FAUNA AND FLORA OF MANGROVE SWAMPS
107
as a nurse tree to the colonization of Rhizophora spp. or other more
valuable Bruguiera spp. (Watson, 1928).
Watson considers the forests of B. gynznorhiza to be “ t h e final
stage in the development of the littoral forests and the beginning of the
transition to inland forms ”. He finds that, once established, there is
little regeneration beneath these trees and that successive humus
deposits and the activities of Thalassina anomala (Herbst) gradually
lift the soil level so that in due course it is raised above the reach of
the tides. At this stage Xylocarpus moluccensis, Intsia bijuga, Ficus
microcarpa, Pandanus spp. and Daerrtonorops leptopus and many other
plants come in.
I n Watson’s opinion, then, a forest of B. gymnorhiza is the transition
t o a well-developed landward fringe.
At Tjilatjap in southern Java, de Haan (1931) also described three
variants of the bruguiera forests. He recognized a Bruguiera gymnorhiza Association developing in his zones A2-A3 (p. 89) on soils
which are mainly firm and flat with few crab hills (i.e. mounds of
Thalassina). Here there are tall trees of B. gymnorhiza in the upper
part of A2 and in zone A3 these become intermingled with tall trees of
Xylocarpus granatum and Heritiera littoralis; clumps of Excoecaria
agallocha occur in places where the soil level has been raised. Ceriops
tagal and C. decandra (Griff.) Ding Hou are sporadic. Undergrowth is
scanty in deep shade, thick in clearings, and consists of Derris heterophylla, Paramignya littoralis Miq., and in the less shady places a dense
growth of Acrostichum spp.
From this he separated a Bruguiera cylindrica Association and a
Xylocarpus-Heritiera Association. These two have much in common,
differing only in the dominant species. Both develop in zones A3-A4
and both are intermediate to the landward fringe. Both occur on more
or less firm clays ; in both the surface is irregular due to the burrowing
activities of crustaceans.
These are open forests in which on the one hand B. cylindrica and
on the other Xylocarpus granatum and Heritiera littoralis are dominant.
With them occur Excoecaria a,gallocha, Xylocarpus moluccensis, Cynometra ramijlora L. and Intsia bijuga.
The undergrowth is usually thick, of Derris heterophylla, Acrostichum
sp. with Nypa in muddy gullies.
I n Australia and Africa forests of B. gymnorhiza extend up to the
landward fringe only where there is abundant rain. I n regions of lower
rainfall they are sandwiched between ceriops thickets and the rhizophora
forest and occupy the middle of the mangrove area.
Bruguiera forests in South East Asia and in Australia frequently
107
as a nurse tree to the colonization of Rhizophora spp. or other more
valuable Bruguiera spp. (Watson, 1928).
Watson considers the forests of B. gynznorhiza to be “ t h e final
stage in the development of the littoral forests and the beginning of the
transition to inland forms ”. He finds that, once established, there is
little regeneration beneath these trees and that successive humus
deposits and the activities of Thalassina anomala (Herbst) gradually
lift the soil level so that in due course it is raised above the reach of
the tides. At this stage Xylocarpus moluccensis, Intsia bijuga, Ficus
microcarpa, Pandanus spp. and Daerrtonorops leptopus and many other
plants come in.
I n Watson’s opinion, then, a forest of B. gymnorhiza is the transition
t o a well-developed landward fringe.
At Tjilatjap in southern Java, de Haan (1931) also described three
variants of the bruguiera forests. He recognized a Bruguiera gymnorhiza Association developing in his zones A2-A3 (p. 89) on soils
which are mainly firm and flat with few crab hills (i.e. mounds of
Thalassina). Here there are tall trees of B. gymnorhiza in the upper
part of A2 and in zone A3 these become intermingled with tall trees of
Xylocarpus granatum and Heritiera littoralis; clumps of Excoecaria
agallocha occur in places where the soil level has been raised. Ceriops
tagal and C. decandra (Griff.) Ding Hou are sporadic. Undergrowth is
scanty in deep shade, thick in clearings, and consists of Derris heterophylla, Paramignya littoralis Miq., and in the less shady places a dense
growth of Acrostichum spp.
From this he separated a Bruguiera cylindrica Association and a
Xylocarpus-Heritiera Association. These two have much in common,
differing only in the dominant species. Both develop in zones A3-A4
and both are intermediate to the landward fringe. Both occur on more
or less firm clays ; in both the surface is irregular due to the burrowing
activities of crustaceans.
These are open forests in which on the one hand B. cylindrica and
on the other Xylocarpus granatum and Heritiera littoralis are dominant.
With them occur Excoecaria a,gallocha, Xylocarpus moluccensis, Cynometra ramijlora L. and Intsia bijuga.
The undergrowth is usually thick, of Derris heterophylla, Acrostichum
sp. with Nypa in muddy gullies.
I n Australia and Africa forests of B. gymnorhiza extend up to the
landward fringe only where there is abundant rain. I n regions of lower
rainfall they are sandwiched between ceriops thickets and the rhizophora
forest and occupy the middle of the mangrove area.
Bruguiera forests in South East Asia and in Australia frequently