Litterfall in four forest stands of Northern Portugal: Production, nutrient concentration and amounts returned to the forest floor

Abstract

Monthly litterfall production, nutrient concentration and nutrient devolution to the forest floor through litterfall were assessed in four forest stands of Castanea sativa Miller (CS), Pseudotsuga menziesii (Mirbel), Franco var. menziesii (PM), Pinus nigra Arnold subsp. laricio (PN) and Pinus pinaster Aiton, (PP), located close to Vila Pouca de Aguiar, Northern Portugal. Mean annual amounts of litterfall measured during two years decreased in the order PN > PP > PM > CS respectively, 6910, 4115, 3934 and 2759 kg ha^-1. Values showed high inter-annual variation, which can be ascribed to the different climatic conditions during the study period. Coniferous species showed a continuous litterfall production, with higher amounts in August and September for PP, September and October for PN and PM. In the case of the CS, there was not litterfall production during part of the year and the highest amounts were observed in October and November. Concerning the proportion of the several components in the litterfall, needles and leaves were largely predominant in the following order PM > CS > PP > PN, respectively 83, 78, 68 and 55 %. Concentration of nitrogen in the leaves of CS and needles of PM was higher (respectively 11.3 and 10.9 g kg^-1) than in PN and PP needles (respectively 7,3 and 5,5 g kg^-1). Concentration of Ca in PM (9,4 g kg^-1) was also higher than in the other species, implying an higher amount of Ca returned to the forest floor (34.5 kg ha^-1 year^-1) in the former than in the other species (9.3 to 14.4 kg ha^-1 year^-1), which positively favour soil surface layer chemical properties in stands of the first species.