Geothermal ecosystems as natural climate change experiments: The ForHot research site in Iceland as a case study

• Published in: Icelandic Agricultural Sciences
• Main Authors: Sigurdsson, Bjarni D., Leblans, Niki, Dauwe, Steven, Guðmundsdóttir, Elín, Gundersen, Per, G. Gunnarsdóttir, Gunnhildur Eva, Holmstrup, Martin, Ilieva-Makulec, Krassimira, Kätterer, Thomas, Marteinsdóttir, Bryndís, Maljanen, Marja, Oddsdóttir, Edda Sigurdís, Ostonen, Ivika, Penuelas, Josep, Poeplau, Christopher, Richter, Andreas, Sigurðsson, Páll, van Bodegom, Peter, Wallander, Håkan, Weedon, James, Janssens, Ivan
• Other Authors: Auðlinda- og umhverfisdeild (LBHÍ), Faculty of Natural Resources and Environmental Sciences (AUI), Líf- og umhverfisvísindastofnun (HÍ), Institute of Life and Environmental Sciences (UI), Verkfræði- og náttúruvísindasvið (HÍ), School of Engineering and Natural Sciences (UI), Landbúnaðarháskóli Íslands, Agricultural University of Iceland, Háskóli Íslands, University of Iceland
• Format: Article in Journal/Newspaper
• Language: English
• Published: Agricultural University of Iceland 2016
• Subjects: Ecosystems; Climate change; Vistkerfi; Loftslagsbreytingar; Jarðhiti; Iceland
• Online Access: https://hdl.handle.net/20.500.11815/468; https://doi.org/10.16886/IAS.2016.05

This work has been supported by a project grant from the Icelandic Research Council (Rannsoknasjoour, ForHot-Forest, Project No 163272-051), a FWO PhD grant from the Research Foundation - Flanders (Grant No 11G1615N), a European Research Council Synergy grant (IMBALANCE-P, Project No 610028), and a Research Council of the University of Antwerp grant (FORHOT TOP-BOF project). This work contributes also to the SNS funded Nordic CAR-ES III project and the ClimMani COST Action (ES1308). The Agricultural University of Iceland and Icelandic Forest Research provided logistical support. We thank the Lorentz Center, Leiden, NL, for a workshop grant in 2014. Sigmundur H. Brink made the map in Fig. 1. This article describes how natural geothermal soil temperature gradients in Iceland have been used to study terrestrial ecosystem responses to soil warming. The experimental approach was evaluated at three study sites in southern Iceland; one grassland site that has been warm for at least 50 years (GO), and another comparable grassland site (GN) and a Sitka spruce plantation (FN) site that have both been warmed since an earthquake took place in 2008. Within each site type, five ca. 50 m long transects, with six permanent study plots each, were established across the soil warming gradients, spanning from unwarmed control conditions to gradually warmer soils. It was attempted to select the plots so the annual warming levels would be ca. +1, +3, +5, +10 and +20°C within each transect. Results of continuous measurements of soil temperature (Ts) from 2013-2015 revealed that the soil warming was relatively constant and followed the seasonal Ts cycle of the unwarmed control plots. Volumetric water content in the top 5 cm of soil was repeatedly surveyed during 2013-2016. The grassland soils were wetter than the FN soils, but they had sometimes some significant warming-induced drying in the surface layer of the warmest plots, in contrast to FN. Soil chemistry did not show any indications that geothermal water had reached the root ...