Enchytraeidae (Oligochaeta)inachangingclimate The climate is undergoing rapid changes with rising atmospheric CO2 concentration, increasing temperature and changes in the hydrological regimes resulting in more frequent Enchytraeidae (Oligochaeta) and intense drought periods. These three climate change factors will, separately and in combination, affect the biotic and abiotic components of the soil ecosystems. Enchytraeids are an important component in soil ecosystems and affect the decomposition processes in a changing climate and the nutrient mineralisation both directly and indirectly by their activity. Ecology and ecophysiology of enchytraeids exposed to climate changes The background for this thesis was to investigate the effect of climate change on fi eld populations of enchytraeids dominated by the species Cognettia sphagnetorum. Field populations of enchytraeids were exposed in a full factorial in-situ experiment to increased CO2, temperature and prolonged drought manipulation for three years. In the short term, enchytraeids appear to be unaffected by climate change when all factors are PhD Thesis, 2009 combined. The negative impact of drought was counteracted when CO2 was present, Kristine Maraldo as drought and CO2 in combination acted additively during summertime. However, in a long-term drought experiment in which C. sphagnetorum was exposed repeatedly to drought during a six year period, the species was, evidently, negatively affected. Even though the enchytraeids had been exposed for a long period, there was no sign of increased drought resistance. Climate change will, beyond doubt, have an impact on the enchytraeids, however, in a non predictable way. But factors such as extreme events, seasonal and interannually variations are all important factors as well, which can strongly infl uence the response of enchytraeids in a future climate. ISBN 978-87-7073-085-3 Enchytraeidae (Oligochaeta) in a changing climate Ecology and ecophysiology of enchytraeids exposed to climate changes PhD thesis, 2009 Kristine Maraldo National Environmental Research Institute Department of Terrestrial Ecology Aarhus University Terrestrial Ecology, Institute of Biology Faculty of Science University of Copenhagen CLIMAITE Data sheet Title: Enchytraeidae (Oligochaeta) in a changing climate Ecology and ecophysiology of enchytraeids exposed to climate changes Subtitle: PhD Thesis Author: Kristine Maraldo1,2 Department: 1Department of Terrestrial Ecology, National Environmental Research Institute, Aarhus University 2Terrestrial Ecology, Institute of Biology Faculty of Science, University of Copenhagen Publisher: National Environmental Research Institute© Aarhus University URL: http://www.neri.dk Year of publication: March 2009 Editing completed: March 2009 Supervisors: Søren Christensen1 and Martin Holmstrup2 1Department of Biology, Evolution biology, University of Copenhagen 2Department of Terrestrial Ecology, National Environmental Research Institute, Aarhus University Keywords: Climate change, enchytraeids, drought, Cognettia sphagnetorum, soil water potential Abstract: The climate is undergoing rapid changes with rising atmospheric CO2 concentration, increasing tem- perature and changes in the hydrological regimes resulting in more frequent and intense drought periods. These three climate change factors will, separately and in combination, affect the biotic and abiotic components of the soil ecosystems. Enchytraeids are an important component in soil ecosystems and affect the decomposition processes and the nutrient mineralisation both directly and indirectly by their activity. The background for this thesis was to investigate the effect of climate change on fi eld popula- tions of enchytraeids dominated by the species Cognettia sphagnetorum. Although enchytraeids are extremely sensitive to long-term desiccation stress, they also have a high degree of resilience when optimal conditions return. Field populations of enchytraeids were exposed in a full factorial in-situ ex- periment to increased CO2, temperature and prolonged drought manipulation for three years. In the short term, enchytraeids appear to be unaffected by climate change when all factors were combined. The negative impact of drought was counteracted when CO2 was present, as drought and CO2 in combination acted additively during summertime. However, in a long-term drought experiment in which C. sphagnetorum was exposed repeatedly to drought during a six year period, the species was, evidently, negatively affected. Even though the enchytraeids had been exposed for a long period, there was no sign of increased drought resistance. Climate change will, beyond doubt, have an impact on the enchytraeids, however, in a non predictable way. But factors such as extreme events, seasonal and interannual variations are all important factors as well, which can strongly infl uence the response of enchytraeids in a future climate. Layout: Tinna Christensen and Kathe Møgelvang Front page picture: Wikimedia commons ISBN: 978-87-7073-085-3 Printed by: The Repro Center – Faculty of Science, Aarhus University Number of pages: 128 Circulation: 50 Internet version: The report is also available in electronic format (pdf) at NERI’s website http://www.dmu.dk/Pub/PhD_KRM.pdf Contents Preface 5 Abstract 7 Danish abstract 9 Review 11 Paper 1 39 Responses to acute and chronic desiccation stress in Enchytraeus (Oligochaeta: Enchytraeidae) Paper 2 53 Recovery of enchytraeid populations after severe drought events Paper 3 73 Counteracting effects of elevated CO2 and drought episodes: studies of enchytraeid populations in dry heathland Paper 4 97 Can fi eld populations of the enchytraeid, Cognettia sphagnetorum, adapt to increased drought stress ? Paper 5 107 Freeze tolerance and accumulation of cryoprotectants in the enchytraeid Enchytraeus albidus (Oligochaeta) from Greenland and Europe Paper 6 117 Effects of copper on enchytraeids in the fi eld under differing soil moisture regimes Enchytraeidae (Oligochaeta) in a changing climate 5 Preface This PhD thesis is submitted to the Faculty of Science, University of Copenhagen, Denmark. All of the work has been conducted at the Department of Terrestrial Ecology at National Environmental Research Institute (NERI), Aarhus University, in Silkeborg, Denmark, dur- ing the past four years. The PhD is apart of the Danish climate change experiment “CLI- MAITE”, which was initiated in 2005. The objective of this PhD was to examine the effect of climate change on enchytraeids both in the fi eld, but also in the laboratory. The introduction of the thesis has the structure of a review paper on the effect of climatic changes on terrestrial enchytraeids. Following the intro- duction are six papers, all concerning the effects of increased climatic stress, with a special focus on drought stress. Four of the papers have been published, one has been submitted, and one is ready for submission. This thesis was fi nanced by the project CLIMAITE (CLIMAte change effects on biological processes In Terrestrial Ecosystems; www.climaite.dk) funded by the The Villum Kann Rasmussen Foundation. I would like to thank several people, who have all contributed to making this PhD possible. First of all, I would like to thank my supervisor Martin Holmstrup at NERI, who has been of great support, inspiration and always has taken the time to talk to me. My internal supervisor Søren Christensen from University of Copenhagen, for always helping when needed. To the people behind the CLIMAITE project, which made it all possible and for some inspiring and pleasant meetings – I am going to miss them! Thank you for introducing me to terrestrial ecol- ogy and special thanks goes to the CLIMAITE PhD group, which has been of great help and a lot of fun. I also owe a large thank you to a range of enchytraeid people, a special thanks goes to Bent Christensen and his wife, who introduced me to the taxonomy of the enchytraeids, to Dr. Valerie Standen, University of Durham, UK for helping collect soil at Moor House, to Dr. Maria Briones and Noela, University of Vigo – thanks to all of you for your help, inspiration and hospitality. Finally, I would like to acknowledge Philip Vernon from the University of Rennes in France for his help during my stay in France and Rudiger Schmelz and Louise Illum Sørensen for collecting soil in Spain and Finland. Thank you, to all my colleagues at NERI in Silkeborg. In particular, I wish to thank Paul Henning Krogh, Zdenek Gavor, Elin Jørgensen, Mette Thomson, John Rytter, Lene Birksø, Charlotte Elisabeth Kler, Ninna Skafsgaard, Frankie Henriksen, Lars Henrik Heckman, Helle Weber Ravn and several others for technical assistance, sparring and a lot of fun. A very special thank goes to my fellow PhD students, Anne Mette Bindesbøl, Stine Slotsbo and Dorthe Jensen for sparring, critical review of this thesis, and lots of good times. Tinna Christensen has been very helpful with graphical assistance, Rebekka Andreasen has been very kind to help with the Danish abstract and Lisbeth Jeppesen are thanked for her correction of the language. Without help and support from friends and family, this thesis would have been an up-hill battle. Finally, I am deeply indebted to Jens, Emma and Anders for always being there and for taking your time to hear about the life of “white earthworms”. SilkSilkeborg,eborg, FFebruaryebruary 2009 KrKKristineistine MMaraldoaraldo Photo: Wikimedia commons Enchytraeidae (Oligochaeta) in a changing climate 7 Abstract The climate is undergoing rapid changes with rising atmospheric