Enhanced forage production under Samanea saman in a subhumid tropical grassland

The effects of isolated, mature Samanea saman trees on herbaceous production and species composition were investigated over the 1993/1994 growing season in a subhumid tropical grassland in north-east Queensland, Australia. Under the crown, the cumulative aboveground biomass over the season was almost 90% above that of the open grassland. This increase was associated with a difference in species composition. The principal grass under the crown was Panicum maximum, while in the open grassland, the dominant species was Urochloa mosambicensis. Near the crown, cumulative biomass was intermediate and this was reflected in a mixed species composition. This study confirms earlier, largely anecdotal reports of the potential beneficial effects of S. saman on forage production, but by itself was unable to explain the mechanism by which this increase occurred.