Ma. Oosthuizen et al., NEIGHBORHOOD ANALYSIS OF COMPETITION BETWEEN 2 NAMAQUALAND EPHEMERAL PLANT-SPECIES, South African journal of botany, 62(5), 1996, pp. 231-235
By using attributes of neighbours, such as number, size and distance,
investigators have developed neighbourhood competition models that are
able to predict plant performance of an individual in a plant populat
ion. A non-linear neighbourhood model proposed by Silander & Pacala (1
985) was applied to performance data (i.e. total above-ground dry mass
) of Dimorphotheca sinuata and Ursinia cakilefolia, two Namaqualand ep
hemeral species. The best neighbourhood size was sought by varying the
neighbourhood size and plotting an interference index against dry mas
s. The non-linear model was then fitted to the data and the r(2) value
s determined for each neighbourhood. Correlations between performance
(total above-ground dry mass) and different interference indices were
much higher in mixtures than in monocultures for both species. Number
of neighbours seemed to be the best predictor of performance for both
D. sinuata and U. cakilefolia in mixtures. In monoculture, the best co
rrelations were obtained when the distance of the neighbours was also
taken into account. Even so, these correlations accounted for less tha
n 50% of the variation in plant mass. Although these neighbourhood mod
els may be useful in describing the inter-individual effects of interf
erence on Namaqualand ephemeral species, it may be difficult to apply
these results in the field.