24 January 2024

In tropical forests, rising temperatures promote the spread of lianas that smother trees by limiting their growth, an Australian study says. With obvious consequences for carbon sequestration

by Matteo Cavallito

 

Some tropical forests would be particularly at risk today when faced with the colonization of lianas, the long climbing plants that suffocate trees and prevent their growth. This phenomenon is favored by climate change and the resulting rise in temperatures that comes with a reduction in rainfall. This is highlighted in a study by the University of the Sunshine Coast in Sippy Downs, Queensland State, Australia.

The impact on carbon sequestration

Australia itself, as well as East Africa, Vietnam, Colombia and other countries located in tropical regions, explains the study published in the journal Global Change Biology, would be home to some of the forests most vulnerable to this problem. According to Andy Marshall, a professor at the University of the Sunshine Coast and co-author of the research, the survey identified “the environmental conditions under which liana vines are likely to outcompete trees and stall recovery in disturbed native forests worldwide.”

Alain Ngute, a professor at the same university and lead author of the study quoted by a statement, highlighted how lianas consequently end up limiting the carbon sequestration capacity of forests, one of the main reservoirs of the element on the Planet, by curbing their regeneration after a human-caused disturbance event such as logging, for instance.

The research

In the study, the authors analyzed “651 vegetation samples representing 26,538 lianas and 82,802 trees from 556 unique locations worldwide, derived from 83 publications.” The results “show that lianas perform better relative to trees (increasing liana-to-tree ratio) when forests are disturbed, under warmer temperatures and lower precipitation and towards the tropical lowlands.”

The survey, moreover, showed how “high competitive success of lianas over trees can persist for decades following disturbances, especially when the annual mean temperature exceeds 27.8°C, precipitation is less than 1614 mm and climatic water deficit (annual evaporative demand that exceeds available water, ed.) is more than 829 mm.”

In summary, “degraded tropical forests with environmental conditions favouring lianas are disproportionately more vulnerable to liana dominance and thus can potentially stall succession, with important implications for the global carbon sink.”

Lianas are important

The findings may help scientists better understand the phenomenon and suggest interventions to encourage forest regeneration. The solution to the problem, in any case, is certainly not the massive removal of lianas. Which, as Marshall notes, still play a key role in maintaining the overall balance of these environments.

“We certainly wouldn’t want this work to lead to forest managers going and cutting out all these vines out of their forests,” he explains. “Liana plays its part in the forest ecosystem and biodiversity by boosting soil fertility and carbon cycling, and can benefit other plants, animals, soils and overall ecosystem function, in both intact and disturbed forests.”