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41 results on '"Euskirchen, E. S."'

1. Warming response of peatland CO2 sink is sensitive to seasonality in warming trends

Author

Helbig, M., Živković, T., Alekseychik, P., Aurela, M., El-Madany, T. S., Euskirchen, E. S., Flanagan, L. B., Griffis, T. J., Hanson, P. J., Hattakka, J., Helfter, C., Hirano, T., Humphreys, E. R., Kiely, G., Kolka, R. K., Laurila, T., Leahy, P. G., Lohila, A., Mammarella, I., Nilsson, M. B., Panov, A., Parmentier, F. J. W., Peichl, M., Rinne, J., Roman, D. T., Sonnentag, O., Tuittila, E.-S, Ueyama, M., Vesala, T., Vestin, P., Weldon, S., Weslien, P., and Zaehle, S.

Published
2022
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3. Role of Land-Surface Changes in Arctic Summer Warming

Author

Chapin, F. S., Sturm, M., Serreze, M. C., McFadden, J. P., Key, J. R., Lloyd, A. H., McGuire, A. D., Rupp, T. S., Lynch, A. H., Schimel, J. P., Beringer, J., Chapman, W. L., Epstein, H. E., Euskirchen, E. S., Hinzman, L. D., Jia, G., Tape, K. D., Thompson, C. D. C., Walker, D. A., and Welker, J. M.

Published
2005

7. Earlier snowmelt may lead to late season declines in plant productivity and carbon sequestration in Arctic tundra ecosystems

Author

Zona, D. (Donatella), Lafleur, P. M. (Peter M.), Hufkens, K. (Koen), Bailey, B. (Barbara), Gioli, B. (Beniamino), Burba, G. (George), Goodrich, J. P. (Jordan P.), Liljedahl, A. K. (Anna K.), Euskirchen, E. S. (Eugénie S.), Watts, J. D. (Jennifer D.), Farina, M. (Mary), Kimball, J. S. (John S.), Heimann, M. (Martin), Göckede, M. (Mathias), Pallandt, M. (Martijn), Christensen, T. R. (Torben R.), Mastepanov, M. (Mikhail), López-Blanco, E. (Efrén), Jackowicz-Korczynski, M. (Marcin), Dolman, A. J. (Albertus J.), Belelli Marchesini, L. (Luca), Commane, R. (Roisin), Wofsy, S. C. (Steven C.), Miller, C. E. (Charles E.), Lipson, D. A. (David A.), Hashemi, J. (Josh), Arndt, K. A. (Kyle A.), Kutzbach, L. (Lars), Holl, D. (David), Boike, J. (Julia), Wille, C. (Christian), Sachs, T. (Torsten), Kalhori, A. (Aram), Song, X. (Xia), Xu, X. (Xiaofeng), Humphreys, E. R. (Elyn R.), Koven, C. D. (Charles D.), Sonnentag, O. (Oliver), Meyer, G. (Gesa), Gosselin, G. H. (Gabriel H.), Marsh, P. (Philip), Oechel, W. C. (Walter C.), Zona, D. (Donatella), Lafleur, P. M. (Peter M.), Hufkens, K. (Koen), Bailey, B. (Barbara), Gioli, B. (Beniamino), Burba, G. (George), Goodrich, J. P. (Jordan P.), Liljedahl, A. K. (Anna K.), Euskirchen, E. S. (Eugénie S.), Watts, J. D. (Jennifer D.), Farina, M. (Mary), Kimball, J. S. (John S.), Heimann, M. (Martin), Göckede, M. (Mathias), Pallandt, M. (Martijn), Christensen, T. R. (Torben R.), Mastepanov, M. (Mikhail), López-Blanco, E. (Efrén), Jackowicz-Korczynski, M. (Marcin), Dolman, A. J. (Albertus J.), Belelli Marchesini, L. (Luca), Commane, R. (Roisin), Wofsy, S. C. (Steven C.), Miller, C. E. (Charles E.), Lipson, D. A. (David A.), Hashemi, J. (Josh), Arndt, K. A. (Kyle A.), Kutzbach, L. (Lars), Holl, D. (David), Boike, J. (Julia), Wille, C. (Christian), Sachs, T. (Torsten), Kalhori, A. (Aram), Song, X. (Xia), Xu, X. (Xiaofeng), Humphreys, E. R. (Elyn R.), Koven, C. D. (Charles D.), Sonnentag, O. (Oliver), Meyer, G. (Gesa), Gosselin, G. H. (Gabriel H.), Marsh, P. (Philip), and Oechel, W. C. (Walter C.)

Abstract

Arctic warming is affecting snow cover and soil hydrology, with consequences for carbon sequestration in tundra ecosystems. The scarcity of observations in the Arctic has limited our understanding of the impact of covarying environmental drivers on the carbon balance of tundra ecosystems. In this study, we address some of these uncertainties through a novel record of 119 site-years of summer data from eddy covariance towers representing dominant tundra vegetation types located on continuous permafrost in the Arctic. Here we found that earlier snowmelt was associated with more tundra net CO₂ sequestration and higher gross primary productivity (GPP) only in June and July, but with lower net carbon sequestration and lower GPP in August. Although higher evapotranspiration (ET) can result in soil drying with the progression of the summer, we did not find significantly lower soil moisture with earlier snowmelt, nor evidence that water stress affected GPP in the late growing season. Our results suggest that the expected increased CO₂ sequestration arising from Arctic warming and the associated increase in growing season length may not materialize if tundra ecosystems are not able to continue sequestering CO₂ later in the season.

Published
2022

8. Closing the winter gap:year-round measurements of soil CO₂ emission sources in Arctic tundra

Author

Pedron, S. A. (Shawn A.), Welker, J. M. (J. M.), Euskirchen, E. S. (E. S.), Klein, E. S. (E. S.), Walker, J. C. (J. C.), Xu, X. (X.), and Czimczik, C. I. (C. I.)

Subjects
carbon flux, vulnerability, radiocarbon, winter, respiration, permafrost
Abstract

Non-growing season CO₂ emissions from Arctic tundra remain a major uncertainty in forecasting climate change consequences of permafrost thaw. We present the first time series of soil and microbial CO₂ emissions from a graminoid tundra based on year-round in situ measurements of the radiocarbon content of soil CO₂ (Δ¹⁴CO₂) and of bulk soil C (Δ¹⁴C), microbial activity, and temperature. Combining these data with land-atmosphere CO₂ exchange allows estimates of the proportion and mean age of microbial CO₂ emissions year-round. We observe a seasonal shift in emission sources from fresh carbon during the growing season (August Δ¹⁴CO₂ = 74 ± 4.7‰, 37% ± 3.4% microbial, mean ± se) to increasingly older soil carbon in fall and winter (March Δ¹⁴CO₂ = 22 ± 1.3‰, 47% ± 8% microbial). Thus, rising soil temperatures and emissions during fall and winter are depleting aged soil carbon pools in the active layer and thawing permafrost and further accelerating climate change.

Published
2022

11. Carbon Fluxes and Microbial Activities From Boreal Peatlands Experiencing Permafrost Thaw

Author

Waldrop, M. P., McFarland, J., Manies, K. L., Leewis, M. C., Blazewicz, S. J., Jones, M. C., Neumann, R. B., Keller, J. K., Cohen, L., Euskirchen, E. S., Edgar, C., Turetsky, M. R., Cable, W. L., Waldrop, M. P., McFarland, J., Manies, K. L., Leewis, M. C., Blazewicz, S. J., Jones, M. C., Neumann, R. B., Keller, J. K., Cohen, L., Euskirchen, E. S., Edgar, C., Turetsky, M. R., and Cable, W. L.

Abstract

Permafrost thaw in northern ecosystems may cause large quantities of carbon (C) to move from soil to atmospheric pools. Because soil microbial communities play a critical role in regulating C fluxes from soils, we examined microbial activity and greenhouse gas production soon after permafrost thaw and ground collapse (into collapse‐scar bogs), relative to the permafrost plateau or older thaw features. Using multiple field and laboratory‐based assays at a field site in interior Alaska, we show that the youngest collapse‐scar bog had the highest CH4 production potential from soil incubations, and, based upon temporal changes in porewater concentrations and 13C‐CH4 and 13C‐CO2, had greater summer in situ rates of respiration, methanogenesis, and surface CH4 oxidation. These patterns could be explained by greater C and N availability in the young bog, while alternative terminal electron accepting processes did not play a significant role. Field diffusive CH4 fluxes from the young bog were 4.1 times greater in the shoulder season and 1.7–7.2 times greater in winter relative to older bogs, but not during summer. Greater relative CH4 flux rates in the shoulder season and winter could be due to reduced CH4 oxidation relative to summer, magnifying the importance of differences in production. Both the permafrost plateau and collapse‐scar bogs were sources of C to the atmosphere due in large part to winter C fluxes. In collapse scar bogs, winter is a critical period when differences in thermokarst age translates to differences in surface fluxes.

Published
2021

12. Global transpiration data from sap flow measurements: The SAPFLUXNET database

Author

Poyatos, R., Granda, V, Flo, V., Adorján, B., Adams, M. A., Aguadé, D., Aidar, M. P. M., Allen, S., Alvarado-Barrientos, M. S., Anderson-Teixeira, K. J., Aparecido, L. M., Altaf Arain, M., Aranda, I., Asbjornsen, H., Baxter, R., Beamesderfer, E., Berry, Z. C., Berveiller, D., Blakely, B., Boggs, J., Bohrer, G., Bolstad, P. V., Bonal, D., Bracho, R., Brito, P., Brodeur, J., Casanoves, F., Chave, J., Chen, H., Cisneros, C., Clark, K., Cremonese, E., Dang, H., David, J. S., David, T. S., Delpierre, N., Desai, A. R., Do, F. C., Dohnal, N., Domec, J. C., Dzikiti, S., Edgar, C., Eichstaedt, R., El-Madany, T. S., Elbers, J., Eller, C. B., Euskirchen, E. S., Ewers, B., Fonti, P., Forner, A., Forrester, D. I., Freitas, H. C., Galvagno, M., Garcia-Tejera, O., Ghimire, C. P., Gimeno, T. E., Grace, J., Granier, A., Griebel, A., Guangyu, Y., Gush, M. B., Hanson, P. J., Hasselquist, N. J., Heinrich, I., Hernandez-Santana, V., Herrmann, V, Hölttä, T., Holwerda, F., Irvine, J., Na Ayutthaya, S. Y., Jarvis, P. J., Jochheim, H., Joly, C. A., Kaplick, J., Kim, H. S., Klemedtsson, L., Kropp, H., Lagergren, F., Lane, P., Lang, P., Lapenas, A., Lechuga, V., Lee, M., Leuschner, C., Limousin, J. M., Linares, J. C., Linderson, M. L., Lindroth, A., Llorens, P., López-Bernal, A., Loranty, M. M., Lüttschwager, D., MacInnis-Ng, C., Maréchaux, I., Martin, T. A., Matheny, A., McDowell, N., McMahon, S., Meir, P., Mészáros, I., Migliavacca, M., Mitchell, P., Mölder, M., Montagnani, L., Moore, G. W., Nakada, R., Niu, F., Nolan, R.H., Norby, R., Novick, K., Oberhuber, W., Obojes, N., Oishi, A. C., Oliveira, R. S., Olen, R., Ourcival, J. M., Paljakka, T., Perez Priego, O., Peri, P. L., Peters, R. L., Pfautsch, S., Pockman, W. T., Preysler, I., Rascher, K., Robinson, G., Rocheteau, A., Rocha, H., Röll, A., Rosado, B. H. P., Rowland, L., Rubtsov, A. V., Sabaté, S., Salmón, Y., Salomon, R. L., Schäfer, K. V. R., Sánchez-Costa, E., Schuld, B., Shashkin, A., Stahl, C., Stojanovic, M., Suárez, J. C., Szatniewska, J, Sun, G., Tatarinov, F., TesaÅ, M, Thomas, F. M., Tor-Ngern, P., Urban, J., Valladares, F., Van Der Tol, C., Van Meerveld, I., Varlagin, A., Voigt, H., Warren, J., Werner, C., Poyatos, R., Granda, V, Flo, V., Adorján, B., Adams, M. A., Aguadé, D., Aidar, M. P. M., Allen, S., Alvarado-Barrientos, M. S., Anderson-Teixeira, K. J., Aparecido, L. M., Altaf Arain, M., Aranda, I., Asbjornsen, H., Baxter, R., Beamesderfer, E., Berry, Z. C., Berveiller, D., Blakely, B., Boggs, J., Bohrer, G., Bolstad, P. V., Bonal, D., Bracho, R., Brito, P., Brodeur, J., Casanoves, F., Chave, J., Chen, H., Cisneros, C., Clark, K., Cremonese, E., Dang, H., David, J. S., David, T. S., Delpierre, N., Desai, A. R., Do, F. C., Dohnal, N., Domec, J. C., Dzikiti, S., Edgar, C., Eichstaedt, R., El-Madany, T. S., Elbers, J., Eller, C. B., Euskirchen, E. S., Ewers, B., Fonti, P., Forner, A., Forrester, D. I., Freitas, H. C., Galvagno, M., Garcia-Tejera, O., Ghimire, C. P., Gimeno, T. E., Grace, J., Granier, A., Griebel, A., Guangyu, Y., Gush, M. B., Hanson, P. J., Hasselquist, N. J., Heinrich, I., Hernandez-Santana, V., Herrmann, V, Hölttä, T., Holwerda, F., Irvine, J., Na Ayutthaya, S. Y., Jarvis, P. J., Jochheim, H., Joly, C. A., Kaplick, J., Kim, H. S., Klemedtsson, L., Kropp, H., Lagergren, F., Lane, P., Lang, P., Lapenas, A., Lechuga, V., Lee, M., Leuschner, C., Limousin, J. M., Linares, J. C., Linderson, M. L., Lindroth, A., Llorens, P., López-Bernal, A., Loranty, M. M., Lüttschwager, D., MacInnis-Ng, C., Maréchaux, I., Martin, T. A., Matheny, A., McDowell, N., McMahon, S., Meir, P., Mészáros, I., Migliavacca, M., Mitchell, P., Mölder, M., Montagnani, L., Moore, G. W., Nakada, R., Niu, F., Nolan, R.H., Norby, R., Novick, K., Oberhuber, W., Obojes, N., Oishi, A. C., Oliveira, R. S., Olen, R., Ourcival, J. M., Paljakka, T., Perez Priego, O., Peri, P. L., Peters, R. L., Pfautsch, S., Pockman, W. T., Preysler, I., Rascher, K., Robinson, G., Rocheteau, A., Rocha, H., Röll, A., Rosado, B. H. P., Rowland, L., Rubtsov, A. V., Sabaté, S., Salmón, Y., Salomon, R. L., Schäfer, K. V. R., Sánchez-Costa, E., Schuld, B., Shashkin, A., Stahl, C., Stojanovic, M., Suárez, J. C., Szatniewska, J, Sun, G., Tatarinov, F., TesaÅ, M, Thomas, F. M., Tor-Ngern, P., Urban, J., Valladares, F., Van Der Tol, C., Van Meerveld, I., Varlagin, A., Voigt, H., Warren, J., and Werner, C.

Abstract

Plant transpiration links physiological responses of vegetation to water supply and demand with hydrological, energy, and carbon budgets at the land-atmosphere interface. However, despite being the main land evaporative flux at the global scale, transpiration and its response to environmental drivers are currently not well constrained by observations. Here we introduce the first global compilation of whole-plant transpiration data from sap flow measurements (SAPFLUXNET, https://sapfluxnet.creaf.cat/, last access: 8 June 2021). We harmonized and quality-controlled individual datasets supplied by contributors worldwide in a semi-automatic data workflow implemented in the R programming language. Datasets include sub-daily time series of sap flow and hydrometeorological drivers for one or more growing seasons, as well as metadata on the stand characteristics, plant attributes, and technical details of the measurements. SAPFLUXNET contains 202 globally distributed datasets with sap flow time series for 2714 plants, mostly trees, of 174 species. SAPFLUXNET has a broad bioclimatic coverage, with woodland/shrubland and temperate forest biomes especially well represented (80% of the datasets). The measurements cover a wide variety of stand structural characteristics and plant sizes. The datasets encompass the period between 1995 and 2018, with 50% of the datasets being at least 3 years long. Accompanying radiation and vapour pressure deficit data are available for most of the datasets, while on-site soil water content is available for 56% of the datasets. Many datasets contain data for species that make up 90% or more of the total stand basal area, allowing the estimation of stand transpiration in diverse ecological settings. SAPFLUXNET adds to existing plant trait datasets, ecosystem flux networks, and remote sensing products to help increase our understanding of plant water use, plant responses to drought, and ecohydrological processes. SAPFLUXNET version 0.1.5 is freely a

Published
2021

14. Shallow soils are warmer under trees and tall shrubs across Arctic and Boreal ecosystems

Author

Kropp, H. (Heather), Loranty, M. M. (Michael M.), Natali, S. M. (Susan M.), Kholodov, A. L. (Alexander L.), Rocha, A. V. (Adrian, V), Myers-Smith, I. (Isla), Abbot, B. W. (Benjamin W.), Abermann, J. (Jakob), Blanc-Betes, E. (Elena), Blok, D. (Daan), Blume-Werry, G. (Gesche), Boike, J. (Julia), Breen, A. L. (Amy L.), Cahoon, S. M. (Sean M. P.), Christiansen, C. T. (Casper T.), Douglas, T. A. (Thomas A.), Epstein, H. E. (Howard E.), Frost, G. V. (Gerald, V), Goeckede, M. (Mathias), Hoye, T. T. (Toke T.), Mamet, S. D. (Steven D.), O'Donnell, J. A. (Jonathan A.), Olefeldt, D. (David), Phoenix, G. K. (Gareth K.), Salmon, V. G. (Verity G.), Sannel, A. B. (A. Britta K.), Smith, S. L. (Sharon L.), Sonnentag, O. (Oliver), Vaughn, L. S. (Lydia Smith), Williams, M. (Mathew), Elberling, B. (Bo), Gough, L. (Laura), Hjort, J. (Jan), Lafleur, P. M. (Peter M.), Euskirchen, E. S. (Eugenie S.), Heijmans, M. M. (Monique M. P. D.), Humphreys, E. R. (Elyn R.), Iwata, H. (Hiroki), Jones, B. M. (Benjamin M.), Jorgenson, M. T. (M. Torre), Gruenberg, I. (Inge), Kim, Y. (Yongwon), Laundre, J. (James), Mauritz, M. (Marguerite), Michelsen, A. (Anders), Schaepman-Strub, G. (Gabriela), Tape, K. D. (Ken D.), Ueyama, M. (Masahito), Lee, B.-Y. (Bang-Yong), Langley, K. (Kirsty), Lund, M. (Magnus), Kropp, H. (Heather), Loranty, M. M. (Michael M.), Natali, S. M. (Susan M.), Kholodov, A. L. (Alexander L.), Rocha, A. V. (Adrian, V), Myers-Smith, I. (Isla), Abbot, B. W. (Benjamin W.), Abermann, J. (Jakob), Blanc-Betes, E. (Elena), Blok, D. (Daan), Blume-Werry, G. (Gesche), Boike, J. (Julia), Breen, A. L. (Amy L.), Cahoon, S. M. (Sean M. P.), Christiansen, C. T. (Casper T.), Douglas, T. A. (Thomas A.), Epstein, H. E. (Howard E.), Frost, G. V. (Gerald, V), Goeckede, M. (Mathias), Hoye, T. T. (Toke T.), Mamet, S. D. (Steven D.), O'Donnell, J. A. (Jonathan A.), Olefeldt, D. (David), Phoenix, G. K. (Gareth K.), Salmon, V. G. (Verity G.), Sannel, A. B. (A. Britta K.), Smith, S. L. (Sharon L.), Sonnentag, O. (Oliver), Vaughn, L. S. (Lydia Smith), Williams, M. (Mathew), Elberling, B. (Bo), Gough, L. (Laura), Hjort, J. (Jan), Lafleur, P. M. (Peter M.), Euskirchen, E. S. (Eugenie S.), Heijmans, M. M. (Monique M. P. D.), Humphreys, E. R. (Elyn R.), Iwata, H. (Hiroki), Jones, B. M. (Benjamin M.), Jorgenson, M. T. (M. Torre), Gruenberg, I. (Inge), Kim, Y. (Yongwon), Laundre, J. (James), Mauritz, M. (Marguerite), Michelsen, A. (Anders), Schaepman-Strub, G. (Gabriela), Tape, K. D. (Ken D.), Ueyama, M. (Masahito), Lee, B.-Y. (Bang-Yong), Langley, K. (Kirsty), and Lund, M. (Magnus)

Abstract

Soils are warming as air temperatures rise across the Arctic and Boreal region concurrent with the expansion of tall-statured shrubs and trees in the tundra. Changes in vegetation structure and function are expected to alter soil thermal regimes, thereby modifying climate feedbacks related to permafrost thaw and carbon cycling. However, current understanding of vegetation impacts on soil temperature is limited to local or regional scales and lacks the generality necessary to predict soil warming and permafrost stability on a pan-Arctic scale. Here we synthesize shallow soil and air temperature observations with broad spatial and temporal coverage collected across 106 sites representing nine different vegetation types in the permafrost region. We showed ecosystems with tall-statured shrubs and trees (>40 cm) have warmer shallow soils than those with short-statured tundra vegetation when normalized to a constant air temperature. In tree and tall shrub vegetation types, cooler temperatures in the warm season do not lead to cooler mean annual soil temperature indicating that ground thermal regimes in the cold-season rather than the warm-season are most critical for predicting soil warming in ecosystems underlain by permafrost. Our results suggest that the expansion of tall shrubs and trees into tundra regions can amplify shallow soil warming, and could increase the potential for increased seasonal thaw depth and increase soil carbon cycling rates and lead to increased carbon dioxide loss and further permafrost thaw.

Published
2020

16. Closing the Winter Gap—Year‐Round Measurements of Soil CO2 Emission Sources in Arctic Tundra.

Author

Pedron, Shawn A., Welker, J. M., Euskirchen, E. S., Klein, E. S., Walker, J. C., Xu, X., and Czimczik, C. I.

Subjects
TUNDRAS, CLIMATE change forecasts, CARBON emissions, SOILS, PLANT litter, SOIL temperature
Abstract

Non‐growing season CO2 emissions from Arctic tundra remain a major uncertainty in forecasting climate change consequences of permafrost thaw. We present the first time series of soil and microbial CO2 emissions from a graminoid tundra based on year‐round in situ measurements of the radiocarbon content of soil CO2 (Δ14CO2) and of bulk soil C (Δ14C), microbial activity, and temperature. Combining these data with land‐atmosphere CO2 exchange allows estimates of the proportion and mean age of microbial CO2 emissions year‐round. We observe a seasonal shift in emission sources from fresh carbon during the growing season (August Δ14CO2 = 74 ± 4.7‰, 37% ± 3.4% microbial, mean ± se) to increasingly older soil carbon in fall and winter (March Δ14CO2 = 22 ± 1.3‰, 47% ± 8% microbial). Thus, rising soil temperatures and emissions during fall and winter are depleting aged soil carbon pools in the active layer and thawing permafrost and further accelerating climate change. Plain Language Summary: The Arctic is warming and large quantities of organic matter in permafrost soils are at risk of becoming decomposed to carbon dioxide (CO2) by microbes. Measurements of soil CO2 emissions do not provide direct estimates of permafrost emissions, however, because CO2 is produced by microbes and plant roots. Using a new sampler, we collected soil CO2 in northern Alaska over 3–6 weeks for 2 years and analyzed its radiocarbon content to distinguish CO2 sources. To calculate CO2 budgets, we added observations of soil and microbial CO2 emissions and soil temperature. We find that microbes rely on fresh plant matter in summer but older organic matter from fall to spring; a process not captured by standard laboratory experiments. Thus, warming permafrost soils are not just more rapidly cycling fresh plant litter but losing organic matter that accumulated over decades to millennia. Key Points: Combining continuous soil CO2 flux with Δ14CO2 observations enables a systematic evaluation of carbon cycling in Arctic soils year‐roundOutside the growing season, soil microorganisms rely on older, local soil carbon pools not captured in short‐term incubation experimentsPermafrost warming and thaw is depleting soil carbon pools; fluxes of older carbon are greatest in summer but dominate emissions in winter [ABSTRACT FROM AUTHOR]

Published
2022
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17. Resilience of Alaska's Boreal Forest to Climatic Change

Author

Chapin, F. S., III, McGuire, A. D, Ruess, R. W, Hollingsworth, T. N, Mack, M. C, Johnstone, J. F, Kasischke, E. S, Euskirchen, E. S, Jones, J. B, Jorgenson, M. T, Kielland, K, Kofinas, G. P, Turetsky, M. R, Yarie, J, Lloyd, A. H, and Taylor, D. L

Subjects
Earth Resources And Remote Sensing
Abstract

This paper assesses the resilience of Alaska s boreal forest system to rapid climatic change. Recent warming is associated with reduced growth of dominant tree species, plant disease and insect outbreaks, warming and thawing of permafrost, drying of lakes, increased wildfire extent, increased postfire recruitment of deciduous trees, and reduced safety of hunters traveling on river ice. These changes have modified key structural features, feedbacks, and interactions in the boreal forest, including reduced effects of upland permafrost on regional hydrology, expansion of boreal forest into tundra, and amplification of climate warming because of reduced albedo (shorter winter season) and carbon release from wildfires. Other temperature-sensitive processes for which no trends have been detected include composition of plant and microbial communities, long-term landscape-scale change in carbon stocks, stream discharge, mammalian population dynamics, and river access and subsistence opportunities for rural indigenous communities. Projections of continued warming suggest that Alaska s boreal forest will undergo significant functional and structural changes within the next few decades that are unprecedented in the last 6000 years. The impact of these social ecological changes will depend in part on the extent of landscape reorganization between uplands and lowlands and on policies regulating subsistence opportunities for rural communities.

Published
2010
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18. Warming response of peatland CO2sink is sensitive to seasonality in warming trends

Author

Helbig, M., Živković, T., Alekseychik, P., Aurela, M., El-Madany, T. S., Euskirchen, E. S., Flanagan, L. B., Griffis, T. J., Hanson, P. J., Hattakka, J., Helfter, C., Hirano, T., Humphreys, E. R., Kiely, G., Kolka, R. K., Laurila, T., Leahy, P. G., Lohila, A., Mammarella, I., Nilsson, M. B., Panov, A., Parmentier, F. J. W., Peichl, M., Rinne, J., Roman, D. T., Sonnentag, O., Tuittila, E.-S, Ueyama, M., Vesala, T., Vestin, P., Weldon, S., Weslien, P., and Zaehle, S.

Abstract

Peatlands have acted as net CO2sinks over millennia, exerting a global climate cooling effect. Rapid warming at northern latitudes, where peatlands are abundant, can disturb their CO2sink function. Here we show that sensitivity of peatland net CO2exchange to warming changes in sign and magnitude across seasons, resulting in complex net CO2sink responses. We use multiannual net CO2exchange observations from 20 northern peatlands to show that warmer early summers are linked to increased net CO2uptake, while warmer late summers lead to decreased net CO2uptake. Thus, net CO2sinks of peatlands in regions experiencing early summer warming, such as central Siberia, are more likely to persist under warmer climate conditions than are those in other regions. Our results will be useful to improve the design of future warming experiments and to better interpret large-scale trends in peatland net CO2uptake over the coming few decades.

Published
2022
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20. The influence of vegetation on shallow soil and air temperature coupling: a Pan-Arctic data synthesis

Author

Kropp, H., Loranty, M. M., Natali, S., Kholodov, A. L., Abbott, B., Abermann, J., Blanc-Betes, E., Blok, D., Blume-Werry, G., Boike, Julia, Breen, A. L., Cahoon, S. M. P., Christiansen, C., Douglas, T. A., Elberling, B., Epstein, H. E., Euskirchen, E. S., Frost, G., Goeckede, M., Gough, L., Heijmans, M., Hjort, J., Hoye, T. T., Humphreys, E., Iversen, C. M., Iwata, H., Jones, B. M., Jorgenson, T., Grünberg, Inge, Kim, Y., Lafleur, P., Laundre, J., Lund, M., Mamet, S., Mauritz, M., Michelsen, A., Myers-Smith, I. H., O'Donnell, J., Olefeldt, D., Phoenix, G. K., Rocha, A. V., Romanovsky, V. E., Salmon, V. G., Sannel, B., Schaepman-Strub, G., Smith, S. L., Sonnentag, O., Tape, K. D., Torn, M. S., Vaughn, L. S., Williams, M., Wilson, C. J., Kropp, H., Loranty, M. M., Natali, S., Kholodov, A. L., Abbott, B., Abermann, J., Blanc-Betes, E., Blok, D., Blume-Werry, G., Boike, Julia, Breen, A. L., Cahoon, S. M. P., Christiansen, C., Douglas, T. A., Elberling, B., Epstein, H. E., Euskirchen, E. S., Frost, G., Goeckede, M., Gough, L., Heijmans, M., Hjort, J., Hoye, T. T., Humphreys, E., Iversen, C. M., Iwata, H., Jones, B. M., Jorgenson, T., Grünberg, Inge, Kim, Y., Lafleur, P., Laundre, J., Lund, M., Mamet, S., Mauritz, M., Michelsen, A., Myers-Smith, I. H., O'Donnell, J., Olefeldt, D., Phoenix, G. K., Rocha, A. V., Romanovsky, V. E., Salmon, V. G., Sannel, B., Schaepman-Strub, G., Smith, S. L., Sonnentag, O., Tape, K. D., Torn, M. S., Vaughn, L. S., Williams, M., and Wilson, C. J.

Published
2018

28. Modeling the effects of fire severity and climate warming on active layer thickness and soil carbon storage of black spruce forests across the landscape in interior Alaska

Author

Genet, H, primary, McGuire, A D, additional, Barrett, K, additional, Breen, A, additional, Euskirchen, E S, additional, Johnstone, J F, additional, Kasischke, E S, additional, Melvin, A M, additional, Bennett, A, additional, Mack, M C, additional, Rupp, T S, additional, Schuur, A E G, additional, Turetsky, M R, additional, and Yuan, F, additional

Published
2013
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29. Temperature and vegetation seasonality diminishment over northern lands

Author

Xu, L., primary, Myneni, R. B., additional, Chapin III, F. S., additional, Callaghan, T. V., additional, Pinzon, J. E., additional, Tucker, C. J., additional, Zhu, Z., additional, Bi, J., additional, Ciais, P., additional, Tømmervik, H., additional, Euskirchen, E. S., additional, Forbes, B. C., additional, Piao, S. L., additional, Anderson, B. T., additional, Ganguly, S., additional, Nemani, R. R., additional, Goetz, S. J., additional, Beck, P. S. A., additional, Bunn, A. G., additional, Cao, C., additional, and Stroeve, J. C., additional

Published
2013
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30. Edge influence on forest structure and composition in fragmented landscapes

Author

Harper, K A, MacDonald, S E, Burton, P J, Chen, J, Brosofske, K D, Saunders, S C, Euskirchen, E S, Roberts, D, Jaiteh, M S, Esseen, P-A, Harper, K A, MacDonald, S E, Burton, P J, Chen, J, Brosofske, K D, Saunders, S C, Euskirchen, E S, Roberts, D, Jaiteh, M S, and Esseen, P-A

Published
2005

34. The role of snow cover and soil freeze/thaw cycles affecting boreal-arctic soil carbon dynamics.

Author

Yi, Y., Kimball, J. S., Rawlins, M. A., Moghaddam, M., and Euskirchen, E. S.

Subjects
CARBON in soils, GLOBAL warming, PLANT growth, ATMOSPHERIC chemistry, VEGETATION & climate
Abstract

Northern Hemisphere permafrost affected land areas contain about twice as much carbon as the global atmosphere. This vast carbon pool is vulnerable to accelerated losses through mobilization and decomposition under projected global warming. Satel- lite data records spanning the past 3 decades indicate widespread reductions (~ 0.8- 1.3 daysdecade-1) in the mean annual snow cover extent and frozen season duration across the pan-Arctic domain, coincident with regional climate warming trends. How the soil carbon pool responds to these changes will have a large impact on regional and global climate. Here, we developed a coupled terrestrial carbon and hydrology model framework with detailed 1-D soil heat transfer representation to investigate the sensitivity of soil organic carbon stocks and soil decomposition to changes in snow cover and soil freeze/thaw processes in the Pan-Arctic region over the past three decades (1982-2010). Our results indicate widespread soil active layer deepening across the pan-Arctic, with a mean decadal trend of 6.6-12.0 (SD) cm, corresponding with widespread warming and lengthening non-frozen season. Warming promotes vegetation growth and soil heterotrophic respiration, particularly within surface soil layers (≤ 0.2 m). The model simulations also show that seasonal snow cover has a large impact on soil temperatures, whereby increases in snow cover promote deeper (≥ 0.5 m) soil layer warming and soil respiration, while inhibiting soil decomposition from sur face (≤ 0.2m) soil layers, especially in colder climate zones (mean annual T ≤ -10 °C). Our results demonstrate the important control of snow cover in affecting northern soil freeze/thaw and soil carbon decomposition processes, and the necessity of considering both warming, and changing precipitation and snow cover regimes in characterizing permafrost soil carbon dynamics. [ABSTRACT FROM AUTHOR]

Published
2015
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35. Importance of recent shifts in soil thermal dynamics on growing season length, productivity, and carbon sequestration in terrestrial high-latitude ecosystems

Author

EUSKIRCHEN, E. S., primary, McGUIRE, A. D., additional, KICKLIGHTER, D. W., additional, ZHUANG, Q., additional, CLEIN, J. S., additional, DARGAVILLE, R. J., additional, DYE, D. G., additional, KIMBALL, J. S., additional, McDONALD, K. C., additional, MELILLO, J. M., additional, ROMANOVSKY, V. E., additional, and SMITH, N. V., additional

Published
2006
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36. The changing effects of Alaska's boreal forests on the climate system.

Author

Euskirchen, E. S., McGuire, A. D., Chapin III, F. S., and Rupp, T. S.

Subjects
*TAIGA ecology, *CLIMATE change, *ALBEDO, *BIOTIC communities, *VEGETATION & climate
Abstract

In the boreal forests of Alaska, recent changes in climate have influenced the exchange of trace gases, water, and energy between these forests and the atmosphere. These changes in the structure and function of boreal forests can then feed back to impact regional and global climates. In this manuscript, we examine the type and magnitude of the climate feedbacks from boreal forests in Alaska. Research generally suggests that the net effect of a warming climate is a positive regional feedback to warming. Currently, the primary positive climate feedbacks are likely related to decreases in surface albedo due to decreases in snow cover. Fewer negative feedbacks have been identified, and they may not be large enough to counterbalance the large positive feedbacks. These positive feedbacks are most pronounced at the regional scale and reduce the resilience of the boreal vegetation - climate system by amplifying the rate of regional warming. Given the recent warming in this region, the large variety of associated mechanisms that can alter terrestrial ecosystems and influence the climate system, and a reduction in the boreal forest resilience, there is a strong need to continue to quantify and evaluate the feedback pathways. [ABSTRACT FROM AUTHOR]

Published
2010
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37. Resilience of Alaska's boreal forest to climatic change.

Author

Chapin III, F. S., McGuire, A. D., Ruess, R. W., Hollingsworth, T. N., Mack, M. C., Johnstone, J. F., Kasischke, E. S., Euskirchen, E. S., Jones, J. B., Jorgenson, M. T., Kielland, K., Kofinas, G. P., Turetsky, M. R., Yarie, J., Lloyd, A. H., and Taylor, D. L.

Subjects
FOREST resilience, TAIGA ecology, CLIMATE change, ALBEDO, HYDROLOGY
Abstract

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Published
2010
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38. Closing the Winter Gap—Year‐Round Measurements of Soil CO2Emission Sources in Arctic Tundra

Author

Pedron, Shawn A., Welker, J. M., Euskirchen, E. S., Klein, E. S., Walker, J. C., Xu, X., and Czimczik, C. I.

Abstract

Non‐growing season CO2emissions from Arctic tundra remain a major uncertainty in forecasting climate change consequences of permafrost thaw. We present the first time series of soil and microbial CO2emissions from a graminoid tundra based on year‐round in situ measurements of the radiocarbon content of soil CO2(Δ14CO2) and of bulk soil C (Δ14C), microbial activity, and temperature. Combining these data with land‐atmosphere CO2exchange allows estimates of the proportion and mean age of microbial CO2emissions year‐round. We observe a seasonal shift in emission sources from fresh carbon during the growing season (August Δ14CO2= 74 ± 4.7‰, 37% ± 3.4% microbial, mean ± se) to increasingly older soil carbon in fall and winter (March Δ14CO2= 22 ± 1.3‰, 47% ± 8% microbial). Thus, rising soil temperatures and emissions during fall and winter are depleting aged soil carbon pools in the active layer and thawing permafrost and further accelerating climate change. The Arctic is warming and large quantities of organic matter in permafrost soils are at risk of becoming decomposed to carbon dioxide (CO2) by microbes. Measurements of soil CO2emissions do not provide direct estimates of permafrost emissions, however, because CO2is produced by microbes and plant roots. Using a new sampler, we collected soil CO2in northern Alaska over 3–6 weeks for 2 years and analyzed its radiocarbon content to distinguish CO2sources. To calculate CO2budgets, we added observations of soil and microbial CO2emissions and soil temperature. We find that microbes rely on fresh plant matter in summer but older organic matter from fall to spring; a process not captured by standard laboratory experiments. Thus, warming permafrost soils are not just more rapidly cycling fresh plant litter but losing organic matter that accumulated over decades to millennia. Combining continuous soil CO2flux with Δ14CO2observations enables a systematic evaluation of carbon cycling in Arctic soils year‐roundOutside the growing season, soil microorganisms rely on older, local soil carbon pools not captured in short‐term incubation experimentsPermafrost warming and thaw is depleting soil carbon pools; fluxes of older carbon are greatest in summer but dominate emissions in winter Combining continuous soil CO2flux with Δ14CO2observations enables a systematic evaluation of carbon cycling in Arctic soils year‐round Outside the growing season, soil microorganisms rely on older, local soil carbon pools not captured in short‐term incubation experiments Permafrost warming and thaw is depleting soil carbon pools; fluxes of older carbon are greatest in summer but dominate emissions in winter

Published
2022
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39. A portable miniaturized laser heterodyne radiometer (mini-LHR) for remote measurements of column CH4 and CO2.

Author

Wilson, E. L., DiGregorio, A. J., Villanueva, G., Grunberg, C. E., Souders, Z., Miletti, K. M., Menendez, A., Grunberg, M. H., Floyd, M. A. M., Bleacher, J. E., Euskirchen, E. S., Edgar, C., Caldwell, B. J., Shiro, B., and Binsted, K.

Subjects
RADIOMETERS, MICROWAVE radiometers, CARBON dioxide lasers, LASERS, GAS absorption & adsorption, RADIO frequency
Abstract

We present the design of a portable version of our miniaturized laser heterodyne radiometer (mini-LHR) that simultaneously measures methane (CH4) and carbon dioxide (CO2) in the atmospheric column. The mini-LHR fits on a backpack frame, operates autonomously, and requires no infrastructure because it is powered by batteries charged by a folding 30 W solar panel. Similar to our earlier instruments, the mini-LHR is a passive laser heterodyne radiometer that operates by collecting sunlight that has undergone absorption by CH4 and CO2. Within the mini-LHR, sunlight is mixed with light from a distributive feedback (DFB) laser centered at approximately 1.64 μm where both gases have absorption features. The laser scans across these absorption features roughly every minute and the resulting beat signal is collected in the radio frequency (RF). Scans are averaged into half hour and hour data products and analyzed using the Planetary Spectrum Generator (PSG) retrieval to extract column mole fractions. Instrument performance is demonstrated through two deployments at significantly different sites in interior Alaska and Hawaii. The resolving power (λ/∆λ) is greater than 500,000 at 1.64 μm with precisions of better than 20 ppb and 1 ppm for CH4 and CO2, respectively. Because mini-LHR instruments are portable and can be co-located, they can be used to characterize bias between larger, stationary, column observing instruments. In addition, mini-LHRs can be deployed quickly to respond to transient events such as methane leaks or can be used for field studies targeting geographical regions. [ABSTRACT FROM AUTHOR]

Published
2019
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41. A portable miniaturized laser heterodyne radiometer (mini-LHR) for remote measurements of column CH4 and CO2.

Author

Wilson, E. L., DiGregorio, A. J., Villanueva, G., Grunberg, C. E., Souders, Z., Miletti, K. M., Menendez, A., Grunberg, M. H., Floyd, M. A. M., Bleacher, J. E., Euskirchen, E. S., Edgar, C., Caldwell, B. J., Shiro, B., and Binsted, K.

Subjects
*RADIOMETERS, *MICROWAVE radiometers, *CARBON dioxide lasers, *LASERS, *GAS absorption & adsorption, *RADIO frequency
Abstract

We present the design of a portable version of our miniaturized laser heterodyne radiometer (mini-LHR) that simultaneously measures methane (CH4) and carbon dioxide (CO2) in the atmospheric column. The mini-LHR fits on a backpack frame, operates autonomously, and requires no infrastructure because it is powered by batteries charged by a folding 30 W solar panel. Similar to our earlier instruments, the mini-LHR is a passive laser heterodyne radiometer that operates by collecting sunlight that has undergone absorption by CH4 and CO2. Within the mini-LHR, sunlight is mixed with light from a distributive feedback (DFB) laser centered at approximately 1.64 μm where both gases have absorption features. The laser scans across these absorption features roughly every minute and the resulting beat signal is collected in the radio frequency (RF). Scans are averaged into half hour and hour data products and analyzed using the Planetary Spectrum Generator (PSG) retrieval to extract column mole fractions. Instrument performance is demonstrated through two deployments at significantly different sites in interior Alaska and Hawaii. The resolving power (λ/∆λ) is greater than 500,000 at 1.64 μm with precisions of better than 20 ppb and 1 ppm for CH4 and CO2, respectively. Because mini-LHR instruments are portable and can be co-located, they can be used to characterize bias between larger, stationary, column observing instruments. In addition, mini-LHRs can be deployed quickly to respond to transient events such as methane leaks or can be used for field studies targeting geographical regions. [ABSTRACT FROM AUTHOR]

Published
2019
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