Litter dynamics recover faster than arthropod biodiversity during tropical forest succession

Litterfall and litter decomposition are key elements of nutrient cycling
in tropical forests, a process in which decomposer communities such as
macro-arthropods play a critical role. Understanding the rate and extent
to which ecosystem function and biodiversity recover during succession is
useful to managing the growing area of tropical successional forest
globally. Using a replicated chronosequence of forest succession (5–15,
15–30, 30–45 years, and primary forest) on abandoned pastures in lowland
tropical wet forest, we examined litterfall, litter chemistry, and effects
of macro-arthropod exclusion on decomposition of two litter types (primary
and 5- to 15-years-old secondary forest). Further, we assessed
macro-arthropod diversity and community composition across the
chronosequence. Overstory cover, litterfall, and litter nutrients reached
levels similar to primary forest within 15–30 years. Young secondary
forest litter (5–15 years) had lower initial N and P content, higher C:N,
and decayed 60 percent faster than primary forest litter. The presence of
macro-arthropods strongly mediated decomposition and nutrient release
rates, increasing litter mass loss by 35–44 percent, N released by 53
percent, and P release by 84 percent. Forest age had no effect on soil
nutrients, rates of litter decomposition, nutrient release, or
macro-arthropod influence. In contrast, abundance and community
composition of macro-arthropods remained significantly lower and distinct
in all ages of secondary compared with primary forest. Order richness was
lower in 5–15 years of secondary compared with primary forest. Our results
suggest that in highly productive tropical wet forest, functional recovery
of litter dynamics precedes recovery of decomposer community structure and
biodiversity.