Organic matter distribution and nutrient fluxes within a sweet chestnut (Castanea sativa Mill) stand of the Sierra de Gata, Spain

Abstract

The aboveground biomass, litterfall and its accumulation, litter weight loss due to decomposition and nutrient pools in relation to soil properties were analyzed in a Castanea sativa Mill. stand in order to better understand the recycling of elements associated with the turnover of organic matter. The aboveground biomass and the nutrient content were estimated by harvesting eight trees. In order to establish regression equations the best fit was obtained by applying the allometric method $Y = aX^b$ ($Y$ = total aboveground biomass, $X$ is DBH). The highest concentration of the elements was found in the foliage and decreased in the following order: leaves $> $ branches $> $ trunk. The elements most concentrated in the leaves were N, Mg, P and K. These concentrations fluctuated consistently throughout the phenological cycle. The leaves are the main vector of the potential return of all nutrients to the holorganic horizon, followed by flowers for N, P and Mg, branches for Ca and fruits for K. Considering both total litter and leaves separately, higher $K$ (Jenny's decomposition constant) and $K$o (Olson's decomposition constant) values were estimated for leaves alone than for total litter. At the end of decomposition period the loss of dry matter was 47% . The decomposition rates of leaves confined to litterbags for the first year were lower than those obtained under natural conditions (22% in the litterbags, $K = 0.44$, $K{\rm o} = 0.39$ under natural conditions).