EPOW - Ecology Picture of the Week

Climber in dense old secondary forest, 
Mabali Forest Reserve, Congo River Basin, 
eastern Democratic Republic of the Congo

Explanation:   Look up.  Way up.  Growing down from the forest canopy, sometimes in profusion, are specialized vines ... also commonly called climbers or lianas.  This is the vertical world of living ropes.  

Climbers indeed are woody vines found in many forests throughout the world, most commonly in lowland tropical forests.   Made up of more than 2500 species from 90 families, climbers are important structural and functional components of forests. 

Most species start from ground level, remain rooted in the soil, and climb their way upwards.  Other species, notably of the genus Ficus (strangler figs) begin by their seeds being deposited on a tree limb in the forest canopy or subcanopy, and then grown downward from there.  Such specializations are called hemiepiphytes, another example of which we visited in an earlier EPOW in Argentina. 

The density and diameter of climbers can make good indicators of the age of a forest and the time since a major stand-replacing disturbance (such as fire, clearcutting, or major wind storm).  They are good indicators in part because studies (Phillips et al. 2005) have revealed that large climbers (with diameters of 10 cm or greater) occur more because of large tree supports than because of soil conditions per se.  Ecologists refer to such uninterrupted forest growth as ecological continuity.  Many plant and animal species closely associated with old forests require ecologically continuous conditions.

Large climbers that strangle and kill their host trees create snags or standing dead trees in the forest, which in turn are used by a very wide variety of cavity-nesting birds, cavity-denning mammals, many insects that feed on the dead wood, and many animals that feed on the insects.  Climbers thus can serve as "keystone" species that greatly affect the distribution and abundance of many other species in the forest ecosystem.

Large "old-growth" 
climbers growing profusely
on an old-growth tree in
Puyehue National Park, 
southern Chile. 

Some wildlife species have adapted to, or at least take direct advantage of, the vertical resources provided by climbers.  An example shown in the photo to the left is a Black-and-White Warbler (Mniotilta varia) gleaning insects from this liana in the Upper Sanguita Jungle near San Blas, western Mexico.

In tropical Africa, the rare and poorly studied Maned Owl (Jubula lettii) is known to hide in daytime roosts among climbers in "gallery forests" along rivers.  Many birds and mammals consume fruits provided by climbers, and use climbers as travel pathways to and within the forest canopy. 

Some birds that rely on climbers as food sources in turn are important seed and fruit dispersal agents in the forest, helping to keep the forest diverse.

Many people of the forest use climbers for food, construction, rope, even medicine, and other uses.  

So, in many ways, climbers support important ecological functional webs in the forest. 

Tough going.  No trail here.  Time for the machete.

Viney tangle in the understory of Mabali Forest Reserve along a very remote corner of Lake Tumba, Democratic Republic of the Congo, in central Africa.  The green color on these climbers may be algae or lichens growing on the climber vines -- epiphytes on epiphytes! 

(And did you notice in the first, tall and skinny photo in the text block, above, how one climber has wrapped and grown around another larger climber?) 

Information:  
    Phillips, O. L., R. V. Martínez, A. M. Mendoza, T. R. Baker, and P. N. Vargas. 2005. Large lianas as hyperdynamic elements of the tropical forest canopy. Ecology 86(5):1250-1258. 
    Schnitzer, S.A. and F. Bongers. 2002. The ecology of lianas and their role in forests. Trends in Ecology and Evolution 17(5):223-230.