A High–Resolution Accumulation Record of Arsenic and Mercury after the First Industrial Revolution from a Peatland in Zoige, Qinghai–Tibet Plateau

The impacts of human activities on Zoige peatlands are poorly documented. We determined the concentrations and accumulation rates of As and Hg in a 210Pb-dated peat profile collected from this area and analyzed the correlations between accumulation rates of both As and Hg and other physicochemical properties. To reconstruct recent conditions of As and Hg, we analyzed peat sediments of Re’er Dam peatland in Zoige using 210Pb and 137Cs dating technologies. The concentrations of total As (86.38 to 174.21μg kg−1) and Hg (7.30 to 32.13 μg kg−1) in the peat profile clearly increased after the first industrial revolution. From AD 1824 to AD 2010, the average accumulation rates were 129.77 μg m−2 yr−1 for As and 18.24 μg m−2 yr−1 for Hg. Based on our results, anthropogenic emissions significantly affected the atmospheric fluxes of As and Hg throughout the past 200 years, and As was also likely to be affected by other factors than atmospheric deposition, which needs further identification by future studies. The historical variations in As and Hg concentrations in Re’er Dam peatland in Zoige mirror the industrial development of China.

Is bog water chemistry affected by increasing N and S deposition from oil sands development in Northern Alberta, Canada?

Nitrogen and sulfur emissions from oil sands operations in northern Alberta, Canada have resulted in increasing deposition of N and S to the region’s ecosystems. To assess whether a changing N and S deposition regime affects bog porewater chemistry, we sampled bog porewater at sites at different distances from the oil sands industrial center from 2009 to 2012 (10-cm intervals to a depth of 1 m) and from 2009 to 2019 (top of the bog water table only). We hypothesized that: (1) as atmospheric N and S deposition increases with increasing proximity to the oil sands industrial center, surface porewater concentrations of NH4+, NO3−, DON, and SO42− would increase and (2) with increasing N and S deposition, elevated porewater concentrations of NH4+, NO3−, DON, and SO42− would be manifested increasingly deeper into the peat profile. We found weak evidence that oil sands N and S emissions affect bog porewater NH4+-N, NO3−-N, or DON concentrations. We found mixed evidence that increasing SO42− deposition results in increasing porewater SO42− concentrations. Current SO42− deposition, especially at bogs closest to the oil sands industrial center, likely exceeds the ability of the Sphagnum moss layer to retain S through net primary production, such that atmospherically deposited SO42− infiltrates downward into the peat column. Increasing porewater SO42− availability may stimulate dissimilatory sulfate reduction and/or inhibit CH4 production, potentially affecting carbon cycling and gaseous fluxes in these bogs.

How Joannites’ economy eradicated primeval forest and created anthroecosystems in medieval Central Europe

During European states’ development, various past societies utilized natural resources, but their impact was not uniformly spatially and temporally distributed. Considerable changes resulted in landscape fragmentation, especially during the Middle Ages. Changes in state advances that affected the local economy significantly drove trajectories of ecosystems’ development. The legacy of major changes from pristine forest to farming is visible in natural archives as novel ecosystems. Here, we present a high-resolution densely dated multi-proxy study covering the last 1500 years from a peatland located in CE Europe. The economic activity of medieval societies was highly modified by new rulers—the Joannites (the Order of St. John of Jerusalem, Knights Hospitaller). We studied the record of these directorial changes noted in the peat profile. Our research revealed a rapid critical land-use transition in the late Middle Ages and its consequences on the peatland ecosystem. The shift from the virgin forest with regular local fires to agriculture correlates well with the raising of local economy and deforestations. Along with the emerging openness, the wetland switched from alkaline wet fen state to acidic, drier Sphagnum-dominated peatland. Our data show how closely the ecological state of wetlands relates to forest microclimate. We identified a significant impact of the Joannites who used the novel farming organization. Our results revealed the surprisingly fast rate of how feudal economy eliminated pristine nature from the studied area and created novel anthroecosystems.

Impact of fire on vegetation, soil microbes and CH4 emission from a degraded tropical peatland

<p>Over the past few decades, tropical peatlands in Southeast Asia have been heavily degraded for multiple land uses, mainly by employing drainage and fire. More importantly, the extent of these degraded areas, primarily covered with ferns and sedges, have increased to almost 10% of the total peatland area in Southeast Asia. In particular, the role of sedges in plant-mediated gas transport to the atmosphere has been recognized as a significant CH<sub>4</sub> pathway in northern peatlands, however, in the Tropics this is still unknown. Within this context, we adopted an integrated approach using on-site measurements (CH<sub>4</sub>, porewater physicochemical characteristics) with genomics to investigate the role of hydrology, vegetation structure, and microbiome on CH<sub>4</sub> emission from fire-degraded tropical peatland in Brunei.</p><p>          We found for the first time that in degraded tropical peatlands of Southeast Asia, sedges transported 70-80% of the total CH<sub>4</sub> emission and significantly varied with values ranging from 1.22±0.13 to 6.15±0.57 mg CH<sub>4</sub> m<sup>-2</sup> hr<sup>-1</sup>, during dry and wet period, respectively. This variation was mainly attributed to water table position along with changes in sedge cover and porewater properties, which created more optimal methanogenesis conditions. Total emissions via this process might increase in the future as the extent of degraded tropical peatlands expands due to more frequent fire episodes and flooding.</p><p>          Further, we used 16S rRNA high-throughput sequencing to investigate the microbiomes in peat profile (above and below water table) as well as rhizo-compartments (Rhizosphere, Rhizoplane, Endosphere) of sedges. We found that the peat profile as well as rhizo-compartments of sedge harboured a higher number of methanogenic archaea in the order Methanomicrobiales and Methanobacteriales, compared to non-burnt and bulk soil, which further explains our findings of higher CH<sub>4</sub> emission from degraded tropical peatland areas covered with sedges. These insights into the impact of fire on hydrology, vegetation structure, and microbial community composition on CH<sub>4</sub> emissions provide an important basis for future studies on CH<sub>4</sub> dynamics in degraded tropical peatland areas.</p>

Microrefugia - limiting factors and unique synergy of environment

<p>Peatlands are a very important ecosystem which are characterized by distinctive vegetation, hydrology, and local climate. In the last decades, much effort was made a better understanding of microrefugia and their importance. Nevertheless, we still have little knowledge about the histories of the refugia. In the day of rapid climate change and increasing anthropogenic pressure, knowledge about the history of sites that represent a refugium of flora or fauna is a key aspect. The aim of this study is reconstructing the history of the glacial relict Betula nana in northern Poland located far from the southern range of its natural distribution. We suppose that the persistence of Betula nana is driven by a) the morphology and geology of the catchment, b) the maintenance of open vegetation on the peatland surface and c) exceptional microclimatic and hydrological conditions. Here, based on recent eco-hydrological monitoring and long-term palaeoecological proxy we try to be understated postglacial refugia of Betula nana from Central Europe (Linje mire). Detailed research was carried out on the peat profile using pollen analysis, to reconstruct the presence of open habitat on the mire during the Holocene. Pollen and macrofossils analysis revealed a continuous presence of Betula nana in the postglacial history of the peatland. Palaeoecological results show the variable situation of the Betula nana population in the peatland over the past 12 ka, indicating a strong relationship between paleohydrology and changes in the occurrence of this species. Our results of 12 years of local monitoring indicated that the mire is characterized by specific local climate and diverse water table depth. A synergy of local relief, microclimates, hydrology, and geology of the catchment affects the Betula nana population during the post-glacial history.</p>

Carbon storage change and δ13C transitions of peat columns in a partially forestry-drained boreal bog

Background and aims In forestry-drained peatlands, drying leads to changes in C cycling which could affect peat δ13C. Furthermore, the δ13C profile of the entire peat column may reveal effects of earlier climatic periods. Methods We measured peat δ13C and C inventories in adjacent peat profiles, two collected from undrained and two from the drained side of a bog that was partially ditch-drained 37 years earlier. The cores were sliced into 10-cm subsamples for analyses; matching of the profiles based on surface levelling, peat stratigraphic correlation and a horizontal ash layer found in both profiles. Results Surface subsidence of 30 cm was observed in the dried site and the uppermost 160 cm in the undrained site contained an excess of 5.9 kg m−2 of C compared with the corresponding strata of the ditch-drained site. The δ13C values increased but markedly only in the thin surface layer of the drained site, indicating low δ13C of the missing C (ca. –30‰). In the deeper strata, dating to Mid-Holocene, high dry bulk density, C%, N%, humification index and low C/N ratio were connected to low δ13C of peat. Conclusions Drainage of 37 years increased δ13C values in the upper peat profile of the drained bog and led to the selective loss of 13C depleted C. Results indicate that C balance studies can be aided by C isotope analyses. Low δ13C values in the peat profile indicate the existence of a wet fen stage during the moist and warm period during Mid-Holocene.