Carbon cycling in mature and regrowth forests globally

K. J. ANDERSON-TEIXEIRA, V. HERRMANN, R. BANBURY MORGAN, B. BOND-LAMBERTY, S. C. COOK-PATTON, A. E. FERSON, H. C. MULLER-LANDAU, M. M. H. WANG

Conservation Ecology Center; Smithsonian’s National Zoo & Conservation Biology Institute; Front Royal, VA 22630, USA

Anthropogenic disturbances have impacted a large and growing proportion of Earth's forests, dramatically altering the global forest carbon (C) budget. As society increasingly seeks to make forests an important component of achieving net-zero C emissions, it is essential to understand how forest C cycles change with stand age as forests recover from stand-clearing disturbances. Here, we draw from the Global Forest Carbon Database, ForC, to provide a macroscopic overview of C cycling in the world's forests, giving special attention to stand age-related variation. Specifically, we use 11,923 ForC records for 34 C cycle variables from 865 geographic locations to characterize ensemble C budgets and quantify trends with stand age for four broad forest types. C cycling rates generally decreased from tropical to temperate to boreal in both mature and regrowth forests, whereas C stocks showed less directional variation. Mature forest net ecosystem production did not differ significantly among biomes. The majority of flux variables, together with most live biomass pools, increased with stand age. This synthetic global overview of C stocks and fluxes across biomes and stand ages provides a baseline for understanding and managing the carbon dynamics of forests in the face of accelerating global change.