Measurements of fine root decomposition rate: Method matters

Abstract

Fine root decomposition plays a major role in biogeochemical cycle in forests. Litterbags and intact cores are predominant methods for measuring fine root decomposition rate. However, their efficacies have not been critically reviewed. In this study, we identify six sources of error for both methods including use of unrepresentative substrates, changes in decomposer community composition, altered effects of living roots and mycorrhizal fungi, differences in experimental duration length and sampling regime, confounding of spatiotemporal resolution, and limited temporal resolution. We present an indirect method to quantify fine root decomposition rate by integrating soil core and minirhizotron measurements into a new equation. The indirect method requires measuring more fine root parameters but can generally overcome the weaknesses associated with litterbag and intact core methods. Directly measuring the decomposition rate inevitably disturbs interactions between roots, soil fauna and rhizosphere microbes, which could significantly undermine the credibility of the estimates. Indirect measurement based on fine root growth and death rates, biomass and necromass that can be assessed reliably should be the future choice.