Ecological Studies, Vol. 163 Analysis and Synthesis Edited by 1.T. Baldwin, Jena, Germany M.M. Caldwell, Logan, USA G. Heldmaier, Marburg, Germany O.L. Lange, Würzburg, Germany H.A. Mooney, Stanford, USA E.-D. Schulze, Jena, Germany U. Sommer, Kiel, Germany Ecological Studies Volumes published since 1997 are listed at the end of this book. Springer-Verlag Berlin Heidelberg GmbH R. Valentini (Ed.) Fluxes of Carbon, Water and Energy of European Forests With 92 Figures, 3 in Color, and 46 Tables Springer Prof. Dr. Riccardo Valentini University of Tuscia Department of Forest Environment and Resources Via S. Camillo de Lellis 01100 Viterbo Italy Cover illustration by courtesy of Dennis and Nicole Baldocchi ISSN 0070-8356 ISBN 978-3-642-07848-4 ISBN 978-3-662-05171-9 (eBook) DOI 10.1007/978-3-662-05171-9 Library of Congress Cataloging-in-Publication Data Fluxes of carbon, water, and energy of European forests I R. Valentini (ed.) p. cm. --(Ecological studies, ; v. 163) Includes bibliographical references (p. ) .. 1. Carbon cycle (Biogeochemistry)--Europe. 2. Forest ecology--Europe. I. Valentini, R. (Riccardo), 1959. QH344 .F58 2002 577.3'44'094--dc21 2002030469 This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permit ted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and per missions for use must always be obtained from Springer-Verlag. Violations are liable for prosecution under the German Copyright Law. http://www.springer.de © Springer-Verlag Berlin Heidelberg 2003 Originally published by Springer-Verlag Berlin Heidelberg New York in 2003. Softcover reprint ofthe hardcover I st edition 2003 The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Production: Friedmut Kröner, 69115 Heidelberg, Germany Cover design: design & production GmbH, Heidelberg Typesetting: Kröner, 69115 Heidelberg, Germany 31/3111 - 5 4 3 2 1 - Printed on acid free paper SPIN 11370604 Preface After years of technological development and its important achievements to make our life easier and more comfortable, human society is going to face one of the most difficult challenges of the last century: to stabilize the concentra tion levels of greenhouse gases in the atmosphere to prevent harmful effects on the climate system. Through a delicate balance between photosynthesis and respiration, terres trial ecosystems, and in particular forests, are today thought to take up a sig nificant part of the carbon dioxide emissions in the atmosphere, sometimes called the "terrestrial carbon sink". However, the location, magnitude, and vulnerability of the carbon dioxide sink of the terrestrial biota are still uncer tain. The suite of traditional tools in an ecologist's toolbox for studying ecosys tem productivity and carbon balance include leaf cuvettes, whole-plant and soil chambers for gas exchange, and biomass and soil carbon inventories. While each of the cited methods has distinct advantages, they are limited with regards to their ability to measure net carbon dioxide exchange of the whole ecosystem across a variety of time scales. This book present a compendium of results of a European project (EURO FLUX), funded by the European Commission through its fourth framework program, aiming to elucidate the role of forests in continental carbon balance. For the first time, a novel technology, eddy covariance, has been used in a net work of investigation sites ranging from Scandinavia to the Mediterranean region to provide direct measurements of carbon, water, and energy fluxes between forests and the atmosphere. Use of the eddy covariance method by specialists and non-specialists has increased in recent years. A citation search of published papers that index the term 'eddy covariance' produced over 200 records and over 500 papers refer ring to the analogous term 'eddy correlation'. We hope that this book will pro vide a useful compendium of both methodological advancements as weH as critical analyses of results on atmosphere-biosphere interactions in European forests, which could stimulate new scientific questions and provide substan- VI Preface tial information to poliey makers engaged today in negotiations of the Kyoto protoeol and related international eonventions for elimate and biodiversity proteetion. Oetober 2002 Viterbo, Italy Riccardo Valentini Bruxelles, Belgium Anver Ghazi, Claus Brüning, Panagiotis Balabanis Contents 1 EUROFLUX: An Integrated Network for Studying the Long-Term Responses of Biospheric Exchanges of Carbon, Water and Energy of European Forests 1 R. VALENTINI 1.1 The Background 1 1.2 The Network of Sites 2 1.3 The Methodology . . 5 1.4 EUROFLUX-Specific Objectives 6 Further Reading . . . . . . . . . . . . . . . 8 2 Methodology for Data Acquisition, Storage, and Treatment 9 M.AuBINET, R. CLEMENT, J.A. ELBERS, T. FOKEN, A. GRELLE, A. IBROM, J. MONCRIEFF, K. PILEGAARD, Ü. RANNIK, C. REBMANN 2.1 Introduction 9 2.2 Theory ... 10 2.3 Material 11 2.4 Data Acquisition, Computation, and Corrections 17 2.4.1 Procedure Outline . . . . . . . . . . . . . . 17 2.4.2 Computation of the Uncorrected Fluxes 18 2.4.3 Correction for Frequency Response Losses 20 2.4.4 Effect of Low Frequency Cut on Fluxes 21 2.4.5 Effect of High Frequency Cut on Fluxes 23 2.5 Quality Contral 26 2.5.1 Raw Data Analysis . . . . . . . . . . . . 26 2.5.2 Stationarity Test . . . . . . . . . . . . . 26 2.5.3 Integral Turbulence Characteristics Test 27 2.5.4 Energy Balance Closure . . . . . . . . . . 27 2.6 Spatial Representativeness of the Fluxes 29 2.7 Night Flux Corrections ......... . 30 VIII Contents Annex: Technical Details About the Software Validation Set 32 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 3 Measurement of Soil Respiration .............. . 37 H. LANKREIJER, I.A. JANSSENS, N. BUCH MANN, B. LONGDOZ, D. EPRON, S. DORE 3.1 Introduction . . . 37 3.1.1 Measuring Soil Respiration 38 3.1.2 Modeling ......... . 40 3.2 Soil CO Efflux Measurements in the EUROFLUX Project 41 2 3.2.1 Chamber Systems . . . . . . . . . . . . . . . 41 3.2.2 Meteorological and Profile Gradient Systems 44 3.2.2.1 Eddy Covariance Below the Canopy (EC) 44 3.2.2.2 Flux-Profile Measurements (P) 44 3.2.2.3 CO Profile in the Soil (SP) .. 45 2 3.2.2.4 Additional Soil Measurements 45 3.3 Comparison of Systems 45 3.4 Discussion 47 3.5 Conclusions 49 References . . . . . . . 49 4 Deciduous Forests (Beech): Carbon and Water Fluxes, Balances, Ecological and Ecophysiological Determinants 55 A. GRANIER, M. AUBINET, D. EPRON, E. FALGE, J. UMUNDSSON, N.O. JENSEN, B. KÖSTNER, G. MATTEUCCI, K. PILEGAARD, M. SCHMIDT, J. TENHUNEN 4.1 Introduction . . . . . . . . . . . . . . 55 4.2 Water Transfer and Water Balance . . 56 4.2.1 Sap Flow in Beech, Tree Transpiration 56 4.2.2 Sap Flow Profile in Trunks ..... . 57 4.2.3 Range of Sap Flow and Among Tree Variation 58 4.2.4 Canopy Conductance for Water Vapor: Effect of Radiation, Vapor Pressure Deficit, Temperature, LAI, and Drought 58 4.2.5 Annual Water Balance ...... . 60 4.3 Carbon Fluxes and Carbon Balance 61 4.3.1 Net Ecosystem Exchange 61 4.3.2 Ecosystem Respiration ... . 62 4.3.3 Soil Respiration ....... . 64 4.3.4 Daily Net Ecosystem Exchange 64 Contents IX 4.3.5 Annual Carbon Balance, Intersite and Interannual Comparison 68 4.4 Conclusions 68 References . . . . . . . . . . . . . . . . . 69 5 Coniferous Forests (Scots and Maritime Pine): Carbon and Water Fluxes, Balances, Ecological and Ecophysiological Determinants ......................... . 71 R. CEULEMANS,A.S. KOWALSKI, P. BERBIGIER, H. DOLMAN, A. GRELLE, I.A. JANSSENS, A. LINDROTH, E. MooRS, U. RANNIK, T.VESALA 5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . .. 71 5.1.1 Aims and Objectives ...................... 71 5.1.2 Scots Pine and Maritime Pine as Representatives of the Genus Pinus in the EUROFLUX Network . . . . . . . . . . . . 71 5.2 Description of Experimental Sites and Data Collection 75 5.3 Results and Observations 77 5.3.1 Climate. . . . 77 5.3.2 Radiation . . . . . . . . . 77 5.3.3 Energy Budget . . . . . . 81 5.3.4 Carbon Dioxide Exchanges 85 5.4 Conclusion 95 References . . . . . . . . . . . . . . . 96 6 Spruce Forests (Norway and Sitka Spruce, Including Douglas Fir): Carbon and Water Fluxes, Balances, Ecological and Ecophysiological Determinants 99 C. BERNHoFER, M. AUBINET, R. CLEMENT, A. GRELLE, T. GRÜNWALD, A. IBROM, P. JARVIS, C. REBMANN, E.-D. SCHULZE, J.D. TENHUNEN 6.1 Introduction ..... 99 6.2 Material and Methods 100 ... 6.3 Results 102 6.3.1 Radiation .. 102 6.3.2 Momentum 103 6.3.2.1 Heat Storage 107 6.3.2.2 Soil Heat Flux 108 6.3.2.3 Canopy Heat Flux 108 6.3.3 Energy Fluxes .. 110