Soil thermal buffer and regeneration niche may favour calcareous fen resilience to climate change

Abstract

Calcareous fens are azonal habitats permanently saturated by groundwater. This is expected to have a buffer effect on soil temperature, alleviating climate changes and allowing plant communities to occupy diverse climatic regions. We analysed the extent of such buffering and its relation with a relevant plant trait, the seed germination niche breadth, along altitudinal gradients in fens of the Cantabrian Mountains (Spain) and the Western Carpathians (Slovakia). In each fen we recorded soil temperature for several years and compared it with WorldClim predictions for air temperature. We also collected seeds from five Cyperaceae fen specialists to evaluate the influence of soil temperature on germination. Although soil temperatures and WorldClim were strongly correlated, their absolute values differed substantially, showing a narrower thermal amplitude and warmer minimum winter temperature in the soil. The greatest differences in soil temperature and germination niche breadth were those between mountain regions. Narrower germination niches correlated with the colder Slovakian winter. Our results suggest that the soil thermal buffer allows species to prevent frost temperatures in winter, but also high summer temperatures in warm regions, explaining their wide distribution ranges. The warm regeneration niche does not match the cooler soils, but shows variability and potential for adaptation. While this findings support resilience to climate warming, changes in precipitation rather than temperature seem to be the main threat for fen persistence.

The complex adaptive character of spring fens as model ecosystems

“…The temperature of the upwelling groundwater, which significantly affects the microclimatic conditions of the studied spring fens on the local scale (Beierkuhnlein and Graesle 1999) strongly reflects the mean annual air temperature in the catchment area (Gerecke 2016) and, thus, is linked to the climatic conditions acting on landscape to continental scale. This strong cross-scale link between micro-climatic conditions (soil temperature) on a local scale and large scale climatic conditions was also observed by Fernández-Pascual et al (2015) for calcareous fens in the Cantabrian Mountains (Spain) and the Western Carpathians (Slovakia) although absolute temperatures differed significantly between micro-and macro-scale. However, further tests have to be conducted for other ecosystems characterised by different degrees of environmental cross-scale links to test this hypothesis about the effect of abiotic cross-scale links on the scale dependence of ecological patterns.…”

Characteristics, Main Impacts, and Stewardship of Natural and Artificial Freshwater Environments: Consequences for Biodiversity Conservation

“…While aquatic and semi-aquatic spring-fen biota (e.g., diatoms or aquatic invertebrates) is substantially affected by water temperature [382,387], terrestrial fen biota (land snails) is affected mostly by air temperature, especially in winter. Vascular plants show intermediate response because they are rooted in permanently waterlogged peat and because water temperature affects their germination [388]. There are good reasons to assume that increasing temperatures will affect especially mires in southern Europe where their current distribution is restricted and species composition depauperate already due to previous Holocene development [351].…”

The ratio between bryophyte functional groups impacts vascular plants in rich fens

“…Generally, species preferring non‐sphagnaceous bryophytes are often reported to rely on generative reproduction in fens (see Meškauskaitė & Naujalis, ; Stammel, Kiehl, & Pfadenhauer,; Vittoz, Wyss, & Gobat, ; Hájková et al., ; Soudzilovskaia et al. ; and Fernández‐Pascual, Jiménez‐Alfaro, Hájek, Díaz, & Pritchard, for germination needs of individual species). Other reasons why individual species prefer non‐sphagnaceous bryophytes may comprise the contrasting effects of brown‐moss and Sphagnum patches on redox conditions that affect phosphorus cycling (Crowley & Bedford 2011) and on species composition of potentially mycorrhizal fungi.…”

“…The analysis of clonal traits indeed showed contrasting strategies for the vascular plants preferring Visser, Bögemann, Van de Steeg, Pierik, and Blom (2000) indeed showed an affinity of C. davalliana to waterlogged sites with high redox potential. Generally, species preferring non-sphagnaceous bryophytes are often reported to rely on generative reproduction in fens (see Meškauskaitė & Naujalis, 2006;Stammel, Kiehl, & Pfadenhauer,2006;Vittoz, Wyss, & Gobat, 2006;Hájková et al, 2009;Soudzilovskaia et al 2011;and Fernández-Pascual Note: In the case of a positive regression coefficient, the species is associated with high pH (g1), high WTD (g2) and a high proportion of non-sphagnaceous bryophytes relative to sphagna (g3). Values of constant regression coefficients are: for regional data set g4 (0.27***); g5 (non-significant); l1 (0.927***) and for continental data set g4 (non-significant); g5 (non-significant); l1 (1***).…”

“…, Jiménez-Alfaro,Hájek, Díaz, & Pritchard, 2015 for germination needs of individual species). Other reasons why individual species prefer nonsphagnaceous bryophytes may comprise the contrasting effects of brown-moss and Sphagnum patches on redox conditions that affect phosphorus cycling(Crowley & Bedford 2011) and on species composition of potentially mycorrhizal fungi.…”