INTERNAL NUTRIENT TRANSLOCATION IN CHESTNUT TREE STEMWOOD .3. DYNAMICS ACROSS AN AGE SERIES OF CASTANEA-SATIVA (MILLER)

Nutrient translocation in chestnut tree stemwood was calculated from t he distribution of nutrient content throughout the tissue life-span. T he dynamics of internal translocation were followed during the crop ro tation by means of an age series of five coppiced stands (2-19 years). N, P, K, Ca and Mg contents in tree rings were estimated from the con centrations along a vertical and radial gradient and from the ring vol ume obtained using stem ring analysis. Real nutrient translocation was calculated stepwise between successive stages in the age Series; appa rent translocation was computed on a complete tree rotation by compari ng the initial content just after the ring was formed with the mineral content in the oldest stand. There was a marked translocation of N, P , K and Ca when the rings were physiologically-active tissues. Real tr anslocation of N, P and K (but not Ca) increased with stand age, obvio usly in parallel with the enlarged stemwood biomass reaching 23.2 and 20.6 kg ha(-1) for IC and N in the last years of rotation, nearly 5 kg ha(-1) for Mg and about 3 kg ha(-1) for Ca and P. Potassium was the m ost mobile element since translocation reached 60% of the total amount immobilized in the stemwood at the end of the rotation, whereas value s for N, P and Mg were approximately 25% and 10% for calcium. Total ap parent translocation leached respectively 39.2 and 32.4 kg ha(-1) for K, N, approximately 12 and 7 kg ha(-1) for Mg and Ca and only 4.4 kg h a(-1) for P. Total apparent translocation as a percentage of total woo d immobilization was 114% for K, 83% for Mg, 63% for P, but only 39% f or N and 24% for calcium. (C) 1996 Annals of Botany Company