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Water tables in high-latitude peatlands are expected to fall because of climate change, with significant consequences for carbon cycling in these ecosystems. At present, the understanding of how climate-induced changes will affect soil microbial communities and functions in peatlands still remains controversial. In this study, we compared the potential activities of soil oxidase and hydrolytic enzymes and microbial communities at different depths in a minerotrophic peatland, part of which had been drained for many years and part of which was natural. The results showed that the microbial communities and enzyme activities differed considerably between the drained peat and the natural peat, and that the degree of change varied by depth in the profile. The soil oxidase activities and hydrolase activities (β-1,4-N-acetylglucosaminidase and acid phosphatase) in the oxic zone (0–10 cm) were higher in the drained peat than in the natural peat, but the β-1,4-glucosidase activities decreased in the oxic zone after drainage. Soil enzyme activities in the anoxic zone were lower in the drained peat than in the natural peat. This suggests that drainage disturbance in this peatland does not support enhanced oxidative enzyme activity as hypothesized by the "enzyme-latch" mechanism. The soil total phospholipid fatty acids (PLFAs) and bacterial, fungal, and actinomycetic PLFAs in the oxic zone were lower in the drained peat than in the natural peat. The total PLFAs and bacterial PLFAs were higher in the transitional zone of the drained peat than the natural peat, but remained similar in the anoxic zone of the drained and natural peat. The fungi/bacteria and gram-positive/gram-negative ratios were lower in the drained peat than in the natural peat. The soil bacterial communities was strongly and positively linked with the β-1,4-glucosidase activities involved in carbon transformation, whereas the fungi was positively associated with oxidase activities driving carbon oxidation. We found that these variations in the microbial communities and enzyme activities were associated with differences in the litter quality, soil organic carbon, soil moisture content, and the pH between the drained peat and natural peat. These observations indicate a modification in microbial communities and their activities reflective of changing peat C cycling. The observed reduction in microbial biomass with peatland drainage appears to have also resulted in reductions in enzyme activity suggesting potential limits to the 'enzyme-latch' mechanism for peatland C loss following longer-term drainage. [ABSTRACT FROM AUTHOR]

[Display omitted] • SOC and its LOC fractions exhibited large microtopographical heterogeneity. • 56% of the total SOC stock is stored in soils in and under hummocks. • Hummock-forming sedge peatlands have a high SOC stock. • Hummock-related carbon in sedge peatlands is sensitive to climate change. Hummock-hollow microtopography is common in the northern peatlands of the world, but its effects on soil organic carbon (SOC) components are still poorly understood. In this study, we investigated effects of microtopography on SOC stocks and soil labile organic carbon (LOC) fractions in a sedge peatland in Changbai Mountain in northeast China. We found that SOC and soil LOC fractions had much heterogeneity in microtopography. SOC concentration in hummocks was significantly higher than under hummocks and in hollows. On average, the total SOC stock to a depth of 0.3 m below the ground surface was 19.00 kg C/m2. Fifty six percent of the total SOC stock was stored in soils in and under hummocks, despite the hummock only covering 30% of the total area. Light fraction organic carbon (LFOC), easily oxidizable organic carbon (EOC), microbial biomass carbon (MBC) and dissolved organic carbon (DOC) in hummocks were significantly higher than under hummocks and in hollows. Redundancy analysis (RDA) identified that SOC explained most variations in soil LOC fractions (59.6%), followed by soil total phosphorus (7.4%) and soil water content (6.6%). Our findings indicate that the hummock is an important carbon pool in the sedge peatland. Hummock-hollow microtopography creates heterogeneity in hydrological conditions and soil physicochemical properties, and thus influences SOC stocks and soil LOC fractions at a small scale. This study highlights the importance of microtopography in carbon storage and cycling and has direct implications for the assessment of the carbon sequestration function in northern peatlands. [ABSTRACT FROM AUTHOR]

Peatlands have declined dramatically in the past century due to agricultural cultivation. The main goal of this study was to assess the impact of soil amendment during farming on the restorability of peatlands. We compared the soil seed banks between the natural peatland and farmed peatlands with two soil amendment types (sand-amended and silt-amended) in the Changbai Mountains, China. We found that the seed density and species richness in silt-amended peatland were higher than the natural peatland, and they were the lowest in the sand-amended peatland. Carex species are foundational species of these wetlands and these dominated both in standing vegetation and soil seed banks of the natural peatland. Carex spp. occurred in the seed banks of silt-amended peatland soils in low seed density, but were absent in the sand-amended peatland. The seed density of peatland species was highest in the surface 10 cm soil depth in the natural peatland, while it was highest in the 10–20 cm soil depth in the silt-amended peatland. Redundancy analysis identified that soil C:N, soil water content, and soil organic carbon explained most variance in seed bank composition. The result illustrates that soil amendment types affect soil, and change soil seed banks and revegetation potentials of peatlands. The silt-amended peatland had a higher revegetation potential than the sand-amended peatland. Removal of surface silt mineral soil is necessary to reduce the weed seeds and promote the recolonization of peatland species in the silt-amended peatland during restoration. [ABSTRACT FROM AUTHOR]

[Display omitted] • Soil bacterial richness and communities differed with altitude and vegetation type. • Soil bacterial richness was mainly controlled by MAAT and MAP. • Soil C/P and MAP were the most important regulators of soil bacterial community. • Soil pH significantly affected bacterial diversity and community but to a less extent. • Soil SMC and C-limitation of microbial metabolism are important regulators of soil SOC. Peatlands are crucial carbon (C) sinks, and the combined activities of soil bacteria and soil abiotic properties play an essential role in regulating the C cycle. However, mountain peatlands are particularly vulnerable to global change, which could lead to a change from C sink to source. Understanding how variations in soil bacterial communities and diversity along an altitude gradient affect C storage through changes in enzyme stoichiometry ratios is essential. To address this issue, this study collected soil samples from six peatlands at different altitudes in the Changbai Mountains, China, which were dominated by either sedge or shrub/ Sphagnum species. The study examined a range of soil physical and chemical properties, quantified bacterial community diversity and structure, and assessed enzyme stoichiometry. The results indicated that bacterial communities varied with altitude and vegetation, with bacterial α-diversity (richness) being higher at lower altitudes and in sedge-dominated peatlands. Mean annual air temperature (MAAT) and mean annual precipitation (MAP) were the primary drivers of bacterial diversity, and soil bacterial community composition was significantly influenced by soil carbon/phosphorus (C/P) ratio and MAP. On the other hand, soil pH had only minor effected in mountain peatlands. Path analysis emphasized the greater importance of soil moisture and microbial C limitations than bacterial richness and community on soil organic carbon (SOC) in mountain peatlands. The study also suggested that increasing bacterial richness and relative abundances of rare phyla could increase soil C concentration in peatlands. Overall, this study provided valuable insights into the regulation of C cycling in mountain peatlands and could help mitigate global climate change. [ABSTRACT FROM AUTHOR]