1 Introduction
Subtropical moss peatlands have important ecological functions, such as biodiversity maintenance, carbon storage and water conservation, and are characterized by their rarity (Li et al. 2018). Microtopography affects the formation and characteristics of moss peatlands, and different microtopography forms different types of moss peatlands (bogs and fens), which are usually occupied by different dominant moss plants (Page et al. 2016; Li et al. 2019). For example, in the Yunnan-Guizhou Plateau of China, the typical subtropical moss peatlands form ombrotrophicPolytrichum bogs (PBs) in the plateau area and minerotrophic Sphagnum fens (SFs) in the low-lying area. Driven by economic interests, moss peatlands all over the world are faced with the disturbance threats of human activities such as agricultural reclamation (Kandel et al. 2018), drainage and afforestation (Sloan et al. 2019), peat mining (Vitovcova et al. 2022; Pospisilova et al. 2023) and fire (Lynda et al. 2023). Drainage and afforestation poses the greatest threat to the patchy moss peatlands in the subtropical region, which greatly reduces their area and causes them to lose their ecological function. Therefore, the protection and restoration of subtropical moss peatlands are urgently needed (Wang et al. 2021).
Soil microorganisms are important drivers of element cycling in peatland ecosystems (Andersen et al. 2013). Studies have found that the most common bacteria in peat are representatives of Proteobacteria and Acidobacteria, which have good adaptability to acidic environments and exhibit a variety of different lifestyles (Lin et al. 2012; Andersen et al. 2013; Urbanová et al. 2014). Other important bacterial groups typically found in peatlands include Actinobacteria, Verrucomicrobia, Planctomycetes, Chloroflexi, Firmicutes and Chlamydiae. The study of peatlands in different climate zones has found that although there are common dominant groups in different peatlands, the correlation between microbial communities and environmental factors is different. In primitive peatlands, the composition and function of soil microbial communities have been shown to vary according to the hydrological conditions, nutritional status, and vegetation composition of a site (Andersen et al. 2013). For example, the relative abundances of Acidobacteria and Proteobacteria showed opposite changes with changes in pH and substrate availability (Smit et al. 2001; Hartman et al. 2008; Urbanová et al. 2014). For example, the water table has been shown to affect the structure of peatland microbial communities or their α diversity (Tian et al. 2019). Other environmental factors, such as nitrogen content (Pankratov et al. 2008), organic matter content, moisture, and phosphorus (Elliott et al. 2008), have also been shown to have an impact on the microbial communities of peatland ecosystems. Compared with high-latitude and tropical peatlands, there are few studies related to subtropical moss peatlands due to their rarity (Alam et al. 2022; Ifo and Garcin 2022; Wilkinson et al. 2023). A few studies have reported that the microbial community of Sphagnum peatlands is affected by microhabitats, and it has been found that groundwater level and total nitrogen content have significant effects on the soil bacterial community of Sphagnum peatlands (Tian et al. 2019). There are few reports on the differences in soil microbial structure and function of different types of subtropical moss peatlands (bogs and fens) and their influencing factors.
Studies of northern peatlands have shown that fens have greater microbial diversity due to additional nutrient input from groundwater, higher pH, and different quality litter compared to nutrient-poor acidic bogs, which mainly obtain nutrients from precipitation (Galand et al. 2005; Kim et al. 2008; Urbanová et al. 2011; Gupta et al. 2012; Lin et al. 2012). Urbanová and Bárta (2016) studied the effects of long-term drainage on different types of peatlands (bogs, fens, swamps) in the Czech Republic and found that fens and swamps were more affected, while bogs were less affected, and the soil microbial structure and function of the three types of peatlands became similar after long-term drainage and suggested that the subsurface microbial community in the drainage sites seems to be driven primarily by the biogeochemical characteristics of peat rather than plant community composition. Compared with long-term drainage disturbance, vegetation is more homogeneous, and long-term drainage and afforestation will make the soil microbial community structure and function of affected bogs and fens more similar to each other (Sloan et al. 2019). Are there significant differences in soil microbial community structure and function between SFs and PBs in the subtropics? Compared with the two types of natural moss peatlands, which swamp forest formed by long-term drainage and afforestation has greater changes than in the soil microbial community? The answers to the above questions will enrich our understanding of the characteristics of different types of moss peatlands in subtropical regions, help us scientifically assess how easy it is for different types of peatlands affected by drainage and afforestation to recover, and provide a theoretical basis for the protection and restoration of moss peatlands in subtropical regions.
This study selected typical subtropical moss peatlands and theCryptomeria swamp forest (CSF) formed by long-term drainage and afforestation in the Yunnan-Guizhou Plateau of China as the research objects. By collecting the topsoil (0-10 cm) that is easily disturbed or strongly affected by climate change, 16S rRNA gene Illumina sequencing technology was used to study the differences in soil bacterial community composition and structure between natural SF, PB and CSF habitats and combined with soil physicochemical properties to explore the important environmental factors affecting the soil bacterial community. We hypothesized that (1) SF has a higher diversity of the soil bacterial community than PB. (2) Compared with PB, the differences in soil bacterial communities between CSF and SF were greater, and this difference was caused by the differences in soil water and nutrients between the different types of peatlands (soil water and nutrients are important factors in this difference).