proportions of the other litter fractions depend mainly on the former cultivation and management practice of the forests, the structure of the stand and the age of the trees. Regarding the concentration of the macronutrients in the litter fractions, leaves are richest in N and Ca, fruits in N and K. In husks. N dominates and Ca. and K do not differ very much. In branches, the N- and Ca-concentrations dominate by far, and the flowers are the richest in N. The return of macronutrients by litterfall is relevant: it is 6.6, 1.5 0.6, and 1.3 kmol ha(-1) a(-1) for N. Ca, Mg. and K, respectively, in Copera. The corresponding values in Morbio are 3.8, 2.2, 0.5, and 0.3 kmol ha(-1) a(-1). The return by litterfall is considerably higher than the import by atmospheric deposition (factors 3.8-5,1 in Morbio and Copera. respectively). In Copera. an amount of nutrient cations which corresponds to approximately 35% of the exchangeable stock in the soil is kept in the ecosystem internal cycle. This is highly relevant with respect to the buffering of acidity and for the prevention of nutrient cation loss due to acidification. (C) 2002 Elsevier Science B.V. All rights reserved.