Perhaps the most easily recognisable adaptations in the moist rainforest are lifeforms such as palms, epiphytes, and climbing plants.
Epiphytes are plants that grow on other plants.
However, epiphytes are not parasites as they do not take any nutrients from their hosts (the trees) though at times there can be so many that they weigh down even large branches and cause breakages.
Many epiphytes spend their entire life high in the canopy in bright sunlight, away from the deeply shaded forest floor. They have specific adaptations to capture water and nutrients. These include the water storing pseudobulbs of some orchid species, and the bracketed leaves of large epiphytic ferns (like Staghorns) that capture falling leaves (for nutrients) and create a peat like deposit that retains water. Epiphytes include angiosperms (flowering plants), ferns, mosses and lichens. The latter are common in cool, wet rainforest types in montane areas, and these forests are sometimes referred to as ‘cloud, elfin, or mossy forest’.
Climbing plants include the lianas (large, woody vines) and the smaller twining vines.
Lianas and vines get their start either as shade tolerant seedlings in the dark forest, or in light gaps created by disturbance. Without the advantage of solid (rigid) stems, they need support to climb into the tree tops. As they grow they eventually attach to a host tree and begin their climb toward the canopy, and life-giving sunlight. They use a variety of climbing strategies and mechanisms such as looping tendrils, thorns, spikes, and downward facing hairs1 to gain a hold on the tree. Once they reach the top of the canopy, they spread laterally and can make up a significant proportion of the photosynthesising leaves of the forest.
Lianas can compete with host plants (trees) for light, and sometimes can even smother the tree canopy. However, they have an important role in the rainforest canopy, adding to the diversity of the forest and its resources (fruits, flowers and leaves), providing both stability and resistance to strong winds, and providing a network of access corridors for the many animals moving between trees in the canopy and down to the forest floor. Even some palms have adopted the climbing habit to reach sunlight, with the best known of these called Rattans (for example, Calamus spp.).
- Schnitzer, A. & Bongers, F. (2002) The ecology of lianas and their role in forests. Trends in Ecology & Evolution. 17 (5) 223-230.