Average leaf litter quality drives the decomposition of single-species, mixed-species and transplanted leaf litters for two contrasting tropical forest types in the Congo Basin (DRC)

Abstract

& Key message Under similar site conditions, leaf litter decomposition beneath Central African rainforests was largely driven by average leaf litter quality. Although significant, the additional variability related to litter mixing and to the decomposition environment was limited. & Context Under given site conditions, litter decomposition is expected to mainly depend on its average quality. However, the additional impacts of litter diversity as well as of the local decomposition environment remain rather inconclusive. & Aims This study investigates the litter mixture effects on decomposition and home-field advantage for two emblematic old growth forest types of the Congo Basin: the Scorodophloeus zenkeri Harms mixed forests and the evergreen Gilbertiodendron dewevrei (De Wild.) J. Léonard monodominant forests. & Methods Based on a litterbag experiment, variations in leaf litter mass loss were measured from the eight most important tree species under mixed and monodominant forests and for all possible two-species combinations. & Results Remaining mass was largely explained (90%) by a multivariate measure of initial litter quality including 11 functional traits, which performed better than any single leaf litter trait. For the litter mixtures, the average deviation from expectation based on simple additive effects ranged from slightly synergistic (+ 2.56%) to slightly antagonistic (− 0.86%) after 1 and 6 months, respectively. Mixture identity and chemical dissimilarity contributed to explaining the mixing effects, yet the effect of chemical dissimilarity at the whole mixture level was only detected through an interaction with incubation time. In addition, the initial decomposition rates of S. zenkeri and G. dewevrei were accelerated under their own forest type. & Conclusion In agreement with the "home-field advantage" theory, our results highlighted that the functional composition of the host forest did have an indirect impact on decomposition. In addition, leaf litter decomposition was mainly controlled by average litter quality, which in turn was closely related to a multivariate measure of green leaf quality. This suggests that increased knowledge of tree species leaf traits in tropical forests would greatly help in better understanding the litter decomposition dynamics.

Soil fauna accelerate litter mixture decomposition globally, especially in dry environments

“…Changes of litter quality dissimilarity in litter mixtures influence the mixtures decomposition directly or indirectly through exchange of complementary resources among decomposers (Cassart et al, 2020;Vos et al, 2013). Differences in species composition in litter mixture can influence the feeding behaviours of soil fauna and their abundance; hence, they influence leaf litter decomposition (Santonja et al, 2017).…”

Perennial Trees Associating with Nitrogen-Fixing Symbionts Differ in Leaf After-Life Nitrogen and Carbon Release

“…The three species occur in the same locality on Guam today, S. nelsonii and I. bijuga occur in the same localities on Rota, and C. micronesica and I. bijuga occur in the same localities on Rota (personal observations). Single species litter that is decomposed in isolation often does not correlate with decomposition of multi-species litter mixtures [54][55][56]. Litter species mixture phenomena remain to be studied for these three Guam trees and the other sympatric tree species that share the forests.…”

Interaction of macroinvertebrates in leaf litter in forest ecosystems: a review

“…In addition, it is worth mentioning that other factors can influence the decomposition of the leaf litter, among them: the physical-chemical environmental conditions, the quality (organic and nutritional) of the substrate (Cassart et al, 2020), and the characteristics of the macro habits and microorganisms present in the leaf litter, commonly called the decomposing community, which directly assist in the fragmentation of the leaf litter allowing the entry of nutrients into the soil in an easy and accelerated way (Souto et al, 2013).…”