This study reveals the regulation of soil carbon pool by fungi in tropical forests under nitrogen deposition

Recently, the team of Wang Faming, director of the Xiaoliang Tropical Coastal Zone Ecosystem Positioning Research Station of the South China Botanical Garden of the Chinese Academy of Sciences (hereinafter referred to as Xiaoliang Station) and researcher of the Ecology Center, revealed the potential and mechanism of nitrogen deposition enhancement by fungi to drive soil organic carbon sequestration in tropical forests based on the long-term simulated nitrogen deposition test site of Xiaoliang Station. Related research papers were published in Functional Ecology.

Fungi are major decomposers of litter and drive the transport of plant-derived carbon to soil, so understanding the response of fungal communities to nitrogen deposition can help to understand the mechanisms underlying soil organic carbon dynamics in tropical forests. According to different ecological functions, fungal communities can be divided into different ecological functional groups. These functional groups generally respond differently to the same environmental changes, but the changes in different ecological functional groups and related functional potentials in tropical forest soils and their relationship with soil organic carbon dynamics in the context of nitrogen deposition are still unclear.

Schematic diagram of the response of fungal communities and functions under nitrogen deposition. Photo courtesy of the research team

Based on the long-term simulated nitrogen deposition test plot at Xiaoliang Station, this study explored the effects of nitrogen deposition on fungal community, functional potential and soil carbon composition of tropical forests. The results found that the total organic carbon, dissolved organic carbon, granular organic carbon and fungal residual carbon in nitrogen-applied soil were higher than those in the control group. The analysis of fungal communities showed that the fungal communities in nitrogen-applied soil were dominated by all-rounder saprophytes, among which leaf saprophytes increased by nearly 93 times compared with the control group. These changes are accompanied by an increase in lignocellulosylase abundance, indicating an increased degradation potential of plant-derived carbon.

In addition, nitrogen application increased the abundance of chitosanase in soil that catalyzes the biosynthesis of amino sugars (fungal residue markers) by 1.37 times, and enhanced the contribution of fungal residual carbon to the organic carbon pool (1.42 times), which were closely related to higher Ca2+ in soil, dissolved organic carbon content and saprophyte abundance involved in organic acid synthesis. These results show that long-term nitrogen deposition input can enhance the abundance and activity of saprophytes, increase soil organic acid yield, and directly or indirectly support fungal growth by releasing nutrients and dissolved organic carbon, resulting in more fungal residual carbon contributing to the soil organic carbon pool and improving the sequestration capacity of soil organic carbon.

The results highlight the importance of fungal ecological functional groups and functional potential changes in the resolution of soil organic carbon dynamics. (Source: China Science News Zhu Hanbin)

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