The biogeochemical cycle in a healthy and highly productive Norway spruce (Picea abies) ecosystem in the Vosges, France
Mohamed, A.D. | Ranger, J.
The biogechemical cycle in a highly productive and healthy Norway spruce (Picea abies (L.) Karst.) stand was studied in the west part of the Vosges Mountains, France. The plot, an 85-year-old plantation established on an acidic brown soil, was considered the healthy control of a series of stands in varying stages of decline in this area. The nutrient reserves were evaluated in the soil and in the living biomass. A classical design was set up and monitored for 3 years to measure the total atmospheric input and the transfer of solution through the ecosystem using tensionless lysimeters. The current soil functioning was dominated by the nitrogen cycle (nitrification) and the occurrence of large amounts of Al in the solution. Nitrification, essentially endogenous, was the main acidifying factor. Nitrates contribute to the leaching of large amounts of Ca and Mg. The mean annual losses in the seepage water at a depth of 60 cm were 17.2 kg ha-1 of N. 10.2 kg ha-1 of Ca, and 6 kg ha-1 of Mg. The mean annual input-output budget of these elements was always negative (-6.3 kg ha-1 for N; -4.7 kg ha-1 for Ca; -2 kg ha-1 for Mg). The seasonal budgets show that the atmospheric input is only helpful to the stand if it occurs during the growing period. The question of the perenniality of the current ecosystem productivity is of paramount interest, even if at present the available soil reserves and the nutrient content of solutions (absolute values and ratios between elements like CalAl and Mg/Al) indicate that tree nutrition is not a limiting factor.
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