Soil profiles characteristics and profiles Podzol Brown Earth

Soil profiles, characteristics and profiles. Podzol. Brown Earth Gley

Podzolization v This is an intense form of leaching. v Occurs when rainfall is greater than precipitation. v The main substances leached out of the soil include iron, aluminium and humus compounds.

Describing Podzols v v v LOCATION – found in Northern coniferous forests OR upland moorland areas. CLIMATE – cold wet climates where precipitation exceeds evaporation. DESCRIPTION – Thin top layer, Ao Horizon, of needles and cones decomposing to form a raw acidic humus (mor). The A horizon has a ash coloured tint to it composed of insoluble silicates. The B horizon has a reddish tint to and an iron pan may form here.

Explaining the formation of Podzol. The soil forming process is very slow because of the cold climate. v Ao Horizon - Thin humus layer because of little humification: v. Trees have needles not leaves. v. Trees do not shed their needles every year. v. Needles break down very slowly. v. Few biota live in this cold climate. v Leaching occurs due to heavy rainfall and melt water. v

Continued…. v v v A Horizon - Zone of Eluviation where humus, iron and clay are leached through the A Horizon. B Horizon - Zone of Illuviation where clay, humus and iron are deposited and accumulated. Giving the red tint to the horizon. Iron pan forms where iron is re-deposited between the A and B horizons. The soil is sometimes waterlogged because the iron pan prevents further downward movement of water. C Horizon – forms from a range of parent material There is very little mixing of the horizons because of lack of living organisims – BIOTA.

Describing Brown Earth Forest Soils. v v v LOCATION – deciduous forests of Europe, Russia and North America. CLIMATE – mild winters and summers, quite wet all year. Temperate maritime. DESCRIPTION – Ao Horizon made up of leaf debris, forms a mild acid humus. The A horizon is a brown layer mergining into the B horizon, brown colour becomes lighter into the C horizon. There are no clearly defined horizons.

Explaining the formation of Brown Earth Forest Soil. v Rich humus layer made up from decaying grasses and herbs and falling leaves every autumn. Compared to Podzol the humification process is quicker because of the warmer climate. Results in a mull humus this is less acidic. v Some leaching throughout the year because precipitation exceeds evaporation.

Continued…. . A horizon has a dark brown colour as humus replaces minerals as they are leached out. Leaching however is less pronounced here. v B horizon is less pronounced in colour because humus becomes less abundant here. v C Horizon is derived from varied parent material. v Mixing of horizons due to presence of soil biota. v Tree roots reach deep into the soil to allow any leached chemicals to be brought back up into the leaves. v

Gleying v Is the inability of soils to shed water quickly. Often found at the foot of hills.

Describing Gley v v v LOCATION – Arctic. Found it sites that are waterlogged. CLIMATE – cold climate. DESCRIPTION – Black Ao horizon, thin layer of black acidic humus. A horizon is poorly drained with a dark grey colour to it. B horizon is blue, grey with iron compounds mixed through it.

Explaining the formation of gley. v Weathering is slow due to cold climate. v Humification is slow because of: v Little vegetation. v Cold and dry v Few biota. v Very little leaching because: v Soil is frozen for most of year. v Subsoil is impermeable permafrost, but some leaching after snow melt.

continued Lack of biota because waterlogged conditions – no oxygen. v Vertical mixing in the soil takes place as a result of the annual freeze thaw cycle. This may result in poorly defined horizons. v The iron compounds in the A horizon have lost their reddish colour to a blue grey colour. v The B horizon is predominantly blue grey indicating virtually continuous water logging, this had developed on a C Horizon derived from an impermeable clay layer. v

Key Words v Illuviation v Eluviation v Humification v Leaching v Capillary Movement v Podzolization, v Gleying