Option 7 Soils and Biome Soils Notice of

Option 7: Soils and Biome Soils

Notice of Use Restrictions v Certain materials in this presentation are included under the Fair Use exemption of the U. S. Copyright Law and/or under the Fair Dealing exemption of the Ireland Copyright and Related Rights Act, 2000 v Materials are included in accordance with the [U. S. ] multimedia fair use guidelines; and v Materials are restricted from further use. v © EDMAN YOST, J. (1999), Copyright Chaos - An Educator's Guide to Copyright Law and “Fair Use”, Intel Teach to the Future CD

Brown Earths: Ireland

Brown Earths in Ireland • Variations in Ireland’s brown earths: – Podzolic brown earths: lowland limestones of central and eastern Ireland, develop where leaching is high, ash-grey A horizon – Acid brown earths: southeast of Ireland, parent material low in lime, such as shale, sandstone, granite, low Ph and acidity can be reversed

Brown Earth Soil Profile • Vegetation layer: deciduous/mixed forest • O horizon: organic material, plant litter and humus, some micro organisms • A horizon: topsoil, dark brown colour, mineral matter and slightly acidic humus, most biological activity takes place here

Brown Earth Soil Profile • B horizon: subsoil, lighter in colour, leaching and organisms movement mean A and B horizons not always obvious, minerals can accumulate here • C horizon sits directly on bedrock, only slightly affected by soil-forming processes (broken rock or regolith) • Unaltered bedrock/parent material

Human Interference: The Sahel

The Sahel • Narrow band of Africa between the Sahara and the savanna and equatorial forests to south • Semi-arid region, receives rain during wet season July to September • Covered by grassland supports a nomadic, pastoral-based society (traditionally moved with rains)

The Sahel • The Sahara desert advancing between 5 and 10 km a year towards Sahel • Desertification http: //www. youtube. com/watch? v=t. D WS 6 Az. Ek. E 0

Desertification • Moving forward of deserts and formation or expansion of degraded soil and vegetation • Results from climate change (drought) and human interference: – Overgrazing – Overcropping – Deforestation

Overgrazing

Overgrazing • Animal ownership a sign of wealth • Increase in cattle and goats increased competition for grazing land • More animals graze than the land can sustain • Young trees and shrubs also cropped by animals

Overgrazing • Wells were sunk to provide better watering of animals • Herders stayed in one place longer putting pressure on grasslands • Wells used up groundwater that had taken centuries to build up • Nomadic turned to sedentary • Intensive fenced in grazing • Soils not left fallow, lost structure • Drained of nutrients, no re-growth, erosion

Overcropping

Overcropping • • Increased demand for food Grazing replaced by crops ‘Fallow year’ abandoned Cash crops (millet and groundnuts) Raise money to pay off international debt Monoculture Land became sterile and crops died Greater area of land now needed to be cultivated

Overcropping • Vegetation removed for crops • Shortage of wood, people burned dry dung for heating and cooking • Used for this instead of fertiliser • Reduced amount of humus • Soil lost protection, wind erosion

Deforestation

Deforestation • Done in order to clear agricultural land • Or for building materials fuel for heating and cooking • Every year half a million trees are cleared and burned in Mali alone • Trees cut down thirty times as fast as they are replaced • If trees near family home are felled women have to walk miles each day for firewood

Deforestation • No resources to replant trees • Little left but sparse, stunted plant cover • Trees slow down wind and roots help bind soil particles • Also absorb moisture during rainfall • Exposed land burned by sun (desertification)

Soil Conservation • • A sustainable resource Must reduce erosion Reclaim land already eroded Methods are being used worldwide not just in the Sahel – Stone lines – Contour ploughing and terracing – Improved farming methods

Soil Conservation • Stone lines: small stones placed across slopes to reduce run-off (Burkino Faso) • Particularly effective where slope is gentle • Stones run parallel with contours • Rain is trapped, increases water table • Also traps soil, seeds and organic matter • 2% land taken up by stones, ups yield by 50%

Soil Conservation • Contour Ploughing: furrows go across the slope following contours • Act like miniature dams • Infiltration increases soil quality and vegetation quality, binding the soil • Can reduce soil erosion by 50% • Common in South-West USA

Soil Conservation • Terracing: steeper slopes, can reduce soil erosion or even prevent it • Slope cut into a series of wide steps • Front of each flat terrace is edged with a mud or stone wall called a bund • Bund traps water • Used in rice cultivation in SE Asia

Soil Conservation • Improved Farming Methods: – Strip Farming: planting crops in widely spaced rows – Filling empty space with another crop, complete ground cover – Vegetation slows water flow – Ideally crops would differ in height, nutrient requirement & harvesting time

Soil Conservation – Shelter Belts: trees or shrubs, along a flat region prone to wind erosion – Break wind force and shelter strips of land between belts – Roots help bind soil – In developing countries these are often fruit growing trees for extra food source – Long term solution

Soil Conservation – New Animal Strains: have been introduced to the Sahel – 1980 s drought, cattle reduced – Poor quality animals – Replaced by smaller, better-quality stock – Meat and milk production increased – Demands on grazing lands decreased – Land has time to recover