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Kwon MJ, Natali SM, Hicks Pries CE, Schuur EAG, Steinhof A, Crummer KG, Zimov N, Zimov SA, Heimann M, Kolle O, Göckede M. Drainage enhances modern soil carbon contribution but reduces old soil carbon contribution to ecosystem respiration in tundra ecosystems. Glob Chang Biol 2019; 25:1315-1325. [PMID: 30681227 DOI: 10.1111/gcb.14578] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2018] [Revised: 01/15/2019] [Accepted: 01/17/2019] [Indexed: 05/06/2023]
Abstract
Warming temperatures are likely to accelerate permafrost thaw in the Arctic, potentially leading to the release of old carbon previously stored in deep frozen soil layers. Deeper thaw depths in combination with geomorphological changes due to the loss of ice structures in permafrost, may modify soil water distribution, creating wetter or drier soil conditions. Previous studies revealed higher ecosystem respiration rates under drier conditions, and this study investigated the cause of the increased ecosystem respiration rates using radiocarbon signatures of respired CO2 from two drying manipulation experiments: one in moist and the other in wet tundra. We demonstrate that higher contributions of CO2 from shallow soil layers (0-15 cm; modern soil carbon) drive the increased ecosystem respiration rates, while contributions from deeper soil (below 15 cm from surface and down to the permafrost table; old soil carbon) decreased. These changes can be attributed to more aerobic conditions in shallow soil layers, but also the soil temperature increases in shallow layers but decreases in deep layers, due to the altered thermal properties of organic soils. Decreased abundance of aerenchymatous plant species following drainage in wet tundra reduced old carbon release but increased aboveground plant biomass elevated contributions of autotrophic respiration to ecosystem respiration. The results of this study suggest that drier soils following drainage may accelerate decomposition of modern soil carbon in shallow layers but slow down decomposition of old soil carbon in deep layers, which may offset some of the old soil carbon loss from thawing permafrost.
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Affiliation(s)
- Min Jung Kwon
- Max Planck Institute for Biogeochemistry, Jena, Germany
- Korea Polar Research Institute, Incheon, South Korea
| | | | - Caitlin E Hicks Pries
- Earth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire
| | - Edward A G Schuur
- Center for Ecosystem Science and Society, and Department of Biological Sciences, Northern Arizona University, Flagstaff, Arizona
| | - Axel Steinhof
- Max Planck Institute for Biogeochemistry, Jena, Germany
| | - K Grace Crummer
- Department of Biology, University of Florida, Gainesville, Florida
| | - Nikita Zimov
- North-East Science Station, Pacific Institute for Geography, Far-Eastern Branch of Russian Academy of Science, Chersky, Republic of Sakha (Yakutia), Russia
| | - Sergey A Zimov
- North-East Science Station, Pacific Institute for Geography, Far-Eastern Branch of Russian Academy of Science, Chersky, Republic of Sakha (Yakutia), Russia
| | - Martin Heimann
- Max Planck Institute for Biogeochemistry, Jena, Germany
- Division of Atmospheric Sciences, Department of Physics, Helsinki University, Helsinki, Finland
| | - Olaf Kolle
- Max Planck Institute for Biogeochemistry, Jena, Germany
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2
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Kwon MJ, Beulig F, Ilie I, Wildner M, Küsel K, Merbold L, Mahecha MD, Zimov N, Zimov SA, Heimann M, Schuur EAG, Kostka JE, Kolle O, Hilke I, Göckede M. Plants, microorganisms, and soil temperatures contribute to a decrease in methane fluxes on a drained Arctic floodplain. Glob Chang Biol 2017; 23:2396-2412. [PMID: 27901306 DOI: 10.1111/gcb.13558] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 10/31/2016] [Accepted: 11/01/2016] [Indexed: 05/06/2023]
Abstract
As surface temperatures are expected to rise in the future, ice-rich permafrost may thaw, altering soil topography and hydrology and creating a mosaic of wet and dry soil surfaces in the Arctic. Arctic wetlands are large sources of CH4 , and investigating effects of soil hydrology on CH4 fluxes is of great importance for predicting ecosystem feedback in response to climate change. In this study, we investigate how a decade-long drying manipulation on an Arctic floodplain influences CH4 -associated microorganisms, soil thermal regimes, and plant communities. Moreover, we examine how these drainage-induced changes may then modify CH4 fluxes in the growing and nongrowing seasons. This study shows that drainage substantially lowered the abundance of methanogens along with methanotrophic bacteria, which may have reduced CH4 cycling. Soil temperatures of the drained areas were lower in deep, anoxic soil layers (below 30 cm), but higher in oxic topsoil layers (0-15 cm) compared to the control wet areas. This pattern of soil temperatures may have reduced the rates of methanogenesis while elevating those of CH4 oxidation, thereby decreasing net CH4 fluxes. The abundance of Eriophorum angustifolium, an aerenchymatous plant species, diminished significantly in the drained areas. Due to this decrease, a higher fraction of CH4 was alternatively emitted to the atmosphere by diffusion, possibly increasing the potential for CH4 oxidation and leading to a decrease in net CH4 fluxes compared to a control site. Drainage lowered CH4 fluxes by a factor of 20 during the growing season, with postdrainage changes in microbial communities, soil temperatures, and plant communities also contributing to this reduction. In contrast, we observed CH4 emissions increased by 10% in the drained areas during the nongrowing season, although this difference was insignificant given the small magnitudes of fluxes. This study showed that long-term drainage considerably reduced CH4 fluxes through modified ecosystem properties.
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Affiliation(s)
- Min Jung Kwon
- Max Planck Institute for Biogeochemistry, Hans-Knöll-Str 10, 07745 Jena, Germany
| | - Felix Beulig
- Aquatic Geomicrobiology, Institute of Ecology, Friedrich Schiller University Jena, Dornburgerstr 159, 07743 Jena, Germany
| | - Iulia Ilie
- Max Planck Institute for Biogeochemistry, Hans-Knöll-Str 10, 07745 Jena, Germany
| | - Marcus Wildner
- Geoecology-Environmental Science: Micrometeorology and Atmospheric Chemistry, Faculty of Biology, Chemistry and Earth Science, University of Bayreuth, Universitätsstr 30, 95447 Bayreuth, Germany
| | - Kirsten Küsel
- Aquatic Geomicrobiology, Institute of Ecology, Friedrich Schiller University Jena, Dornburgerstr 159, 07743 Jena, Germany
- German Centre for Integrative Biodiversity Research (iDiv), Deutscher Platz 5d, 04103, Leipzig, Germany
| | - Lutz Merbold
- Department of Environmental Systems Science, Institute of Agricultural Sciences, ETH Zurich, Universitätstr 16, 8092 Zürich, Switzerland
| | - Miguel D Mahecha
- Max Planck Institute for Biogeochemistry, Hans-Knöll-Str 10, 07745 Jena, Germany
- German Centre for Integrative Biodiversity Research (iDiv), Deutscher Platz 5d, 04103, Leipzig, Germany
| | - Nikita Zimov
- North-East Science Station, Pacific Institute for Geography, Far-Eastern Branch of Russian Academy of Science, PO Box 18, Cherskii, Republic of Sakha (Yakutia), Russia
| | - Sergey A Zimov
- North-East Science Station, Pacific Institute for Geography, Far-Eastern Branch of Russian Academy of Science, PO Box 18, Cherskii, Republic of Sakha (Yakutia), Russia
| | - Martin Heimann
- Max Planck Institute for Biogeochemistry, Hans-Knöll-Str 10, 07745 Jena, Germany
- Division of Atmospheric Sciences, Department of Physics, PO Box 64, FI-00014 University of Helsinki, Helsinki, Finland
| | - Edward A G Schuur
- Center for Ecosystem Science and Society, Department of Biological Sciences, Northern Arizona University, PO Box 5620, Flagstaff, AZ 86011, USA
| | - Joel E Kostka
- School of Biology, Georgia Institute of Technology, North Avenue, Atlanta, GA 30332, USA
| | - Olaf Kolle
- Max Planck Institute for Biogeochemistry, Hans-Knöll-Str 10, 07745 Jena, Germany
| | - Ines Hilke
- Max Planck Institute for Biogeochemistry, Hans-Knöll-Str 10, 07745 Jena, Germany
| | - Mathias Göckede
- Max Planck Institute for Biogeochemistry, Hans-Knöll-Str 10, 07745 Jena, Germany
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3
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Anthony KMW, Zimov SA, Grosse G, Jones MC, Anthony PM, Chapin FS, Finlay JC, Mack MC, Davydov S, Frenzel P, Frolking S. A shift of thermokarst lakes from carbon sources to sinks during the Holocene epoch. Nature 2014; 511:452-6. [PMID: 25043014 DOI: 10.1038/nature13560] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2013] [Accepted: 06/02/2014] [Indexed: 11/09/2022]
Abstract
Thermokarst lakes formed across vast regions of Siberia and Alaska during the last deglaciation and are thought to be a net source of atmospheric methane and carbon dioxide during the Holocene epoch. However, the same thermokarst lakes can also sequester carbon, and it remains uncertain whether carbon uptake by thermokarst lakes can offset their greenhouse gas emissions. Here we use field observations of Siberian permafrost exposures, radiocarbon dating and spatial analyses to quantify Holocene carbon stocks and fluxes in lake sediments overlying thawed Pleistocene-aged permafrost. We find that carbon accumulation in deep thermokarst-lake sediments since the last deglaciation is about 1.6 times larger than the mass of Pleistocene-aged permafrost carbon released as greenhouse gases when the lakes first formed. Although methane and carbon dioxide emissions following thaw lead to immediate radiative warming, carbon uptake in peat-rich sediments occurs over millennial timescales. We assess thermokarst-lake carbon feedbacks to climate with an atmospheric perturbation model and find that thermokarst basins switched from a net radiative warming to a net cooling climate effect about 5,000 years ago. High rates of Holocene carbon accumulation in 20 lake sediments (47 ± 10 grams of carbon per square metre per year; mean ± standard error) were driven by thermokarst erosion and deposition of terrestrial organic matter, by nutrient release from thawing permafrost that stimulated lake productivity and by slow decomposition in cold, anoxic lake bottoms. When lakes eventually drained, permafrost formation rapidly sequestered sediment carbon. Our estimate of about 160 petagrams of Holocene organic carbon in deep lake basins of Siberia and Alaska increases the circumpolar peat carbon pool estimate for permafrost regions by over 50 per cent (ref. 6). The carbon in perennially frozen drained lake sediments may become vulnerable to mineralization as permafrost disappears, potentially negating the climate stabilization provided by thermokarst lakes during the late Holocene.
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Affiliation(s)
- K M Walter Anthony
- Water and Environmental Research Center, University of Alaska, Fairbanks, Alaska 99775-5860, USA
| | - S A Zimov
- Northeast Scientific Station, Pacific Institute for Geography, Far-East Branch, Russian Academy of Sciences, Cherskii 678830, Russia
| | - G Grosse
- 1] Geophysical Institute, University of Alaska, Fairbanks, Alaska 99775-7320, USA [2] Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Potsdam 14473, Germany
| | - M C Jones
- 1] Water and Environmental Research Center, University of Alaska, Fairbanks, Alaska 99775-5860, USA [2] US Geological Survey, Reston, Virginia 20192, USA
| | - P M Anthony
- Water and Environmental Research Center, University of Alaska, Fairbanks, Alaska 99775-5860, USA
| | - F S Chapin
- Institute of Arctic Biology, University of Alaska, Fairbanks, Alaska 99775-7000, USA
| | - J C Finlay
- Department of Ecology, Evolution and Behavior, University of Minnesota, Saint Paul, Minnesota 55108, USA
| | - M C Mack
- Department of Biology, University of Florida, Gainesville, Florida 32611, USA
| | - S Davydov
- Northeast Scientific Station, Pacific Institute for Geography, Far-East Branch, Russian Academy of Sciences, Cherskii 678830, Russia
| | - P Frenzel
- Max Planck Institute for Terrestrial Microbiology, Marburg 35043, Germany
| | - S Frolking
- Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, New Hampshire 03824-3525, USA
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4
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Wild B, Schnecker J, Bárta J, Čapek P, Guggenberger G, Hofhansl F, Kaiser C, Lashchinsky N, Mikutta R, Mooshammer M, Šantrůčková H, Shibistova O, Urich T, Zimov SA, Richter A. Nitrogen dynamics in Turbic Cryosols from Siberia and Greenland. Soil Biol Biochem 2013; 67:85-93. [PMID: 24302785 PMCID: PMC3819518 DOI: 10.1016/j.soilbio.2013.08.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2013] [Revised: 08/01/2013] [Accepted: 08/03/2013] [Indexed: 05/16/2023]
Abstract
Turbic Cryosols (permafrost soils characterized by cryoturbation, i.e., by mixing of soil layers due to freezing and thawing) are widespread across the Arctic, and contain large amounts of poorly decomposed organic material buried in the subsoil. This cryoturbated organic matter exhibits retarded decomposition compared to organic material in the topsoil. Since soil organic matter (SOM) decomposition is known to be tightly linked to N availability, we investigated N transformation rates in different soil horizons of three tundra sites in north-eastern Siberia and Greenland. We measured gross rates of protein depolymerization, N mineralization (ammonification) and nitrification, as well as microbial uptake of amino acids and NH4+ using an array of 15N pool dilution approaches. We found that all sites and horizons were characterized by low N availability, as indicated by low N mineralization compared to protein depolymerization rates (with gross N mineralization accounting on average for 14% of gross protein depolymerization). The proportion of organic N mineralized was significantly higher at the Greenland than at the Siberian sites, suggesting differences in N limitation. The proportion of organic N mineralized, however, did not differ significantly between soil horizons, pointing to a similar N demand of the microbial community of each horizon. In contrast, absolute N transformation rates were significantly lower in cryoturbated than in organic horizons, with cryoturbated horizons reaching not more than 32% of the transformation rates in organic horizons. Our results thus indicate a deceleration of the entire N cycle in cryoturbated soil horizons, especially strongly reduced rates of protein depolymerization (16% of organic horizons) which is considered the rate-limiting step in soil N cycling.
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Affiliation(s)
- Birgit Wild
- University of Vienna, Department of Microbiology and Ecosystem Science, Division of Terrestrial Ecosystem Research, Althanstrasse 14, 1090 Vienna, Austria
- Austrian Polar Research Institute, 1090 Vienna, Austria
| | - Jörg Schnecker
- University of Vienna, Department of Microbiology and Ecosystem Science, Division of Terrestrial Ecosystem Research, Althanstrasse 14, 1090 Vienna, Austria
- Austrian Polar Research Institute, 1090 Vienna, Austria
| | - Jiří Bárta
- University of South Bohemia, Department of Ecosystems Biology, Branišovská 31, 37005 České Budějovice, Czech Republic
| | - Petr Čapek
- University of South Bohemia, Department of Ecosystems Biology, Branišovská 31, 37005 České Budějovice, Czech Republic
| | - Georg Guggenberger
- Leibniz Universität Hannover, Institut für Bodenkunde, Herrenhäuser Strasse 2, 30419 Hannover, Germany
| | - Florian Hofhansl
- University of Vienna, Department of Microbiology and Ecosystem Science, Division of Terrestrial Ecosystem Research, Althanstrasse 14, 1090 Vienna, Austria
| | - Christina Kaiser
- University of Vienna, Department of Microbiology and Ecosystem Science, Division of Terrestrial Ecosystem Research, Althanstrasse 14, 1090 Vienna, Austria
- International Institute for Applied Systems Analysis (IIASA), Schlossplatz 1, 2361 Laxenburg, Austria
| | - Nikolaj Lashchinsky
- Central Siberian Botanical Garden, Siberian Branch of Russian Academy of Sciences, St. Zolotodolinskaya 101, 630090 Novosibirsk, Russia
| | - Robert Mikutta
- Leibniz Universität Hannover, Institut für Bodenkunde, Herrenhäuser Strasse 2, 30419 Hannover, Germany
| | - Maria Mooshammer
- University of Vienna, Department of Microbiology and Ecosystem Science, Division of Terrestrial Ecosystem Research, Althanstrasse 14, 1090 Vienna, Austria
| | - Hana Šantrůčková
- University of South Bohemia, Department of Ecosystems Biology, Branišovská 31, 37005 České Budějovice, Czech Republic
| | - Olga Shibistova
- Leibniz Universität Hannover, Institut für Bodenkunde, Herrenhäuser Strasse 2, 30419 Hannover, Germany
- VN Sukachev Institute of Forest, Siberian Branch of Russian Academy of Sciences, Akademgorodok, 660036 Krasnoyarsk, Russia
| | - Tim Urich
- Austrian Polar Research Institute, 1090 Vienna, Austria
- University of Vienna, Department of Ecogenomics and Systems Biology, Althanstrasse 14, 1090 Vienna, Austria
- University of Bergen, Department of Biology/Centre for Geobiology, Allégaten 41, 5007 Bergen, Norway
| | - Sergey A. Zimov
- Northeast Scientific Station, Pacific Institute for Geography, Far-East Branch of Russian Academy of Sciences, 678830 Chersky, Republic of Sakha, Russia
| | - Andreas Richter
- University of Vienna, Department of Microbiology and Ecosystem Science, Division of Terrestrial Ecosystem Research, Althanstrasse 14, 1090 Vienna, Austria
- Austrian Polar Research Institute, 1090 Vienna, Austria
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5
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Walter KM, Zimov SA, Chanton JP, Verbyla D, Chapin FS. Methane bubbling from Siberian thaw lakes as a positive feedback to climate warming. Nature 2006; 443:71-5. [PMID: 16957728 DOI: 10.1038/nature05040] [Citation(s) in RCA: 198] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2005] [Accepted: 07/03/2006] [Indexed: 11/08/2022]
Abstract
Large uncertainties in the budget of atmospheric methane, an important greenhouse gas, limit the accuracy of climate change projections. Thaw lakes in North Siberia are known to emit methane, but the magnitude of these emissions remains uncertain because most methane is released through ebullition (bubbling), which is spatially and temporally variable. Here we report a new method of measuring ebullition and use it to quantify methane emissions from two thaw lakes in North Siberia. We show that ebullition accounts for 95 per cent of methane emissions from these lakes, and that methane flux from thaw lakes in our study region may be five times higher than previously estimated. Extrapolation of these fluxes indicates that thaw lakes in North Siberia emit 3.8 teragrams of methane per year, which increases present estimates of methane emissions from northern wetlands (< 6-40 teragrams per year; refs 1, 2, 4-6) by between 10 and 63 per cent. We find that thawing permafrost along lake margins accounts for most of the methane released from the lakes, and estimate that an expansion of thaw lakes between 1974 and 2000, which was concurrent with regional warming, increased methane emissions in our study region by 58 per cent. Furthermore, the Pleistocene age (35,260-42,900 years) of methane emitted from hotspots along thawing lake margins indicates that this positive feedback to climate warming has led to the release of old carbon stocks previously stored in permafrost.
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Affiliation(s)
- K M Walter
- Institute of Arctic Biology, University of Alaska Fairbanks, Alaska 99775, USA.
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6
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Affiliation(s)
- Sergey A Zimov
- North-East Scientific Station, Pacific Institute for Geography, Russian Academy of Sciences, Cherskii, Republic of Sakha 678830, Russia.
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7
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Chapin FS, Hoel M, Carpenter SR, Lubchenco J, Walker B, Callaghan TV, Folke C, Levin SA, Mäler KG, Nilsson C, Barrett S, Berkes F, Crépin AS, Danell K, Rosswall T, Starrett D, Xepapadeas A, Zimov SA. Building resilience and adaptation to manage Arctic change. Ambio 2006; 35:198-202. [PMID: 16944645 DOI: 10.1579/0044-7447(2006)35[198:braatm]2.0.co;2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Unprecedented global changes caused by human actions challenge society's ability to sustain the desirable features of our planet. This requires proactive management of change to foster both resilience (sustaining those attributes that are important to society in the face of change) and adaptation (developing new socioecological configurations that function effectively under new conditions). The Arctic may be one of the last remaining opportunities to plan for change in a spatially extensive region where many of the ancestral ecological and social processes and feedbacks are still intact. If the feasibility of this strategy can be demonstrated in the Arctic, our improved understanding of the dynamics of change can be applied to regions with greater human modification. Conditions may now be ideal to implement policies to manage Arctic change because recent studies provide the essential scientific understanding, appropriate international institutions are in place, and Arctic nations have the wealth to institute necessary changes, if they choose to do so.
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Affiliation(s)
- F Stuart Chapin
- Institute of Arctic Biology, University of Alaska, Fairbanks 99775, USA.
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8
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Affiliation(s)
- Sergey A Zimov
- Northeast Scientific Station, Pacific Institute for Geography (Far East Branch), Russian Academy of Sciences, Post Office Box 18, Cherskii, Republic of Sakha 678830, Russia
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9
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Chapin FS, Callaghan TV, Bergeron Y, Fukuda M, Johnstone JF, Juday G, Zimov SA. Global change and the boreal forest: thresholds, shifting states or gradual change? Ambio 2004; 33:361-5. [PMID: 15387075 DOI: 10.1579/0044-7447-33.6.361] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Changes in boreal climate of the magnitude projected for the 21st century have always caused vegetation changes large enough to be societally important. However, the rates and patterns of vegetation change are difficult to predict. We review evidence suggesting that these vegetation changes may be gradual at the northern forest limit or where seed dispersal limits species distribution. However, forest composition may be quite resilient to climate change in the central portions of a species range until some threshold is surpassed. At this point, changes can be rapid and unexpected, often causing a switch to very different ecosystem types. Many of these triggers for change are amenable to management, suggesting that our choice of policies in the coming decades will substantially influence the ecological and societal consequences of current climatic change.
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Affiliation(s)
- F Stuart Chapin
- Institute of Arctic Biology, University of Alaska, Fairbanks 99775, USA.
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10
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Chapin FS, Mcguire AD, Randerson J, Pielke R, Baldocchi D, Hobbie SE, Roulet N, Eugster W, Kasischke E, Rastetter EB, Zimov SA, Running SW. Arctic and boreal ecosystems of western North America as components of the climate system. Glob Chang Biol 2000; 6:211-223. [PMID: 35026938 DOI: 10.1046/j.1365-2486.2000.06022.x] [Citation(s) in RCA: 135] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Synthesis of results from several Arctic and boreal research programmes provides evidence for the strong role of high-latitude ecosystems in the climate system. Average surface air temperature has increased 0.3 °C per decade during the twentieth century in the western North American Arctic and boreal forest zones. Precipitation has also increased, but changes in soil moisture are uncertain. Disturbance rates have increased in the boreal forest; for example, there has been a doubling of the area burned in North America in the past 20 years. The disturbance regime in tundra may not have changed. Tundra has a 3-6-fold higher winter albedo than boreal forest, but summer albedo and energy partitioning differ more strongly among ecosystems within either tundra or boreal forest than between these two biomes. This indicates a need to improve our understanding of vegetation dynamics within, as well as between, biomes. If regional surface warming were to continue, changes in albedo and energy absorption would likely act as a positive feedback to regional warming due to earlier melting of snow and, over the long term, the northward movement of treeline. Surface drying and a change in dominance from mosses to vascular plants would also enhance sensible heat flux and regional warming in tundra. In the boreal forest of western North America, deciduous forests have twice the albedo of conifer forests in both winter and summer, 50-80% higher evapotranspiration, and therefore only 30-50% of the sensible heat flux of conifers in summer. Therefore, a warming-induced increase in fire frequency that increased the proportion of deciduous forests in the landscape, would act as a negative feedback to regional warming. Changes in thermokarst and the aerial extent of wetlands, lakes, and ponds would alter high-latitude methane flux. There is currently a wide discrepancy among estimates of the size and direction of CO2 flux between high-latitude ecosystems and the atmosphere. These discrepancies relate more strongly to the approach and assumptions for extrapolation than to inconsistencies in the underlying data. Inverse modelling from atmospheric CO2 concentrations suggests that high latitudes are neutral or net sinks for atmospheric CO2 , whereas field measurements suggest that high latitudes are neutral or a net CO2 source. Both approaches rely on assumptions that are difficult to verify. The most parsimonious explanation of the available data is that drying in tundra and disturbance in boreal forest enhance CO2 efflux. Nevertheless, many areas of both tundra and boreal forests remain net sinks due to regional variation in climate and local variation in topographically determined soil moisture. Improved understanding of the role of high-latitude ecosystems in the climate system requires a concerted research effort that focuses on geographical variation in the processes controlling land-atmosphere exchange, species composition, and ecosystem structure. Future studies must be conducted over a long enough time-period to detect and quantify ecosystem feedbacks.
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Affiliation(s)
- F S Chapin
- Institute of Arctic Biology, University of Alaska, Fairbanks, AK 99775, USA
| | - A D Mcguire
- US Geological Survey, Alaska Cooperative Fish and Wildlife Research Unit, University of Alaska, Fairbanks, AK 99775, USA
| | - J Randerson
- Department of Atmospheric Sciences, University of California, Berkeley, CA 94720, USA
| | - R Pielke
- Department of Atmospheric Sciences, Colorado State University, Fort Collins, CO 80523, USA
| | - D Baldocchi
- Atmospheric Turbulence and Diffusion Division, PO Box 2456, Oak Ridge, TN 37831, USA
| | - S E Hobbie
- Department of Ecology, Evolution, and Behaviour, University of Minnesota, St. Paul MN 55108, USA
| | - N Roulet
- Department of Geography, McGill University, Montreal, Quebec, Canada H3A 2K6
| | - W Eugster
- Institute of Geography, University of Bern, CH-3012 Bern, Switzerland
| | - E Kasischke
- ERIM International, Inc., PO Box 134008, Ann Arbor, MI 48113-4008, USA
| | - E B Rastetter
- Ecosystem Center, Marine Biological Laboratory, Woods Hole, MA 02543, USA
| | - S A Zimov
- North-East Science Station, PO Box 18, Cherskii, Republic of Sakha (Yakutia), 678830 Russia, School of Forestry, University of Montana, Missoula, MT 59812-1063, USA
| | - S W Running
- North-East Science Station, PO Box 18, Cherskii, Republic of Sakha (Yakutia), 678830 Russia, School of Forestry, University of Montana, Missoula, MT 59812-1063, USA
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11
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Zimov SA, Davidov SP, Zimova GM, Davidova AI, Chapin FS, Chapin MC, Reynolds JF. Contribution of disturbance to increasing seasonal amplitude of atmospheric CO2. Science 1999; 284:1973-6. [PMID: 10373112 DOI: 10.1126/science.284.5422.1973] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Recent increases in the seasonal amplitude of atmospheric carbon dioxide (CO2) at high latitudes suggest a widespread biospheric response to high-latitude warming. The seasonal amplitude of net ecosystem carbon exchange by northern Siberian ecosystems is shown to be greater in disturbed than undisturbed sites, due to increased summer influx and increased winter efflux. Increased disturbance could therefore contribute significantly to the amplified seasonal cycle of atmospheric carbon dioxide at high latitudes. Warm temperatures reduced summer carbon influx, suggesting that high-latitude warming, if it occurred, would be unlikely to increase seasonal amplitude of carbon exchange.
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Affiliation(s)
- SA Zimov
- North-East Scientific Station, Pacific Institute for Geography, Far-East Branch, Russian Academy of Sciences, Republic of Sakha, Yakutia, 678830 Cherskii, Russia. Institute of Arctic Biology, University of Alaska, Fairbanks, AK 99775-7000
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