Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Rapid Vegetation Succession and Coupled Permafrost Dynamics in Arctic Thaw Ponds in the Siberian Lowland Tundra
    Magnússon, Rúna ; Limpens, J. ; Huissteden, Jacobus van; Kleijn, D. ; Maximov, Trofim C. ; Rotbarth, Ronny ; Sass-Klaassen, U.G.W. ; Heijmans, M.M.P.D. - \ 2020
    Journal of Geophysical Research: Biogeosciences 125 (2020)7. - ISSN 2169-8953
    Thermokarst features, such as thaw ponds, are hotspots for methane emissions in warming lowland tundra. Presently we lack quantitative knowledge on the formation rates of thaw ponds and subsequent vegetation succession, necessary to determine their net contribution to greenhouse gas emissions. This study sets out to identify development trajectories and formation rates of small‐scale (<100 m2), shallow arctic thaw ponds in north‐eastern Siberia. We selected 40 ponds of different age classes based on a time‐series of satellite images and measured vegetation composition, microtopography, water table, and thaw depth in the field and measured age of colonizing shrubs in thaw ponds using dendrochronology. We found that young ponds are characterized by dead shrubs, while older ponds show rapid terrestrialization through colonization by sedges and Sphagnum moss. While dead shrubs and open water are associated with permafrost degradation (lower surface elevation, larger thaw depth), sites with sedge and in particular Sphagnum display indications of permafrost recovery. Recruitment of Betula nana on Sphagnum carpets in ponds indicates a potential recovery toward shrub‐dominated vegetation, although it remains unclear if and on what timescale this occurs. Our results suggest that thaw ponds display potentially cyclic vegetation succession associated with permafrost degradation and recovery. Pond formation and initial colonization by sedges can occur on subdecadal timescales, suggesting rapid degradation and initial recovery of permafrost. The rates of formation and recovery of small‐scale, shallow thaw ponds have implications for the greening/browning dynamics and carbon balance of this ecosystem.
    Global plant trait relationships extend to the climatic extremes of the tundra biome
    Thomas, H.J.D. ; Bjorkman, A.D. ; Myers-Smith, I.H. ; Elmendorf, S.C. ; Kattge, J. ; Diaz, S. ; Vellend, M. ; Blok, D. ; Cornelissen, J.H.C. ; Forbes, B.C. ; Henry, G.H.R. ; Hollister, R.D. ; Normand, S. ; Prevéy, J.S. ; Rixen, C. ; Schaepman-Strub, G. ; Wilmking, M. ; Wipf, S. ; Cornwell, W.K. ; Beck, P.S.A. ; Georges, D. ; Goetz, S.J. ; Guay, K.C. ; Rüger, N. ; Soudzilovskaia, N.A. ; Spasojevic, M.J. ; Alatalo, J.M. ; Alexander, H.D. ; Anadon-Rosell, A. ; Angers-Blondin, S. ; Beest, M. te; Berner, L.T. ; Björk, R.G. ; Buchwal, A. ; Buras, A. ; Carbognani, M. ; Christie, K.S. ; Collier, L.S. ; Cooper, E.J. ; Elberling, B. ; Eskelinen, A. ; Frei, E.R. ; Grau, O. ; Grogan, P. ; Hallinger, M. ; Heijmans, M.M.P.D. ; Hermanutz, L. ; Hudson, J.M.G. ; Johnstone, J.F. ; Hülber, K. ; Iturrate-Garcia, M. ; Iversen, C.M. ; Jaroszynska, F. ; Kaarlejarvi, E. ; Kulonen, A. ; Lamarque, L.J. ; Lantz, T.C. ; Lévesque, E. ; Little, C.J. ; Michelsen, A. ; Milbau, A. ; Nabe-Nielsen, J. ; Nielsen, S.S. ; Ninot, J.M. ; Oberbauer, S.F. ; Olofsson, J. ; Onipchenko, V.G. ; Petraglia, A. ; Rumpf, S.B. ; Shetti, R. ; Speed, J.D.M. ; Suding, K.N. ; Tape, K.D. ; Tomaselli, M. ; Trant, A.J. ; Treier, U.A. ; Tremblay, M. ; Venn, S.E. ; Vowles, T. ; Weijers, S. ; Wookey, P.A. ; Zamin, T.J. ; Bahn, M. ; Blonder, B. ; Bodegom, P.M. van; Bond-Lamberty, B. ; Campetella, G. ; Cerabolini, B.E.L. ; Chapin, F.S. ; Craine, J.M. ; Dainese, M. ; Green, W.A. ; Jansen, S. ; Kleyer, M. ; Manning, P. ; Niinemets, ; Onoda, Y. ; Ozinga, W.A. ; Peñuelas, J. ; Poschlod, P. ; Reich, P.B. ; Sandel, B. ; Schamp, B.S. ; Sheremetiev, S.N. ; Vries, F.T. de - \ 2020
    Nature Communications 11 (2020)1. - ISSN 2041-1723

    The majority of variation in six traits critical to the growth, survival and reproduction of plant species is thought to be organised along just two dimensions, corresponding to strategies of plant size and resource acquisition. However, it is unknown whether global plant trait relationships extend to climatic extremes, and if these interspecific relationships are confounded by trait variation within species. We test whether trait relationships extend to the cold extremes of life on Earth using the largest database of tundra plant traits yet compiled. We show that tundra plants demonstrate remarkably similar resource economic traits, but not size traits, compared to global distributions, and exhibit the same two dimensions of trait variation. Three quarters of trait variation occurs among species, mirroring global estimates of interspecific trait variation. Plant trait relationships are thus generalizable to the edge of global trait-space, informing prediction of plant community change in a warming world.

    Reply to ‘Early-life exposure to the Chinese Famine and subsequent T2DM’
    Li, Chihua ; Tobi, Elmar W. ; Heijmans, Bastiaan T. ; Lumey, L.H. - \ 2020
    Nature Reviews Endocrinology 16 (2020). - ISSN 1759-5029 - p. 125 - 126.
    Impact of broiler breeder nutrition, body composition and weight on chick quality
    Heijmans, J. ; Duijster, M. ; Kwakkel, R.P. ; Brand, H. van den - \ 2019
    In: Proceedings of the 22nd European Symposium on Poultry Nutrition. - World's Poultry Science Association (WPSA) - ISBN 9788394276065 - p. 265 - 265.
    Reply to ‘Chinese famine and the diabetes mellitus epidemic’
    Li, Chihua ; Tobi, Elmar W. ; Heijmans, Bastiaan T. ; Lumey, L.H. - \ 2019
    Nature Reviews Endocrinology (2019). - ISSN 1759-5029
    The permafrost is thawing. But how fast?
    Heijmans, M.M.P.D. - \ 2019
    The power to define resilience in social–hydrological systems: Toward a power‐sensitive resilience framework
    Dewulf, Art ; Karpouzoglou, Timos ; Warner, Jeroen ; Wesselink, Anna ; Mao, Feng ; Vos, Jeroen ; Tamas, Peter ; Groot, Annemarie E. ; Heijmans, Annelies ; Ahmed, Farhana ; Hoang, Long ; Vij, Sumit ; Buytaert, Wouter - \ 2019
    Wiley Interdisciplinary Reviews: Water 6 (2019)6. - ISSN 2049-1948
    Since the early work on defining and analyzing resilience in domains such as engineering, ecology and psychology, the concept has gained significant traction in many fields of research and practice. It has also become a very powerful justification for various policy goals in the water sector, evident in terms like flood resilience, river resilience, and water resilience. At the same time, a substantial body of literature has developed that questions the resilience concept's systems ontology, natural science roots and alleged conservatism, and criticizes resilience thinking for not addressing power issues. In this study, we review these critiques with the aim to develop a framework for power‐sensitive resilience analysis. We build on the three faces of power to conceptualize the power to define resilience. We structure our discussion of the relevant literature into five questions that need to be reflected upon when applying the resilience concept to social–hydrological systems. These questions address: (a) resilience of what, (b) resilience at what scale, (c) resilience to what, (d) resilience for what purpose, and (e) resilience for whom; and the implications of the political choices involved in defining these parameters for resilience building or analysis. Explicitly considering these questions enables making political choices explicit in order to support negotiation or contestation on how resilience is defined and used.
    The effect of the Chinese Famine on type 2 diabetes mellitus epidemics
    Li, Chihua ; Tobi, Elmar W. ; Heijmans, Bastiaan T. ; Lumey, L.H. - \ 2019
    Nature Reviews Endocrinology 15 (2019). - ISSN 1759-5029 - p. 313 - 314.

    The Chinese Famine has been widely interpreted as an important contributor to subsequent epidemics of type 2 diabetes mellitus. Our re-examination of available studies challenges this apparent relationship. The definition of famine exposure and control selection needs more attention in future studies to better understand this potential association.

    Tundra Trait Team : A database of plant traits spanning the tundra biome
    Bjorkman, Anne D. ; Myers-Smith, Isla H. ; Elmendorf, Sarah C. ; Normand, Signe ; Thomas, Haydn J.D. ; Alatalo, Juha M. ; Alexander, Heather ; Anadon-Rosell, Alba ; Angers-Blondin, Sandra ; Bai, Yang ; Baruah, Gaurav ; Beest, Mariska te; Berner, Logan ; Björk, Robert G. ; Blok, Daan ; Bruelheide, Helge ; Buchwal, Agata ; Buras, Allan ; Carbognani, Michele ; Christie, Katherine ; Collier, Laura S. ; Cooper, Elisabeth J. ; Cornelissen, J.H.C. ; Dickinson, Katharine J.M. ; Dullinger, Stefan ; Elberling, Bo ; Eskelinen, Anu ; Forbes, Bruce C. ; Frei, Esther R. ; Iturrate-Garcia, Maitane ; Good, Megan K. ; Grau, Oriol ; Green, Peter ; Greve, Michelle ; Grogan, Paul ; Haider, Sylvia ; Hájek, Tomáš ; Hallinger, Martin ; Happonen, Konsta ; Harper, Karen A. ; Heijmans, Monique M.P.D. ; Henry, Gregory H.R. ; Hermanutz, Luise ; Hewitt, Rebecca E. ; Hollister, Robert D. ; Hudson, James ; Hülber, Karl ; Iversen, Colleen M. ; Jaroszynska, Francesca ; Jiménez-Alfaro, Borja - \ 2018
    Global Ecology and Biogeography 27 (2018)12. - ISSN 1466-822X - p. 1402 - 1411.
    alpine - Arctic - plant functional traits - tundra

    Motivation: The Tundra Trait Team (TTT) database includes field-based measurements of key traits related to plant form and function at multiple sites across the tundra biome. This dataset can be used to address theoretical questions about plant strategy and trade-offs, trait–environment relationships and environmental filtering, and trait variation across spatial scales, to validate satellite data, and to inform Earth system model parameters. Main types of variable contained: The database contains 91,970 measurements of 18 plant traits. The most frequently measured traits (> 1,000 observations each) include plant height, leaf area, specific leaf area, leaf fresh and dry mass, leaf dry matter content, leaf nitrogen, carbon and phosphorus content, leaf C:N and N:P, seed mass, and stem specific density. Spatial location and grain: Measurements were collected in tundra habitats in both the Northern and Southern Hemispheres, including Arctic sites in Alaska, Canada, Greenland, Fennoscandia and Siberia, alpine sites in the European Alps, Colorado Rockies, Caucasus, Ural Mountains, Pyrenees, Australian Alps, and Central Otago Mountains (New Zealand), and sub-Antarctic Marion Island. More than 99% of observations are georeferenced. Time period and grain: All data were collected between 1964 and 2018. A small number of sites have repeated trait measurements at two or more time periods. Major taxa and level of measurement: Trait measurements were made on 978 terrestrial vascular plant species growing in tundra habitats. Most observations are on individuals (86%), while the remainder represent plot or site means or maximums per species. Software format: csv file and GitHub repository with data cleaning scripts in R; contribution to TRY plant trait database (www.try-db.org) to be included in the next version release.

    Power-sensitive resilience in flood-prone deltas
    Dewulf, A.R.P.J. ; Karpouzoglou, T.D. ; Warner, J.F. ; Hoang, P.L. ; Binh Nguyen Thanh, ; Tri, Van Pham Dang ; Ahmed, Farhana ; Wesselink, Anna ; Vos, J.M.C. ; Mao, Feng ; Buytaert, Wouter ; Tamas, P.A. ; Vij, S. ; Groot, A.M.E. ; Heijmans, E.P.M. - \ 2018
    Selective Survival of Embryos Can Explain DNA Methylation Signatures of Adverse Prenatal Environments
    Tobi, Elmar W. ; Heuvel, Joost van den; Zwaan, Bas J. ; Lumey, L.H. ; Heijmans, Bastiaan T. ; Uller, Tobias - \ 2018
    Cell Reports 25 (2018)10. - ISSN 2211-1247 - p. 2660 - 2667.e4.
    developmental origins - DNA methylation - plasticity - selection

    An adverse intrauterine environment is associated with long-term physiological changes in offspring. These are believed to be mediated by epigenomic marks, including DNA methylation (DNAm). Changes in DNAm are often interpreted as damage or plastic responses of the embryo. Here, we propose that stochastic DNAm variation, generated during remodeling of the epigenome after fertilization, contributes to DNAm signatures of prenatal adversity through differential survival of embryos. Using a mathematical model of re-methylation in the early embryo, we demonstrate that selection, but not plasticity, will generate a characteristic reduction in DNAm variance at loci that contribute to survival. Such a reduction in DNAm variance was apparent in a human cohort prenatally exposed to the Dutch famine, illustrating that it is possible to detect a signature of selection on epigenomic variation. Selection should be considered as a possible mechanism linking prenatal adversity to subsequent health and may have implications when evaluating interventions.

    Plant functional trait change across a warming tundra biome
    Bjorkman, Anne D. ; Myers-Smith, Isla H. ; Elmendorf, Sarah C. ; Normand, Signe ; Rüger, Nadja ; Beck, Pieter S.A. ; Blach-Overgaard, Anne ; Blok, Daan ; Cornelissen, J.H.C. ; Forbes, Bruce C. ; Georges, Damien ; Goetz, Scott J. ; Guay, Kevin C. ; Henry, Gregory H.R. ; Hillerislambers, Janneke ; Hollister, Robert D. ; Karger, Dirk N. ; Kattge, Jens ; Manning, Peter ; Prevéy, Janet S. ; Rixen, Christian ; Schaepman-Strub, Gabriela ; Thomas, Haydn J.D. ; Vellend, Mark ; Wilmking, Martin ; Wipf, Sonja ; Carbognani, Michele ; Hermanutz, Luise ; Lévesque, Esther ; Molau, Ulf ; Petraglia, Alessandro ; Soudzilovskaia, Nadejda A. ; Spasojevic, Marko J. ; Tomaselli, Marcello ; Vowles, Tage ; Alatalo, Juha M. ; Alexander, Heather D. ; Anadon-Rosell, Alba ; Angers-Blondin, Sandra ; Beest, Mariska te; Berner, Logan ; Björk, Robert G. ; Buchwal, Agata ; Buras, Allan ; Christie, Katherine ; Heijmans, Monique M.P.D. ; Ozinga, Wim A. - \ 2018
    Nature 526 (2018). - ISSN 0028-0836 - p. 57 - 62.
    The tundra is warming more rapidly than any other biome on Earth, and the potential ramifications are far-reaching because of global feedback effects between vegetation and climate. A better understanding of how environmental factors shape plant structure and function is crucial for predicting the consequences of environmental change for ecosystem functioning. Here we explore the biome-wide relationships between temperature, moisture and seven key plant functional traits both across space and over three decades of warming at 117 tundra locations. Spatial temperature–trait relationships were generally strong but soil moisture had a marked influence on the strength and direction of these relationships, highlighting the potentially important influence of changes in water availability on future trait shifts in tundra plant communities. Community height increased with warming across all sites over the past three decades, but other traits lagged far behind predicted rates of change. Our findings highlight the challenge of using space-for-time substitution to predict the functional consequences of future warming and suggest that functions that are tied closely to plant height will experience the most rapid change. They also reveal the strength with which environmental factors shape biotic communities at the coldest extremes of the planet and will help to improve projections of functional changes in tundra ecosystems with climate warming.
    Stedenbouwers van de toekomst
    Heijmans, Erik - \ 2018
    Publisher Correction to : Background invertebrate herbivory on dwarf birch (Betula glandulosa-nana complex) increases with temperature and precipitation across the tundra biome
    Barrio, Isabel C. ; Lindén, Elin ; Beest, Mariska Te; Olofsson, Johan ; Rocha, Adrian ; Soininen, Eeva M. ; Alatalo, Juha M. ; Andersson, Tommi ; Asmus, Ashley ; Boike, Julia ; Bråthen, Kari Anne ; Bryant, John P. ; Buchwal, Agata ; Bueno, C.G. ; Christie, Katherine S. ; Egelkraut, Dagmar ; Ehrich, Dorothee ; Fishback, Lee Ann ; Forbes, Bruce C. ; Gartzia, Maite ; Grogan, Paul ; Hallinger, Martin ; Heijmans, Monique M.P.D. ; Hik, David S. ; Hofgaard, Annika ; Holmgren, Milena ; Høye, Toke T. ; Huebner, Diane C. ; Jónsdóttir, Ingibjörg Svala ; Kaarlejärvi, Elina ; Kumpula, Timo ; Lange, Cynthia Y.M.J.G. ; Lange, Jelena ; Lévesque, Esther ; Limpens, Juul ; Macias-Fauria, Marc ; Myers-Smith, Isla ; Nieukerken, Erik J. van; Normand, Signe ; Post, Eric S. ; Schmidt, Niels Martin ; Sitters, Judith ; Skoracka, Anna ; Sokolov, Alexander ; Sokolova, Natalya ; Speed, James D.M. ; Street, Lorna E. ; Sundqvist, Maja K. ; Suominen, Otso ; Tananaev, Nikita ; Tremblay, Jean Pierre ; Urbanowicz, Christine ; Uvarov, Sergey A. ; Watts, David ; Wilmking, Martin ; Wookey, Philip A. ; Zimmermann, Heike H. ; Zverev, Vitali ; Kozlov, Mikhail V. - \ 2018
    Polar Biology 41 (2018)8. - ISSN 0722-4060 - p. 1653 - 1654.
    The above mentioned article was originally scheduled for publication in the special issue on Ecology of Tundra Arthropods with guest editors Toke T. Høye . Lauren E. Culler. Erroneously, the article was published in Polar Biology, Volume 40, Issue 11, November, 2017. The publisher sincerely apologizes to the guest editors and the authors for the inconvenience caused.
    Green Up The City! - Do urban greening initiatives lead to green gentrification in the Netherlands?
    Bree, J. de; Heijmans, M. ; Michailidi, E. ; Negru, R.M. ; Pelgrim, I. ; Smith, A. ; Jacobs, J. ; Haas, W. de; Wentink, C.Q. - \ 2018
    DNA methylation as a mediator of the association between prenatal adversity and risk factors for metabolic disease in adulthood
    Tobi, Elmar W. ; Slieker, Roderick C. ; Luijk, René ; Dekkers, Koen F. ; Stein, Aryeh D. ; Xu, Kate M. ; Slagboom, P.E. ; Zwet, Erik W. Van; Lumey, L.H. ; Heijmans, Bastiaan T. ; T'Hoen, Peter A. ; Pool, René ; Greevenbroek, Marleen M. Van; Stehouwer, Coen D. ; Kallen, Carla J. Van Der; Schalkwijk, Casper G. ; Wijmenga, Cisca ; Zhernakova, Sasha ; Tigchelaar, Ettje F. ; Beekman, Marian ; Deelen, Joris ; Heemst, Diana Van; Veldink, Jan H. ; Berg, Leonard H. Van Den; Duijn, Cornelia M. Van; Hofman, Albert ; Uitterlinden, André G. ; Jhamai, P.M. ; Verbiest, Michael ; Verkerk, Marijn ; Breggen, Ruud Van Der; Rooij, Jeroen Van; Lakenberg, Nico ; Mei, Hailiang ; Bot, Jan ; Zhernakova, Dasha V. ; Hof, Peter Van 't; Deelen, Patrick ; Nooren, Irene ; Moed, Matthijs ; Vermaat, Martijn ; Jan Bonder, Marc ; Dijk, Freerk Van; Arindrarto, Wibowo ; Kielbasa, Szymon M. ; Swertz, Morris A. ; Isaacs, Aaron ; Franke, Lude - \ 2018
    Science Advances 4 (2018)1. - ISSN 2375-2548
    Although it is assumed that epigenetic mechanisms, such as changes in DNA methylation (DNAm), underlie the relationship between adverse intrauterine conditions and adult metabolic health, evidence from human studies remains scarce. Therefore, we evaluated whether DNAm in whole blood mediated the association between prenatal famine exposure and metabolic health in 422 individuals exposed to famine in utero and 463 (sibling) controls. We implemented a two-step analysis, namely, a genome-wide exploration across 342, 596 cytosine-phosphate-guanine dinucleotides (CpGs) for potential mediators of the association between prenatal famine exposure and adult body mass index (BMI), serum triglycerides (TG), or glucose concentrations, which was followed by formalmediation analysis.DNAm mediated the association of prenatal famine exposure with adult BMI and TG but not with glucose. DNAm at PIM3 (cg09349128), a gene involved in energy metabolism, mediated 13.4% [95% confidence interval (CI), 5 to 28%] of the association between famine exposure and BMI. DNAm at six CpGs, including TXNIP (cg19693031), influencing b cell function, and ABCG1 (cg07397296), affecting lipid metabolism, together mediated 80% (95% CI, 38.5 to 100%) of the association between famine exposure and TG. Analyses restricted to those exposed to famine during early gestation identified additional CpGs mediating the relationship with TG near PFKFB3 (glycolysis) and METTL8 (adipogenesis). DNAm at the CpGs involved was associated with gene expression in an external data set and correlated with DNAm levels in fat depots in additional postmortem data. Our data are consistent with the hypothesis that epigenetic mechanisms mediate the influence of transient adverse environmental factors in early life on long-termmetabolic health. The specific mechanism awaits elucidation.
    Depth-based differentiation in nitrogen uptake between graminoids and shrubs in an Arctic tundra plant community
    Wang, Peng ; Limpens, Juul ; Nauta, Ake ; Huissteden, Corine van; Rijssel, Sophie Quirina van; Mommer, Liesje ; Kroon, Hans de; Maximov, Trofim C. ; Heijmans, Monique M.P.D. - \ 2018
    Journal of Vegetation Science 29 (2018)1. - ISSN 1100-9233 - p. 34 - 41.
    N - Arctic tundra - Dwarf shrubs - Graminoids - Niche differentiation - Nutrient uptake - Plant functional types - Rooting depth - Soil depth
    Questions: The rapid climate warming in tundra ecosystems can increase nutrient availability in the soil, which may initiate shifts in vegetation composition. The direction in which the vegetation shifts will co-determine whether Arctic warming is mitigated or accelerated, making the understanding of successional trajectories urgent. One of the key factors influencing the competitive relationships between plant species is their access to nutrients, depending on the depth where they take up most nutrients. However, nutrient uptake at different soil depths by tundra plant species that differ in rooting depth is unclear. Location: Kytalyk Nature Reserve, northeast Siberia, Russia. Methods: We injected 15N to 5 cm, 15 cm and the thaw front of the soil in a moist tussock tundra. The absorption of 15N by grasses, sedges, deciduous shrubs and evergreen shrubs from the three depths was compared. Results: The results clearly show a vertical differentiation of N uptake by these plant functional types, corresponding to their rooting strategy. Shallow-rooting dwarf shrubs were more capable of absorbing nutrients from the upper soil than from deeper soil. Deep-rooting grasses and sedges were more capable of absorbing nutrients from deeper soil than the dwarf shrubs. The natural 15N abundances in control plants also indicate that graminoids can absorb more nutrients from the deeper soil than dwarf shrubs. Conclusions: Our results show that graminoids and shrubs in the Arctic differ in their N uptake strategies, with graminoids profiting from nutrients released at the thaw front, while shrubs mainly forage in upper soil layers. Our results suggest that tundra vegetation will become graminoid-dominated as permafrost thaw progresses and nutrient availability increases in the deep soil.
    Short-term root and leaf decomposition of two dominant plant species in a Siberian tundra
    Wang, Peng ; Ruijven, Jasper van; Heijmans, Monique M.P.D. ; Berendse, Frank ; Maksimov, Ayal ; Maximov, Trofim C. ; Mommer, Liesje - \ 2017
    Pedobiologia 65 (2017). - ISSN 0031-4056 - p. 68 - 76.
    Arctic tundra - Betula nana - Eriophorum vaginatum - Home-field advantage - Leaf litter - Root litter

    In tundra ecosystems, global warming is expected to accelerate litter decomposition and to lead to shifts in vegetation composition. To understand these shifts, it is important to understand the interactions between global warming, vegetation composition, litter quality and decomposition in the tundra. In addition, it is important to consider root litter since roots are the major part of plant biomass in the tundra. In order to increase our understanding of decomposition, and root decomposition in particular, we performed a litter transplant experiment in northeastern Siberia, in which we measured mass loss for leaf and root litter (live and dead material) of the two dominant plant species, graminoid Eriophorum vaginatum and shrub Betula nana, in three vegetation types (E. vaginatum or B. nana dominated and mixed vegetation) during the growing season.Our results show that although leaf decomposition did not differ between the two species, root decomposition showed significant differences. Mass loss of live roots was higher for E. vaginatum than for B. nana, but mass loss of E. vaginatum dead roots was lowest. In addition, we found evidence for home-field advantage in litter decomposition: litter of a plant decomposed faster in vegetation where it was dominant. Mass loss rates of the litter types were significantly correlated with phosphorus content, rather than nitrogen content. This indicates that phosphorus limits decomposition in this tundra site.The low decomposition rate of B. nana live roots compared to E. vaginatum live roots suggests that the acceleration of decomposition in the Arctic may be partly counteracted by the expected expansion of shrubs. However, more information on litter input rates and direct effects of climate change on decomposition rates are needed to accurately predict the effects of climate change on carbon dynamics in tundra ecosystems.

    Thaw pond development and initial vegetation succession in experimental plots at a Siberian lowland tundra site
    Li, Bingxi ; Heijmans, Monique M.P.D. ; Blok, Daan ; Wang, Peng ; Karsanaev, Sergey V. ; Maximov, Trofim C. ; Huissteden, Jacobus van; Berendse, Frank - \ 2017
    Plant and Soil 420 (2017)1-2. - ISSN 0032-079X - p. 147 - 162.
    Arctic tundra - Betula nana - Permafrost degradation - Thermokarst - Vegetation dynamics

    Background and aims: Permafrost degradation has the potential to change the Arctic tundra landscape. We observed rapid local thawing of ice-rich permafrost resulting in thaw pond formation, which was triggered by removal of the shrub cover in a field experiment. This study aimed to examine the rate of permafrost thaw and the initial vegetation succession after the permafrost collapse. Methods: In the experiment, we measured changes in soil thaw depth, plant species cover and soil subsidence over nine years (2007–2015). Results: After abrupt initial thaw, soil subsidence in the removal plots continued indicating further thawing of permafrost albeit at a much slower pace: 1 cm y−1 over 2012–2015 vs. 5 cm y−1 over 2007–2012. Grass cover strongly increased after the initial shrub removal, but later declined with ponding of water in the subsiding removal plots. Sedges established and expanded in the wetter removal plots. Thereby, the removal plots have become increasingly similar to nearby ‘natural’ thaw ponds. Conclusions: The nine years of field observations in a unique shrub removal experiment at a Siberian tundra site document possible trajectories of small-scale permafrost collapse and the initial stage of vegetation recovery, which is essential knowledge for assessing future tundra landscape changes.

    Tea and coffee consumption in relation to DNA methylation in four European cohorts
    Ek, Weronica E. ; Tobi, Elmar W. ; Ahsan, Muhammad ; Lampa, Erik ; Ponzi, Erica ; Kyrtopoulos, Soterios A. ; Georgiadis, Panagiotis ; Lumey, L.H. ; Heijmans, Bastiaan T. ; Botsivali, Maria ; Bergdahl, Ingvar A. ; Karlsson, Torgny ; Rask-Andersen, Mathias ; Palli, Domenico ; Ingelsson, Erik ; Hedman, Åsa K. ; Nilsson, Lena Maria ; Vineis, Paolo ; Lind, Lars ; Flanagan, James M. ; Johansson, Åsa - \ 2017
    Human Molecular Genetics 26 (2017)16. - ISSN 0964-6906 - p. 3221 - 3231.

    Lifestyle factors, such as food choices and exposure to chemicals, can alter DNAmethylation and lead to changes in gene activity. Two such exposures with pharmacologically active components are coffee and tea consumption. Both coffee and tea have been suggested to play an important role inmodulating disease-risk in humans by suppressing tumour progression, decreasing inflammation and influencing estrogenmetabolism. Thesemechanismsmay bemediated by changes in DNA methylation. To investigate if DNAmethylation in blood is associated with coffee and tea consumption, we performed a genome-wide DNAmethylation study for coffee and tea consumption in four European cohorts (N=3,096). DNAmethylation wasmeasured fromwhole blood at 421,695 CpG sites distributed throughout the genome and analysed inmen and women both separately and together in each cohort. Meta-analyses of the results and additional regional-level analyses were performed. After adjusting formultiple testing, themeta-analysis revealed that two individual CpG-sites,mapping to DNAJC16 and TTC17, were differentiallymethylated in relation to tea consumption in women. No individual sites were associated withmen or with the sex-combined analysis for tea or coffee. The regional analysis revealed that 28 regions were differentiallymethylated in relation to tea consumption in women. These regions contained genes known to interact with estradiolmetabolismand cancer. No significant regions were found in the sex-combined andmale-only analysis for either tea or coffee consumption.

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