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Soil microorganisms are important bioactive components of wetland ecosystems. Their abundances and enzyme activities directly influence biogeochemical cycle processes and are strongly associated with vegetation type. Our study aims to investigate the changes in microbial gene abundances and enzyme activities in Sanjiang Plain wetlands under different vegetation types, namely, Carex lasiocarpa , Deyeuxia purpurea , Glyceria acutiflora subsp. japonica , Oryza sativa , and Phragmites australis. Our results demonstrated that soil microbial gene abundances and enzyme activities were greatly affected by changes in vegetation type and soil chemical properties. The abundances of the carbon fixation gene (cbbL) and activities of ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) in topsoil and subsoil were higher in C. lasiocarpa and D. purpurea wetlands than in other wetlands. This result indicated that the C. lasiocarpa and D. purpurea wetlands have stronger carbon fixation capacity than other wetlands. The highest nif H, nir K, and nir S gene abundances in subsoil were found in the D. purpurea wetland, indicating that soil microorganisms in subsoil under D. purpurea have stronger nitrogen fixation capacity and denitrification potential compared with those in subsoils under other vegetation types. The significantly higher nif H, nir K, and nir S gene abundances in topsoil than in subsoil in the C. lasiocarpa and G. acutiflora wetlands illustrated that topsoil has higher nitrogen fixation and denitrification capacity than subsoil. Redundancy analysis revealed that the cumulative interpretation rates of ammonia-N and dissolved organic carbon (DOC) for soil microbial gene abundances and enzyme activities were 73.1 % and 85.4 %, respectively, showing that ammonia-N and DOC are crucial drivers inducing alterations in soil microbial gene abundances and enzyme activities. Overall, our research clarified the mechanism underlying the linkage among plants, soil, and microorganisms in wetlands and improved the theoretical basis for predicting the effect of wetland vegetation changes on microbial function under the influence of future climate change and human activities. • Microbial abundances and enzyme activities were vegetation type-dependent. • Topsoil microbial abundances were higher than subsoil in C. lasiocarpa wetland. • Soil enzyme activities were strongly associated with soil carbon components. • Microbial abundances and enzyme activities were affected by ammonia-N and DOC. [ABSTRACT FROM AUTHOR]

Plant species composition influences belowground ecosystem function. However, there are few data on the interactive effects of plant diversity and soil function. We surveyed plant species diversity, and determined soil carbon (C), nitrogen (N) fractions and enzyme activity in five peatlands with different vegetation-types. We also investigated the interactions between plant species diversity and richness, and soil biochemical properties. We found a close relationship between plant species diversity and total carbon (TC) in both surface (0–15 cm) and subsoil (15–30 cm) layers. Plant diversity and richness positively correlated with soil dissolved organic carbon (DOC), NH 4 +-N in both soil layers and subsoil moisture and total nitrogen (TN), as well as topsoil pH. Plant species diversity and richness were also positively correlated with subsoil moisture, pH, protease, acid phosphatase activity and topsoil urease activity. Soil β-glucosidase, invertase, urease, protease, and acid phosphatase activity positively correlated with soil TC, TN, DOC, available N and soil moisture. Our findings demonstrate that plant community diversity is linked with soil C and N turnover through soil enzyme activity. These results will improve our ability to more fully understand the linkages between aboveground and belowground components in peatland ecosystems. • Plant species diversity and richness positively correlated with soil DOC and NH 4 +-N. • Soil moisture and pH affected plant distribution, species diversity and richness. • Soil TC, TN, DOC, and moisture were important factors influencing enzyme activity. • Plant community diversity is linked with soil C and N turnover through soil enzyme. [ABSTRACT FROM AUTHOR]

Peatlands in permafrost region are large carbon pools sensitive to global warming. However, the effects of increased temperature on carbon emissions and associated microbial abundances of peatlands under anaerobic condition remain largely unknown, especially when considering depths. For supplementing the deficiency about this, we collected soil from 0 to 150 cm depth of a permafrost peatland in the Great Hing'an Mountain and incubated at 5 and 15 °C for 55 days under anaerobic condition. Soil CO 2 and CH 4 emissions were detected during incubation, and inorganic nitrogen, dissolved organic carbon, and carbon-cycling microbial abundances were analyzed at the end of incubation. Results showed that emission rates and cumulative emissions amount of CO 2 and CH 4 at 15 °C across all soil depths were higher than those observed at 5 °C. Specifically, 0–20 cm and 20–40 cm layers had the highest CO 2 emission rates and cumulative emission amounts, whereas the 40–60 cm and 60–80 cm layers had the highest CH 4 emission rates and cumulative emission amounts. Mean temperature sensitivity (Q 10) values of CO 2 and CH 4 were 2.39 and 55.49 respectively. Q 10 values of bacteria, fungi, archaea, methanogen, and methanotroph abundances were 1.17, 3.85, 1.75, 1.68, and 1.66 respectively, which were calculated by the abundance ratio of microbial functional gene at 15 °C and 5 °C. Similar to the trend of CO 2 emissions, high bacteria, fungi, archaea, methanogen, and methanotroph functional gene abundances were also observed in 0–20 cm and 20–40 cm layers, and such abundances increased along with temperature increasing. In sum, elevated temperature enhances the carbon emission of peatland in permafrost region, and the warming simulated CO 2 emission is linked to the abundances of carbon-cycling microorganisms. • Soil CO 2 and CH 4 emissions at 15 °C are higher than at 5 °C across all soil depths. • Active layer soil has the highest CO 2 emission amounts in permafrost peatland. • CH 4 emissions are highest in the transition layer and its adjacent active layer. • Warming stimulated CO 2 emission is linked to C-cycling related microbial abundance. [ABSTRACT FROM AUTHOR]

Global warming may have a great impact on soil organic carbon (SOC) turnover in permafrost peatlands. The response of microbial residues, as precursors of SOC, to climate warming remains unknown. A 6-year in situ warming experiment was conducted in the permafrost peatlands of Great Hing'an Mountains. Three commonly used amino sugars (glucosamine, GluN; galactosamine, GalN; muramic acid, MurA), for the quantification of microbial residues, were determined in two depths (0–15 cm, shallow soil; 15–30 cm, deep soil) of the bulk and rhizosphere soil of the shrub and Eriophorum vaginatum L. The amount of GluN, GalN, and MurA in deep shrub rhizosphere soil in the warming treatment decreased by 12.65%, 26.11%, and 14.78%, respectively, as compared to that in the control treatment. Yet, warming did not alter the amount of amino sugars in shallow and deep bulk soil. Warming decreased the concentrations of GluN, MurA, and total amino sugars in the deep rhizosphere soil of Eriophorum vaginatum L. by 22.04%, 26.14%, and 18.71%, respectively. Amino sugars in the deep rhizosphere soil of Eriophorum vaginatum L. had a higher temperature sensitivity than those in the deep bulk soil, while total amino sugars in the shallow rhizosphere soil of Eriophorum vaginatum L. had a lower temperature sensitivity than those in the deep rhizosphere soil. • Warming decreased deep rhizosphere soil amino sugars in permafrost peatlands. • Warming did not affect amino sugars in bulk soil. • Amino sugars contributed slightly to SOC in permafrost peatlands. [ABSTRACT FROM AUTHOR]