Population and the environment - soils and human activities

what is the classification system for soil types?

zonal

what are the three categories of the zonal system?

zonal, intrazonal, azonal

what is zonal soil?

mature soils, reflecting climatic conditions and associated vegetation

what is intrazonal soil?

soil reflecting the dominance of other factors, e.g. characteristics of the parent rock

what is azonal soil?

immature and skeletal soil, with poorly developed profiles

what state is zonal soil in?

dynamic equilibrium

what 3 things is zonal soil in dynamic equilibrium with?

climate, vegetation, parent matter

what two things make up soil?

1. minerals from weathered bedrock

2. organic matter from vegetation

what are the 5 soil horizons in order?

O, A, E, B, C (and then bedrock)

what is the O horizon?

loose, partially decayed organic matter

what is the A horizon?

topsoil with high humus content

what is the E horizon?

pale layer of silt and sand, from which clay, iron, and other materials have been leached

what is the B horizon?

zone in which the minerals leached from E accumulate

what is the C horizon?

mainly broken bedrock

what is leaching?

when water moves minerals and nutrients down through the soil profile

where are latosols found?

TRFs

how does the TRF climate impact bedrock weathering?

high temp and humidity → fast chemical weathering

how deep can latosols get?

30 to 40 m

why is the latosol O horizon thick?

year-round plant growth

why is the latosol A horizon thin?

as soon as leaf litter decomposes, the nutrients are absorbed by vegetation - so don’t stay in the soil

why does latosol have a lot of leaching?

rainfall higher than evapotranspiration → soil moisture surplus

what mineral is leached in latosols? Which horizon?

silicate from B horizon

why is the latosol B horizon red?

iron and aluminium are less soluble so don’t get leached

why are latosols poor for agriculture?

low nutrient content

why are latosols even worse for agriculture when the trees are removed?

soil has no protection from heavy rainfall, increasing leaching

what is slash and burn?

clearing one small area at a time for growing crops → after one season, it is allowed to recover

why does slash and burn improve agriculture in latosols?

burning adds nutrients to the soil

why are latosols useful for building?

the laterite horizon is soft when moist, but hard when dry

how is a laterite horizon formed?

build-up of minerals in the soil

where do podzols occur?

cool temperate climates in the northern hemisphere

what is higher in podzol areas, precipitation or evapotranspiration?

precipitation

under which 2 biomes are podzols usually found?

1. coniferous woodland

2. heather moorland

(both are taiga)

what is the O horizon in podzols?

layer of coniferous needles/heather leaf litter

what is the A horizon like in podzols? (3 details)

1. narrow

2. acidic

3. nutrients leached from it by water

how does acidity impact leaching in podzols?

water in soil is more able to dissolve minerals e.g. iron and aluminium

what layer does podzol leaching create?

pale E horizon of quartz sand and silt

where do minerals accumulate in podzols? What colour does this make it?

B horizon, making it reddish-brown

what is a hard pan/iron pan?

hard, continuous layer of iron in the B horizon of very well-developed podzols

why is arable farming difficult in podzols? (3 reasons)

1. acidity

2. lack of nutrients

3. iron pan causes waterlogging, damaging crops

what two things are needed for arable farming on podzols?

1. treatment with lime to reduce acidity

2. artificial fertilisation

why do podzols have a poor nutrient cycle?

coniferous trees do not take up certain elements → these are not added to the soil from falling needles

what 3 elements are not taken up by conifers?

1. calcium

2. magnesium

3. potassium

what two human activities are associated with podzol areas in the UK?

1. sheep farming

2. grouse breeding and shooting (patches of heather are burnt for this)

how much money does the UK get from grouse shooting annually?

£150 million