Mixed forests store more soil organic carbon than pure forests

Soil stores large amounts of organic carbon, whose dynamic changes can cause huge impact on the global climate system. Forest succession is a long-term ecological process that can exert powerful effects on soil organic carbon (SOC) due to the variation in plant community composition, microenvironment, plant debris stock, soil nutrient availability and microbial community composition among different successional stages.

Clarifying the dynamic changes of SOC across the forest successional series will provide insights into global soil carbon cycle and improve the accuracy of terrestrial carbon cycle models. However, existing literature mostly focus on the changes in SOC at the surface soil across forest succession, while the SOC buried in deep soil is often neglected. Moreover, how SOC quality change across the forest successional series remains unclear. Despite these limitations, there lacks a comprehensive investigation on the changes in SOC stock and quality across the forest succession.

In a study published in the KeAi journal Forest Ecosystems, a team of researchers investigated the stock and quality of SOC at 1-m soil profile across a subalpine forest series located at southeast of Tibetan Plateau. The series include shrub, deciduous broad-leaved forest, broadleaf-conifer mixed forest, middle-age coniferous forest and mature coniferous forest.

The researchers found that the SOC stock exhibited a hump-shaped response pattern from initial to terminal forest successional stage and the mixed forest stored highest SOC compared with other forest type. This is attributed to the higher wood debris storage in mixed forest.

Meanwhile, the SOC quality in mixed forest was poorer than that of the other forest types. In addition, deep soil was found to contain on average 66% of the topmost metre’s SOC stocks. Notably, SOC quality in deep soil was better than that of surface soil. These findings highlight the importance of mixed forest and plant debris in maintaining forest carbon sequestration. The high proportion of SOC stock and better SOC quality indicate that deep soil have tremendous potential to release plentiful carbon dioxide under global change.

According to Fei Li, first author of this study, the findings have the following implications: (1) more mixed forest should be constructed on the further forest management and cultivation to promote terrestrial carbon sequestration; (2) preserving plant debris is a critical strategy for sustainable forest management; and (3) surface and deep soil should be separated when models simulate the dynamic changes of SOC under global change.

Contact author details: 

Fei Li, Zhejiang Provincial Key Laboratory of Plant Evolutionary Ecology and Conservation, School of Life Sciences, Taizhou University, Taizhou 318000, China, flissrs@yeah.net

Funder: 

This research was supported by National Natural Science Foundation of China (Nos. 32001139, 32071554).

Conflict of interest:

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

See the article: 

Li, F., et al., The changes in soil organic carbon stock and quality across a subalpine forest successional series, Forest Ecosystems, Volume 11, 2024, 100203, https://doi.org/10.1016/j.fecs.2024.100203.