There were no significant differences in rhizome biomass of speargrass in
hedgerows and control plots at the beginning of data collection in November
1987 and in the months of December and February. Significant differences
between treatments occurred thereafter. Biomass of speargrass rhizomes in
the control plot declined sharply in February 1988 after the bush-fire. As
speargrass regrowth appeared with the onset of rains in 1988, rhizome
biomass increased steadily till November 1988 (Fig. 4). Rhizome biomass in
the control plot almost doubled between November 1987 when sampling
started and November 1988 when the last sample was taken. Since speargrass
spreads mainly by rhizomes, such increase in rhizome biomass will
strongly suggest great potential for persistence and spread. Decline in
rhizome biomass was identical in the control and leucaena plot until March
1988. This period corresponded with the peak of the dry season when
moisture stress would be expected to reduce vegetative growth of most plants
to a minimum. Whereas there was recovery and increase in biomass in the
control plot during the rains (April-September), speargrass biomass did not
increase in leucaena plots but rather leveled out during the same period, and
finally declined during the dry season in 1988. There was a sharp decline in