Dynamics of nonstructural carbohydrates and biomass yield in a fodder legume tree at different harvest intensities

Tropical tree fodder is harvested by frequent prunings, and resprouting dep ends on nonstructural carbohydrate reserves in the remaining tree parts. We studied the effects of three pruning intensities (removal of ail leaves an d branches leaving 1 m of stem once a year (T-12), or every 6 months (T-6), and about 50% pruning every 2 months (P-2)) on regrowth and the dynamics o f soluble sugars and starch in the legume tree Gliricidia sepium (Jacq.) Wa lp. growing under humid tropical conditions in Guadeloupe, Lesser Antilles. Carbohydrates were sampled in roots, stems and branches. Among pruned tree s, trees in the T-6 harvest regime had the highest leaf fodder yield (0.73 kg tree(-1) year(-1)). High litter loss reduced leaf yield of T-12 trees, b ut compared with the other treatments, T-12 trees produced the most branch biomass (3.43 kg tree(-1)). Among treatments, P-2 trees had an intermediate leaf fodder yield and the lowest branch production. Sucrose, glucose and f ructose were the most common sugars in all biomass compartments. Mannose, p initol and an unidentified cyclitol were relatively abundant in branches. R oot sugar and starch concentrations were unaffected by harvest regime. Ther e was a significant interactive effect of harvest intensity and regrowth ti me on stem sugar concentration. Stem starch concentration was highest in T- 12 trees. After a year of fodder harvesting, whole-tree reserves of nonstru ctural carbohydrates were highest in T-12 trees; however, a larger proporti on of reserves were located in roots and stems of T-6 and P-2 trees. These reserves, which were not lost in pruning and contributed to regrowth of G. sepium after pruning, may explain the relatively small effects of harvestin g regime on soluble sugar and starch concentrations.