Numerical models have been developed to quantify the magnitude, investigate the spatial and temporal variations, and understand the underlying mechanisms and environmental controls of CH4 fluxes within terrestrial ecosystems. These CH4 models are also used for integrating multi-scale CH4 data, such as laboratory-based incubation and molecular analysis, field observational experiments, remote sensing, and aircraft-based measurements across a variety of terrestrial ecosystems.
The analysis of numerous models published in the last 4 decades reveal that (1) the focus of CH4 models has shifted from theoretical to site- and regional-level applications over the past 40 years, (2) large discrepancies exist among models in terms of representing CH4 processes and their environmental controls, and (3) significant data– model and model–model mismatches are partially attributed to different representations of landscape characterization and inundation dynamics.
Xiaofeng and his colleagues summarize 40 terrestrial CH4 models to characterize their strengths and weaknesses and to suggest a roadmap for model improvement. Three areas for future improvements and applications of terrestrial CH4models are (1) CH4 models should more explicitly represent the mechanisms underlying land–atmosphere CH4 exchange, with an emphasis on improving and validating individual CH4 processes over depth and horizontal space, (2) models should be developed that are capable of simulating CH4 emissions across highly heterogeneous spatial and temporal scales, particularly hot moments and hotspots, and (3) efforts should be invested to develop model benchmarking frameworks that can easily be used for model improvement, evaluation, and integration with data from molecular to global scales. These improvements in CH4 models would be beneficial for the Earth system models and further simulation of climate-carbon cycle feedbacks.
Xu, X., F. Yuan, P. J. Hanson, S.D. Wullschleger, P.E. Thornton, W.J. Riley, X. Song, D.E. Graham, C. Song, and H. Tian (2016). Reviews and syntheses: Four decades of modeling methane cycling in terrestrial ecosystems. Biogeosciences 13: 3735-3755. doi: 10.5194/bg-13-3735-2016
