Soils in ireland 16

BY4215

Soil formation in Ireland

Influenced by parent material, relief, organisms, time, climate, anthropogenic activity

Pedogenic processes

Leaching (water removes soluble substances), Podzolisation (organic matter, Fe/Al mobilization), Gleying (anaerobic reduction of iron in waterlogged soils)

Other pedogenic processes

Illuviation (clay, iron, organic matter accumulate in B horizon), Calcification (CaCO3 accumulates), Paludification (peat forms on previously dry vegetated land)

Parent material

Solid rock (weathered, >200 m elevation), superficial deposits (glacial drifts, alluvium), organic matter

Igneous rocks

Granite (slow-cooled, coarse-grained), Basalt (rapid-cooling, fine-grained), Rhyolite (rapid-cooling, silica-rich, fine-grained/glassy)

Sedimentary rocks

Pure limestone (CaCO3 from marine organisms/precipitation), Impure limestone (contains clay, siliceous matter, Mg), Sandstone (compacted cemented sand), Shale (compacted silt/clay, fissile)

Metamorphic rocks

Schist (recrystallized, foliated, flaky)

Bedrock geology Ireland

Cavan/Monaghan (Palaeozoic shales, grits, greywackes), Louth/Meath (limestones, shales, siltstones), SE (sedimentary + igneous), S/SW (Old Red Sandstone, shale, limestone), W Galway/Mayo (granite/metamorphic), Donegal (schist, quartzite, granite intrusions), Centre (Carboniferous limestones, Palaeozoic shales/sandstone)

Recent geology

Two major glacial episodes (Munster 200–130 ka, Midlandian 75–10 ka), Irish Sea Ice Sheet (max 25–23 ka, marine sediments in Wexford/Meath), last ice sheet disappeared ~10,000 years ago

Glacial landforms

Cirques (bowl-shaped hollows), Glacial valleys (U-shaped), Drumlins (oval hills), Moraines (ridges, lateral/terminal), Kames/kame terraces/eskers (meltwater deposits), erratics (transported boulders)

Woodlands in Ireland

1928: 98,000 ha (~1%), 2021: 769.6k ha (~11%), growth due to afforestation, natural regeneration

Climate

Cool temperate, maritime

Anthropogenic activities

Agriculture (habitat loss, ammonia emissions, biodiversity impact), Urbanization (habitat loss, pollution), Resource extraction (peat, minerals), Transportation/energy (GHG, air pollution, fossil fuels)

Current/future influences

Mining, urbanization, land use change, climate, atmospheric deposition

Soil formation

Plants deposit organic matter, residues decomposed by fauna, organic matter enhances nutrient/water, horizon development, organic acids aid weathering, leaching may remove nutrients

Soil profile

Vertical sequence of layers (horizons) differing in colour, texture, structure, porosity, chemistry, organic matter

Soil horizons

Master horizons O, A, E, B, C, R; A/E/B

Brown earth soil

Poorly defined horizons, well-drained, fertile, A horizon rich in mull humus, B horizon lighter, C horizon parent material

Grey-brown podzolic soils (alfisols)

A horizon high organic, leached E horizon, Bt horizon clay/sesquioxides accumulation, parent material often calcareous

Podzol soil

O top layer, bleached E horizon, dark reddish B horizon (Fe/Al/OM accumulation)

Forest floor layers

L (litter), F (partly decomposed), H (well decomposed)

Organic horizons

Oi (fibric, slightly decomposed), Oe (hemic, intermediately), Oa (sapric, highly decomposed)

Classification of soils Ireland

Great Soil Groups I–XI (Ombrotrophic Peat, Minerotrophic Peat, Rendzinas, Lithosols, Alluvial, Groundwater Gleys, Surface-water Gleys, Podzols, Brown Podzolics, Luvisols, Brown Earths)

Rendzinas

Shallow (<50 cm), carbonate-rich, surface over parent material, Co. Clare/Sligo/Roscommon

Brown Earth

Mature, uniform, little leaching, occur Co. Galway/Limerick

Brown Podzolics

Calcareous parent, clay translocation, B2t horizon, central Ireland, limestone underlain

Podzols

Leached surface horizons, fine particle translocation, acidification, Fe/Al mobilization, poorly drained, hill/mountain areas

Groundwater/Surface-water Gleys

Poor drainage, waterlogged, unsuitable for cultivation/intensive grassland, wet low-lying areas, shale/sandstone associated

Lithosols

Skeletal stony soils over bedrock, steep/coastal/high elevation, rough grazing

Peat

Biogenic deposit, accumulation exceeds decay, depth >0.3 m, >30% organic matter

Peat formation processes

Terrestrialisation, Paludification; decomposition inhibited by moisture, temperature, pH

Peatlands Ireland

1.174 M ha (17%), minerotrophic and ombrotrophic, fen, raised bog, blanket bog, low/high level

Land use of peatlands

Blanket bog and raised bog stages, woody peat, forest, reed swamp

Peat properties

pH, ash content, N content, Ksat varies by layer (YS, OS, WF, RS, B1/B2)

Climate action plan peatlands

Rehabilitate 11,000 ha by 2022, 22,000 ha by 2026, low-input peat grassland measures, redesign peatland forests for carbon balance

The Curragh, Co. Kildare

Example of Irish peatland

Plaggen soils

Addition of material to improve fertility, raise surface, liming peat, coastal soil improvement with shelly sand/seaweed

Céide Fields

5,000-year-old site, forest clearance/climate change favored peat formation