CHANGES IN NODULE AND ROOT BIOMASS OF SESBANIA-SESBAN AND LEUCAENA-LEUCOCEPHALA FOLLOWING COPPICING

A pot study was conducted to measure the extent of and determine the factors controlling fine root and nodule shedding following coppicing of Sesbania sesban and Leucaena leucocephala. Fine (< 2 mm) root biomass decreased below pre-cutting values, but the decreases were not statistically significant in either species. Living (white) nodule biomass decreased and dead (brown) nodule biomass increased significantly two weeks after cutting in both species. These changes were relatively greater in Sesbania than in Leucaena. In the uncut treatments of both species, fine root and nodule biomass were correlated with leaf biomass, and in the cut treatments, root and nodule biomass returned to near this apparent equilibrium by two weeks after cutting. Stem growth rate per unit leaf area was not different between cut and uncut treatments, nor was it correlated with root:leaf ratios in either species. Leucaena allocated a greater fraction of its total biomass below-ground, and a greater fraction of its below-ground biomass to coarse (> 2 mm) roots than Sesbania. These results are consistent with the hypothesis that relatively lower allocation to below-ground storage tissue is the cause for Sesbania's relatively greater sensitivity to cutting.