Geo‐ecological studies on two ultramafic sites in western Ireland

Abstract

Ultramafic soils are found in many sites around the world where they can vary from exceptionally barren to reasonably fertile. Two ultramafic sites in western Ireland were studied: grassland at Dawros, County Galway and grassy heath near the base of Croagh Patrick, County Mayo. Rock and soil chemistry was examined along with foliar nutrients (at Dawros only). Ellenberg reaction values of all plant species recorded were determined. Two bioassays were conducted to determine relative differences in fertility between ultramafic and adjacent non‐ultramafic soils and to assess nutrient limitation in the Croagh Patrick soil. Both soils showed many of the chemical characteristics typical of other ultramafic sites including a moderately high nickel concentration; in general, soil metal concentrations were higher in Dawros soils. However, nitrogen, phosphorus and calcium (with a calcium:magnesium ratio c. 0.6) were all at high concentrations at Dawros leading to a fertile grassland with both calcicole and calcifuge species present spanning six Ellenberg reaction values. Foliar nutrient concentrations were not unusual although calcium:magnesium ratios were approximately double in non‐ultramafic soils compared to ultramafic soils. Croagh Patrick soil had lower concentrations of most nutrients and presented a grassy heath vegetation with more acidic reaction values. The bioassays showed plant growth to be reduced in this soil relative to that at Dawros and to be clearly limited by phosphorus availability. Whilst these two Irish ultramafic sites do not show the extreme features associated with other sites across the world they indicate the global diversity of serpentine ecologies.

A global forum on ultramafic ecosystems: from ultramafic ecology to rehabilitation of degraded environments

“…Many articles published in this Special Issue address biodiversity of ultramafic ecosystems, the existence of specific communities of poorly studied organisms in ultramafic environments or the existence of yet unreported hyperaccumulator species. They include a full geoecological study of two ultramafic ecosystems in Ireland (Brearley 2018 ). The use of hand-held X-ray fluorescence (XRF) instruments for the scanning of thousands of herbarium specimens was presented as a powerful tool to uncover hyperaccumulating plant taxa in herbarium collections (Gei et al 2018).…”

Geo-ecological insights on the island of Inchcailloch in Loch Lomond, Scotland: a small serpentine outcrop in a mixed geological setting

“…In terms of foliar elemental concentrations, they were all generally sufficient for adequate plant growth (Pugnaire, 2001). Of course, serpentine soils have an unusual chemical composition, but foliar Co, Cr, Mg and Ni were all low when compared with other UK serpentine sites (Proctor 1992) and comparable to Irish grasslands and heaths with minimal serpentine effects (Brearley 2018;Brearley et al 2020). Proctor (1992) presented an extensive dataset on foliar elemental concentrations in UK serpentine sites, and boreo-temperate ecosystems have a much lower occurrence of hyperaccumulator species than Mediterranean or tropical ecosystems (Teptina et al 2018) so the generally low foliar metals are not unexpected.…”

“…This variability in Ca is likely due to geological factors (McGahan et al 2008(McGahan et al , 2009 as associated with the serpentinite is a serpentinite in limestone breccia that will have weathered and been mixed together during soil formation. The second reason for the lack of a noticeable serpentine effect is the moderate-to-high total P concentrations that were comparable to Lime Hill (Stirlingshire) (Johnston and Proctor 1979) or Irish grasslands and heathlands (Brearley 2018). The third reason is the generally low total concentrations of soil metals such as Ni (< 1250 μg g −1 ) or Cr (< 944 μg g −1 ).…”

Ultramafic vegetation and soils in the circumboreal region of the Northern Hemisphere

“…The most thorough treatments available to date are of ultramafic vegetation in the Scandinavian region (Rune 1953;Rune and Westerberg 1992;Nyberg Berglund et al 2004) and eastern North America ). Some ultramafic communities in Britain (Proctor 1992), including the Lizard peninsula in England and outcrops in Anglesey, Wales (Proctor and Woodell 1971), Scotland (Steele 1955), Cornwall (Coombe and Frost 1956a, b) and Unst outcrop in Shetland (Spence 1957(Spence , 1958(Spence , 1959Shewry and Peterson 1976;Carter et al 1987) and Ireland (Brearley 2018) have also received some attention.…”