Published online by Cambridge University Press: 10 July 2009
The growth response of Paspalum vaginatum S.W. and P. orbiculare Forst to different environmental conditions and the interactions between the two species were deter-mined experimentally in order to find out some of those factors which may be responsible for the species distribution. There was no difference in response (as measured by growth) of P. vaginatum to any of the soils tested but this was not so for P. orbiculare. P. vaginatum grew signifi-cantly better in waterlogged soil than in either moist or dry soil, while the soil moisture condi-tions had no significant effect on the growth of P. orbiculare. Salinity in the range of 0-50% that of sea water had no significant effect on the growth of P. vaginatum, however higher salinity significantly suppressed the growth. In P. orbiculare, salinity above 10% caused a signi-ficant decrease in growth to the extent that the species did not survive at 100% sea water concentration. In competition, P. vaginatum was the stronger competitor in red earth, the soil from its natural habitat, under saline conditions and in waterlogged conditions. The results are discussed in relation to the natural habitats of the species and used to explain, in part, their distribution.