Characteristics of root decomposition based on in situ experiments in a tropical rainforest in Sarawak, Malaysia: impacts of root diameter and soil biota

Abstract

Tropical forests contribute significantly to the stability of global carbon (C) balance; however, little is known about root litter decomposition in tropical rainforests. In this study, we aimed to (1) characterise the effect of soil depth, root diameter and soil organisms on root litter decomposition and (2) estimate the contribution of root decomposition to soil carbon dioxide (CO2) efflux in a tropical rainforest in Malaysian Borneo. We incubated soil chambers with fine and coarse root litterbags at varying soil depths. Soil chambers were covered with nets of different mesh sizes, and CO2 efflux was monitored from the top of each soil chamber during the incubation. Our results showed that coarse roots decomposed faster than fine roots. There was no impact of soil depth, but soil animals and fungi had a significant impact on coarse root decomposition from 398 days after the start of the experiment. Soil CO2 efflux increased linearly with C loss from root decomposition, indicating that 40% of the CO2 efflux originates from root litter. The variation in root decomposition rates suggests the possible role of root litter in soil C storage and emission in a tropical rainforest.