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The Canopy VINES AND LIANAS
Creepers, vines, and lianas (woody vines) are abundant in the canopy and make up a significant proportion of the vegetation in tropical rainforest. There are over 2,500 species of vines from about 90 families [Liana distribution]. They range from small, indiscreet vines that grow against the tree to giant lianas thick as trees that seemingly hang in the middle of the forest independent of trees. Some of the larger woody lianas may exceed 3000 feet in length. Rattan is well-known liana for its use in furniture and ropes. Rattan also produces large, edible fruits - a favorite of primates. Lianas are vines that begin life on the ground as small self-supporting shrubs and rely on other plants to reach the light-rich environment of the upper canopy. Because lianas use the architecture of other plants for support, they devote relatively little to structural support and instead allocate more resources to leaf production and stem/root elongation for rapid growth. Since lianas are rooted throughout their life (unlike other structural parasites like epiphytes and hemiepiphytes), they take nothing from the tree besides support. Schnitzer and Bongers (2002) review some of the mechanisms lianas use to ascend to the heights of the canopy:
Hemiepiphytes rely on a different strategy. These plants start life in the canopy as an epiphyte and grow down to the ground. Hemiepiphytes grow extremely slowly due to dry conditions in the canopy but once the roots reach the ground and tap into the nutrients of the leaf litter, growth rates accelerate. One of the best known hemiepiphytes is the Strangler Fig. Creepers are among the many rainforest species that change their leaf structure as they grow. The plants, especially those of the Araceae family, start as a shrub on the forest floor and gravitate toward dark objects, usually tree trunks. When they reach the tree, the climbers grow vertically up the tree held fast by the triangular flattened leaves. The leaves are so positioned to catch reflected light. Once the vine reaches the bright upper regions of the canopy, the leaves are modified to grow away from the tree in order to intercept more direct sunlight. Lianas are a huge problem for rainforest trees, and numerous species have developed means of discouraging their growth. Many palm and tree ferns regularly drop frons, while other trees may lose limbs to rid themselves of lianas. Francis Putz, who studied Panamanian lianas, suggested it may be advantageous for trees to sway out of phase from their neighbors because this would tend to snap vine connections and kink lianas, cutting off transport systems. Some lianas have adapted to this mechanism by coiling and bending so they are spring-like and able to better able absorb the shock (Putz 1980) Lianas play an important role in forest dynamics "including surpressing tree regeneration, increasing tree mortality, providing a valuable food source for animals and physically linking trees together, thereby providing canopy-to-canopy access for arboreal animals." Schnitzer and Bongers (2002). Furthermore lianas contribute to overall plant diversity in tropical forests (especially in and around light gaps and forest edges where lianas are notably abundant due to the increased availablity of light). With their high photosynthetic production and sizeable biomass, lianas also make a significant contribution to carbon sequestration. OTHER PLANT AND ANIMAL RELATIONSHIPS Canopy trees have coexisted with insects for millions of years and many have developed unique relationships beyond pollination. Myrmecophytes or ant-plants are common in the rainforest. For example in South America, the Cecropia tree is colonized by Azteca ants. The tree is segmented like bamboo, providing compartments for ant colonization. A queen establishes a nest in one of the hollow chambers, while other cells are inhabited by workers until entire tree becomes a colony. The workers fend off the plant from all invaders -- including insects and epiphytes -- although they do not attack the three-toed sloths which feed exclusively on the leaves of Cecropia. The plant entices worker ants to stay and protect it by offering oil and sugars provided through leaf hairs and special structures at base of the leaf stem. Other plant species have similar relations with ants including some orchid species, bromeliads, Acacia, and Rubiaceae among others. To learn more about these ant-plant relationships check out http://biology.bangor.ac.uk/treborth/Epiphytes/Epiphytes-symbioses.html [external] and http://waynesword.palomar.edu/acacia.htm [external] Other tree species have mechanisms to prevent burdensome epiphytes which can add so much weight (especially when full of water after a rainstorm) that they can bring the tree down. The "Naked Indian" or Gumbo Limbo tree [Bursera simaruba] of South America and the Krystonia tree of Southeast Asia are among several species of tree that have peeling bark which prevents epiphytes and creepers from getting a hold or finding a suitable place to start growth. Other species produce toxins in their bark to ward off infestation by pests and to discourage the growth of epiphytes and lianas. |
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Canopy Index |
Study Structure Vines & Lianas Locomotion Other Mammals Amphibians, Reptiles, Invertebrates - - - - - |
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Copyright Rhett Butler 1994-2005 
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