PREDICTING COMPETITIVE INTERACTIONS BETWEEN PIONEER PLANT-SPECIES BY USING PLANT TRAITS

A competitive effect hierarchy for 15 Namaqualand pioneer plant specie s was established by using the mean mass of the phytometer (Dimorphoth eca sinuata) when grown in combination with itself and 14 other specie s. There were no clear groupings of species in the hierarchy. This com petitive hierarchy (gradient) indicated which species are strong compe titors (resulting in a low phytometer mass) with D. sinuata and which species are weak competitors (resulting in a high phytometer mass). Ea ch plant species has a certain combination of plant traits which deter mines its life history strategy and competitive ability. Regressions o f various plant traits (measured on plants grown singly) against phyto meter biomass indicated which traits were significantly correlated. Th e traits, most being size-related, were: maximum shoot mass, total mas s, stem mass, reproductive mass, leaf area, stem allocation, specific leaf area (SLA), vegetative height x diameter, leaf area ratio (LAR); and mean number of days to flower initiation. A forward stepwise multi ple regression of the significant traits was used to determine an equa tion to predict competitive effect.