Implementing methane dynamics into the LPJmL6 model

Abstract. We extend the Dynamic Global Vegetation Model LPJmL to version 6.0 by explicitly representing methane (CH4) dynamics within the coupled carbon–nitrogen–water system. The implementation (i) prognoses water-table depth and wetland extent using a CTI–TOPMODEL framework, (ii) solves sub-daily, vertically explicit mass balances for CH4 and O2 including diffusion, ebullition, and plant-mediated transport, (iii) represents methanogenesis and methanotrophy with temperature- and moisture-dependent kinetics, and (iv) integrates land-use and rice management effects alongside inundation-tolerant plant functional types. This architecture enables consistent simulation of CH4, carbon dioxide (CO2) and nitrous oxide (N2) emissions from natural wetlands and managed systems together with the soil CH4 sink. Extensive benchmarking against global datasets shows that LPJmL6 reproduces the magnitude and regional–temporal variability of CH4 flux pathways while maintaining strong skill in the simulated terrestrial carbon, nitrogen, and water budgets. The model thus provides a coherent, process-based framework to quantify CH4 within the coupled carbon–nitrogen–water system, elucidate interactions with vegetation and soils, and assess how land-use, wetland conservation and restoration, and rice management options affect methane and overall greenhouse–gas budgets in support of climate-mitigation strategies.