Liana Effects on Carbon Storage and Uptake in Mature and Secondary Tropical Forests

Abstract

Lianas are a key structural component of tropical forests, where they represent approximately 25 \% of woody plant species. Lianas reduce tree growth, inhibit tree regeneration and increase tree mortality. Thus, lianas are able to reduce carbon stored as tree biomass. Infestation rates on trees by lianas are stronger in shade-tolerant species with high wood density, which store more carbon than fast-growing species. Therefore, lianas may promote shifts in species composition and threaten tree carbon storage capacity of tropical forests. Lianas have shown consistent increases in density and biomass in tropical regions in the last decade, which may have profound consequences for forest dynamics. In this chapter, we review available evidence of liana effects on carbon cycling in mature and secondary tropical forests. Secondary forests now cover larger areas than mature forests, but their role in carbon cycling is unclear. Lianas are more prevalent in early stages of succession, and could have disproportionate effects on carbon uptake in secondary forests. Current knowledge indicates that lianas could reduce carbon stocks by up to 50 \% and reduce carbon increment by 10 \% in mature tropical forests. In secondary forests, evidence is quite limited; but one study found that lianas reduce 9-18 \% of carbon accumulation in treefall gaps. Changes in composition by lianas are not yet supported by literature. We identify research needs required to improve predictions of how tropical carbon sinks will respond to liana increases.