Primary succession and the effect of first arrivals on subsequent development of forest types

Abstract

The three Krakatau islands in Indonesia were completely denuded by the great eruption in 1883. One century after the eruption, the vegetation of Rakata on the one hand and of Panjang and Sertung on the other are quite different. Indigenous or exogenous Neonauclea seeds successfully formed Neonauclea forest on Rakata island but compltely failed to do so on Panjang and Sertung islands. The dispersal of seeds, soil conditions and volcanic activity of Anak Krakatau were all found to be contributing factors.

The Timonius and Dysoxylum forests found on Panjang and Sertung originated on both islands after the appearance of Anak Krakatau. These dominants have larger seeds than Neonauclea and were able to germinate and grow under the regenerated mixed forest canopy but it was not so easy for them to colonize the Neonauclea forest. At the present time, their invasion progresses only gradually on Rakata.

Ardisia scrub on steep coastal slopes on the Satsunan islands, SW Japan, is thought to be a somewhat parallel case of the retarding effect on the subsequent development of communities of the first arrivals. Ardisia scrub in these habitats appears to be a stable community, withstanding salt-laden wind. This shrub produces a number of stem and root sprouts, in a mop-headed growth. Their drupes are carried by birds and few seedlings were found in the scrub. The scrub floor was heavily shaded when its canopy was covered by lianes. The deep shade and frugivore activity prevent the invasion of other dominant species which would change the scrub into another type of forest. In milder habitats the scrub gradually becomes tall and the number of sprouts decreases, the forest then changes into another type such as Persea or Castanopsis forest.