Carbon and nutrient amounts in aboveground biomass, understory and soil in a pine stand chronosequence

Abstract

Biomass and nutrient amounts accumulated in the above ground biomass along the rotation period of maritime pine stands of the Leiria National Forest were evaluated. Amounts of biomass and nutrients of understory were also assessed. Furthermore, mass and nutrients in organic soil layers, as well as nutrient amounts in mineral soil layers (up to 100 cm depth) were evaluated. A strong increment of above ground biomass and accumulated nutrients was observed along the rotation period, with maximum at the end. A similar increment of organic C and nutrients was also observed in the mineral soil layers in the later rotation stage, being mostly allocated to the top soil layers (0-20 cm). Organic C was equally distributed by the above ground biomass and mineral soil, while N and Ca were mostly allocated to the soil. Phosphorus was largely allocated to the organic soil layers and harvest residues, and Mg and K showed an intermediate pattern. Results suggest that system disturbances associated with stand exploitation (harvesting, log removal, harvest residues removal, microclimate changes) may provoke strong variations on the organic C stock and nutrient availability. Proper site management to avoid organic matter and nutrient losses are crucial to assure system sustainability.