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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]

Peatlands are some of the largest carbon reservoirs in terrestrial ecosystems and play a key role in the global carbon cycle. Understanding peatland development, carbon accumulation processes, and the peatland response to varying forcing factors over different temporal and spatial scales helps reveal the underlying processes and general patterns of these ecosystems. To assess the role of climate and local conditions in peatland development, the basal samples from 23 peat cores and three well dated long peat cores were used to explore peatland initiation, lateral expansion, and carbon accumulation rate in the Baijianghe peatland located in the Changbai Mountains, Northeast China. Our results reveal that the Baijianghe peatland was initiated from forest conditions at 7.9 cal. kyr BP and then expanded laterally by paludification. The rapid expansion between 5 and 4 cal. kyr BP likely resulted from high precipitation and gentle topography. The mean carbon accumulation rates of the three long peat cores were 36.3, 39.1 and 48.4 g C m−2 yr−1, respectively, which are higher than rates from the northern peatlands. Both climate and local conditions have exerted an important influence on carbon accumulation rates in the Baijianghe peatland since the middle Holocene. The carbon accumulation patterns between 5 and 1.5 cal. kyr BP were probably linked to local conditions rather than climatic settings, including topography, hydrological conditions, and plant composition. The consistently decreasing carbon accumulation rate values at all locations within the BJH peatland over the last 1.5 cal. kyr BP suggests that climate is the primary control. This study highlights the varying primary controls on the process of peatland development and reveals the important role of local conditions in carbon accumulation. [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]

Drainage is known to reduce carbon sequestration in peatlands, but its effect on the stability of carbon pool and changes in recalcitrant organic carbon fractions remain relatively unknown, especially in temperate montane peatlands. We investigated the effect of drainage on physicochemical properties and organic carbon fractions of six peat cores from drained and near-pristine areas of Baijianghe peatland, NE China, basing on 210Pb and AMS 14C dating. The vegetation biomass and biomass-C sequestration were also measured in both areas. The loss of total soil carbon accumulation due to drainage was 7.5 kg m−2 (− 25%), equivalent to a complete consumption of carbon accumulated for nearly 170 years in the near-pristine area. Vegetation succession after drainage had a little positive effect on ecosystem carbon sequestration, with an increase of 0.26 kg m−2, which compensated for only 3.5% of the peat soil carbon loss. Notably, over 80% of the total carbon loss after drainage was attributed to the loss of the recalcitrant carbon fraction. The study emphasizes the crucial impact of drainage on carbon sequestration in temperate peatlands. Our findings suggest that continuous water table drawdown induced by drainage, together with drought driven by climate warming, will further reduce carbon sequestration in drained peatlands. There is an urgent need to restore hydrology of peatlands in order to mitigate the long-lasting negative effect of drainage. [ABSTRACT FROM AUTHOR]

Quantifying the temporal and spatial patterns of temperature sensitivity (Q10) of soil respiration (Rs) as well as its controlling factors is critical to reveal the response the soil ecological processes to global warming and improve carbon budget estimations at a regional scale. The seasonal and annual variations in the temperature response of Rs were assessed during the two growing seasons in 2011 and 2012 in four different vegetation sites in a meadow steppe of the Songnen Plain, China. The Q10 values across all sites exhibited significant seasonal variations with a minimum value (1.81–2.34) occurring during summer and a peak value (3.82–4.54) occurring in either spring or autumn. The mean seasonal Q10 values showed no significant differences among the four different vegetation types. On the annual scale, however, the Chloris virgata site had significantly higher annual Q10 values (3.67–4.22) than the other three community sites in 2011 and 2012 and over the two years (2.01–3.67), indicating that the response of the Rs to climate warming may vary with vegetation type. The soil temperature and moisture had interactive effects on the variations of Q10 values. Soil temperature was the dominant factor influencing Q10 values, while soil moisture was an additional contributor to the variations of Q10. Due to the significant temporal and spatial variations in soil respiration response to temperature, acclimation of Rs to temperature variation should be taken into account in forecasting future terrestrial carbon cycle and its feedback to global warming. [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]

Soil faunal communities play key roles in maintaining soil nutrient cycling. Affected by different land-use types, soil environment and soil faunal communities change significantly. However, few studies have focused on the aforementioned observations in coastal zones, which provide suitable habitats for many species of concern. Here, we investigated the changes in soil mesofaunal communities under different land-use types, including cotton fields, jujube trees, ash trees, a saline meadow, and wetlands. The variations in land-use types affected the community composition and diversity of soil mesofauna in the coastal zones. The taxa of soil mesofauna had different responses to land-use types in the coastal zones. Isotomidae was regarded as an indicator taxon of the coastal cropland regions. Entomobryidae was considered to be an indicator taxon of coastal artificial trees. Meanwhile, Onychiuridae and three taxa (Brachycera, Armadillidiidae, and Gammaridae) were indicator taxa of the coastal terrestrial ecosystem and the coastal wetland ecosystem, respectively. Thus, we suggested that specific soil mesofaunal taxa were considered to be appropriate bioindicators for land-use types in the coastal zones. The results of this study were helpful to develop guidelines for coastal biodiversity and ecosystem conservation in the future. [ABSTRACT FROM AUTHOR]

• The Dongfanghong peatland originated in 1011 cal. CE post Millennium Eruption, expanding laterally through paludification. • The carbon accumulation averaged 118 g C/m2/yr, ranging from 38 to 374 g C/m2/yr. • Climate mainly governed multi-centennial carbon accumulation rates. • Hydrological conditions regulated both lateral expansion and carbon accumulation. Peatlands are terrestrial ecosystems with high carbon sequestration efficiency, providing critical feedback on climate change. It is crucial to understand how peatland development and carbon accumulation respond to various factors to reveal the future direction of carbon reservoirs under changing climatic conditions. To assess the impact of climate and hydrological conditions on the development and carbon accumulation of peatlands, 15 peat core samples were analyzed to examine the processes of lateral expansion in the Dongfanghong (DFH) peatland, a minerotrophic fen located in the Changbai Mountains of northeast China. Accelerator Mass Spectrometry 14C, total organic carbon, dry bulk density, testate amoebae, δ13C of α-cellulose in Carex spp. and plant macrofossil analyses were conducted on a high-resolution peat core. The proxies were used to calculate carbon accumulation rate (CAR) and reconstruct water table depth as well as surface moisture and vegetation development of the DFH peatland. Our findings indicated that the DFH peatland was initiated at 1011 cal. CE and experienced paludification during the last millennium. The expansion of the DFH peatland was primarily determined by hydrological conditions rather than climatic factors such as total solar irradiance and regional temperature. The rapid expansion between 1500 and 1700 cal. CE was likely resulted from relatively low precipitation and a decrease in water table/surface moisture. CAR generally correlated with total solar irradiance, regional temperature, and precipitation, suggesting that climate may be crucial for CAR in DFH peatlands over multi-centennial timescales. However, the increased CAR under relatively dry conditions suggested that the CAR were regulated by hydrological conditions over a centennial timescale. This study highlighted the important roles of climate and hydrological conditions in the lateral expansion and CAR of the peatland in minerotrophic fen and that there may be a threshold for hydrology during the process of peatland development and carbon accumulation. [ABSTRACT FROM AUTHOR]

Northwest China (NW China) falls within Arid Central Asia (ACA) and has a climate dominated by westerly winds, a fragile ecosystem, and a high sensitivity to climate change. Paleoenvironmental reconstructions of this region can assist in understanding the general processes contributing to environmental variation in such arid areas. This study examined a dated sedimentary core containing both peat and lacustrine deposits obtained from the shore of the Bosten Lake, NW China. The study aimed to reconstruct paleoenvironmental variations over the last 3,000 years and to explore the possible drivers of peatland development over the last millennium. An examination of grain size and δ13C was conducted to investigate lake level variation. The results showed that the lake level of the Bosten Lake declined gradually between 2,905 and 480 cal yr BP and increased thereafter, consistent with other records of the Bosten Lake. At a centennial timescale, the lake level was high under a wet climate during the Dark Age Cold Period (DACP), whereas it decreased significantly during the Medieval Warm Period (MWP). The inferred "cold and wet" and "warm and dry" patterns indicated climatic characteristics of a "westerlies-dominated climatic regime". In addition, the persistent decreasing lake level during the MWP resulted in Phragmites peatland initiation and development along the shores of the Bosten Lake. [ABSTRACT FROM AUTHOR]

Herbaceous marsh is the most widely distributed type of marsh wetland ecosystem, and has important ecological functions such as water conservation, climate regulation, carbon storage and fixation, and sheltering rare species. The carbon sequestration function of herbaceous marsh plays a key role in slowing climate warming and maintaining regional environmental stability. Vegetation biomass is an important index reflecting the carbon sequestration capacity of wetlands. Investigating the biomass of marsh vegetation can provide a scientific basis for estimating the carbon storage and carbon sequestration capacity of marshes. Based on field survey data of aboveground biomass of herbaceous marsh vegetation and the distribution data set of marsh in China, we analyzed the aboveground biomass and its spatial distribution pattern of herbaceous marsh on a national scale for the first time. The results showed that in China the total area of herbaceous marsh was 9.7×104 km2, the average density of aboveground biomass of herbaceous marsh vegetation was 227.5±23.0 g C m−2 (95% confidence interval, the same below), and the total aboveground biomass was 22.2±2.2 Tg C (1 Tg=1012 g). The aboveground biomass density of herbaceous marsh vegetation is generally low in Northeast China and the Tibetan Plateau, and high in central North China and coastal regions in China. In different marsh distribution regions of China, the average biomass density of herbaceous marsh vegetation from small to large was as follows: temperate humid and semi-humid marsh region (182.3±49.3 g C m−2)

• Hillslope topography is essential for local hydrology and peatland formation. • Microtopographic patterning enhances the positive water balance of the peatland. • Feedback between plant growth and pool development reinforces the stability of the peatland. Some sloping peatlands in northern regions often develop surface microtopographic patterns to maintain their water balance and ecosystem functioning. However, we do not know whether and how spatial patterning would influence the water balance and peat formation of permafrost-affected peatlands in relatively dry regions. Here we used data from the field observations and Unmanned Aerial Vehicle (UAV) survey of a slope peatland at an elevation of around 4800 m in the hinterland of the Qinghai-Tibetan Plateau (QTP) to document and understand the topographic controls of water balance and vegetation growth. Our terrain analysis result shows that the peatland—located on the middle section of a hillslope—has a gentle slope of 5.6° ± 2.5°, while the non-peatland upper section has a steep slope of 12° ± 4.5°. The great upstream catchment area and the presence of shallow impermeable permafrost likely create a saturated condition for peat formation. Our UAV results show obvious spatial patterning of abundant pools and ridges across this peatland, and pool sizes and ridge abundance increase with increasing slopes, suggesting that slope-controlled water flow gradient is the main driver of ridge formation and that ridges is to slow down the runoff. UAV-derived greenness values show a positive relationship with the total pool extent locally (R2 = 0.60) and decrease with increasing distance from the individual pools, suggesting sensitive responses of vegetation growth to surface moisture. Thus, enhanced vegetation growth and likely resultant great peat accumulation immediately around pools potentially further differentiate surface microtopography, strengthening the pool stability. We conclude that the local slope gradient, surface patterning (pools and ridges) and permafrost interact together to regulate water flow and maintain water balance, which in turn regulate the vegetation growth, peat accumulation and peatland stability. Our study implies that the delicate water balance maintained partly by microtopography is sensitive to climate change—especially potential extreme hydroclimate events—and natural and human-induced disturbances that may modify the surface patterning and weaken the peatland's stability, affecting the carbon sequestration ability of this type of peatlands. [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]

Soil microbes and their functions play important roles in the sustainable development of agricultural ecosystems but are vulnerable to climate change and human activity. We measured the contents of microbial phospholipid fatty acids (PLFAs) and enzymatic activities in various soil types (dark-brown soil, albic soils, black soil, chestnut soil, and chernozem) in three climatic zones (humid zone, subhumid zone, and semi-arid zone) of the Songnen Plain in northeastern China. The objectives were to investigate the spatial variations in community structure of soil microbes and to evaluate the functional potential of the microbes in croplands in northeastern China. The C-acquiring activities were highest in the chernozem soil of the semi-arid zone, but N-acquiring and P-acquiring activities and peroxidase were highest in the albic soil of the humid and subhumid zone. Phosphorus deficiencies were indicated by the reduced ratios of N- relative to P-acquiring activity and C-relative to P-acquiring activity in the croplands compared with the global average. Different groups of PLFA contents were highest in the dark-brown soil of the humid zone and the chestnut soil of the semi-arid zone. The community compositions of the microbes varied amongst the soil types and climatic zones, with the ratios of fungi/bacteria and Gram-positive/Gram-negative bacteria highest in chernozemic soil of the semi-arid zone. The variations in soil enzyme activities and microbial community structure were more dependent on climate conditions than soil type. Soil pH, soil organic C content, and the C/N ratio were the most important factors affecting the spatial patterns of the soil enzyme activities and microbial-community compositions across soil types and climatic zones. Mean annual precipitation and clay content strongly influenced enzymatic activities and microbial-community compositions, respectively, when each variable was used as the only factor. Their effects, however, were negligible when combined with other factors. Balanced chemical fertilizer with scientific N-P-K ratio should be applied instead of only N fertilizers. The other combination of different conservational agricultural practices, such as application of organic fertilizer, not tilling, crop rotation, and intercropping, would be more beneficial for restoring the community compositions and functions of soil microbes and achieving sustainable agricultural development. • C-acquiring activity was highest, but N- and P-acquiring activity was lowest in semi-arid zone. • The croplands were deficit in P especially in the semi-arid zone indicated by lnBG:lnNAG:lnAP. • Soil PLFAs decreased with soil C and nutrients decreasing from humid zone to semi-arid zone. • Soil G+/G− and F/B ratios were highest in semi-arid zone but lowest in humid zone. • Microbial community and activities were differentiated by soil pH and C/N ratio. [ABSTRACT FROM AUTHOR]

• The moisture changes in NE China over the past 16,000 years show the spatiotemporal out-of-phase pattern. • The moisture in southern NE China and western China was mainly controlled by the East Asian summer monsoon. • The moisture in northern NE China was mainly controlled by the Westerlies during the late Holocene. • The moisture in eastern NE China was mainly controlled by the Northeast monsoon during the last deglaciation. There is a strong chance that the 21 st century warming will cause differences in precipitation distribution over the globe. Northeast (NE) China is a unique area whose atmospheric circulation is still a controversial subject and is likely to be strongly impacted by global warming. Thus, a good understanding of the past variations in effective moisture in NE China will be benefit for the prediction of future hydrological changes. In this study, we use basal peat ages and published paleoclimate records to evaluate the spatial and temporal patterns and possible forcing mechanisms for the moisture changes in NE China over the past 16,000 years. Basal peat ages suggest that the moisture conditions in different regions of NE China show as a spatiotemporal out-phase pattern. In addition, the paleoclimate records of 17 sites also indicate that NE China experienced a spatiotemporal out-phase pattern of moisture changes along northwest-southeast direction since the last deglaciation. The moisture in southern NE China experienced increasing trend during the period of 16-8 cal ka BP, with the maximum moisture occurring 8-3 cal ka BP and decreasing trend after 3 cal ka BP. The moisture pattern in western NE China is similar to that in southern NE China. It experienced increasing trend during the period of 16-8 cal ka BP, the maximum moisture during the period 8-4 cal ka BP and decreasing trend from 4 cal ka BP to present. The moisture in eastern NE China experienced wet conditions from 16 cal ka BP to 4 cal ka BP, and decreasing trend after 4 cal ka BP. In central NE China, two relatively wet periods occurred during the periods of 13-8 cal ka BP and 6-3 cal ka BP, respectively. In addition, two wet periods occurred during the periods of 14-11 cal ka BP and 7-1 cal ka BP in northern NE China, respectively. The moisture patterns between NE China and other regions of China are also compared in this study. We propose that the possible forcing mechanisms for the moisture changes in NE China were different for each 4000 year interval. During the period of 16-12 cal ka BP, the weak East Asian summer monsoon (EASM) and strong Northeast monsoon (NEM) were the major water vapor sources of NE China. During the period of 12-8 cal ka BP, the increasing EASM and strong NEM were still the major water vapor sources of NE China. During the period of 8-4 cal ka BP, the strongest EASM was the major water vapor sources of the whole NE China. Furthermore, the increasing Westerlies slightly penetrated into northern NE China during this period. From 4 cal ka BP to present, the decreasing EASM provided precipitation for the most regions of NE China. The Westerlies reached the maximum and further penetrated into the whole northern NE China during this period. [ABSTRACT FROM AUTHOR]

The past ecosystem responses to climate variability makes it possible to view the sensitivity of ecosystems to climate-forced state shifts. To test the hypothesis that the development of peatland in the Changbai Mountains responds to the variability of the East Asian summer monsoon (EASM), the developmental history of the Hani peatland was investigated based on peat basal ages. It can be concluded that the development of Hani peatland is the paludification. The development of the northern region started 13,685 cal. yr BP, while that of the southern region was initiated 7705 cal. yr BP. In addition, the moisture changes and development of the Hani peatland can be divided into three periods. From 16 to 7 ka cal. BP, the increase in the EASM was induced by the lower sea level and southward displacement of the Western Pacific Subtropical High (WPSH), resulting in increasing moisture in the Hani peatland. Peat was gradually established in the northern region. From 7 to 2 ka cal. BP, the increased relative sea level and northward displacement of the WPSH induced the maximum EASM. The EASM and Northeast Monsoon (NEM) induced the maximum moisture in the Hani peatland. Both the northern and southern regions were covered with peat during this period. Since 2 ka cal. BP, the decreasing EASM might be related to the seasonal decrease in the Northern Hemisphere summer insolation and ENSO intensity. Thus, the decreasing EASM induced the decrease in the moisture in the Hani peatland. Peat further accumulated in both the northern and southern regions. This study will help to understand the future EASM behavior in NE China and the development of similar peatlands in response to ongoing and future climatic change. Unlabelled Image • The development of Hani peatland mainly experienced the paludification. • The maximum moisture in northeast China was during the period of 7–2 ka cal. BP. • The moisture in northeast China was mainly supported by the East Asian summer monsoon. • The East Asian summer monsoon was controlled by different forcing mechanisms during different periods. [ABSTRACT FROM AUTHOR]

The density of maar lake type peatlands in the Changbai Mountain areas, northeast (NE) China is among the highest in the world. These deposition systems include both peat and limnic deposits, providing valuable sites to study their evolutionary history shaped by their sensitivity to climate-forced state shifts. To investigate the maar lake-mire shift in response to hydroclimatic variability, we examined developmental history of the Jinchuan peatland based on sedimentary facies, grain-size, physical and chemical properites, plant macrofossils and peat basal age. The results indicate that the Jinchuan peatland mainly originated from paludification in a maar lake from approximately 7000 cal. BP. Its water level continuously increased since the Middle Holocene, reaching the peak during the period of 5000–4000 cal. yr BP. The outward expansions of Jinchuan peatland suggest a climate–driven model based on which water level variability superimposes the underlying basin morphology. The hydroclimatic variability and peatland development history can be divided into three periods. From 12 to 7 ka cal. BP, the increasing East Asian summer monsoon (EASM) was the major water vapor source of Jinchuan peatland. The strong evaporation effects induced by the strong Winter Asian winter monsoon (WAWM) and the maximum sea surface temperatures (SSTs) of Japan Sea might have changed the Jinchuan maar lake into dry upland. From 7 to 4 ka cal. BP, the maximum EASM and increasing Westerly jet (WJ) provided water vapor for the peatland. The decreasing EAWM and SSTs of Japan Sea resulted in decreased evaporation effects. The moisture and water level in Jinchuan peatland gradually increased. The peat covered 68.97% of the area during this period. Since 4 ka cal. BP, the decreased EASM and the maximum WJ provided water vapor for the Jinchuan peatland. The weak EAWM and the lower SSTs of Japan Sea induced lower evaporation effects. The moisture and water level in the peatland reached the maximum. Subsequently, peat area further expanded and covered the remaining 31.03% area. This study reveals a remarkable link between the maar lake-mire shift and hydroclimatic variability, which is significant for future prediction of maar lake-mire ecosystem shifts under global climate change. Image 1 • Jinchuan peatland developed from approximately 7 ka cal. BP to present. • Maar lake-mire transition was related to the climate-driven water level variability. • East Asian summer monsoon was the major water vapor source of NE China. • Evaporation effects are more important than precipitation in controlling the moisture changes in NE China. [ABSTRACT FROM AUTHOR]

Extreme precipitation often persists for multiple days with variable duration but has usually been examined at fixed duration. Here we show that considering extreme persistent precipitation by complete event with variable duration, rather than a fixed temporal period, is a necessary metric to account for the complexity of changing precipitation. Observed global mean annual‐maximum precipitation is significantly stronger (49.5%) for persistent extremes than daily extremes. However, both globally observed and modeled rates of relative increases are lower for persistent extremes compared to daily extremes, especially for Southern Hemisphere and large regions in the 0‐45°N latitude band. Climate models also show significant differences in the magnitude and partly even the sign of local mean changes between daily and persistent extremes in global warming projections. Changes in extreme precipitation therefore are more complex than previously reported, and extreme precipitation events with varying duration should be taken into account for future climate change assessments. Key Points: Precipitation from persistent extremes is increasing in most global land regionsGlobally observed and modeled persistent precipitation maxima relative increases are lower compared to daily extremesThe increases in annual‐maximum persistent precipitation per degree global warming across models are independent of the emissions scenario [ABSTRACT FROM AUTHOR]

• Natural and rewetted peatlands were compared under uniform water level gradients. • Rewetted peatland shifted toward natural peatland as the water level rose. • Enzymatic activities exhibited contrasting trends in two peatland types. • High water levels led to archaea-dominated slower processes in natural peatlands. • Biological differences were attributed to lower pH and nutrient limitation. Peatland restoration is an efficient approach to enhance soil carbon sequestration and mitigate climate change. However, successful restoration outcomes require an in-depth comprehension of the underlying soil ecological processes following restoration. To gain a processed perspective on the distinctions between natural and rewetted peatlands, this study compared the soil properties, enzymatic activities, and bacterial and archaeal community structures under uniform water level gradients. The results confirmed our hypothesis that the ecological processes between rewetted and natural peatlands vary significantly. Although the rewetted peatland exhibited different soil properties compared to the natural peatland, increasing water levels resulted in a shift in soil physicochemical properties and hydrolase activities toward those of the natural peatland. This highlights the importance of maintaining a high water level for successful peatland restoration. However, enzymatic activities in the rewetted and natural peatlands exhibited opposite trends with increased water levels, with the natural peatland exhibiting lower polyphenol oxidase activity (-56.7%), higher archaeal diversity (7.3%) and lower bacterial diversity (-2.1%). As the water level increased, ecological processes in the natural peatland shifted from bacteria-dominated faster processes to archaea-dominated slower processes, while no such trends were observed in the rewetted peatland. The study suggest that the lower pH and more restrictive nutrient conditions in the natural peatland, which were altered by rice cultivation with fertilization and vegetation deterioration in the rewetted peatland, may contribute to the biological differences between the two peatland types. These differences may hinder the restoration process after rewetting. Therefore, to enhance the effectiveness of peatland restoration, particularly in the context of rich fens, it is necessary to consider measures that can promote the development of a nutrient-limited and acidic environment aside from rewetting. [ABSTRACT FROM AUTHOR]

Soil microorganisms form an important component of the Earth’s biosphere and play an integral role in carbon, nitrogen and phosphorus cycling. Several biotic and abiotic factors affect the biogeographical distributions of soil microbial biomass (MB) and communities on geographical scales; however, the extent to which soil microbial communities are influenced by these factors is not yet clear. We examined and compared the biomass and structure of soil microbial communities within and between nine mature undisturbed forest ecosystems along the 3700-km North-South Transect in Eastern China (NSTEC). The results showed that soil MB and phospholipid fatty acids (PLFAs) increased with latitude. The structure of the microbial community in boreal forest soils was comparable with that in temperate forests but was significantly different from the microbial communities in warm temperate, subtropical and tropical forests. The mean annual temperature, soil organic carbon, soil total nitrogen and soil easily soluble phosphorus were the main predictors of latitudinal variance in the soil microbial communities. Soils within the same climatic types had similar properties, and soil MB and PLFAs seemed to change along gradients in the various forest types along the NSTEC. Microbial communities showed spatial variation and were dependent on soil properties and climate but were relatively independent of plant functional traits and litter quality. The results suggested that soil microbes could improve the ecosystem models so that they simulate the microbial mechanisms of carbon (C) and nutrient cycling. [ABSTRACT FROM AUTHOR]

Soil enzymes, as indicators of microbial metabolism, play an important role in nutrient biogeochemistry at the ecosystem level. In this study, we present information from a comprehensive analysis of the latitudinal variations in, and stoichiometric relationships between, soil β-glucosidase (BG), N -acetylglucosaminidase (NAG), leucine aminopeptidase (LAP), and acid phosphatase (AP) in nine forest ecosystems along the North-South Transect in eastern China. The results showed that soil BG and NAG activities were higher in temperate forests than in subtropical and tropical forests. Soil AP activities were the opposite, which indicates that microbial nutrient demand in tropical forests was limited by the nutrient phosphorus (P). Soil BG and NAG activities were significantly and negatively correlated with mean annual temperature (MAT), mean annual precipitation (MAP), the soil carbon (C):P and soil nitrogen (N):P ratios, but not with the soil C:N ratio. Soil NAG and AP activities were inversely correlated with soil pH, and soil AP activity increased as soil pH decreased. The latitudinal variations in the C:N, C:P, and N:P acquisition ratios represented by ln(BG):ln(LAP + NAG):ln(AP) activities across ecosystems were significantly and negatively related to MAP and MAT. The C:P and N:P acquisition ratios were positively related to soil pH but negatively related to the soil C:P and N:P ratios. The C:N and C:P acquisition ratios were also negatively correlated with leaf C:N, C:P, and N:P ratios. This study provides useful information about environmental controls on enzyme stoichiometry, and also highlights the stoichiometric and energy limitations on the metabolism of soil microbes. [ABSTRACT FROM AUTHOR]

• Soil PLFAs increased with altitude in the sedge dominated peatlands but decreased with altitude in the shrub/ Sphagnum dominated peatland. • Soil microbes were co-limited by C and P with the limitations greater in the sedge dominated peatlands than in the shrub/ Sphagnum dominated peatlands. • The P limitation was greater at the high altitudes than that at the low altitudes. • Soil PLFAs and community was regulated by soil physical properties and nutrients, respectively. • The C and P limitation was regulated by soil physical properties and nutrient ratios, respectively. Soil microbes regulate the storage of carbon (C) in peatlands, which is facilitated by nutrients. To date, few researchers have examined the spatial distribution of soil microbial biomass, microbial community structure, and their metabolic nutrient limitations in mountain peatlands at different altitudes. This study aimed to improve the knowledge of how and why soil microbial biomass and their metabolic nutrient limitations varied with altitude. We investigated the phospholipid fatty acids (PLFAs) and enzymatic stoichiometry in surface (0–20 cm) and subsurface (20–50 cm) soil from peatlands with different types of vegetation in the Changbai Mountains. Overall, the soil microbial PLFAs were higher in the sedge-dominated peatlands than in the shrub/ Sphagnum- dominated peatlands. The soil microbial PLFAs in the sedge-dominated peatlands were elevated at high altitudes but decreased with altitude in the shrub/ Sphagnum- dominated peatlands. The soil fungal/bacterial ratios (F/B) in the surface soil increased with altitude in the sedge-dominated peatlands but not in the shrub/ Sphagnum- dominated peatlands. The Gram-positive/Gram-negative bacteria ratios (G+/G−) in the surface soil decreased with altitude in the sedge-dominated and shrub/ Sphagnum- dominated peatlands. The soil F/B ratios were higher, but the G+/G− ratios were lower in the shrub/ Sphagnum- dominated peatlands than in the sedge-dominated peatlands. The soil pH and nutrient ratios explained most of the differences in soil bacterial and fungal PLFAs, respectively. However, the total nutrients of soil were the primary regulators of soil F/B and G+/G−. The soil microbial activities suffered from C- and phosphorus (P)- limitations in the mountain peatlands. The limitations were worse in the shrub/ Sphagnum- dominated peatlands than in the sedge-dominated peatlands. The P limitations were greater at high altitude than at low altitude in both types of peatlands. The C and P limitations on soil microbial metabolism were primarily controlled by soil physical properties and nutrient ratios, respectively. [ABSTRACT FROM AUTHOR]

For model-based quantitative reconstructions of past vegetation cover on the scale of landscapes, pollen productivity estimates (PPEs) are key input parameters. In this study, we employed a random sampling strategy to collect moss polsters at 20 sites in Changbai Mountain, northeastern China. A detailed vegetation survey within 1000-m radius around each sampling point was carried out and digitized vegetation maps were used for vegetation data compilation. A forest map at the scale of 1:25,000 was used to extract information about vegetation for the area between 1000 and 5000 m from each sampling point. Using the ERV (Extended R-Value) model, pollen productivity was estimated for Larix , Pinus , Juglans , Ulmus , Tilia , Betula and Fraxinus relative to Quercus . Estimates of pollen fall speeds for the eight taxa as well as the relevant source area of pollen (RSAP) were also obtained. Three different ERV sub-models were tested against the data. The sub-model 3 produced the best goodness of fit and the PPE values calculated with this sub-model show that Betula (5.04), Pinus (3.11), Juglans (1.94) and Ulmus (1.40) are high pollen producers with higher PPEs than Quercus while Fraxinus (0.76), Larix (0.30), Tilia (0.16) are low pollen producers compared to Quercus . The high pollen producers are all anemophilous species, while low pollen producing plants include both entomophilous, such as Fraxinus , Tilia and anemophilous species such as Larix . The estimated RSAP for the eight tree pollen taxa is about 2000–2500 m. [ABSTRACT FROM AUTHOR]

Sphagnum dominates the moss layer in northern peatlands, but its dominance has decreased while there has been an expansion of other moss genera in some peatlands of NE China since the 1960s. To discover the mechanisms underlying this succession, we performed a four-month reciprocal transplant experiment in Hani Peatland with three Sphagnum species, Sphagnum palustre, S. magellanicum, and S. fuscum and one other moss Polytrichum strictum. Performance of the four mosses and the environmental factors: height above water table (HWT), vascular plant cover and pH, electrical conductivity, base cations, and N and P concentrations in water in the four moss habitats were measured. Biomass production in S. palustre was negatively affected by HWT. Phosphorus had a positive effect on biomass production in S. magellanicum and Polytrichum. None of the environmental factors had any effect on S. fuscum. Overall, the three Sphagnum species deteriorated in P. strictum hummocks, while P. strictum exhibited a wider ecological amplitude and maintained or increased its vigour levels in Sphagnum hummocks. Biomass production in S. palustre and S. magellanicum was negatively affected by P. strictum indicating the competitive ability of P. strictum. Our results suggest that its wide ecological amplitude and competitive ability may explain why P. strictum can expand and replace Sphagnum in some northern peatlands. [ABSTRACT FROM AUTHOR]

Peatlands are one of the most significant carbon reservoirs in the terrestrial ecosystem. Understanding past peatland carbon accumulation processes and their responses to varying external and internal forcing factors would help reveal the general development patterns of peatland ecosystems and provide useful insights into projecting the fate of carbon reservoirs into the future. In this paper, the basal ages of 17 peat cores were used to explore the lateral expansion processes of the Laolike peatland, northeast China. Two cores were selected to calculate carbon accumulation rates (CAR) and reconstruct moisture/precipitation records based on δ13C and grain size analyses. The basal ages show that the peatland was initiated at 12.1 cal kyr BP, then laterally expanded with its fastest rate occurring during the early Holocene, and reached its largest area around 6 cal kyr BP. The time-weighted mean CAR in the Laolike peatland ranged from 31.1 to 52.9 g C/m2/yr (with an average of 42 g C/m2/yr) during the Holocene. The peatland experienced a high CAR of 52.5 g C/m2/yr from 11.7 to 5 cal kyr BP, followed by a low CAR of 35.1 g C/m2/yr after 5 cal kyr BP. Both lateral expansion and vertical accretion are consistent with the summer insolation, climate seasonality, and the strength of the East Asia summer monsoon (EASM) over multi-millennium timescales, where the CAR correlated well with δ13C and grain size, implying moisture/precipitation might be the primary factors controlling carbon accumulation over millennium timescales. Local conditions, such as topography and hydrology, also played an important role in the process of peatland initiation and lateral expansion, as well as the discrepant CAR within the peatland. This study reveals the roles of climate and local conditions in peatland initiation, expansion, and CAR during the Holocene. In addition, we provide a window for a better understanding of the driving factors of peatland development in the temperate zones of the Northern Hemisphere. • Climate conditions are the primary control on the lateral expansion and vertical accretion of Laolike peatland over multi-millennium timescales. • Moisture/precipitation affects carbon accumulation of Laolike peatland over millennium timescales. • Local conditions play an important role in the lateral expansion and the internal differences of carbon accumulation rate. [ABSTRACT FROM AUTHOR]

• Soil enzyme activities had varied by microtopography and season. • Water table position (WTP) explained most variation in soil enzyme activity. • Hydrolase and oxidase activities respond oppositely to change of WTP and nutrient. Soil enzyme activities play a pivotal role in ecosystem processes, such as organic carbon decomposition or nitrogen and phosphorus mineralization. Thus, enzyme activities measurements can provide insights into the rates of ecosystem-level processes in peatlands. Hummock-hollow microtopography is a common feature in boreal peatlands, but its influence on soil enzyme activity is not well understood. We investigated the effects of hummock-hollow microtopography on activities of three soil hydrolases (β-1,4-glucosidase (βG), 4-N-acetylglucosaminidase (NAG), and acid phosphatase (AP)) and one oxidase (peroxidase (PER)), as well as environmental variables in a sedge-dominated peatland in Changbai Mountains, in northeast China. We found that soil enzyme activities had large microtopographical and seasonal heterogeneity. During the growing season, the activities of three soil hydrolases (βG, NAG and AP) in hummocks were 6.6, 4.6 and 5.5 times higher than those in hollows, while the PER activity in hollows was 1.9 times higher than in hummocks. Soil enzyme activities in hummocks exhibited obvious seasonal variation, with the βG, AP and PER presenting minimum values in summer and peak values in spring and autumn. Principal component analysis (PCA) indicated that soil enzyme activity had larger microtopographical heterogeneity than seasonal variations. Water table position explained most variation (74.1%) in soil enzyme activity, followed by soil temperature (5.5%) and pH (3.1%) based on ordination analysis using RDA. We conclude that hummock-hollow microtopography creates heterogeneity in hydrologic conditions, soil temperature and nutrients, and thus influences soil enzyme activity involved in carbon and nutrient cycling in sedge-dominated peatlands. This information stresses the importance of hummock-hollow microtopography in regulating carbon and nutrient cycling in northern peatlands. [ABSTRACT FROM AUTHOR]

• Drainage upregulated the BDG, NAG, and PHO activities. • The preserved carbon and nutrients changed slightly due to drainage. • Severe nutrient-deficiency protected stored carbon during the short-term drainage. • Vegetation shifts compensated for the carbon loss during the long-term drainage. Lowering of water table owing to climate warming and drainage has threatened the large reservoir of the preserved carbon (C) in peatlands. However, the consequent effects on northern nutrient-deficient peatlands are still under-investigated. Here, we compared a short- (42 days) with a long-term (30 years) drainage experiment, and quantified the activities of the decomposition-related extracellular enzymes as well as C, nitrogen (N) and phosphorus (P) stoichiometries in a minerotrophic peatland in northeastern China. The results showed that the key hydrolytic enzymatic activities increased by 2–145% and 25–465% under short- and long-term drainage respectively, but the preserved nutrients and C in the peat did not vary considerably. The minerotrophic peatland seems to be a complex adaptive system with great resilience to tackle the short- and long-term drainage with two disparate mechanisms. Specifically, the intrinsic nature of severe nutrient-deficiency may weaken enzymatic constraints on decomposition (the 'enzymatic latch' mechanism) during the short-term drainage. In contrast, the increases in phenolics input and litter quality due to the shift in vegetation composition may alleviate the threat to C stores during the long-term drainage. These distinct regulatory mechanisms over the course of progressive lowering of water table may potentially provide new insights to assess the risk and benefit of drainage in peatlands. [ABSTRACT FROM AUTHOR]