Liana cutting for restoring tropical forests: a rare palaeotropical trial

Abstract

Liana growth following forest disturbance is threatening the tropical carbon sink by delaying or preventing recovery. Tree growth can be stimulated by liana cutting; however, its applicability for conservation management remains uncertain, particularly in Africa (the least-studied continent for ecological restoration) and against pervasive barriers such as wildfires. We conducted a small-scale trial to investigate tree sapling regeneration following liana cutting in a lowland African forest prone to low intensity wildfires. We employed a BACI design comprising eighteen 25 m2 plots of sapling trees in liana-infested areas. After 5 years of liana cutting, we saw greater recruitment, stem growth and net biomass. Wildfires caused 51% mortality and probably masked liana cutting influences on species and survival, but may have encouraged stem recruitment through interaction with liana cutting. Incorporating our data into a first quantitative review of previous studies, we found that tree growth, recruitment and net growth rates were all consistently higher where lianas were either absent or removed (respectively: 80%, 215%, 633%; n = 14, 3, 4). Tree growth impacts were approximately equivalent across size-classes and continents. We give recommendations for improved plot and sample sizes, but conclude that liana cutting is a promising restoration method for lowland tropical forests, including Africa.