© 2001 Heron Publishing—Victoria, Canada
Dynamics of nonstructural carbohydrates and biomass yield in a fodder legume tree at different harvest intensities
Heli Garcia (1), Pekka Nygren (1, 2, 3) and Lucienne Desfontaines (4)
1. Department of Forest Ecology, Tropical Silviculture Unit, Box 28, FIN-00014 University of Helsinki, Finland / 2. Center for Agroforestry, 203S Anheuser-Busch Natural Resources Building, University of Missouri, Columbia, MO 65201, USA / 3. Author to whom correspondence should be addressed (pekka.nygren@helsinki.fi) / 4. Unité Agropèdoclimatique, INRA Centre Antilles-Guyane, Domaine Duclos, 97170 Petit-Bourg, Guadeloupe / Received May 8, 2000
Summary
Tropical tree fodder is harvested by frequent prunings, and resprouting depends on nonstructural carbohydrate reserves in
the remaining tree parts. We studied the effects of three pruning intensities (removal of all leaves and 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
of soluble sugars and starch in the legume tree Gliricidia sepium (Jacq.) Walp. growing under humid tropical conditions in Guadeloupe, Lesser Antilles. Carbohydrates were sampled in roots,
stems and branches. Among pruned trees, 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, but 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
fructose were the most common sugars in all biomass compartments. Mannose, pinitol and an unidentified cyclitol were relatively
abundant in branches. Root sugar and starch concentrations were unaffected by harvest regime. There was a significant interactive
effect of harvest intensity and regrowth time on stem sugar concentration. Stem starch concentration was highest in T-12 trees.
After a year of fodder harvesting, whole-tree reserves of nonstructural carbohydrates were highest in T-12 trees; however,
a larger proportion 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 harvesting regime on soluble sugar and starch concentrations.
Keywords:
agroforestry, defoliation, Gliricidia sepium, humid tropics, soluble sugars, starch.
