Leaf litter decomposition -- Estimates of global variability based on Yasso07 model

TL;DR

This study presents the Yasso07 model, a globally applicable tool for estimating litter decomposition rates based on initial litter chemistry and climate, highlighting its potential to improve understanding of carbon cycling and climate feedbacks.

Contribution

The paper introduces the Yasso07 model, which accurately estimates global litter decomposition variability using a large dataset and Bayesian uncertainty analysis, advancing previous models.

Findings

Yasso07 effectively predicts litter mass loss across diverse climates.

Model estimates show significant differences in decomposition rates between litter types.

Uncertainty analysis confirms model reliability for climate and litter quality effects.

Abstract

Litter decomposition is an important process in the global carbon cycle. It accounts for most of the heterotrophic soil respiration and results in formation of more stable soil organic carbon (SOC) which is the largest terrestrial carbon stock. Litter decomposition may induce remarkable feedbacks to climate change because it is a climate-dependent process. To investigate the global patterns of litter decomposition, we developed a description of this process and tested the validity of this description using a large set of foliar litter mass loss measurements (nearly 10 000 data points derived from approximately 70 000 litter bags). We applied the Markov chain Monte Carlo method to estimate uncertainty in the parameter values and results of our model called Yasso07. The model appeared globally applicable. It estimated the effects of litter type (plant species) and climate on mass loss with little systematic error over the first 10 decomposition years, using only initial litter chemistry, air temperature and precipitation as input variables. Illustrative of the global variability in litter mass loss rates, our example calculations showed that a typical conifer litter had 68% of its initial mass still remaining after two decomposition years in tundra while a deciduous litter had only 15% remaining in the tropics. Uncertainty in these estimates, a direct result of the uncertainty of the parameter values of the model, varied according to the distribution of the litter bag data among climate conditions and ranged from 2% in tundra to 4% in the tropics. This reliability was adequate to use the model and distinguish the effects of even small differences in litter quality or climate conditions on litter decomposition as statistically significant.