| 31 Jul 2026
Shifts in genes encoding enzymes that degrade plant- and microbial-derived carbon affect soil organic carbon pools in different subtropical forests of China
Abstract. Microbial transformation of plant- and microbial-derived carbon plays a central role in soil organic carbon (SOC) formation and stabilization, yet how microbial carbon-degrading potential links forest type to SOC accumulation and persistence remains poorly understood. Here, we investigated three representative subtropical forest types—broadleaf, coniferous, and bamboo forests—and integrated litter quality, soil physicochemical properties, SOC fractions, and metagenomic data. Using the CAZyme database, we quantified genes encoding enzymes involved in the degradation of plant- and microbial-derived carbon and evaluated their relationships with environmental factors and SOC fractions. Forest type significantly altered both the abundance and diversity of genes encoding carbon-degrading enzymes, with a clear decoupling between these two metrics. Litter quality and soil environmental conditions jointly regulated these functional genes and directly influenced SOC, mineral-associated organic carbon (MAOC), dissolved organic carbon (DOC), and microbial biomass carbon (MBC), but not particulate organic carbon (POC). Instead, POC was significantly associated with the abundance of genes encoding enzymes involved in the degradation of plant- and microbial-derived carbon. SOC and MAOC were more strongly linked to genes encoding enzymes that degrade fungal-derived carbon, whereas MBC was more closely associated with genes encoding enzymes involved in bacterial peptidoglycan degradation. Broadleaf forests showed significantly higher SOC and MAOC contents and greater carbon stability than coniferous and bamboo forests. These findings indicate that microbial carbon-degrading potential represents an important functional pathway linking forest type to SOC accumulation and stabilization, highlighting the role of microbial functional traits in regulating soil carbon persistence in subtropical forest ecosystems.
The paper describes the relationships among litter properties, soil organic carbon (SOC), carbon fractions, and genes encoding enzymes across three subtropical forest types. The abstract clearly summarizes the main findings of the study and provides a conclusion that is likely to capture readers’ interest.
The authors proposed three main objectives: (i) to assess how genes encoding carbohydrate-active enzymes (CAZymes) respond to different forest types; (ii) to identify relationships between CAZyme genes and soil and litter properties; and (iii) to determine how these factors are associated with SOC across forest types. To address these objectives, the authors measured a range of litter and soil properties, evaluated SOC and its carbon fractions, and characterized the abundance and diversity of genes encoding enzymes involved in carbon degradation through metagenomic sequencing and annotation against the CAZy database.
The introduction effectively presents the key concepts needed to understand the study and clearly identifies relevant knowledge gaps. The information provided is clear, sufficient, and supported by up-to-date references. Moreover, the rationale for the study is well established and convincing, and the objectives and hypotheses are clearly stated.
The methods and data analyses are generally appropriate for addressing the proposed objectives. However, additional methodological information is needed, particularly in the metagenomics section, to ensure that the study is sufficiently detailed and reproducible.
The results are clearly described, and the figures adequately represent the data collected during the study. I suggest using a different color palette in most figures, preferably one with greater contrast, to facilitate the differentiation of groups and improve the overall readability of the figures.
The discussion is concise, well structured, and provides insightful interpretations of the findings. Nevertheless, some of the interpretations and suggestions would benefit from additional supporting analyses or data. Finally, although the conclusion is well written, it could more explicitly address the findings associated with each of the objectives proposed at the beginning of the study.
Overall, although the methodological and analytical approaches used in this study are not particularly novel, the authors make good use of these approaches to address the proposed objectives and present their findings clearly. Furthermore, while differences in litter and soil properties, SOC, and carbon fractions among forest types are not a new concept, the inclusion of the enzymatic profile adds value to the study by providing further insight into soil carbon degradation and the potential roles of soil properties and carbon pools in this process.
Additional comments and minor corrections are included in the attached file.