Liana

A liana is a long-stemmed woody vine that grows from the ground.

These plants use trees or other vertical supports to climb toward the forest canopy. They do this to reach direct sunlight. It is important to note that liana is not a specific taxonomic grouping. Instead, it describes a particular habit of plant growth. This is similar to how we use the terms "tree" or "shrub." The word itself comes from a French dialect meaning "to sheave."

Lianas are most common in tropical moist broadleaf forests. You can also find them in temperate rainforests and deciduous forests. Some examples of temperate lianas include the Clematis or Vitis genera, which contains wild grapes. These plants play a huge role in forest ecology. They often form thick bridges across the canopy. These bridges provide paths for many arboreal animals. Invertebrates like ants use them, as do lizards, rodents, sloths, monkeys, and lemurs. In the eastern tropical forests of Madagascar, lemurs use these webs to increase their mobility. Many lemurs actually prefer trees that have lianas because of their roots.

While lianas are not parasitic, they do live at the expense of their hosts. They do not take nutrients directly from the host tree. However, their presence can cause significant harm. Lianas can cause mechanical abrasion or strangulation of the host. This means they rub against or squeeze the tree. They can also make a host tree more likely to suffer from wind or ice damage. Because of these stresses, trees with lianas have twice the probability of dying. Furthermore, lianas can prevent seedlings from establishing. This can change how a forest regenerates over time. Studies show that forests without lianas can grow 150% more fruit.

Lianas also change how trees react to physical stress. In some cases, lianas act as anchors. They can provide lateral support to weaker trees during strong winds. This connects a weak tree to a stronger one to keep it upright. However, this connection can become a danger during a storm. If one tree falls, the lianas can pull many other connected trees down with it. Because of these risks, some tree species have evolved ways to avoid or shed lianas. This helps them remain free of the climbing vines.

One way scientists distinguish lianas from trees is through their stiffness. This is measured by the Young's modulus of the stem. Trees and shrubs usually have flexible young twigs and stiff older trunks. Lianas often show the opposite pattern. They frequently have stiff young growths and more flexible older growth at the base. Some lianas have even evolved flat, ribbon-like stems to handle these stresses. This includes certain Bauhinia, Entada, and Tetrastigma species. Some plants, like Serjania icthyoctonia, even have ribbons that divide into parallel strands.

Some lianas can reach truly massive sizes. In Surinam, a Bauhinia species has reached great lengths. A researcher named Hawkins accepted a length of 1.5 km for an Entada phaseoloides. That is roughly one mile of vine!

The longest monocot liana is Calamus manan. Professor Melchior Treub recorded that this plant can reach 100 meters.

Lianas belong to many different plant families. These include the Fabaceae family, which contains many species like Entada and Pueraria. The Sapindaceae family also includes several liana types. Other examples include the Bignoniaceae and Vitaceae families. Because they belong to so many different groups, lianas represent a successful way of life for many different kinds of plants. They show how plants can adapt to the crowded environment of a forest to reach the light.