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<article language="en">
	<journal>
		<journal_title>Biogeosciences</journal_title>
		<journal_url>www.biogeosciences.net</journal_url>
		<issn>1726-4170</issn>
		<eissn>1726-4189</eissn>
		<volume_number>6</volume_number>
		<issue_number>12</issue_number>
		<publication_year>2009</publication_year>
	</journal>
	<doi>10.5194/bg-6-2895-2009</doi>
	<article_url>http://www.biogeosciences.net/6/2895/2009/</article_url>
	<abstract_html>http://www.biogeosciences.net/6/2895/2009/bg-6-2895-2009.html</abstract_html>
	<fulltext_pdf>http://www.biogeosciences.net/6/2895/2009/bg-6-2895-2009.pdf</fulltext_pdf>
	<start_page>2895</start_page>
	<end_page>2906</end_page>
	<publication_date>2009-12-09</publication_date>
	<article_title content_type="html">A young afforestation area in Iceland was a moderate sink to CO&lt;sub&gt;2&lt;/sub&gt; only a decade after scarification and establishment</article_title>
	<authors>
		<author numeration="1" affiliations="1,3">
			<name>B. Bjarnadottir</name>
			<email>brynhildur@skogur.is</email>
		</author>
		<author numeration="2" affiliations="2">
			<name>B. D. Sigurdsson</name>
		</author>
		<author numeration="3" affiliations="3">
			<name>A. Lindroth</name>
		</author>
	</authors>
	<affiliations>
		<affiliation numeration="1" content_type="html">Icelandic Forest Research, Mogilsa, 116 Reykjavik, Iceland</affiliation>
		<affiliation numeration="2" content_type="html">Agricultural University of Iceland, Hvanneyri, 311 Borgarnes, Iceland</affiliation>
		<affiliation numeration="3" content_type="html">Geobiospheric Science Centre, Physical Geography and Ecosystems Analysis, Lund University, Lund, Sweden</affiliation>
	</affiliations>
	<abstract content_type="html">This study reports on three years (2004–2006) of measurements of net
ecosystem exchange (NEE) over a young Siberian larch plantation in Iceland
established on previously grazed heathland pasture that had been scarified
prior to planting. The study evaluated the variation of NEE and its
component fluxes, gross primary production (GPP) and ecosystem respiration
(R&lt;sub&gt;e&lt;/sub&gt;), with the aim to clarify how climatic factors controlled the
site&apos;s carbon balance. The young plantation acted as a relatively strong
sink for CO&lt;sub&gt;2&lt;/sub&gt; during all of the three years, with an annual net
sequestration of &amp;minus;102, &amp;minus;154, and &amp;minus;67 g C m&lt;sup&gt;&amp;minus;2&lt;/sup&gt; for 2004, 2005, and 2006,
respectively. This variation was more related to variation in carbon efflux
(R&lt;sub&gt;e&lt;/sub&gt;) than carbon uptake (GPP). The abiotic factors that showed the
strongest correlation to R&lt;sub&gt;e&lt;/sub&gt; were air temperature during the growing
season and soil water potential. The GPP mostly followed the seasonal
pattern in irradiance, except in 2005, when the plantation experienced
severe spring frost damage that set the GPP back to zero. It was not
expected that the rather slow-growing Siberian larch plantation would be such
a strong sink for atmospheric CO&lt;sub&gt;2&lt;/sub&gt; only twelve years after site
preparation and afforestation.</abstract>
	<references>
		<reference numeration="1" content_type="text"> % vor jede Referenz Arnalds, O.: Volcanic soils of Iceland, CATENA, 56, 3–20, 2004. </reference>
		<reference numeration="2" content_type="text"> Aubinet, M., Grelle, A., Ibrom, A., Rannik, Ü., Moncrieff, J., Foken, T., Kowalski, A.S., Martin, P.H., Berbigier, P., Bernhofer, C., Clement, R., Elbers, J., Grainer, A., Grüntwald, T., Morgenstern, K., Pilegaard, K., Rebmann, C., Snijders, W., Valentini, R., and Vesala, T.: Estimates of the annual net carbon and water exchange of forest: The EUROFLUX methodology, Adv. Ecol. Res., 30, 113–175, 2000. </reference>
		<reference numeration="3" content_type="text"> Baldocchi, D., Falge, E., Gu, L., Olson, R., Hollinger, D., Running, S., Anthoni, P., Bernhofer, C., Davis, K., Evans, R., Fuentes, J., Goldstein, A., Katul, G., Law, B., Lee, X., Malhi, Y., Meyers, T., Munger, W., Oechel, W., Paw U, K. T., Pilegaard K., Schmid, H. P., Valentini, R., Verma, S., Vesala, T., Wilson, K., and Wofsyn, S.: FLUXNET: A new tool to study the temporal and spatial variability of ecosystem-scale carbon dioxide, water vapor, and energy flux densities, B. Am. Meteorol. Soc., 82(11), 22~pp., 2001. </reference>
		<reference numeration="4" content_type="text"> Bergh, J. and Linder, S.: Effects of soil warming during spring on photosynthetic recovery in boreal Norway spruce stands, Glob. Change Biol., 5, 245–253, 1999. </reference>
		<reference numeration="5" content_type="text"> Bergh, J., Freeman, M., Sigurdsson, B., Kellomäki, S., Laitinen, K., Niinistö, S., Peltola, H., and Linder, S.: Modelling the short-term effects of climate change on the productivity of selected tree species in Nordic countries, Forest Ecol. Manage., 183, 327–340, 2003. </reference>
		<reference numeration="6" content_type="text"> Bjarnadottir, B., Sigurdsson, B. D., and Lindroth, A.: Estimate of annual carbon balance of a young Siberian larch (Larix sibirica) plantation in Iceland, Tellus, 59B, 891–899, 2007a. </reference>
		<reference numeration="7" content_type="text"> Bjarnadottir, B., Inghammar, A. C., Brinker, M. M., and Sigurdsson, B. D.: Single tree biomass and volume functions for young Siberian larch trees (Larix sibirica) in eastern Iceland, Icel. Agric. Sci., 20, 125–135, 2007b. </reference>
		<reference numeration="8" content_type="text"> Black, T. A., Chen, W. J., Barr, A. G., Arain, M. A., Chen, Z., Nesic, Z., Hogg, E. H., Neumann, H. H., and Yang, P. C.: Increased carbon sequestration by a boreal deciduous forest in years with a warm spring, Geophys. Res. Lett., 27, 1271–1274, 2000. </reference>
		<reference numeration="9" content_type="text"> Black, T. A., Gaumont-Guay, D., Jassal, R. S., Amiro, B. D., Jarvis, P. G., Gower, S. T., Dunn, A., Kelliher, F. M., and Wofsy, S.: Measurement of CO&lt;sub&gt;2&lt;/sub&gt; exchange between Boreal forest and the atmosphere, in: The Carbon Balance of Forest Biomes, edited by: Griffiths, H. and Jarvis, P. G., Taylor and Francis Group, UK, 151–185, ISBN 1-8599-6214-9, 2005. </reference>
		<reference numeration="10" content_type="text"> Burba, G. G., Andersson, D. J., XU, L., and McDermitt, D. K.: Correcting apparent off-season CO&lt;sub&gt;2&lt;/sub&gt; uptake due to surface heating of an open path gas analyzer: Progress report of an ongoing study, in: 27th Confercence on Agricultural and Forest Meteorology, American Meteorological Society, San Diego, CA., P4-4, 12~pp., 2006. </reference>
		<reference numeration="11" content_type="text"> Carrara, A., Kowalski, A. S., Neirynck, J., Janssens, I. A., Curiel Yuste, J., and Ceulemans, R.: Net ecosystem CO&lt;sub&gt;2&lt;/sub&gt; exchange of mixed forest in Belgium over 5 years, Agr. Forest Meteorol., 119, 209–227, 2003. </reference>
		<reference numeration="12" content_type="text"> Cook, A. C., Tissue, D. T., Roberts, S. W., and Oechel, W. C.: Effects of long-term elevated [CO&lt;sub&gt;2&lt;/sub&gt;] from natural CO&lt;sub&gt;2&lt;/sub&gt; springs on Nardus stricta: photosynthesis, biochemistry, growth and phenology, Plant Cell Environ., 21, 417–425, 1998. </reference>
		<reference numeration="13" content_type="text"> Davidson, E. A., Belk, E., and Boone, R. D.: Soil water content and temperature as independent or confounded factors controlling soil respiration in a temperate mixed hardwood forest, Glob. Change Biol., 4, 217–227, 1998. </reference>
		<reference numeration="14" content_type="text"> Davidson, E. A., Janssens, I. A., and Luo, Y.: On the variability of respiration in terrestrial ecosystems: moving beyond $Q_10$, Glob. Change Biol., 12, 154–164, 2006. </reference>
		<reference numeration="15" content_type="text"> Don, A., Rebmann, C., Kolle, O., Schere-Lorenzen, M., and Schulze, E.-D.: Impact of afforestation-associated management changes on the carbon balance of grassland, Glob. Change Biol., 15, 1990–2002, 2009. </reference>
		<reference numeration="16" content_type="text"> Dunn, A., Barford, C. C., Wofsy, S. C., Goulden, M. L., and Daube, B. C.: A long-term record of carbon exchange in a boreal black spruce forest: means, responses to interannual variability, and decadal trends, Glob. Change Biol., 13, 577–590, 2007. </reference>
		<reference numeration="17" content_type="text"> Falge, E., Baldocchi, D., Olson, R., Anthoni, P., Aubinet, M., Bernhofer, C., Burba, G. G., Ceulemans, R., Clement, R., Dolman, H., Granier, A., Gross, P., Grünwald, T., Hollinger, D., Jensen, N. O., Katul, G., Eronen, P., Kowalski, A., Lai, C. T., Law, B., Meyers, T., Moncrieff, J., Moors, E., Muner, J. W., Pilegaard, K., Rannik, Ü., Rebmann, C., Suyker, A., Tenhunen, J., Tu, K., Verma, S., Vesala, T., Wilson, K., and Wofsy, S.: Gap filling strategies for defensible annual sums of net ecosystem exchange, Agr. Forest Meteorol., 107, 43–69, 2001. </reference>
		<reference numeration="18" content_type="text"> Falge, E., Tenhunen, J., Baldocchi, D., Aubinet, M., Bakwin, P., Berb igier, P., Bernhofer, C., Bonnefond, J.-M., Burba, G., Clement, R., Davis, K. J., Elbers, J. A., Falk, M., Goldstein, A. H., Grelle, A., Granier, A., Grünwald, T., Gu\dhmundsson, J., Hollinger, D., Janssens, I. A., Keronen, P., Kowalski, A. S., Katul, G., Law, B. E., Malhi, Y., Meyers, T., Monson, R. K., Moors, E., Munger, J. W., Oechel, W., Paw U, K. T. P., Pilegaard, K., Rannik, Ü., Rebmann, C., Suyker, A., Thorgeirsson, H., Tirone, G., Turnipseed, A., Wilson, K., and Wofsy, S.: Phase and amplitude of ecosystem carbon release and uptake potentials as derived from FLUXNET measurements, Agr. Forest Meteorol., 113, 75–95, 2002. </reference>
		<reference numeration="19" content_type="text"> Goulden, M. L., Wofsy, S. C., Harden, J. W., Trumbore, S. E., Crill, P. M., Gower, T., Fries, T., Daube, B. C., Fan, S. M., Sutton, D. J., Bazzaz, A., and Munger, J. W.: Sensitivity of boreal forest carbon balance to soil thaw, Science, 279, 214–217, 1998. </reference>
		<reference numeration="20" content_type="text"> Granier, A., Reichstein, M., Bréda, N., Janssens, I. A., Falge, E., Ciais, P., Grünwald, T., Aubinet, M., Berbigier, P., Bernhofer, C., Buchmann, N., Facini, O., Grassi, G., Heinesch, B., Ilvesniemi, H., Keronen, P., Knohl, A., Köstner, B., Lagergren, F., Lindroth, A., Longdoz, B., Loustau, D., Mateus, J., Montagnani, L., Nys, C., Moors, E., Papale, D., Peiffer, D. M., Pilegaard, K., Pita, G., Pumpanen, J., Rambal, S., Rebmann, C., Rodrigues, A., Seufert, G., Tenhunen, J., Vesala, T., and Wang, Q.: Evidence for soil water control on carbon and water dynamics in European forests during the extremely dry year: 2003, Agr. Forest Meteorol., 143, 123–145, 2007. </reference>
		<reference numeration="21" content_type="text"> Gu\dhmundsdóttir, G. and Sigurdsson, B. D.: Photosynthetic temperature response of mountain birch (\textitBetula pubescens Ehrh.) in comparison with three other broadleaved tree species in Iceland, Icel. Agric. Sci., 18, 43–51, 2005. </reference>
		<reference numeration="22" content_type="text"> Gunnarsson, E.: Skógræktarári\dh 2007, Skógræktarriti\dh (Icelandic Forestry), 2, 98–101, 2008. </reference>
		<reference numeration="23" content_type="text"> Heimann, M. and Reichstein, M.: Terrestrial ecosystem carbon dynamics and climate feedbacks, Nature, 451, 289–292, 2008. </reference>
		<reference numeration="24" content_type="text"> Högberg, P., Bhupinderpal, S., Löfvenius, M. O., and Nordgren, A.: Partitioning of soil respiration into its autotrophic and heterotrophic components by means of tree-girdling in old boreal spruce forest, Forest Ecol. Manage., 257, 1764–1767, 2009. </reference>
		<reference numeration="25" content_type="text"> Hyvönen, R., Ågren, G. I., Linder, S., Persson, T., Cotrufo, M. F., Ekblad, A., Freeman, M., Grelle, A., Janssens, I. A., Jarvis, P. G., Kellomäki, S., Lindroth, A., Loustau, D., Lundmark, T., Norby, R. J., Oren, R., Pilegaard, K., Ryan, M. G., Sigurdsson, B. D., Strömgren, M., van Oijen, M., and Wallin, G.: The likely impact of elevated [CO&lt;sub&gt;2&lt;/sub&gt;], nitrogen deposition, increased temperature and management on carbon sequestration in temperate and boreal forest ecosystems: a literature review, New Phytol., 171, 275–296, 2007. </reference>
		<reference numeration="26" content_type="text"> IPCC.: Summary for Policymakers. Forth Assessment Report. Working Group I, in: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, edited by: Solomon, S., Qin, D., Manning, M., Chen, Z., Marquis, M., Averyt, K. B., Tignor, M., and Miller, H. L: Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 2007. </reference>
		<reference numeration="27" content_type="text"> Jónsson, J. &amp;#x00C1;.: &amp;#x00C1;hrif skógræktara\dhger\dha á vi\dharvöxt og flæ\dhi kolefnis í asparskógi (Effects of forest management practices on wood increment and carbon fluxes), M. S thesis at the Biology department, University of Iceland, Reykjavik, 94~pp., 2007. </reference>
		<reference numeration="28" content_type="text"> Kowalski, A. S., Loustau, D., Berbigier, P., Manca, G., Tedeschi, V., Borghetti, M., Valentini, R., Kolari, P., Berninger, F., Rannik, Ü., Hari, P., Rayment, M., Mencuccini, M., Moncrieff, J., and Grace, J.: Paired comparisons of carbon exchange between undisturbed and regenerating stands in four managed forests in Europe, Glob. Change Biol., 10, 1707–1723, 2004. </reference>
		<reference numeration="29" content_type="text"> Lagergren, F., Grelle, A., Lankreijer, H., Mölder, M., and Lindroth, A.: Current carbon balance of the forested area in Sweden and its sensitivity to global change as simulated by biome-BGC, Ecosystems, 9, 894–908, 2006. </reference>
		<reference numeration="30" content_type="text"> Lagergren, F., Lindroth, A., Dellwik, E., Ibrom, A., Lankreijer, H., Launiainen, S., Mölder, M., Kolari, P., Pilegaard, K., and Vesala, T.: Biophysical controls on CO&lt;sub&gt;2&lt;/sub&gt; fluxes of three Northern forests bases on long-term eddy covariance data, Tellus, 60B, 143–152, 2008. </reference>
		<reference numeration="31" content_type="text"> Law, B. E., Falge, E., Gu, L., Baldocchi, D. D., Bakwin, P., Berbigier, P., Davis, K., Dolman, A. J., Falk, M., Fuentes, J. D., Goldstein, A., Granier, A., Grelle, A., Hollinger, D., Janssens, I. A., Jarvis, P. G., Jensen, N. O., Katul, G., Mahli, Y., Matteucci, G., Meyers, T., Monson, R., Munger, W., Oechel, W., Olson, R., Pilegaard, K., Paw U, K. T., Thorgeirsson, H., Valentini, R., Verma, S., Vesala, T., Wilson, K., and Wofsy, S.: Environmental controls over carbon dioxide and water vapor exchange of terrestrial vegetation, Agr. Forest Meteorol., 113, 97–120, 2002. </reference>
		<reference numeration="32" content_type="text"> Lindroth, A., Grelle, A., and Morén, A. S.: Long-term measurements of boreal forest carbon balance reveal large temperature sensitivity, Glob. Change Biol., 4, 443–450, 1998. </reference>
		<reference numeration="33" content_type="text"> Lindroth, A., Lagergren, F., Aurela, M., Bjarnadottir, B., Christensen, T., Dellwik, E., Grelle, A., Ibrom, A., Johansson, T., Lankreijer, H., Launiainen, S., Laurila, T., Mölder, M., Nikinmaa, E., Pilegaard, K., Sigurdsson, B. D., and Vesala, T.: Leaf area index is the principal scaling parameter for both gross photosynthesis and ecosystem respiration of Northern deciduous and coniferous forests, Tellus, 60B, 129–142, 2008. </reference>
		<reference numeration="34" content_type="text"> Lindroth, A., Lagergren, F., Grelle, A., Klemedtsson, L., Langvall, O., Weslien, P., and Tuulik, J.: Storms can cause Europe-wide reduction in forest carbon sink, Glob. Change Biol., 15, 346–355, 2009. </reference>
		<reference numeration="35" content_type="text"> Linkosalo, T., Carter, T. R., Häkkinen, R., and Hari, P.: Predicting spring phenology and frost damage risk of Betula spp. under climatic warming: a comparison of two models, Tree Physiol., 20, 1175–1182, 2000. </reference>
		<reference numeration="36" content_type="text"> Lloyd, J., and Taylor, J. A.: On the temperature dependence of soil respiration, Funct. Ecol., 8, 315–323, 1994. </reference>
		<reference numeration="37" content_type="text"> Lyck, C. and Bergstedt, A.: Use and Availability of Larch wood in Northern Europe - a literature review, Report from the Royal Veterinary and Agricultural University, Unit of Forestry, Copenhagen, Denmark, 66~pp., 2004. </reference>
		<reference numeration="38" content_type="text"> Magnani, F., Mencuccini, M., Borghetti, M., Berbigier, P., Berninger, F., Delzon, S., Grelle, A., Hari, P., Jarvis, P. G., Kolari, P., Kowalski, A. S., Lankreijer, H., Law, B. E., Lindroth, A., Loustau, D., Manca, G., Moncrieff, J. B., Rayment, M., Tedeschi, V., Valentini, R., and Grace, J.: The human footprint in the carbon cycle of temperate and boreal forests, Nature, 447, 849–851, 2007. </reference>
		<reference numeration="39" content_type="text"> Magn\&apos;usson, B.: Soil respiration on the volcanic island Surtsey, Iceland in 1987 in relation to vegetation, Surtsey Research Progress Report, 10, 9–16, 1992. </reference>
		<reference numeration="40" content_type="text"> Medlyn, B. E., Berbigier, P., Clement, R., Grelle, A., Loustau, D., Linder, S., Wingate, L., Jarvis, P. G., Sigurdsson, B. D., and McMurtrie, R. E.: Carbon balance of coniferous forests growing in contrasting climates: Model-based analysis, Agr. Forest Meteorol., 131, 97–124, 2005. </reference>
		<reference numeration="41" content_type="text"> Morales, P., Hickler, T., Rowell, D. P., Smith, B., and Sykes, M. T.: Changes in European ecosystem productivity and carbon balance driven by regional climate model output, Glob. Change Biol., 13, 108–122, 2007. </reference>
		<reference numeration="42" content_type="text"> Paul, K. I., Polglase, P. J., Nyakuengama, J. G., and Khanna, P. K.: Change in soil carbon following afforestation, Forest Ecol. Manage., 168, 241–257, 2002. </reference>
		<reference numeration="43" content_type="text"> Piao, S., Ciais, P., Friedlingstein, P., Peylin, P., Reichstein, M., Luyssaert, S., Margoils, H., Fang, J., Barr, A., Chen, A., Grelle, A., Hollinger, D. Y., Laurila, T., Lindroth, A., Richardson, A. D., and Vesala, T.: Net carbon dioxide losses of northern ecosystems in response to autumn warming, Nature, 451, 49–53, 2008. </reference>
		<reference numeration="44" content_type="text"> Reichstein, M., Papale, D., Valentini, R., Aubinet, M., Bernhofer C., Knohl, A., Laurila, A., Lindroth, A., Moors, E., Pilegaard, K., and Seufert G.: Determinanats of terrestrial ecosystem carbon balance inferred from European eddy covariance flux sites. Geophys. Res. Lett., 34, L01402, doi:10.1029/2006GL0278880, 2007. </reference>
		<reference numeration="45" content_type="text"> Roberntz, P. and Stockfors, J.: Effects of elevated CO&lt;sub&gt;2&lt;/sub&gt; concentration and nutrition on net photosynthesis, stomatal conductance and needle respiration of field-grown Norway spruce trees, Tree Physiol., 18, 223–241, 1998. </reference>
		<reference numeration="46" content_type="text"> Schindlbacher, A., Zechmeister-Boltenstern, S., and Jandl, R.: Experimental forest soil warming: response of autotrophic and heterotrophic soil respiration to a short-term 10&amp;deg;C temperature rise, Plant Soil, 303, 323–330, 2008. </reference>
		<reference numeration="47" content_type="text"> Sigurdsson, B. D.: Ecosystem carbon fluxes of Leymus arenarius and Honkenya peploides in relation to water availability, Surtsey Research, 12, 77–80, 2009. </reference>
		<reference numeration="48" content_type="text"> Sigurdsson, B. D., Roberntz, P., Freeman, M., Saxe, H., Næss, M., Thorgeirsson, H., and Linder, S.: Impact studies on Nordic forests: effects of elevated CO&lt;sub&gt;2&lt;/sub&gt; and fertilization on gas exchange, Can. J. Forest Res., 32, 779–788, 2002. </reference>
		<reference numeration="49" content_type="text"> Sigurdsson, B. D., Magnusson, B., Elmarsdottir, &amp;#x00C1;., and Bjarnadottir, B.: Biomass and composition of understory vegetation and the forest floor carbon stock across Siberian larch and mountain birch chronosequences in Iceland, Ann. Forest Sci., 62, 881–888, 2005. </reference>
		<reference numeration="50" content_type="text"> Suni, T., Berninger, F., Vesala, T., Markkanen, T., Hari, P., Mäkelä, A., Ilvesniemi, H., Hänninen, H., Nikinmaa, E., Huttula, T., Laurila, T., Aurela, M., Grelle, A., Lindroth, A., Arneth, A., Shibistova, O., and Lloyd, J.: Air temperature triggers the recovery of evergreen boreal forest photosynthesis in spring, Glob. Change Biol., 9, 1410–1426, 2003a. </reference>
		<reference numeration="51" content_type="text"> Suni, T., Berninger, F., Markkanen, T., Keronen, P., Rannik, Ü., and Vesala, T.: Interannual variability and timing of growing-season CO&lt;sub&gt;2&lt;/sub&gt; exchange in a boreal forest, J. Geophys. Res., 108(D9), 4265, doi:10.1029/2002JD002381, 2003b. </reference>
		<reference numeration="52" content_type="text"> Tang, J., Bolstad, P. V., and Martin, J. G.: Soil carbon fluxes and stocks in a Great Lakes forest chronosequence, Glob. Change Biol., 15, 145–155, 2009. </reference>
		<reference numeration="53" content_type="text"> Traustason, B. and Snorrason, A.: Spatial distribution of forests and woodlands in Iceland in accordance with the CORINE land cover classification, Icel. Agric. Sci., 21, 39–47, 2008. </reference>
		<reference numeration="54" content_type="text"> Troeng, E. and Linder, S.: Gas exchange in a 20-year-old stand of Scots pine. I. Net photosynthesis of current and one-year-old shoots within and between seasons, Physiol. Plant., 54, 7–14, 1982. </reference>
		<reference numeration="55" content_type="text"> UNFCCC: The Kyoto Protocol – to the Convention on Climate Change, UNEP/IUC, Geneva Executive Center, UNEP/IUC/98/9, 1998. </reference>
		<reference numeration="56" content_type="text"> Valentini, R., Matteucci, G., Dolman, A. J., Schulze, E.-D., Rebmann, C., Moors, E. J., Granier, A., Gross, P., Jensen, N. O., Pilegaard, K., Lindroth, A., Grelle, A., Bernhofer, C., Grünwald, T., Aubinet, M., Ceulemans, R., Kowalski, A. S., Vesala, T., Rannik, Ü., Berbigier, P., Loustau, D., Gu\dhmundsson, J., Thorgeirsson, H., Ibrom, A., Morgenstern, K., Clement, R., Moncrieff, J., Montagnani, L., Minerbi, S., and Jarvis, P. G.: Respiration as the main determinant of carbon balance in European forests, Nature, 404, 861–865, 2000. </reference>
		<reference numeration="57" content_type="text"> Webb, E. K., Pearman, G. I., and Leuning, R.: Correction of flux measurements for density effects due to heat and water vapour transfer, Q. J. Roy. Meteorol. Soc., 106, 85–100, 1980. </reference>
		<reference numeration="58" content_type="text"> Xu, M., DeBiase, T. A., Qi, Y., Goldstein, A., and Liu, Z.: Ecosystem respiration in a young ponderosa pine plantation in the Sierra Nevada Mountains, California, Tree Physiol., 21, 309–318, 2001. </reference>
	</references>
</article>

