TY - JOUR A1 - Selle, Benny A1 - Knorr, Klaus-Holger A1 - Lischeid, Gunnar T1 - Mobilisation and transport of dissolved organic carbon and iron in peat catchments-Insights from the Lehstenbach stream in Germany using generalised additive models JF - Hydrological processes N2 - During the last decades, increasing exports of both dissolved organic carbon (DOC) and iron were observed from peat catchments in North America and Europe with potential consequences for water quality of streamwater and carbon storages of soils. As mobilisation and transport processes of DOC and iron in peat catchments are only partly understood, the purpose of this study was to elucidate these processes in an intensively monitored and studied system. Specifically, it was hypothesised that dissimilatory iron reduction in riparian peatland soils mobilises DOC initially adsorbed to iron minerals. During stormflow conditions, both DOC and iron will be transported into the stream network. Ferrous iron may be reoxidised at redox interfaces on its way to the stream, and subsequently, ferric iron could be transported together with DOC as complexes. To test these hypotheses, generalised additive models (GAMs) were applied to 14 years of weekly time series of discharge and concentrations of selected solutes measured in a German headwater stream called Lehstenbach. This stream drains a 4.19-km(2) forested mountain catchment; one third of which is covered by riparian peatland soils. We interpreted results of different types of GAM in the way that (a) iron reduction drove the mobilisation of DOC from peatland soils and that (b) both iron and DOC were transported as complexes after their joint mobilisation to and within the steam. It was speculated that low nitrate availability in the uppermost wetland soil layer, particularly during the growing season, promoted iron reduction and thus the mobilisation of DOC. However, the influence of nitrate on the DOC mobilisation remains relatively uncertain. This influence could be further investigated using methods similar to the GAM analysis conducted here for other catchments with long-term data as well as detailed measurements of the relevant species in riparian wetland soils and the adjacent stream network. KW - dissolved organic carbon (DOC) KW - generalised additive models (GAMs) KW - headwater catchments KW - iron KW - peatlands KW - time series analysis Y1 - 2019 U6 - https://doi.org/10.1002/hyp.13552 SN - 0885-6087 SN - 1099-1085 VL - 33 IS - 25 SP - 3213 EP - 3225 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Treat, Claire C. A1 - Kleinen, Thomas A1 - Broothaerts, Nils A1 - Dalton, April S. A1 - Dommain, Rene A1 - Douglas, Thomas A. A1 - Drexler, Judith Z. A1 - Finkelstein, Sarah A. A1 - Grosse, Guido A1 - Hope, Geoffrey A1 - Hutchings, Jack A1 - Jones, Miriam C. A1 - Kuhry, Peter A1 - Lacourse, Terri A1 - Lahteenoja, Outi A1 - Loisel, Julie A1 - Notebaert, Bastiaan A1 - Payne, Richard J. A1 - Peteet, Dorothy M. A1 - Sannel, A. Britta K. A1 - Stelling, Jonathan M. A1 - Strauss, Jens A1 - Swindles, Graeme T. A1 - Talbot, Julie A1 - Tarnocai, Charles A1 - Verstraeten, Gert A1 - Williams, Christopher J. A1 - Xia, Zhengyu A1 - Yu, Zicheng A1 - Valiranta, Minna A1 - Hattestrand, Martina A1 - Alexanderson, Helena A1 - Brovkin, Victor T1 - Widespread global peatland establishment and persistence over the last 130,000 y JF - Proceedings of the National Academy of Sciences of the United States of America N2 - Glacial-interglacial variations in CO2 and methane in polar ice cores have been attributed, in part, to changes in global wetland extent, but the wetland distribution before the Last Glacial Maximum (LGM, 21 ka to 18 ka) remains virtually unknown. We present a study of global peatland extent and carbon (C) stocks through the last glacial cycle (130 ka to present) using a newly compiled database of 1,063 detailed stratigraphic records of peat deposits buried by mineral sediments, as well as a global peatland model. Quantitative agreement between modeling and observations shows extensive peat accumulation before the LGM in northern latitudes (> 40 degrees N), particularly during warmer periods including the last interglacial (130 ka to 116 ka, MIS 5e) and the interstadial (57 ka to 29 ka, MIS 3). During cooling periods of glacial advance and permafrost formation, the burial of northern peatlands by glaciers and mineral sediments decreased active peatland extent, thickness, and modeled C stocks by 70 to 90% from warmer times. Tropical peatland extent and C stocks show little temporal variation throughout the study period. While the increased burial of northern peats was correlated with cooling periods, the burial of tropical peat was predominately driven by changes in sea level and regional hydrology. Peat burial by mineral sediments represents a mechanism for long-term terrestrial C storage in the Earth system. These results show that northern peatlands accumulate significant C stocks during warmer times, indicating their potential for C sequestration during the warming Anthropocene. KW - peatlands KW - carbon KW - methane KW - carbon burial KW - Quaternary Y1 - 2019 U6 - https://doi.org/10.1073/pnas.1813305116 SN - 0027-8424 VL - 116 IS - 11 SP - 4822 EP - 4827 PB - National Acad. of Sciences CY - Washington ER - TY - JOUR A1 - Marcisz, Katarzyna A1 - Jassey, Vincent E. J. A1 - Kosakyan, Anush A1 - Krashevska, Valentyna A1 - Lahr, Daniel J. G. A1 - Lara, Enrique A1 - Lamentowicz, Lukasz A1 - Lamentowicz, Mariusz A1 - Macumber, Andrew A1 - Mazei, Yuri A1 - Mitchell, Edward A. D. A1 - Nasser, Nawaf A. A1 - Patterson, R. Timothy A1 - Roe, Helen M. A1 - Singer, David A1 - Tsyganov, Andrey N. A1 - Fournier, Bertrand T1 - Testate amoeba functional traits and their use in paleoecology JF - Frontiers in Ecology and Evolution N2 - This review provides a synthesis of current knowledge on the morphological and functional traits of testate amoebae, a polyphyletic group of protists commonly used as proxies of past hydrological changes in paleoecological investigations from peatland, lake sediment and soil archives. A trait-based approach to understanding testate amoebae ecology and paleoecology has gained in popularity in recent years, with research showing that morphological characteristics provide complementary information to the commonly used environmental inferences based on testate amoeba (morpho-)species data. We provide a broad overview of testate amoeba morphological and functional traits and trait-environment relationships in the context of ecology, evolution, genetics, biogeography, and paleoecology. As examples we report upon previous ecological and paleoecological studies that used trait-based approaches, and describe key testate amoebae traits that can be used to improve the interpretation of environmental studies. We also highlight knowledge gaps and speculate on potential future directions for the application of trait-based approaches in testate amoeba research. KW - protists KW - functional traits KW - morphological traits KW - ecology KW - peatlands KW - lakes KW - soils KW - trait-based approaches Y1 - 2020 U6 - https://doi.org/10.3389/fevo.2020.575966 SN - 2296-701X VL - 8 PB - Frontiers Media CY - Lausanne ER -