Research finds a mechanistic explanation for global patterns of liana abundance and distribution

A central goal of ecology is to determine the mechanisms that explain large-scale patterns of abundance and distribution of the earth’s organisms. For most organisms, however, these mechanisms remain elusive. In an article in the August 2005 issue of The American Naturalist, Stefan A. Schnitzer reports that the abundance of lianas (woody vines), a taxonomically diverse and important group of plants, actually decreases in tropical forests as mean annual precipitation increases, a pattern precisely the opposite of that of nearly all other plant types.

Schnitzer proposes a novel mechanistic theory to explain this pattern, drawing support from several independent lines of empirical evidence. The theory is based on the ability of lianas to undergo less water stress and thus grow during seasonal droughts, while their competitors remain mostly dormant. This capacity for dry season growth gives lianas a competitive advantage that, over many decades, may result in higher abundance of lianas in seasonal tropical forests. In aseasonal wet forests, however, this competitive advantage is lost, explaining the relative paucity of lianas. The theory is then extended to explain the striking patterns of liana abundance at two additional spatial scales: the decrease in lianas along the latitudinal gradient, from the tropics northward, and the clumped distribution of lianas at the local, within-forest scale.

This researcj explains both the patterns of abundance and distribution of an important group of plants, as well as provides a framework that can be used to predict the change in liana abundance worldwide with global climate change.