Plant-derived carbon contribution to soil organic carbon accumulation increases with tropical lowland forest restoration

Abstract

Natural restoration of tropical forests is an effective strategy for mitigating global climate change and enhancing ecosystem carbon stocks. Although studies have shown soil organic carbon storage following forest restoration efforts, the responses of organic carbon sources and their stabilisation to these restoration practices remain unclear. In this study, we employed amino sugars and lignin phenols as biomarkers to explore the contributions of microbial necromass and plant lignin components to soil organic carbon across a chronosequence of tropical lowland forest restorations (<30, >40, >70 years and old-growth forests). Following forest restoration, the concentration of amino sugars in soil organic carbon substantially decreased, whereas the concentration of lignin phenols showed no notable change. The contribution of microbially derived carbon to soil organic carbon steadily declined from 55 % to 33 % as forest restoration progressed, while the contribution of plant-derived carbon increased from 2.7 % to 3.4 %. Microbial-derived carbon remained the dominant source of soil organic carbon accumulation, although its proportion in the organic carbon pool decreased during the restoration process. The Mantel test and structural equation models showed that soil nutrient availability (available phosphorus, available nitrogen, and inorganic nitrogen) and microbial biomass nitrogen were the primary variables influencing microbially derived carbon, whereas plant-derived carbon was regulated by plant root biomass and microbial biomass nitrogen. These findings highlight the importance of combining plant lignin and microbial necromass in regulate soil organic carbon accumulation during tropical forest restoration. This study supports the development of effective carbon management strategies for tropical forests.