Carbon dioxide fluxes and vegetation structure in rewetted and pristine peatlands in Finland and Estonia

Vast areas of peatlands have been drained for forestry endangering their carbon sink function. Peatland rewetting aims at mitigating the situation through restoring the hydrology and vegetation of these areas. We compared the carbon dioxide (CO2) fluxes and phy-tomass on four pairs of rewetted and pristine peatland sites in Finland and Estonia, and described correlations between phytomass and CO2 fluxes. We measured the net ecosystem exchange of CO2 (NEE), respiration and photosynthesis over one growing season using manual chambers, and biomass of plant functional types (PFT) on rewetted sites and their pristine counterparts. Although pair-wise differences in the vegetation were small, pristine sites were on average stronger CO2 sinks than rewetted sites. Respiration was higher in hummocks while no differences were found in photosynthesis between hummocks and hollows. No clear relationship between the biomasses of PFTs and NEE was found. Generally, however, CO2 uptake decreased with increase in Sphagnum biomass. © 2019, Finnish Environment Institute. All rights reserved.Peer reviewe

Possibilities for Detailed Dating of Peat Bog Deposits

Geochemical and palynological data as well as radiocarbon dating were used to study the peat bog deposits in Niinsarre bog, northeast Estonia. The aim of this study was to establish criteria for determining a detailed chronology, which is important, for example, in studying paleoevents and historical monitoring. In some cases, we can use cumulative pollen data, as well as cumulative chemical and peat bulk density data.This material was digitized as part of a cooperative project between Radiocarbon and the University of Arizona Libraries.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Winter climate change increases physiological stress in calcareous fen bryophytes

Calcareous spring fens are among the rarest and most endangered wetland types worldwide. The majority of these ecosystems can be found at high latitudes, where they are affected by above average rates of climate change. Particularly winter temperatures are increasing, which results in decreased snow cover. As snow provides an insulating layer that protects ecosystems from subzero temperatures, its decrease is likely to induce stress to plants. To investigate the sensitivity of the bryophyte community – key to the functioning of calcareous spring fens – to changing climatic conditions, we studied the annual variation in ecophysiology of two dominant bryophytes: Campylium stellatum and Scorpidium scorpioides. Further, a snow removal experiment was used to simulate the effect of changing winter conditions. In both species, we observed lowest efficiency of photosystem II (Fv/Fm) in spring, indicating physiological stress, and highest chlorophyll-a, -b and carotenoid concentrations in autumn. Snow removal exacerbated physiological stress in bryophytes. Consequently Fv/Fm, pigment concentrations and chlorophyll to carotenoids ratios declined, while chlorophyll-a to -b ratios increased. Moreover, these effects of winter climate change cascaded to the growing season. C. stellatum, a low hummock inhabitor, suffered more from snow removal (annual mean decline in Fv/Fm 7.7% and 30.0% in chlorophyll-a) than S. scorpioides, a hollow species (declines 5.4% and 14.5%, respectively). Taken together, our results indicate that spring fen bryophytes are negatively impacted by winter climate change, as a result of longer frost periods and increased numbers of freeze-thaw cycles in combination with higher light intensity and dehydration.</p

Controls of Sphagnum growth and the role of winter

Abstract Sphagnum is the major genus in northern peatlands that contributes to peat formation and carbon sequestration. Sphagnum growth in summer has been fairly well studied but the information about growth in autumn and winter is limited. Therefore, we studied how the growth of Sphagnum is seasonally distributed with a particular interest on possible winter growth. The linear increment and biomass production of three Sphagum species was measured in three Northern European bogs over a year. In all sites, our results indicate the highest annual linear increment in S. angustifolium (28 mm), followed by S. magellanicum (20 mm) and S. fuscum (13 mm), but the biomass production was fairly even among the species (189, 192 and 215 g m−2, respectively). Both linear increment and biomass production depended mostly on meteorological parameters rather than ecophysiological or microsite properties. The seasonal measurements revealed a significant linear increment and biomass production during the winter that accounted for ca. 10% and ca. 5% from the annual values, respectively. Moreover, the mean daily rates of linear increment in autumn often exceeded the increment in summer. Our results thus indicate the ability for year-around growth of Sphagna if the conditions are favorable, including during boreal winter

Freeze-thaw cycles simultaneously decrease peatland photosynthetic carbon uptake and ecosystem respiration

Decreasing snow cover in winter resulting from climate warming increases the incidence of freeze-thaw cycles (FTCs) in many ecosystems, including peatlands. As peatland ecosystems form a globally significant long-term carbon storage, understanding the effects of changing conditions in winter on carbon dynamics is essential. We studied how FTCs affect peatland carbon cycling by conducting mesocosm experiments with Sphagnum. Our results indicate an overall impeding effect of FTCs on Sphagnum photosynthesis, chlorophyll content, ecosystem respiration and enzymatic processes. A threefold reduction in photosynthesis in the FTC treatment was related to a decrease in chlorophyll content, showing that Sphagnum physiologically suffers from repeated FTCs. In the FTC treatment beta-glucosidase and phosphatase enzymatic activities decreased by 50% and 30%, respectively, whilst alanine remained unaffected, indicating that in peat soils short-term FTCs affect the carbon and phosphorus cycles, but not the nitrogen cycle. Long-term effects of FTCs deserve further studies.Peer reviewe

Freeze-thaw cycles simultaneously decrease peatland photosynthetic carbon uptake and ecosystem respiration

Decreasing snow cover in winter resulting from climate warming increases the incidence of freeze–thaw cycles (FTCs) in many ecosystems, including peatlands. As peatland ecosystems form a globally significant long-term carbon storage, understanding the effects of changing conditions in winter on carbon dynamics is essential. We studied how FTCs affect peatland carbon cycling by conducting mesocosm experiments with Sphagnum. Our results indicate an overall impeding effect of FTCs on Sphagnum photosynthesis, chlorophyll content, ecosystem respiration and enzymatic processes. A threefold reduction in photosynthesis in the FTC treatment was related to a decrease in chlorophyll content, showing that Sphagnum physiologically suffers from repeated FTCs. In the FTC treatment β-glucosidase and phosphatase enzymatic activities decreased by 50% and 30%, respectively, whilst alanine remained unaffected, indicating that in peat soils short-term FTCs affect the carbon and phosphorus cycles, but not the nitrogen cycle. Long-term effects of FTCs deserve further studies.</p