Lianas are woody vines found in various forest ecosystems. These plants rely on other vegetation for structural support to ascend towards sunlight. This climbing habit allows them to access the light-rich upper canopy without investing heavily in a thick, self-supporting trunk.
What are Lianes?
Lianas are woody vines that root in the soil but depend on other plants, primarily trees, for physical support to climb upwards. The term “liana” describes a growth form, similar to “tree” or “shrub,” rather than a specific taxonomic group; many different plant families contain liana species. They are characterized by long, flexible stems that can reach over 1.5 kilometers long.
These woody climbers use various mechanisms to ascend, including twining their stems around trunks and branches, developing tendrils to latch onto supports, or utilizing thorns, spikes, and adhesive roots to grip tree bark. Once lianas reach the forest canopy, they can spread horizontally, creating extensive networks that connect multiple trees. This strategy allows them to efficiently reach sunlight. Lianas are abundant in tropical rainforests and also occur in temperate forests, such as wild grapes (Vitis).
Impact on Trees and Forest Dynamics
Lianas influence the trees they inhabit and the broader forest ecosystem. They compete with trees for resources such as light, water, and soil nutrients, often reducing tree growth and reproduction. Forests without lianas can produce substantially more fruit, sometimes 150% more.
The presence of lianas also increases tree mortality. Trees with lianas are approximately twice as likely to die compared to those without. Lianas contribute to tree mortality by causing mechanical damage, such as abrasion and strangulation, and by making host trees more susceptible to damage from ice and wind. If one liana-laden tree falls, the interconnected liana network can pull down multiple adjacent trees, creating a domino effect that amplifies forest disturbance.
Lianas also alter forest regeneration patterns, especially in canopy gaps created by fallen trees. They proliferate rapidly in these disturbed areas, outcompeting tree seedlings and saplings for light and space, inhibiting tree recruitment and slowing forest recovery. This can lead to a shift in forest composition, reducing tree species richness in gaps and even stalling secondary succession.
Lianes as Wildlife Habitat
Lianas play a role in supporting forest animals by providing both structural connections and direct resources. Their extensive networks create natural bridges high in the forest canopy, serving as aerial pathways for arboreal animals. This allows creatures such as monkeys, sloths, lemurs, lizards, and various invertebrates to move between trees without descending to the forest floor, where predators may be present.
Beyond facilitating movement, lianas offer other benefits to wildlife. Their foliage provides shelter for arboreal animals, while their stems offer perches and grips for climbing and flying species. Many liana species also produce fruits, flowers, nectar, and extrafloral nectar, which serve as food sources for birds, primates, and insects. This positively influences bird abundance and diversity within the forest canopy.