Effects of long-term drainage and afforestation on carbon utilization function of soil microbial communities vary between the types of subtropical moss peatlands

Abstract

Subtropical moss peatlands are valuable delicate ecosystems that play crucial roles in biodiversity preservation, carbon sequestration, and water retention. However, driven by economic interests, a large area of subtropical moss peatlands in the Yunnan-Guizhou Plateau of China has been used for drainage and afforestation of a Cryptomeria japonica forest, leading to changes in the ecological functions of the peatlands. The Biolog EcoPlate™ method was used to study the differences in the carbon utilization functions of the soil microbial communities between a typical natural Sphagnum fen (SF), a natural Polytrichum bog (PB) and a Cryptomeria swamp forest that were formed by long-term drainage and afforestation (more than 20 years) in the region. Combined with measurements of the soil physicochemical properties, the effects of drainage and afforestation on different types of moss peatlands and the underlying mechanisms were explored. The results showed that long-term drainage and afforestation significantly increased the soil microbial carbon utilization activity and functional diversity in the SF, but no significant effects were observed in the PB. Drainage and afforestation did not significantly alter the proportion structures of the soil microbial carbon source utilization in the SF or PB but did significantly affect soil microbial preferences for specific carbon source utilization in the SF. Carbohydrates, amino acids, carboxylic acids and polymers were the main carbon sources utilized by the microbial communities in the three vegetation types. The soil volumetric water content (SVW) and available phosphorus (AP) content were significant factors affecting the functional characteristics of soil microbial carbon utilization. There was a significant negative correlation between the SVW and the activity of soil microbial carbon source utilization and functional diversity, and there was a significant positive correlation between the AP and polymer utilization activity. Moreover, the SVW significantly and indirectly affected overall carbon source utilization by influencing the utilization of carbohydrates. In the restoration of subtropical moss peatlands affected by drainage and afforestation, in addition to emphasizing vegetation restoration, the SF restoration should be focused on the restoration of water conditions, while the PB restoration should be focused on the restoration of nutrients (such as AP).