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The policy and practice of ecological restoration and conservation in China obtained some remarkable results. For example, Sphagnum moss growing on abandoned farmland, which was peatland before agricultural use, has rapidly expanded the wetland area in SW China. Microorganisms such as testate amoebae are sensitive to environmental change and thus have been widely used as ecological indicators in various habitats. We analyzed differently aged Sphagnum growing plots on a Sphagnum growing farmland and natural Sphagnum plots in SW China to examine how Sphagnum-dwelling testate amoeba communities and corresponding protozoic silicon (Si) pools respond to ecological restoration practice. We found that abundance, taxon richness, and diversity of testate amoebae were higher in Sphagnum growing farmland plots compared to natural Sphagnum plots. Protozoic Si pools showed an increase with Sphagnum growing time representing increased Si accumulation by idiosomic testate amoeba shells. However, protozoic Si pools were negatively correlated with taxon richness and diversity of testate amoebae. Our results showed that (i) natural Sphagnum plots were not characterized by the expected higher biodiversity of testate amoebae compared to Sphagnum growing plots and (ii) consequently protozoic Si pool quantity in natural Sphagnum plots was less driven by biodiversity of testate amoebae than expected. We concluded our results to underline the value of (i) environmental restoration policy in general and (ii) testate amoeba communities and corresponding protozoic Si pools for Si cycling in restoration areas of peatlands in particular. Based on our results, we recommend a sustainable cultivation of Sphagnum moss and an additional establishment of protected areas, where no Sphagnum harvesting occurs. These protected Sphagnum areas might represent hot spots of undisturbed testate amoeba communities and corresponding protozoic Si pools and thus of microbial Si cycling. [ABSTRACT FROM AUTHOR]

Many peatlands are exposed to intermittent burning but the implications of this burning for microbial communities have been little-studied. Here we consider the impacts of burning on the dominant protists of peatland ecosystems, the testate amoebae. To do this we used a ‘natural experiment’, a peatland exposed to wildfire where fire-fighting activity left a combination of unburned and heavily burned areas in close proximity. We assessed the change in testate amoebae three days after the end of the fire. We find that burning led to a large change in taxon composition, primarily noted by a shift from taxa with tests constructed of idiosomes to those constructed of xenosomes. The most likely explanation for this change is the direct destruction of mostly idiosome tests by extreme heat. Although we did not differentiate live individuals from empty tests it is probable that the fire led to a significant change in the testate amoeba community. This change may have interesting implications for the structure of microbial food webs, for biogenic silica cycling and for palaeoecological reconstruction in burned peatlands. This is clearly a topic which deserves more research attention. [ABSTRACT FROM AUTHOR]

Hyalospheniids are among the most common and conspicuous testate amoebae in high-latitude peatlands and forest humus. These testate amoebae were widely studied as bioindicators and are increasingly used as models in microbial biogeography. However, data on their diversity and ecology are still very unevenly distributed geographically: notably, data are lacking for low-latitude peatlands. We describe here a new species, Nebela jiuhuensis, from peatlands near the Middle Yangtze River reach of south-central China with characteristic morphology. The test (shell) has hollow horn-like lateral extensions also found in N. saccifera, N. equicalceus (=N. hippocrepis), and N. ansata, three large species restricted mostly to Sphagnum peatlands of Eastern North America. Mitochondrial cytochrome oxidase ( COI) data confirm that N. jiuhuensis is closely related to the morphologically very similar North American species N. saccifera and more distantly to N. ansata within the N. penardiana group. These species are all found in wet mosses growing in poor fens. Earlier reports of morphologically similar specimens found in South Korea peatlands suggest that N. jiuhuensis may be distributed in comparable peatlands in Eastern Asia (China and Korea). The discovery of such a conspicuous new species in Chinese peatlands suggests that many new testate amoebae species are yet to be discovered, including potential regional endemics. Furthermore, human activities (e.g., drainage, agriculture, and pollution) have reduced the known habitat of N. jiuhuensis, which can thus be considered as locally endangered. We, therefore, suggest that this very conspicuous micro-organism with a probably limited geographical distribution and specific habitat requirement should be considered as a flagship species for microbial biogeography as well as local environmental conservation and management. [ABSTRACT FROM AUTHOR]

• Peatland degradation caused a significant loss of testate amoeba (TA) biodiversity. • Unexpectedly, this loss was accompanied by an increase in TA biosilicification. • TA biodiversity was not coupled to protozoic biogeochemical silicon (Si) cycling. • New insights into microbial biogeochemical Si cycling on a continental scale. Anthropogenic peatland degradation is a global threat. As peatlands store large amounts of carbon (C) their potential for mitigation of climate change has been emphasized recently. Global C cycling is linked to silicon (Si) fluxes from the continents into the oceans. These fluxes in turn are driven by biosilicification, the incorporation of inorganic Si into living organisms, in terrestrial ecosystems. Biosilicification by testate amoeba (TA) communities and its potential for Si cycling has been highlighted since the beginning of the 21st century. However, the effects of peatland degradation on TA biodiversity and corresponding protozoic biosilicification on a continental scale remained unresolved so far. We show that TA biodiversity in Asian peatlands is strongly affected by the grade of human impact. This biodiversity decline was accompanied by an unexpected increase in protozoic biosilicification. Our findings provide new insights into the interactions between the biodiversity of soil microorganisms and biogeochemical Si cycling. [ABSTRACT FROM AUTHOR]

The article focuses on a study which examined the biodiversity and hydro-ecological selection of testate amoebae from Dajiuhu peatland in Shennongjia, Central China. Samples were collected from microsites within the peatland. Results of the study showed high variations in the morphology of testate amoebae in 136 Sphagnum samples. The study observed that variations in shell morphology can be attributed to different moisture conditions in their habitat.

Testate amoebae from a large fen peatland of China were investigated in August 2009. Thirty-six testate amoebae species belonging to 16 genera and one rotifer were identified. Three relatively drier indicator species, Assulina muscorum, Assulina seminulum, and Trinema-corythion type, were the dominate species, comprising 54% of total amoebae shells. Non-metric multidimensional scaling (NMS) ordination divided the testate amoebae assemblages into two groups – a drier group including A. muscorum, A. seminulum, Euglypha rotunda type, Trinema-corythion type, and Plagiopyxis callida and a wetter group including Centropysis cassis, Cyphoderia ampulla, Difflugia oblonga, Difflugia lanceolata, Euglypha strigosa type, Nebela galeata, Nebela lageniformis, and Quadruella symmetrica. Pearson correlations showed that most testate amoebae species between the two groups are negatively correlated, reflecting the possible influence of a moisture gradient. However, the ubiquitous distributions of other testate amoebae in the two-dimensional NMS ordination map suggested that factors other than moisture are also influencing the testate amoebae community in the fen. [ABSTRACT FROM AUTHOR]

Testate amoebae (TA) are a common and diverse group of protists and are especially abundant in peatlands. The structure of peatland TA communities is well correlated to surface moisture and water table depth (WTD). For that reason, TA are widely used as proxy indicators in ecological and palaeoecological studies. Peatlands are abundant across Asia, but the diversity and ecology of the TA that inhabit these systems are poorly documented. It is therefore unclear whether TA can be used as palaeohydrological indicators in the manner in which they commonly are in Europe and North-America. There is particular uncertainty as to the efficacy of this approach in the lower latitudes. We compiled existing and new data on testate amoebae from 1124 Sphagnum -dominated samples from 42 individual peatlands covering broad latitudinal (25°–66° N) and longitudinal (68°–129° E) ranges. Using a consensus taxonomic framework, we built a checklist of TA and developed TA-based hydrological transfer functions for Asian peatlands. The results showed that three models, weighted averaging (WA), weighted average partial least squares (WA-PLS), and maximum likelihood (ML), predicted similar WTD values for full samples, while the modern analogue technique (MAT) produced the strongest (R2 boot = 0.58) relationship between observed and estimated water-table depths (WTDs). Removing outlier samples improved the R2 values of observed vs. estimated WTDs, with ML then demonstrating the strongest predictive power (R2 boot = 0.68, RMSEP boot = 8.98 cm). The predictive capability of the developed WTD transfer function is comparable to equivalent models for Europe and North America and thus can be used for palaeohydrological reconstructions for boreal to subtropical peatlands in Asia. • A testate amoebae taxonomic checklist was compiled from Asian peatlands. • We developed continental scale testate amoeba-based hydrological transfer functions. • The water-table depth transfer functions can be used for paleohydrological reconstructions. [ABSTRACT FROM AUTHOR]

• Land-use change affected testate amoebae and corresponding protozoic silicon pools. • Protozoic Si pools significantly decreased in croplands compared to peatlands. • Drainage of peatlands was found to represent a key factor for decreasing Si pools. • This decrease represents anthropogenic desilication at the microorganismic level. Many peatlands have been damaged by human activities like Sphagnum harvesting and draining reflected in reduced peatland areas and ecosystem functioning. Peatlands generally play an important role in global silicon (Si) cycling and maintain huge numbers of testate amoebae (TA). However, there is a lack of knowledge on (i) the quantity of protozoic Si pools (represented by siliceous shells of TA) in peatlands and (ii) how these pools respond to land use changes caused by human influence. In our study, we quantified protozoic Si pools in the Dajiuhu National Wetland Park, China, with a focus on the comparison between peatland and cropland areas (i.e., former peatland drained for agriculture). We found protozoic Si pools to (i) represent an important biogenic silica fraction in peatlands and (ii) significantly differ between peatlands and croplands with soil moisture as a key factor for protozoic Si pool quantity showing a significant decrease of these pools in drained areas (i.e., in croplands). From our results we concluded the decrease of protozoic Si pools due to land-use change to represent another example (apart from the loss of phytogenic Si) for anthropogenic desilication in agricultural biogeosystems in general. [ABSTRACT FROM AUTHOR]

Simple Summary: Deciphering the relationship between microbiome of keystone species Sphagnum palustre and potential function in the Erxianyan peatland ecosystems is important in the context of global peatland degradation. We evaluated the S. palustre tank microbiome and predicted the potential ecological functions. In total, 38 phyla, 55 classes, 122 orders and 490 genera were detected. Proteobacteria and Firmicutes are the dominant endophytes in S. palustre. Core microbiomes are mainly found in 7 phyla, 9 classes, 15 orders, 22 families and 42 genera. Functions predictive of microbial communities are involved in nitrogen fixation, carbon cycle, nitrate metabolism, sulfate respiration and chitinolysis, which may enable the Sphagnum to adapt to harsh environmental conditions. This study provides new insights into the relationship between Sphagnum-associated microbiomes and their potential ecological functions in subalpine peatlands. Sphagnum is a fundamental ecosystem of engineers, including more than 300 species around the world. These species host diverse microbes, either endosymbiotic or ectosymbiotic, and are key to carbon sequestration in peatland ecosystems. However, the linkages between different types of Sphagnum and the diversity and ecological functions of Sphagnum-associated microbiomes are poorly known, and so are their joint responses to ecological functions. Here, we systematically investigated endophytes in Sphagnum palustre via next-generation sequencing (NGS) techniques in the Erxianyan peatland, central China. The total bacterial microbiome was classified into 38 phyla and 55 classes, 122 orders and 490 genera. The top 8 phyla of Proteobacteria (33.69%), Firmicutes (11.94%), Bacteroidetes (9.42%), Actinobacteria (6.53%), Planctomycetes (6.37%), Gemmatimonadetes (3.05%), Acidobacteria (5.59%) and Cyanobacteria (1.71%) occupied 78.31% of total OTUs. The core microbiome of S. palustre was mainly distributed mainly in 7 phyla, 9 classes, 15 orders, 22 families and 43 known genera. There were many differences in core microbiomes compared to those in the common higher plants. We further demonstrate that the abundant functional groups have a substantial potential for nitrogen fixation, carbon cycle, nitrate metabolism, sulfate respiration and chitinolysis. These results indicate that potential ecological function of Sphagnum palustre in peatlands is partially rooted in its microbiomes, and that incorporating into functional groups of Sphagnum-associated microbiomes can promote mechanistic understanding of Sphagnum ecology in subalpine peatlands. [ABSTRACT FROM AUTHOR]

Here we present multiproxy inorganic geochemical records from a peat core (ZK5) from the Dajiuhu Basin in central China to investigate peatland deposition processes and atmospheric metal pollution and to explore their relationships with East Asian monsoon change and human activities in the Middle Yangtze Valley since 20,000 cal yr BP. The peat physicochemical data including total organic carbon (TOC), trace elements, and grain-size show that the site has changed from a lake during the cold-wet Last Glacial Maximum (LGM; 20,000–18,000 cal yr BP), to a marshy wetland during the mild last deglaciation (18,000–11,500 cal yr BP) and a peatland during the mostly warm and dry Holocene (11,500 cal yr BP–present). This general sequence corresponds with changes in East Asian monsoon indicated by stalagmites δ18O records and boreal summer insolation. Marked decreases in trace element concentrations correspond to two periods of peatland expansion during the abrupt hydroclimatic transitions from the LGM to the last deglaciation and from the last deglaciation to the early Holocene. Warm-dry mid-Holocene might induce high organic matter decomposition in peat sediments. Increasing natural element concentrations since the late Holocene are correlated with the weakening of the summer monsoon and elevated atmospheric dust deposition. Increasing Cu and Pb concentrations in peat record indicate large-scale Cu smelting during the Bronze Age and excessive coal burning during the 10th century or so. The anthropogenic heavy metals were transported by prevailing East Asian summer monsoon and deposited in the Dajiuhu Basin during periods of heightened human activities. Our compilation of heavy metals records across China confirmed the noticeable impacts of the historical human activity on deposition environments during the late Holocene. Consequently, trace elements from the Dajiuhu Basin are reliable proxies for capturing monsoon climate-induced peatland deposition response and present important evidence for a historical atmospheric heavy metal pollution in the Middle Yangtze Valley. Our results offer useful references for peatland evolution and protection under the background of global change. Unlabelled Image • Peat trace elements document the deposition environment and metal culture succession. • Peatland processes since the LGM are linked with climate phases and monsoon changes. • Abrupt hydroclimatic transitions accelerated pond infilling. • High Cu content responded to the intensified Cu melting in the Bronze Age. • Coal burning for ironing and use of lead glazed ceramics caused atmospheric Pb pollution at around 10th century. [ABSTRACT FROM AUTHOR]

Depth to water table (DWT, the depth from the water surface to the top of the peat surface) is one of the most important environmental variables related to the habitat types and distribution of vegetation within a subalpine peatland. The distribution of phytolith assemblages and basic environmental data from 43 surface soil samples with significant ecological and hydrological gradients were investigated to generate transfer functions for quantitative reconstruction of paleoenvironmental changes in Dajiuhu peatland, central China. Detrended correspondence analysis (DCA) and redundancy analysis (RDA) were employed to explore the relationship between main environmental variables and phytolith morphotypes and distributions. Our results indicate that the spatial distribution of phytoliths was significantly correlated with the DWT (25% variance), total organic carbon (TOC, 10% variance) and magnetic susceptibility (χ, 7% variance). We established the transfer functions for the significant variables based on modern analogue technique (MAT), weighted averaging techniques (WA) and weighted averaging partial least squares (WA-PLS), and model performance was assessed using bootstrap cross-validation. The high correspondence of the predicted DWT results based on phytolith-environment calibration data with observed data reflects that the phytolith-based WA-PLS is a reliable effective calibration method for the quantitative DWT reconstruction of ombrotrophic (rain-fed) subalpine peatland. [ABSTRACT FROM AUTHOR]

In order to explore the impacts of past climate changes on the origin and evolution of Lake Poyang, the biggest freshwater lake in China, eight periods of palaeoenvironmental changes were constructed to depict the history of climate change over the past 3500 years based on the palynological records and carbon isotopic excursions. The climate regime was associated with the presence of a deciduous and evergreen broad-leaved forest/a mixed needle broad-leaved forest and strong/weak solar variability. Palaeohydrology change reconstructed by the percentage of aquatics and stable carbon isotopes demonstrated that the wet episode was associated with the developed lacustrine facies and enhanced El Niño–Southern Oscillation (ENSO) activities. The presence of the united open lake (Lake Poyang) during 2000–1200 cal. a BP was linked to a long wet period caused by the strong ENSO activities. At the decadal-centennial timescales, climate changes together with the ENSO activities might have played a great role on the regional hydrological condition and sedimentary evolution in southern Lake Poyang. The correlations of the palaeotemperature and palaeohydrology with the multi-proxy data from the Northern Hemisphere all suggest that palaeotemperature change with the monsoon intensity is linked to the solar variations, but palaeohydrology change has a striking consistency with the ENSO activities. The distinct hydrothermal diversification (warm-wet, warm-dry, cold-wet, cold-dry) revealed by the palaeotemperature and palaeohydrology changes will provide important clues about the origin and evolution of Lake Poyang in the Holocene and a better understanding of the interactions between solar radiation, ENSO activity and lake deposition in the middle Yangtze River Valley. [ABSTRACT FROM AUTHOR]

Highlights: [•] The δ13C values of n-alkanes (δ13Calk) in Dajiuhu peatland were investigated. [•] They displayed site-dependent relationships with water level. [•] Most sites showed a positive correlation between δ13Calk and water level. [•] Influence of methanotrophs on δ13Calk was not apparent in non-submerged Sphagnum. [ABSTRACT FROM AUTHOR]

Abstract: Samples of Sphagnum palustre and peat from the Erxianyan peatland, central China, were analyzed for lipids and their carbon isotopes to investigate how lipid distributions respond to hydrological change and to evaluate the importance of the contribution of microbial lipids to the peat moss. The lipids in samples collected from different hydrological settings in and around a pond and in the central part of the bog show clear variation along the hydrological gradient, with higher n-C23/n-C25 alkane ratio values and lower ACL (average chain length) values of long chain n-alkanes, n-fatty alcohols and n-fatty acids at the wetter sites. Although the relationship between the S. palustre lipids and the hydrological conditions can be partially overprinted in peat by an input from vascular plants, lipid ratios such as P aq and ACL can provide useful qualitative information about Sphagnum contributions. In addition, lipid composition and carbon isotope values provide information about microbial activity associated with S. palustre. The occurrence of a high abundance of 7-methylheptadecane in submerged S. palustre is an indication of cyanobacteria in the living peat moss. The relatively 13C-depleted carbon isotope values of the n-C23 alkane could result from the influence of symbiotic methanotrophs on the carbon available for assimilation by S. palustre. [Copyright &y& Elsevier]

The distributions of microbial tetraether lipids, i.e. glycerol dialkyl glycerol tetraethers (GDGTs), were investigated in a variety of Chinese soils featured by a wide range of pH values in different climate zones. The bacterial branched GDGTs and archaeal isoprenoid GDGTs were found to be widely distributed in Chinese soils and their relative abundance was controlled primarily by soil pH. The bacterial bGDGTs usually dominate over archaeal iGDGTs in abundance when the soil pH is below 8.0. However, archaeal iGDGTs become dominant and the abundance of halophilic archaea characterized by GDGT V without cyclopentyl ring increases dramatically in the alkaline soil with pH greater than 8.0. The relative abundance of archaeal iGDGTs to bacterial bGDGTs was defined here as RAI index. The RAI index decreases with elevated soil pH and a linear correlation is found between them, indicating that the relative abundance of archaeal iGDGTs to bacterial bGDGTs increases with increased pH. The RAI index thus could be a novel proxy of the pH values of paleosol. The terrestrial input index, BIT (Branched and Isoprenoid Tetraethers Index), decreases with increased soil pH, suggesting that soil pH should be taken into consideration when the terrestrial contribution to marine sediments is estimated by BIT index. Moreover, the TEX86 index cannot be used to reconstruct sea surface temperature in the sediments featured by a large terrestrial input. [ABSTRACT FROM AUTHOR]