Effect of nitrogen supply on nutrient uptake in Corsican pine.
The growth of Corsican pine (Pinus nigra var. maritima) on a nitrogen-deficient site in the Moray Forest declined progressively while up to 36% of the total nitrogen became immobilized in trees and humus. Application of nitrogen fertilizer at rates of 84 to 504 kg N/ha per yr for three years increased growth for calculated periods of eight to thirteen years. Recovery of fertilizer nitrogen within the ecosystem was almost complete at the lowest rate of application but losses increased linearly with further increases in rate. Growth responses after the fertilizer applications had ceased can be explained in terms of the excess nitrogen accumulated within the trees. It is calculated that, at the maximum growth rate for the site (20 m3/ha per yr, Yield Class 16), uptakes of nutrients would be 69 kg of nitrogen, 6 kg of phosphorus, 28 kg of potassium, 34 kg of calcium and 11 kg of magnesium per hectare per year; about two-thirds of these quantities would subsequently be released by the trees.