A liana is a long-stemmed, woody vine that is rooted in the soil at ground level and uses trees, as well as other means of vertical support, to climb up to the canopy in search of direct sunlight.

Lianas are characteristic of tropical moist deciduous forests (especially seasonal forests), but may be found in temperate rainforests and temperate deciduous forests. Lianas can form bridges amidst the forest canopy, providing arboreal animals with paths across the forest. These bridges can protect weaker trees from strong winds. Lianas compete with forest trees for sunlight, water and nutrients from the soil. Forests without lianas grow 150% more fruit; trees with lianas have twice the probability of dying.

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