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 the distribution of nutrient content throughout the tissue life-span. The dynamics of internal translocation were followed during the crop rotation 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 concentrations along a vertical and radial gradient and from the ring volume obtained using stem ring analysis. Real nutrient translocation was calculated stepwise between successive stages in the age Series; apparent translocation was computed on a complete tree rotation by comparing 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 translocation of N, P and K (but not Ca) increased with stand age, obviously 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 most mobile element since translocation reached 60% of the total amount immobilized in the stemwood at the end of the rotation, whereas values for N, P and Mg were approximately 25% and 10% for calcium. Total apparent 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 ha(-1) for P. Total apparent translocation as a percentage of total wood immobilization was 114% for K, 83% for Mg, 63% for P, but only 39% for N and 24% for calcium. (C) 1996 Annals of Botany Company