The New Neotropical Companion

Lianas

A liana is a woody vine rooted in the ground that

typically gets its start when a forest opening or gap is

created, permitting light penetration. Lianas begin as

shrubs but eventually become vines, retaining their

woody stems. Lianas are not restricted to the tropics.

There are many woody vines in the temperate zone, such

as the familiar Poison Ivy (Toxicodendron radicans).

But lianas are sufficiently abundant throughout many

tropical rain forests that they represent a distinct

characteristic of these ecosystems.

Tendrils from the liana branches entwine neighboring

trees as they climb upward, reaching the tree crown as

both tree and liana grow. Lianas spread in the crown,

and a single liana may eventually loop through several

tree crowns. Lianas seem to drape limply, winding

through tree crowns or hanging as loose ropes

parallel to the main bole. Their stems remain rooted

in the ground, often at multiple points, and are oddly

shaped, often being flattened, lobed, coiled like a rope,

or spiraling in a helix (plates 3- 36– 38). The thinnest

have remarkable springiness and will often support a

person’s weight, at least for a short time. Lianas have

exceptionally long vessels within their stems, and when

a section of a liana is severed water runs out.

Liana is a growth form, not a family of plants, and

thus lianas are represented among many different plant

families (e.g., Fabaceae, Sapindaceae, Cucurbitaceae,

Bignoniaceae, Vitaceae, Smilacaceae, and Polygonaceae,

to name but a few). Lianas, like tropical trees, can be

difficult to identify, but some lianas can be identified

to the level of genus by noting the distinctive cross-

sectional shapes of their stems.

In a classic study of liana abundance by Francis Putz

in Panama, a single hectare (10,000 m^2 , or about 2.5

ac) hosted 1,597 climbing lianas, distributed among

43% of the canopy trees. In the understory, 22% of the

upright plants were lianas, and lianas were particularly

common in forest gaps. A heavy liana burden reduced

the survival rate of trees, making them more likely to be

toppled by winds. Fallen lianas merely grew back into

other trees. When tree falls bring lianas to the ground,

the vines may be sufficiently dense so as to reduce the

speed with which trees reattain canopy status.

Hemiepiphytes

Hemiepiphytes are among the most important and

unusual of plant growth forms in the tropics. Primary

Plate 3- 36. This helix- shaped liana stem is typical of many

types of lianas, woody vines that are abundant in many

tropical forests. Photo by Scott Shumway.

Plate 3- 38. Lianas begin as seeds in the ground and grow

toward trees, which they can eventually entwine as they grow

upward to canopy level. Photo by John Kricher.

Plate 3- 37. Lianas weave conspicuously through many tropical

forests. Photo by John Kricher.

chapter 3 rain forest: the realm of the plants 51