Research report: Tree species type is more strongly associated with MAOC stocks than stand origin in forest ecosystems

Forest soils hold a large share of the carbon that keeps climate-warming emissions out of the atmosphere, but not all of that carbon is equally secure. A new research article published in Plant and Soil examines which factors matter more for the stable, long-lived fraction of soil organic carbon: whether a forest is natural or planted, or which type of trees grow there. The study’s central finding is that tree species type is more strongly associated with mineral-associated organic carbon, or MAOC, stocks than stand origin is.

The researchers assessed plant and soil carbon pools, litter and fine root inputs, and microbial traits across natural and planted forests and across coniferous and broadleaf forests. They identified the key drivers of two distinct soil carbon fractions: particulate organic carbon, known as POC, and mineral-associated organic carbon.

The results showed clear patterns across both contrasts. Natural forests had higher stocks of soil organic carbon, MAOC, and POC than planted forests. At the same time, coniferous forests had higher soil organic carbon and MAOC stocks than broadleaf forests. These two comparisons set the stage for the study’s key question: which of the two classifications, stand origin or species type, is more closely tied to each carbon fraction.

The answer differed depending on the fraction. MAOC was more strongly associated with species type, whereas POC was more strongly associated with stand origin. In other words, the more stable, mineral-bound carbon tracked which kind of trees dominated the stand, while the more particulate carbon tracked whether the forest was natural or planted.

Fine root inputs emerged as important contributors to soil carbon accumulation. The study distinguished between root quantity and root quality in explaining the two carbon fractions. Root quantity was linked to higher POC stocks in natural forests, suggesting that the sheer amount of fine root material entering the soil helps build the particulate pool in stands that developed naturally.

Root quality told a different story. In coniferous forests, higher MAOC stocks were associated with root quality traits, particularly the lignin and non-structural carbohydrate content of roots. This points to the chemical composition of root inputs, rather than their volume, as a key pathway through which coniferous stands accumulate the more stable, mineral-bound carbon fraction.

The authors conclude that stand origin and species type play contrasting roles in regulating different soil carbon fractions.

As a research article, the study frames soil organic carbon stability as critical for climate change mitigation, noting that although both stand origin and tree species type can regulate soil carbon sequestration, their relative importance for soil carbon stability had remained poorly understood. By separating POC from MAOC and linking each to distinct drivers, root quantity versus root quality, the work offers a framework for thinking about how forest composition and management choices shape the persistence of carbon below ground.

Subject of Research: How stand origin and tree species type relate to soil organic carbon fractions in forest ecosystems

Article Title: Tree species type is more strongly associated with MAOC stocks than stand origin in forest ecosystems

Article References: Zhang, M., Xie, M., Yu, Z., Guo, Y., Zheng, Y., Liu, Y., & Wang, G. (2026). Tree species type is more strongly associated with MAOC stocks than stand origin in forest ecosystems. Plant and Soil. https://doi.org/10.1007/s11104-026-09164-5

Image Credits: AI Generated

DOI: 10.1007/s11104-026-09164-5

Keywords: soil organic carbon, mineral-associated organic carbon, particulate organic carbon, forest soils, tree species, stand origin, fine roots, carbon sequestration, coniferous forests, broadleaf forests, carbon stability, microbial traits