Tropical tree and liana community recovery through secondary succession

Abstract

Secondary forests (i.e. forests regrowing after land abandonment) are increasing in area throughout the tropics, harbouring great potential for carbon sequestration and biodiversity conservation. The rate of recovery of these forests is well understood for tree communities in early and mid-stages of tropical forest succession (< 50 years). However, studies of successional liana communities lag behind, and few late successional studies exist for either trees or lianas. Processes such as the recovery of species composition and above-ground biomass can take place over centuries, and as such they are poorly quantified by current studies. Here I investigate forest recovery over the late stages of succession for tree and liana communities. Chapters 2 and 3 study biodiversity and structural recovery in tree communities in mid-to-late-stage successional forest (aged 40 – 120 years) in Panama. I find that species and functional diversity recover by mid-succession, but species richness and rare species do not recover to old-growth levels. Species community composition can converge on old-growth communities 120-years into succession, but I also find divergent successional pathways caused by a long-lived pioneer’s dominance. Leaf traits showed little variation in the mid-to-late stages of succession, but plant-stature related traits continued to change into late succession suggesting plant height as a major mechanism for competition for light in late successional stages. Chapter 4 examines the relationship between liana density and basal area across successional and climatic gradients spanning four countries in the Neotropics. I find that liana density and basal area is higher in moist/wet forests than dry forests, contrary to previous findings. Liana density is highest in early succession, and I find that liana dominance is most likely in highly seasonal tropical forests. These findings will help inform tropical forest recovery and confirm the value of old secondary forests for tree and liana communities.