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

Sigurðsson, Bjarni D.; Leblans, Niki I. W.; Dauwe, Steven; Guðmundsdóttir, Elín; Gundersen, Per; Gunnarsdóttir, Gunnhildur; Holmstrup, Martin; Ilieva-Makulec, Krassimira; Kätterer, Thomas; Marteinsdóttir, Bryndís; Maljanen, Marja; Oddsdóttir, Edda Sigurdís; Ostonen, Ivika; Peñuelas, Josep; Poeplau, Christopher; Richter, Andreas; Sigurðsson, Páll; Bodegom, Peter M. van; Wallander, Håkan; Weedon, James T.; Janssens, Ivan A.

doi:10.16886/ias.2016.05

Cited by 63 publications

(137 citation statements)

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“…The study was conducted at the ForHot research site (Sigurdsson et al., ), which is located in the Hengill geothermal area, 40 km east of Reykjavik, Iceland (64°00′01″N, 21°11′09″W; 100–225 m a.s.l.). The dominant soil type in this area is Brown Andosol.…”

Section: Methodsmentioning

confidence: 99%

“…In this grassland, two areas that had been subjected to geothermal warming for different periods of time were studied. One area had probably been warmed for centuries, based on different historical sources and soil profile surveys, and no change in the location of the hotspots had been recorded during the preceding 50 years (Sigurdsson et al., ). This grassland was termed “LWG” (“Long‐term Warming Grassland”).…”

Section: Methodsmentioning

confidence: 99%

“…This grassland was termed “LWG” (“Long‐term Warming Grassland”). The second grassland, which was located 2 km SE from LWG, had been warmed since 29 May 2008, when a large earthquake shifted geothermal systems to previously unwarmed soils (Sigurdsson et al., ). This study area was termed “SWG” (“Short‐term Warming Grassland”).…”

Section: Methodsmentioning

confidence: 99%

“…One way to assess the long‐term impact of warming on terrestrial communities is the use of natural geothermal temperature gradients within local areas establishing “outdoor laboratories” (O'Gorman et al., ). Although geothermal warming does not influence the temperature of the above‐ground atmosphere to any great extent (Sigurdsson et al., ), such systems may be used to test hypotheses about the influence of warming per se on soil organisms. In this study, we make use of both recent (short‐term) and long‐term geothermal warming of Icelandic soils to examine the responses of soil invertebrates to both recent and long‐term warming.…”

Section: Introductionmentioning

confidence: 99%

“…In these areas, and in similar nearby grassland areas that had been heated for more than 50 years (also due to geothermal heating), we compared the Collembola communities along soil temperature gradients ranging from unwarmed soils to soils warmed by c . 10°C (Sigurdsson et al., ). This allowed us to compare short‐term and long‐term responses of Collembola communities to soil warming.…”

Section: Introductionmentioning

confidence: 99%

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Functional diversity of Collembola is reduced in soils subjected to short‐term, but not long‐term, geothermal warming

et al. 2018

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Human activities have caused global changes of atmospheric chemistry resulting in increased temperature especially in the colder regions of the northern hemisphere. Since warming of the environment can have drastic effects on terrestrial ecosystems it is important to experimentally evaluate the extent of such effects in long‐term field‐based experiments. In this study we make use of both recent (short‐term) and long‐term geothermal warming of Icelandic soils to examine the responses of Collembola, an ecologically important group of soil invertebrates, to warming. On the basis of metabolic scaling theory, we hypothesized that species of small size would be more successful in warmed soils than species of larger size. Further we expected that top‐soil‐dwelling species would benefit more from warming than deep‐soil‐dwelling species. In order to test these hypotheses we sampled Collembola along replicated gradients of increasing temperature in areas that had been heated for about 6 years and more than 50 years respectively. Collembola were identified to species level, counted and the community‐weighted mean trait scores for six functional and ecological traits were calculated. Results show that both short‐term and long‐term soil warming caused a shift towards a higher relative abundance of species with small body size. Furthermore, abundance of top‐soil‐dwelling Collembola tended to increase after short‐term warming, but the opposite was observed after long‐term warming. Using trait‐based diversity indices (FRic and RaoQ), we show that functional richness and diversity of Collembola communities was significantly reduced (almost halved) as a result of short‐term soil warming to about 10°C above normal, but this effect was not detected in plots equally warmed for more than 50 years. This indicates that the functional diversity of Collembola communities have high resilience towards soil warming in a long‐term perspective. A http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.13058/suppinfo is available for this article.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Functional diversity of Collembola is reduced in soils subjected to short‐term, but not long‐term, geothermal warming

et al. 2018

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Selection against early flowering in geothermally heated soils is associated with pollen but not prey availability in a carnivorous plant

Valdés

Helmutsdóttir

Marteinsdóttir

et al. 2022

American J of Botany

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Premise In high‐latitude environments, plastic responses of phenology to increasing spring temperatures allow plants to extend growing seasons while avoiding late frosts. However, evolved plasticity might become maladaptive if climatic conditions change and spring temperatures no longer provide reliable cues for conditions important for fitness. Maladaptative phenological responses might be related to both abiotic factors and mismatches with interacting species. When mismatches arise, we expect selection to favor changes in phenology. Methods We combined observations along a soil temperature gradient in a geothermally heated area with pollen and prey supplementation experiments and examined how phenotypic selection on flowering time in the carnivorous plant Pinguicula vulgaris depends on soil temperature, and pollen and prey availability. Results Flowering advanced and fitness decreased with increasing soil temperature. However, in pollen‐supplemented plants, fitness instead increased with soil temperature. In heated soils, there was selection favoring later flowering, while earlier flowering was favored in unheated soils. This pattern remained also after artificially increasing pollen and prey availability. Conclusions Plant–pollinator mismatches can be an important reason why evolved plastic responses of flowering time to increasing spring temperatures become maladaptive under novel environmental conditions, and why there is selection to delay flowering. In our study, selection for later flowering remained after artificially increasing pollen availability, suggesting that abiotic factors also contribute to the observed selection. Identifying the factors that make evolved phenological responses maladaptive under novel conditions is fundamental for understanding and predicting evolutionary responses to climate warming.

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Maladaptive plastic responses of flowering time to geothermal heating

Ehrlén

Valdés

Helmutsdóttir³

et al. 2023

Ecology

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Phenotypic plasticity might increase fitness if the conditions under which it evolved remain unaltered, but becomes maladaptive if the environment no longer provides reliable cues for subsequent conditions. In seasonal environments, timing of reproduction can respond plastically to spring temperature, maximizing the benefits of a long season while minimizing the exposure to unfavorable cold temperatures. However, if the relationship between early spring temperatures and later conditions changes, the optimal response might change. In geothermally heated ecosystems, the plastic response of flowering time to springtime soil temperature that has evolved in unheated areas is likely to be non‐optimal, because soil temperatures are higher and decoupled from air temperatures in heated areas. We therefore expect natural selection to favor a lower plasticity and a delayed flowering in these areas. Using observational data along a natural geothermal warming gradient, we tested the hypothesis that selection on flowering time depends on soil temperature and favors later flowering on warmer soils in the perennial Cerastium fontanum. In both study years, plants growing in warmer soils began flowering earlier than plants growing in colder soils, suggesting that first flowering date (FFD) responds plastically to soil temperature. In one of the two study years, selection favored earlier flowering in colder soils but later flowering in warmer soils, suggesting that the current level of plastic advance of FFD on warmer soils may be maladaptive in some years. Our results illustrate the advantages of using natural experiments, such as geothermal ecosystems, to examine selection in environments that recently have undergone major changes. Such knowledge is essential to understand and predict both ecological and evolutionary responses to climate warming.

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

Cited by 63 publications

References 11 publications

Functional diversity of Collembola is reduced in soils subjected to short‐term, but not long‐term, geothermal warming

Functional diversity of Collembola is reduced in soils subjected to short‐term, but not long‐term, geothermal warming

Selection against early flowering in geothermally heated soils is associated with pollen but not prey availability in a carnivorous plant

Maladaptive plastic responses of flowering time to geothermal heating

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