Litter dynamics recover faster than arthropod biodiversity during tropical forest succession

Abstract

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 macroarthropods 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.Abstract in Spanish is available with online material.

Fast recovery of soil macrofauna in regenerating forests of the Amazon

“…In a similar approach, Cole et al. (2020) did not find significant differences in the abundances of functional groups across a forest chronosequence. However, a systematic increase in abundance mean values was shown for predators and detritivores, suggesting that the lack of significant trends may be related to the low sample size (Cole et al., 2020).…”

“…Overall, our results for macrofauna align with others for plants and vertebrates highlighting the resilience of tropical forests (Acevedo‐Charry & Aide, 2019; Norden et al., 2009; Poorter et al., 2016). Secondary forests may take a long time to become as diverse as primary forests, but they quickly recover a large part of their biodiversity and ecological functions (Cole et al., 2020, this study; Lennox et al., 2018; Rozendaal et al., 2019), and they can provide critical ecosystem services, such as carbon sequestration (Chazdon et al., 2016; Foley et al., 2007). Therefore, the implementation of global‐scale strategies to let secondary forest grow is of upmost importance.…”

“…invertebrates larger than 2 mm; Anderson & Ingram, 1993) were sorted by hand from samples and classified into broad taxonomic groups with similar trophic niche (following Anderson & Ingram, 1993). Taxonomic groups were further classified into functional groups (detritivores, predators and phytophages) based on their trophic level and relevance for soil functions (following Cole et al., 2020). These procedures broadly followed the Tropical Soil Biology and Fertility protocol described in Anderson and Ingram (1993).…”

“…Only the abundant taxonomic groups were analysed (those occurring in more than 20% of the samples). Functional groups (detritivores, predators and phytophages) followed the classification of Cole et al (2020). The response variable of the models was assigned as 1 when abundances were above the median of the abundances in the group and 0 otherwise, therefore it is interpreted as a proxy of abundance.…”

“…Bihn et al, 2008;Eggleton et al, 1996;Hopp et al, 2010;Szinwelski et al, 2012;Yoshima et al, 2013), although changes in abundance, diversity and composition are less consistent among studies. Macrofauna diversification is likely driven by the increase in litter fall and chemical diversity as forests get older (Cole et al, 2016(Cole et al, , 2020, certainly aided by the increasing activity of earthworms, termites and ants that promote soil microhabitat heterogeneity (Lavelle et al, 2016). Studies of swidden cultivation also show that the resilience of forests to regenerate decreases after frequent slash-and-burn events (Jakovac et al, 2015;Neto et al, 2019).…”