33 research outputs found
Pan-European δ<sup>1</sup><sup>3</sup>C values of air and organic matter from forest ecosystems
No full textWe present carbon stable isotope, delta C-13, results from air and organic matter samples collected during 98 individual field campaigns across a network of Carboeuroflux forest sites in 2001 (14 sites) and 2002 (16 sites). Using these data, we tested the hypothesis that delta C-13 values derived from large-scale atmospheric measurements and models, which are routinely used to partition carbon fluxes between land and ocean, and potentially between respiration and photosynthesis on land, are consistent with directly measured ecosystem-scale delta C-13 values. In this framework, we also tested the potential of delta C-13 in canopy air and plant organic matter to record regional-scale ecophysiological patterns. Our network estimates for the mean delta C-13 of ecosystem respired CO2 and the related 'discrimination' of ecosystem respiration, delta(er) and Delta(er), respectively, were -25.6 +/- 1.9 parts per thousand and 17.8 +/- 2.0 parts per thousand in 2001 and -26.6 +/- 1.5 parts per thousand and 19.0 +/- 1.6 parts per thousand in 2002. The results were in close agreement with delta C-13 values derived from regional-scale atmospheric measurement programs for 2001, but less so in 2002, which had an unusual precipitation pattern. This suggests that regional-scale atmospheric sampling programs generally capture ecosystem delta C-13 signals over Europe, but may be limited in capturing some of the interannual variations. In 2001, but less so in 2002, there were discernable longitudinal and seasonal trends in delta(er). From west to east, across the network, there was a general enrichment in C-13 (similar to 3 parts per thousand and similar to 1 parts per thousand for the 2 years, respectively) consistent with increasing Gorczynski continentality index for warmer and drier conditions. In 2001 only, seasonal C-13 enrichment between July and September, followed by depletion in November (from about -26.0 parts per thousand to -24.5 parts per thousand to -30.0 parts per thousand), was also observed. In 2001, July and August delta(er) values across the network were significantly related to average daytime vapor pressure deficit (VPD), relative humidity (RH), and, to a lesser degree, air temperature (T-a), but not significantly with monthly average precipitation (P-m). In contrast, in 2002 (a much wetter peak season), delta(er) was significantly related with T-a, but not significantly with VPD and RH. The important role of plant physiological processes on delta(er) in 2001 was emphasized by a relatively rapid turnover (between 1 and 6 days) of assimilated carbon inferred from time-lag analyses of delta(er) vs. meteorological parameters. However, this was not evident in 2002. These analyses also noted corresponding diurnal cycles of delta(er) and meteorological parameters in 2001, indicating a rapid transmission of daytime meteorology, via physiological responses, to the delta(er) signal during this season. Organic matter delta C-13 results showed progressive C-13 enrichment from leaves, through stems and roots to soil organic matter, which may be explained by C-13 fractionation during respiration. This enrichment was species dependent and was prominent in angiosperms but not in gymnosperms. delta C-13 values of organic matter of any of the plant components did not well represent short-term delta(er) values during the seasonal cycle, and could not be used to partition ecosystem respiration into autotrophic and heterotrophic components
Productivity, Respiration, and Light-Response Parameters of World Grassland and Agroecosystems Derived From Flux-Tower Measurements
No full textGrasslands and agroecosystems occupy one-third of the terrestrial area, but their contribution to the global carbon cycle remains uncertain. We used a set of 316 site-years of CO(2) exchange measurements to quantify gross primary productivity, respiration, and light-response parameters of grasslands, shrublands/savanna, wetlands, and cropland ecosystems worldwide. We analyzed data from 72 global flux-tower sites partitioned into gross photosynthesis and ecosystem respiration with the use of the light-response method (Gilmanov, T. G., D. A. Johnson, and N. Z. Saliendra. 2003. Growing season CO(2) fluxes in a sagebrushsteppe ecosystem in Idaho: Bowen ratio/energy balance measurements and modeling. Basic and Applied Ecology 4:167-183) from the RANGEFLUX and WORLDGRASSAGRIFLUX data sets supplemented by 46 sites from the FLUXNET La Thuile data set partitioned with the use of the temperature-response method (Reichstein, M., E. Falge, D. Baldocchi, D. Papale, R. Valentini, M. Aubinet, P. Berbigier, C. Bernhofer, N. Buchmann, M. Falk, T. Gilmanov, A. Granier, T. Grunwald, K. Havrankova, D. Janous, A. Knohl, T. Laurela, A. Lohila, D. Loustau, G. Matteucci, T. Meyers, F. Miglietta, J.M. Ourcival, D. Perrin, J. Pumpanen, S. Rambal, E. Rotenberg, M. Sanz, J. Tenhunen, G. Seufert, F. Vaccari, T. Vesala, and D. Yakir. 2005. On the separation of net ecosystem exchange into assimilation and ecosystem respiration: review and improved algorithm. Global Change Biology 11: 1.424-1439). Maximum values of the quantum yield (alpha = 75 mmol.mol(-1)), photosynthetic capacity (A(max) = 3.4 mg CO(2) . m(-2).s-1), gross photosynthesis (P(g,max) = 1.16 g CO(2) . m(-2).d(-1)), and ecological light-use efficiency (epsilon(ecol) = 59 mmol . mol(-1)) of managed grasslands and high-production croplands exceeded those of most forest ecosystems, indicating the potential of nonforest ecosystems for uptake of atmospheric CO(2). Maximum values of gross primary production (8 600 g CO(2) . m(-2).yr(-1)), total ecosystem respiration (7 900 g CO(2) . m(-2).yr(-1)), and net CO(2) exchange (2 400 g CO(2) . m(-2).yr(-1)) were observed for intensively managed grasslands and high-yield crops, and are comparable to or higher than those for forest ecosystems, excluding some tropical forests. On average, 80% of the nonforest sites were apparent sinks for atmospheric CO(2), with mean net uptake of 700 g CO(2) . m(-2).yr(-1) for intensive grasslands and 933 g CO(2) . m(-2).d(-1) for croplands. However, part of these apparent sinks is accumulated in crops and forage, which are carbon pools that are harvested, transported, and decomposed off site. Therefore, although agricultural fields may be predominantly sinks for atmospheric CO(2), this does not imply that they are necessarily increasing their carbon stock
Productivity, Respiration, and Light-Response Parameters of World Grassland and Agroecosystems Derived From Flux-Tower Measurements
No full textGrasslands and agroecosystems occupy one-third of the terrestrial area, but their contribution to the global carbon cycle remains uncertain. We used a set of 316 site-years of CO2 exchange measurements to quantify gross primary productivity, respiration, and light-response parameters of grasslands, shrublands/savanna, wetlands, and cropland ecosystems worldwide. We analyzed data from 72 global flux-tower sites partitioned into gross photosynthesis and ecosystem respiration with the use of the light-response method (Gilmanov, T. G., D. A. Johnson, and N. Z. Saliendra. 2003. Growing season CO2 fluxes in a sagebrush-steppe ecosystem in Idaho: Bowen ratio/energy balance measurements and modeling. Basic and Applied Ecology 4:167–183) from the RANGEFLUX and WORLDGRASSAGRIFLUX data sets supplemented by 46 sites from the FLUXNET La Thuile data set partitioned with the use of the temperature-response method (Reichstein, M., E. Falge, D. Baldocchi, D. Papale, R. Valentini, M. Aubinet, P. Berbigier, C. Bernhofer, N. Buchmann, M. Falk, T. Gilmanov, A. Granier, T. Grünwald, K. Havránková, D. Janous, A. Knohl, T. Laurela, A. Lohila, D. Loustau, G. Matteucci, T. Meyers, F. Miglietta, J. M. Ourcival, D. Perrin, J. Pumpanen, S. Rambal, E. Rotenberg, M. Sanz, J. Tenhunen, G. Seufert, F. Vaccari, T. Vesala, and D. Yakir. 2005. On the separation of net ecosystem exchange into assimilation and ecosystem respiration: review and improved algorithm. Global Change Biology 11:1424–1439). Maximum values of the quantum yield (a=75 mmol·mol-1), photosynthetic capacity (Amax=3.4 mg CO2·m-2·s-1), gross photosynthesis (Pg,max=116 g CO2·m-2·d-1), and ecological light-use efficiency (ecol=59 mmol·mol-1) of managed grasslands and high-production croplands exceeded those of most forest ecosystems, indicating the potential of nonforest ecosystems for uptake of atmospheric CO2. Maximum values of gross primary production (8600 g CO2·m-2·yr-1), total ecosystem respiration (7900 g CO2·m-2·yr-1), and net CO2 exchange (2400 g CO2·m-2·yr-1) were observed for intensively managed grasslands and high-yield crops, and are comparable to or higher than those for forest ecosystems, excluding some tropical forests. On average, 80% of the nonforest sites were apparent sinks for atmospheric CO2, with mean net uptake of 700 g CO2·m-2·yr-1 for intensive grasslands and 933 g CO2·m-2·d-1 for croplands. However, part of these apparent sinks is accumulated in crops and forage, which are carbon pools that are harvested, transported, and decomposed off site. Therefore, although agricultural fields may be predominantly sinks for atmospheric CO2, this does not imply that they are necessarily increasing their carbon stoc
Productivity, Respiration, and Light-Response Parameters of World Grassland and Agroecosystems Derived From Flux-Tower Measurements
No full textGrasslands and agroecosystems occupy one-third of the terrestrial area, but their contribution to the global carbon cycle remains uncertain. We used a set of 316 site-years of CO2 exchange measurements to quantify gross primary productivity, respiration, and light-response parameters of grasslands, shrublands/savanna, wetlands, and cropland ecosystems worldwide. We analyzed data from 72 global flux-tower sites partitioned into gross photosynthesis and ecosystem respiration with the use of the light- response method (Gilmanov, T. G., D. A. Johnson, and N. Z. Saliendra. 2003. Growing season CO2 fluxes in a sagebrush- steppe ecosystem in Idaho: Bowen ratio/energy balance measurements and modeling. Basic and Applied Ecology 4:167–183) from the RANGEFLUX and WORLDGRASSAGRIFLUX data sets supplemented by 46 sites from the FLUXNET La Thuile data set partitioned with the use of the temperature-response method (Reichstein, M., E. Falge, D. Baldocchi, D. Papale, R. Valentini, M. Aubinet, P. Berbigier, C. Bernhofer, N. Buchmann, M. Falk, T. Gilmanov, A. Granier, T. Gru ̈nwald, K. Havra ́nkova ́, D. Janous, A. Knohl, T. Laurela, A. Lohila, D. Loustau, G. Matteucci, T. Meyers, F. Miglietta, J. M. Ourcival, D. Perrin, J. Pumpanen, S. Rambal, E. Rotenberg, M. Sanz, J. Tenhunen, G. Seufert, F. Vaccari, T. Vesala, and D. Yakir. 2005. On the separation of net ecosystem exchange into assimilation and ecosystem respiration: review and improved algorithm. Global Change Biology 11:1424–1439). Maximum values of the quantum yield (a 5 75 mmol ? mol21), photosynthetic capacity (Amax 5 3.4 mg CO2 ? m22 ? s21), gross photosynthesis (Pg,max 5 116 g CO2 ? m22 ? d21), and ecological light-use efficiency (eecol 5 59 mmol ? mol21) of managed grasslands and high-production croplands exceeded those of most forest ecosystems, indicating the potential of nonforest ecosystems for uptake of atmospheric CO2. Maximum values of gross primary production (8 600 g CO2 ? m22 ? yr21), total ecosystem respiration (7 900 g CO2 ? m22 ? yr21), and net CO2 exchange (2 400 g CO2 ? m22 ? yr21) were observed for intensively managed grasslands and high-yield crops, and are comparable to or higher than those for forest ecosystems, excluding some tropical forests. On average, 80% of the nonforest sites were apparent sinks for atmospheric CO2, with mean net uptake of 700 g CO2 ? m22 ? yr21 for intensive grasslands and 933 g CO2 ? m22 ? d21 for croplands. However, part of these apparent sinks is accumulated in crops and forage, which are carbon pools that are harvested, transported, and decomposed off site. Therefore, although agricultural fields may be predominantly sinks for atmospheric CO2, this does not imply that they are necessarily increasing their carbon stock.
A passive sampling method for radiocarbon analysis of atmospheric CO<sub>2</sub> using molecular sieve
No full textRadiocarbon (14C) analysis of atmospheric CO2 can provide information on CO2 sources and is potentially valuable for validating inventories of fossil fuel-derived CO2 emissions to the atmosphere. We tested zeolite molecular sieve cartridges, in both field and laboratory experiments, for passively collecting atmospheric CO2. Cartridges were exposed to the free atmosphere in two configurations which controlled CO2 trapping rate, allowing collection of sufficient CO2 in between 1.5 and 10 months at current levels. 14C results for passive samples were within measurement uncertainty of samples collected using a pump-based system, showing that the method collected samples with 14C contents representative of the atmosphere. δ13C analysis confirmed that the cartridges collected representative CO2 samples, however, fractionation during passive trapping means that δ13C values need to be adjusted by an amount which we have quantified. Trapping rate was proportional to atmospheric CO2 concentration, and was not affected by exposure time unless this exceeded a threshold. Passive sampling using molecular sieve cartridges provides an easy and reliable method to collect atmospheric CO2 for 14C analysis
Controls on winter ecosystem respiration in temperate and boreal ecosystems
No full textWinter CO2 fluxes represent an important component of the annual carbon budget in northern ecosystems. Understanding winter respiration processes and their responses to climate change is also central to our ability to assess terrestrial carbon cycle and climate feedbacks in the future. However, the factors influencing the spatial and temporal patterns of winter ecosystem respiration (Reco) of northern ecosystems are poorly understood. For this reason, we analyzed eddy covariance flux data from 57 ecosystem sites ranging from ~35° N to ~70° N. Deciduous forests were characterized by the highest winter Reco rates (0.90 ± 0.39 g C m-2 d-1), when winter is defined as the period during which daily air temperature remains below 0 °C. By contrast, arctic wetlands had the lowest winter Reco rates (0.02 ± 0.02 g C m-2 d-1). Mixed forests, evergreen needle-leaved forests, grasslands, croplands and boreal wetlands were characterized by intermediate winter Reco rates (g C m-2 d-1) of 0.70(±0.33), 0.60(±0.38), 0.62(±0.43), 0.49(±0.22) and 0.27(±0.08), respectively. Our cross site analysis showed that winter air (Tair) and soil (Tsoil) temperature played a dominating role in determining the spatial patterns of winter Reco in both forest and managed ecosystems (grasslands and croplands). Besides temperature, the seasonal amplitude of the leaf area index (LAI), inferred from satellite observation, or growing season gross primary productivity, which we use here as a proxy for the amount of recent carbon available for Reco in the subsequent winter, played a marginal role in winter CO2 emissions from forest ecosystems. We found that winter Reco sensitivity to temperature variation across space (QS) was higher than the one over time (interannual, QT). This can be expected because QS not only accounts for climate gradients across sites but also for (positively correlated) the spatial variability of substrate quantity. Thus, if the models estimate future warming impacts on Reco based on QS rather than QT, this could overestimate the impact of temperature change
Thermal adaptation of net ecosystem exchange
No full textThermal adaptation of gross primary production and ecosystem respiration has been well documented over broad thermal gradients. However, no study has examined their interaction as a function of temperature, i.e. the thermal responses of net ecosystem exchange of carbon (NEE). In this study, we constructed temperature response curves of NEE against temperature using 380 site-years of eddy covariance data at 72 forest, grassland and shrubland ecosystems located at latitudes ranging from ~29° N to 64° N. The response curves were used to define two critical temperatures: transition temperature (<i>T</i><sub>b</sub>) at which ecosystem transfer from carbon source to sink and optimal temperature (<i>T</i><sub>o</sub>) at which carbon uptake is maximized. <i>T</i><sub>b</sub> was strongly correlated with annual mean air temperature. <i>T</i><sub>o</sub> was strongly correlated with mean temperature during the net carbon uptake period across the study ecosystems. Our results imply that the net ecosystem exchange of carbon adapts to the temperature across the geographical range due to intrinsic connections between vegetation primary production and ecosystem respiration
Correction to Collaborators in Acknowledgments in: Decision-Making on Withholding or Withdrawing Life Support in the ICU: A Worldwide Perspective (Chest (2017) 152(2) (321–329), (S0012369217308206), (10.1016/j.chest.2017.04.176))
No full textThe authors have reported to CHEST that the collaborators from the ICON Investigators were omitted from the Acknowledgments in “Decision-Making on Withholding or Withdrawing Life Support in the ICU: A Worldwide Perspective” (Chest. 2017;152(2):321-329). The corrected Acknowledgments are as follows: ∗ICON Investigators: E. Tomas, E. Amisi Bibonge, B. Charra, M. Faroudy, L. Doedens, Z. Farina, D. Adler, C. Balkema, A. Kok, S. Alaya, H. Gharsallah, D. Muzha, A. Temelkov, G. Georgiev, G. Simeonov, G. Tsaryanski, S. Georgiev, A. Seliman, S. Vrankovic, Z. Vucicevic, I. Gornik, B. Barsic, I. Husedzinovic, P. Pavlik, J. Manak, E. Kieslichova, R. Turek, M. Fischer, R. Valkova, L. Dadak, P. Dostal, J. Malaska, R. Hajek, A. Židková, P. Lavicka, J. Starkopf, Z. Kheladze, M. Chkhaidze, V. Kaloiani, L. Medve, A. Sarkany, I. Kremer, Z. Marjanek, P. Tamasi, I. Krupnova, I. Vanags, V. Liguts, V. Pilvinis, S. Vosylius, G. Kekstas, M. Balciunas, J. Kolbusz, A. Kübler, B. Mielczarek, M. Mikaszewska-Sokolewicz, K. Kotfis, B. Tamowicz, W. Sulkowski, P. Smuszkiewicz, A. Pihowicz, E. Trejnowska, N. Hagau, D. Filipescu, G. Droc, M. Lupu, A. Nica, R. Stoica, D. Tomescu, D. Constantinescu, G. Valcoreanu Zbaganu, S. Adriana, V. Bagin, D. Belsky, S. Palyutin, S. Shlyapnikov, D. Bikkulova, A. Gritsan, G. Natalia, E. Makarenko, V. Kokhno, A. Tolkach, E. Kokarev, B. Belotserkovskiy, K. Zolotukhin, V. Kulabukhov, L. Soskic, I. Palibrk, R. Jankovic, B. Jovanovic, M. Pandurovic, V. Bumbasirevic, B. Uljarevic, M. Surbatovic, N. Ladjevic, G. Slobodianiuk, V. Sobona, A. Cikova, A. Gebhardtova, C. Jun, S. Yunbo, J. Dong, S. Feng, M. Duan, Y. Xu, X. Xue, T. Gao, X. Xing, X. Zhao, C. Li, G. Gengxihua, H. Tan, J. Xu, L. Jiang, Q, Tiehe, Q, Bingyu, Q, Shi, Z. Lv, L. Zhang, L. Jingtao, Z. Zhen, Z. Wang, T. Wang, L. Yuhong, Q, Zhai, Y. Chen, C. Wang, W. Jiang, W. Ruilan, Y. Chen, H. Xiaobo, H. Ge, T. Yan, C. Yuhui, J. Zhang, F. Jian-Hong, H. Zhu, F. Huo, Y. Wang, C. Li, M. Zhuang, Z. Ma, J. Sun, L. Liuqingyue, M. Yang, J. Meng, S. Ma, K. Lee, Y. Kang, L. Yu, Q, Peng, Y. Wei, W. Zhang, R. Sun, A. Yeung, W. Wan, K. Sin, M. Wijanti, U. Widodo, H. Samsirun, T. Sugiman, C. Wisudarti, T. Maskoen, N. Hata, Y. Kobe, Y. Shimomura, D. Miyazaki, S. Nunomiya, S. Uchino, N. Kitamura, K. Yamashita, S. Hashimoto, H. Fukushima, N. Nik Adib, L. Tai, B. Tony, R. Bigornia, R. Bigornia, R. Bigornia, J. Palo, S. Chatterjee, B. Tan, A. Kong, S. Goh, C. Lee, C. Pothirat, B. Khwannimit, P. Theerawit, P. Pornsuriyasak, A. Piriyapatsom, A. Mukhtar, A. Nabil Hamdy, H. Hosny, A. Ashraf, M. Mokhtari, S. Nowruzinia, A. Lotfi, F. Zand, R. Nikandish, O. Moradi Moghaddam, J. Cohen, O. Sold, T. Sfeir, A. Hasan, D. Abugaber, H. Ahmad, T. Tantawy, S. Baharoom, H. Algethamy, A. Amr, G. Almekhlafi, R. Coskun, M. Sungur, A. Cosar, B. Güçyetmez, O. Demirkiran, E. Senturk, H. Ulusoy, H. Atalan, S. Serin, I. Kati, Z. Alnassrawi, A. Almemari, K. Krishnareddy, S. Kashef, A. Alsabbah, G. Poirier, J. Marshall, M. Herridge, M. Herridge, R. Fernandez, G. Fulda, S. Banschbach, J. Quintero, E. Schroeder, C. Sicoutris, R. Gueret, R. Kashyap, P. Bauer, R. Nanchal, R. Wunderink, E. Jimenez, A. Ryan, A. Ryan, A. Ryan, A. Ryan, A. Ryan, A. Ryan, A. Ryan, D. Prince, J. Edington, F. Van Haren, A. Bersten, B. Richards, M. Kilminster, D. Sturgess, M. Ziegenfuss, S. O'Connor, J. Lipman, L. Campbell, R. Mcallister, B. Roberts, P. Williams, R. Parke, P. Seigne, R. Freebairn, D. Nistor, C. Oxley, P. Young, R. Valentini, N. Wainsztein, P. Comignani, M. Casaretto, G. Sutton, P. Villegas, C. Galletti, J. Neira, D. Rovira, J. Hidalgo, F. Sandi, E. Caser, M. Thompson, M. D'agostino Dias, L. Fontes, M. Lunardi, N. Youssef, S. Lobo, R. Silva, J. Sales Jr, L. Madeira Campos Melo, M. Oliveira, M. Fonte, C. Grion, C. Feijo, V. Rezende, M. Assuncao, A. Neves, P. Gusman, D. Dalcomune, C. Teixeira, K. Kaefer, I. Maia, V. Souza Dantas, R. Costa Filho, F. Amorim, M. Assef, P. Schiavetto, J. Houly, J. Houly, F. Bianchi, F. Dias, C. Avila, J. Gomez, L. Rego, P. Castro, J. Passos, C. Mendes, C. Grion, G. Colozza Mecatti, M. Ferrreira, V. Irineu, M. Guerreiro, S. Ugarte, V. Tomicic, C. Godoy, W. Samaniego, I. Escamilla, I. Escamilla, L. Castro Castro, G. Libreros Duque, D. Diaz-Guio, F. Benítez, A. Guerra Urrego, R. Buitrago, G. Ortiz, M. Villalba Gaviria, D. Salas, J. Ramirez-Arce, E. Salgado, D. Morocho, J. Vergara, M. Chung Sang, C. Orellana-Jimenez, L. Garrido, O. Diaz, D. Resiere, C. Osorio, A. De La Vega, R. Carrillo, V. Sanchez, A. Villagomez, R. Martinez Zubieta, M. Sandia, M. Zalatiel, M. Poblano, D. Rodriguez Gonzalez, F. Arrazola, L. Juan Francisco, S. A. Ñamendys-Silva, M. Hernandez, D. Rodriguez Cadena, I. Lopez Islas, C. Ballesteros Zarzavilla, A. Matos, I. Oyanguren, J. Cerna, R. Quispe Sierra, R. Jimenez, L. Castillo, R. Ocal, A. Sencan, S. Mareque Gianoni, A. Deicas, J. Hurtado, G. Burghi, A. Martinelli, I. Von Der Osten, C. Du Maine, M. Bhattacharyya, S. Bandyopadhyay, S. Yanamala, P. Gopal, S. Sahu, M. Ibrahim, D. Rathod, N. Mukundan, A. Dewan, P. Amin, S. Samavedam, B. Shah, D. Gurupal, B. Lahkar, A. Mandal, M. Sircar, S. Ghosh, V. Balasubramani, F. Kapadia, S. Vadi, K. Nair, S. Tripathy, S. Nandakumar, J. Sharma, A. Kar, S. Jha, K. Zirpe Gurav, M. Patel, A. Bhavsar, D. Samaddar, A. Kulkarni, M. Hashmi, W. Ali, S. Nadeem, K. Indraratna, A. Margarit, P. Urbanek, J. Schlieber, J. Reisinger, J. Auer, A. Hartjes, A. Lerche, T. Janous, E. Kink, W. Krahulec, K. Smolle, M. Van Der Schueren, P. Thibo, M. Vanhoof, I. Ahmet, G. Philippe, P. Dufaye, O. Jacobs, V. Fraipont, P. Biston, A. Dive, Y. Bouckaert, E. Gilbert, B. Gressens, E. Pinck, V. Collin, J. L. Vincent, J. De Waele, R. Rimachi, D. Gusu, K. De Decker, K. Mandianga, L. Heytens, X. Wittebole, S. Herbert, V. Olivier, W. Vandenheede, P. Rogiers, P. Kolodzeike, M. Kruse, T. Andersen, V. Harjola, K. Saarinen, M. Leone, A. Durocher, S. Moulront, A. Lepape, M. Losser, P. Cabaret, E. Kalaitzis, E. Zogheib, P. Charve, B. Francois, J. Lefrant, B. Beilouny, X. Forceville, B. Misset, F. Jacobs, F. Bernard, D. Payen, A. Wynckel, V. Castelain, A. Faure, P. Lavagne, L. Thierry, M. Moussa, A. Vieillard-Baron, M. Durand, M. Gainnier, C. Ichai, S. Arens, C. Hoffmann, M. Kaffarnik, C. Scharnofske, I. Voigt, C. Peckelsen, M. Weber, J. Gille, A. Lange, G. Schoser, A. Sablotzki, U. Jaschinski, A. Bluethgen, F. Vogel, A. Tscheu, T. Fuchs, M. Wattenberg, T. Helmes, S. Scieszka, M. Heintz, S. Sakka, J. Kohler, F. Fiedler, M. Danz, Y. Sakr, R. Riessen, T. Kerz, A. Kersten, F. Tacke, G. Marx, T. Volkert, A. Schmutz, A. Nierhaus, S. Kluge, P. Abel, R. Janosi, S. Utzolino, H. Bracht, S. Toussaint, M. Giannakou Peftoulidou, P. Myrianthefs, A. Armaganidis, C. Routsi, A. Xini, E. Mouloudi, I. Kokoris, G. Kyriazopoulos, S. Vlachos, A. Lavrentieva, P. Partala, G. Nakos, A. Moller, S. Stefansson, J. Barry, R. O'Leary, C. Motherway, M. Faheem, E. Dunne, M. Donnelly, T. Konrad, E. Bonora, C. Achilli, S. Rossi, G. Castiglione, A. Peris, D. Albanese, N. Stocchetti, G. Citerio, L. Mozzoni, E. Sisillo, P. De Negri, M. Savioli, P. Vecchiarelli, F. Puflea, V. Stankovic, G. Minoja, S. Montibeller, P. Calligaro, R. Sorrentino, M. Feri, M. Zambon, E. Colombaroli, A. Giarratano, T. Pellis, C. Capra, M. Antonelli, A. Gullo, C. Chelazzi, A. De Capraris, N. Patroniti, M. Girardis, F. Franchi, G. Berlot, M. Buttigieg, H. Ponssen, J. Ten Cate, L. Bormans, S. Husada, M. Buise, B. Van Der Hoven, A. Reidinga, M. Kuiper, P. Pickkers, G. Kluge, S. Den Boer, J. Kesecioglu, H. Van Leeuwen, H. Flaatten, S. Mo, V. Branco, F. Rua, E. Lafuente, M. Sousa, N. Catorze, M. Barros, L. Pereira, A. Vintém De Oliveira, J. Gomes, I. Gaspar, M. Pereira, M. Cymbron, A. Dias, E. Almeida, S. Beirao, I. Serra, R. Ribeiro, P. Povoa, F. Faria, Z. Costa-E-Silva, J. Nóbrega, F. Fernandes, J. Gabriel, G. Voga, E. Rupnik, L. Kosec, M. Kerin Povšic, I. Osojnik, V. Tomic, A. Sinkovic, J. González, E. Zavala, J. Pérez Valenzuela, L. Marina, P. Vidal-Cortés, P. Posada, A. Ignacio Martin-Loeches, N. Muñoz Guillén, M. Palomar, J. Sole-Violan, A. Torres, M. Gonzalez Gallego, G. Aguilar, R. Montoiro Allué, M. Argüeso, M. Parejo, M. Palomo Navarro, A. Jose, N. Nin, F. Alvarez Lerma, O. Martinez, E. Tenza Lozano, S. Arenal López, M. Perez Granda, S. Moreno, C. Llubia, C. De La Fuente Martos, P. Gonzalez-Arenas, N. Llamas Fernández, B. Gil Rueda, I. Estruch Pons, N. Cruza, F. Maroto, A. Estella, A. Ferrer, L. Iglesias Fraile, Q, Brigida, A. Quintano, M. Tebar, F. Frutos-Vivar, A. Reyes, A. Rodríguez, A. Abella, S. García Del Valle, S. Yus, E. Maseda, J. Berezo, A. Tejero Pedregosa, C. Laplaza, R. Ferrer, J. Rico-Feijoo, M. Rodríguez, P. Monedero, K. Eriksson, D. Lind, D. Chabanel, H. Zender, K. Heer, B. Frankenberger, S. Jakob, A. Haller, S. Mathew, R. Downes, C. Barrera Groba, A. Johnston, R. Meacher, R. Keays, P. Haji-Michael, C. Tyler, A. Ferguson, S. Jones, D. Tyl, A. Ball, J. Vogel, M. Booth, P. Downie, M. Watters, S. Brett, M. Garfield, L. Everett, S. Heenen, S. Dhir, Z. Beardow, M. Mostert, S. Brosnan, N. Pinto, S. Harris, A. Summors, N. Andrew, A. Rose, R. Appelboam, O. Davies, E. Vickers, B. Agarwal, T. Szakmany, S. Wimbush, K. Williams, R. Pearse, R. Hollands, J. Kirk-Bayley, N. Fletcher, B. Bray, D. Brealey. The online version of the article has been corrected
Precipitation as driver of carbon fluxes in 11 African ecosystems
No full textThis study reports carbon and water fluxes between the land surface and atmosphere in eleven different ecosystems types in Sub-Saharan Africa, as measured using eddy covariance (EC) technology in the first two years of the CarboAfrica network operation. The ecosystems for which data were available ranged in mean annual rainfall from 320 mm (Sudan) to 1150 mm (Republic of Congo) and include a spectrum of vegetation types (or land cover) (open savannas, woodlands, croplands and grasslands). Given the shortness of the record, the EC data were analysed across the network rather than longitudinally at sites, in order to understand the driving factors for ecosystem respiration and carbon assimilation, and to reveal the different water use strategies in these highly seasonal environments.
Values for maximum net carbon assimilation rates (photosynthesis) ranged from −12.5 μmol CO2 m−2 s−1 in a dry, open Millet cropland (C4-plants) up to −48 μmol CO2 m−2 s−1 for a tropical moist grassland. Maximum carbon assimilation rates were highly correlated with mean annual rainfall (r2=0.74). Maximum photosynthetic uptake rates (Fpmax) were positively related to satellite-derived fAPAR. Ecosystem respiration was dependent on temperature at all sites, and was additionally dependent on soil water content at sites receiving less than 1000 mm of rain per year. All included ecosystems dominated by C3-plants, showed a strong decrease in 30-min assimilation rates with increasing water vapour pressure deficit above 2.0 kPa
On the separation of net ecosystem exchange into assimilation and ecosystem respiration: review and improved algorithm
No full textpeer reviewedThis paper discusses the advantages and disadvantages of the different methods that separate net ecosystem exchange (NEE) into its major components, gross ecosystem carbon uptake (GEP) and ecosystem respiration (R-eco). In particular, we analyse the effect of the extrapolation of night-time values of ecosystem respiration into the daytime; this is usually done with a temperature response function that is derived from long-term data sets. For this analysis, we used 16 one-year-long data sets of carbon dioxide exchange measurements from European and US-American eddy covariance networks. These sites span from the boreal to Mediterranean climates, and include deciduous and evergreen forest, scrubland and crop ecosystems. We show that the temperature sensitivity of R-eco, derived from long-term (annual) data sets, does not reflect the short-term temperature sensitivity that is effective when extrapolating from night- to daytime. Specifically, in summer active ecosystems the long-term temperature sensitivity exceeds the short-term sensitivity. Thus, in those ecosystems, the application of a long-term temperature sensitivity to the extrapolation of respiration from night to day leads to a systematic overestimation of ecosystem respiration from half-hourly to annual time-scales, which can reach > 25% for an annual budget and which consequently affects estimates of GEP. Conversely, in summer passive (Mediterranean) ecosystems, the long-term temperature sensitivity is lower than the short-term temperature sensitivity resulting in underestimation of annual sums of respiration. We introduce a new generic algorithm that derives a short-term temperature sensitivity of R-eco from eddy covariance data that applies this to the extrapolation from night- to daytime, and that further performs a filling of data gaps that exploits both, the covariance between fluxes and meteorological drivers and the temporal structure of the fluxes. While this algorithm should give less biased estimates of GEP and R-eco, we discuss the remaining biases and recommend that eddy covariance measurements are still backed by ancillary flux measurements that can reduce the uncertainties inherent in the eddy covariance data
