Climbers
Many climbers which reach the canopy top have crowns of the form, and often the size, of a tree crown. These climbers commonly have a freely hanging woody stem, and can be conveniently referred to as big woody climbers. They are represented in very many families of plants. All except two species of the curious gymnosperm Gnetum are big woody climbers (and are very readily identified from the raised hoops at nodes on the stems. Amongst the commonest big woody climbers are Annonaceae, Bauhinia, Mezoneuron, Strychnos, and Uncaria. The climbing palms, the rattans, are another important class of big woody climbers which are a particularly pungent feature of the rain forests of our region, especially the western part.
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Epiphytes, climbers and stranglers
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Most big woody climbers are photophytes and grow prolifically in clearings and cm forest fringes, giving rise to the popular myth of the impenetrable dense jungle. They spring up in gaps and grow with the crowns of young trees, so are carried up with the growing height of the replacement canopy. They also spring up after logging operations and may prove a serious hindrance to the growth of a new forest; for example, Mezonuron sumatranum is especially bad in Sabah and species of Merremia there and in the Solomons and Uncaria species are common in the whole region. In the survey on Kolombangara just mentioned it was found that there were more species (5o versus 38 per hectare) and individuals (47o versus 194) of big woody climber, and they were of smaller average girth (107mm versus 143 mm) in places believed on other grounds to be first regeneration regrowth forest (Whitmore 1974).
The other group of climbers are the bole climbers, which grow close to a tree adhering by one of various means (Richards 1952). In the same survey in the Solomons there was found to he marked stratification within this synusia. Topmost, and distinctly photophytic, was the climbing pandan Freycinetia solomonensis, found on upper boles and in the lower parts of crowns and occasionally also seen in gaps in the canopy at or near ground level. Below this occurred a mixed group of Araceac, themselves stratified. Lowest was a belt of the fern Stenochlaena, most markedly skiophytic.
Comparing forests in the Solomons of known approximate age, including areas near Munda which had regrown since felling by the Japanese in the pacific War, the abundance and number of species of hole climbers and epiphytes was seen to increase markedly with age. It is a truism that these synusiae are sparse in secondary forest.
Stranglers
Stranglers are plants which start life as epiphytes and send down roots to the ground which increase in number and girth and self-graft on contact under pressure, ultimately encasing the host tree which often then dies, and true stranglers developing a dense, tight, stem-like structure of often-anastomosing roots must be distinguished from the banyan type which starts life similarly but forms a much more open structure of roots, descending from the limbs and commonly covering an area up to 20 m across. Where banyans are common, as in the Salomons, they are a considerable hindrance to silviculture. Several species of Schefflera and Fagraea are stranglers, at least facultatively, and strangling species of Timonius (New Guinea and Solomons), Spondias (Philippines), and even a member of the Scrophulariaceae Wightia (see van Steenis 1972) are now known.
REFERENCE :
Whitmore, T.C, 1975, Tropical Rain Forests of the Far East , 1st Edition, Oxford University Press, Oxford.
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