Natural regeneration increases ecosystem production and functional
diversity in an abandoned Afrotropical moist forest landscape
Abstract
The growing trend of agricultural abandonment necessitates understanding
the development of regrowth forests on old fields in the context of
forest restoration. However, the successional patterns of ecosystem
functioning and functional diversity of afrotropical regrowth forests
are rarely examined. We assessed whether aboveground biomass (AGB) and
functional diversity (FD) vary with restoration age and proximity to
old-growth forests, compared AGB and FD between regrowth and old-growth
forests to measure restoration success and investigated the FD – AGB
relationship. We sampled trees in 63 plots (2000 m2 each) in a regrowth
forest and 5 plots in an old‐growth forest in 2011, 2014 and 2017. We
calculated AGB using diameter, height and wood density. We collated
species functional traits (dispersal modes, habitat types, fruit sizes
and regeneration guilds) and computed FD measures (richness, evenness,
dispersion, divergence and RaoQ’s entropy). AGB and FD measures
(richness, dispersion and RaoQ) increased with restoration age.
Functional divergence declined with increasing distance to the
old-growth forest. Within 22 years, regrowth forests regained 22% of
the AGB and recovered all FD measures of the old-growth forest. We found
positive, negative and quadratic relationships between AGB and FD
depending on the FD measure and forest type. We demonstrate that
regrowth forests increase ecosystem production and functional diversity
in abandoned areas, however they cannot substitute old-growth forests.
Considering multiple measures of functional diversity in different
habitats provides a better understanding of the influence of functional
diversity on ecosystem functioning.