Abstract
Spatial distribution was analysed for all plot trees and representative tree species in two duplicate I-ha plots established in a foothill rain forest 16 km west from Padang, West Sumatra, Indonesia. All tree trunks ≥ 8 cm dbh were distributed randomly in both plots. Spatial correlation between dead trees and recruited trees during the 8-year period was locally negative while broadly positive, suggesting that the random spatial pattern is dynamically maintained by mechanisms of density-dependent regulation.
All of five abundant canopy/subcanopy non-pioneer species, i.e. Hopea dryobalanoides, Gonystylus forbesii, Cleistanthus glandulosus, Mastixia trichotoma, and Grewia florida, and typical pioneer Macaranga spp., including M. gigantea, M. hypoleuca, M. pruinosa and M. triloba, showed a clumped distribution, particularly for smaller size classes. Two subcanopy non-pioneer species, Mastixia and Grewia showed a shift from a regularly decreasing density with height in one plot with larger gap area to bimodal height distribution in the other plot with smaller gap area. They also showed a similar tendency in spatial pattern such that the negative spatial correlation was observed between seedlings (< 1 m high) and poles (1-10 m high) and between poles and tall trees (≥10 m high) in the plot with larger gap area but that was found between seedlings and tall trees in the plot with smaller gap area. Such pattern was also observed for gap-demanding Macaranga spp., and they were concluded to be less tolerant than Hopea, Gonystylus and Cleistanthus, in which no height distribution difference nor spatial pattern difference was observed between two plots. These more tolerant species showed a positive correlation between tall trees and seedlings, but no correlation between tall trees and poles. These results reflect the dynamic alternation of tree species within a limited area of forest.
