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

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


Titill: Geothermal ecosystems as natural climate change experiments: The ForHot research site in Iceland as a case study
Aðrir titlar: Jarðhitavistkerfi sem náttúrulegar loftslagsbreytingatilraunir: ForHot verkefnið á Íslandi sem sýnidæmi.
Höfundur: Sigurdsson, Bjarni D.   orcid.org/0000-0002-4784-5233
Leblans, Niki   orcid.org/0000-0001-6154-1538
Dauwe, Steven
Guðmundsdóttir, Elín
Gundersen, Per   orcid.org/0000-0002-9199-4033
G. Gunnarsdóttir, Gunnhildur Eva   orcid.org/0000-0002-7514-9470
Holmstrup, Martin   orcid.org/0000-0001-8395-6582
Ilieva-Makulec, Krassimira
Kätterer, Thomas   orcid.org/0000-0002-1751-007X
Marteinsdóttir, Bryndís   orcid.org/0000-0003-3779-7327
... 11 fleiri höfundar Sýna alla höfunda
Útgáfa: 2016
Tungumál: Enska
Umfang: 53-71
Háskóli/Stofnun: Landbúnaðarháskóli Íslands
Agricultural University of Iceland
Deild: Auðlinda- og umhverfisdeild (LBHÍ)
Faculty of Natural Resources and Environmental Sciences (AUI)
Birtist í: IAS;29
ISSN: 2298-786X
DOI: 10.16886/IAS.2016.05
Efnisorð: Ecosystems; Climate change; Vistkerfi; Loftslagsbreytingar; Jarðhiti
URI: https://hdl.handle.net/20.500.11815/468

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Tilvitnun:

Bjarni D. Sigurdsson, et al. 2016. Geothermal ecosystems as natural climate change experiments: The ForHot research site in Iceland as a case study. Icelandic Agricultural Sciences 29, 53-71, doi: 10.16886/IAS.2016.05

Útdráttur:

 
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 zone, but soil pH did increase somewhat with warming, which was probably linked to vegetation changes. As expected, the potential decomposition rate of organic matter increased significantly with warming. It was concluded that the natural geothermal gradients at the ForHot sites in Iceland offered realistic conditions for studying terrestrial ecosystem responses to warming with minimal artefacts.
 
Þessi grein lýsir því hvernig jarðhitasvæði hérlendis hafa verið notuð til að rannsaka áhrif hlýnunar á norðlæg þurrlendisvistkerfi. Rannsóknirnar fóru fram á þremur stöðum í Ölfusi, í næsta nágrenni Hveragerðis: i) í graslendum sem hafa verið undir áhrifum jarðvegshlýnunar í langan tíma (GO), eða allavega í 50 ár, ii) í samskonar graslendum sem byrjuðu fyrst að hitna vorið 2008 eftir Suðurlandsskjálftann (GN) og iii) í gróðursettum 50 ára sitkagrenisskógi sem einnig byrjaði að hitna vorið 2008 (FN). Á hverjum stað voru lögð út fimm um 50 m löng snið, þvert á hitastigla svæðanna, og sex fastir mælireitir lagðir út á hverju sniði þannig að einn var á óupphituðum jarðvegi (samanburðarreitur) en hinir á síheitari jarðvegi. Reynt var að velja þannig að upphitunin yrði sem næst +1, +3, +5, +10 og +20 °C. Samfelldar mælingar á jarðvegshita reitanna 2013-2015 sýndu að upphitunin hélst tiltölulega stöðug og jarðvegshiti þeirra sveiflaðist líkt og í óupphituðum reitum milli árstíða. Vatnsinnihald yfirborðsjarðvegs (0-5 cm) var mælt reglulega yfir tímabilið 2013-2016. Graslendin höfðu að jafnaði rakari yfirborðsjarðveg en skógurinn, en þau, ólíkt skóginum, sýndu einnig stundum marktæka uppþornun á heitustu reitunum. Efnagreiningar sýndu engin merki þess að jarðhitavatn næði upp í jarðveg svæðanna. Sýrustig jarðvegs hækkaði aðeins (varð basískara) með auknum hita sem tengdist líklega gróðurfarsbreytingum. Niðurbrotsgeta á lífrænu efni jókst með jarðvegshita í öllum reitunum, eins og búist var við. Lokaniðurstaðan var að jarðhitasvæði ForHot verkefnisins framkölluðu aðstæður sambærilegar við ýmsar stýrðar jarðvegsupphitunartilraunir erlendis sem notaðar eru til að rannsaka áhrif hlýnunar á þurrlendisvistkerfi.
 

Athugasemdir:

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.

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