Carbon and nutrient inputs by litterfall into three chestnut high forest stands in Northern Portugal

Litter fall in three high forest chestnut stands, located in different soil types, in Bornes, Marão and Padrela, northern Portugal, with 45, 63 and 65 years old, respectively, was collected during two years in December by a 0.5x0.5 m square method. Four kinds of samples were collected in this study – (1) leaf litter composed by vegetal materials resulting from the litter fall of the year; (2) leaf litter composed by a mixture of vegetal materials in different decomposition stages; (3) soil from 0-5 cm depth and (4) soil from 5-10 cm depth. Litter of the year was separated into the fractions leaves, branches, fruits and burs. All fractions were dried at 70°C, weighted and concentrations of N, P, K, Ca, Mg, S, B and C were measured. The total amount of litter in the three chestnut stands was 8.3, 7.7 and 12.4 Mg ha-1year-1, respectively. Leaves are the main constituents of the total litter with 54, 62 and 50 %, respectively. The proportions of the other litter fractions range from 10 to 19 % for the burs, 20 to 32 % for the branches and 4 to 10 % for the fruits. Regarding the amounts of the nutrients in the litter fractions, in general, leaves are rich in N>Ca>Mg>K>P>S; fruits are rich in N>K>Mg>Ca>P>S. In the branches, N and Ca amounts dominate clearly and the burs are rich in N and K. The return of nutrients by litterfall is relevant: it ranges from 57-142 kg ha-1 year-1 for N, 5-10 kg ha-1 year-1 for P, 13-45 kg ha-1 year-1 for K, 28-65 kg ha-1 year-1 for Ca, 18-34 kg ha-1 year-1 for Mg, 2-8 kg ha-1 year-1 for S and 87-117 g ha-1 year-1 for B. Carbon in the litterfall ranges between 4 and 6.3 Mg ha-1 year-1. It was verified that the biomass nutrients concentrations are strongly dependent on the soil as has been reported by other authors