Land use changes, such as growth in urban areas, farming and forestry, as a catalyst for altering the flows and stores in these cycles.

  • Created by: EmilyM17
  • Created on: 22-05-19 09:14
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  • Land use changes, such as growth in urban areas, farming and forestry, as a catalyst for altering the flows and stores in these cycles.
    • Urbanisation
      • Artificial surfaces are largely impermeable so allow little or no infiltration and provide minimal storage capacity to buffer run-off
      • Urban areas have drainage systems designed to remove water rapidly = high proportion of water from precipitation flows quickly into streams and rivers
        • This leads to a rapid rise in water level
      • Urbanisation also encroaches on floodplains, this reduces water storage capacity in drainage basins, increasing river flow and flood risks
    • Farming
      • Clearance of forest for farming reduces carbon storage in both above and below-ground biomas
      • Soil storage is reduced by ploughing and the exposure of soil organic matter to oxidation
      • Losses of carbon occur when harvesting of crops occurs with only small amounts of organic matter returned to the soils
      • Soil erosion invariably accompanies arable faming. Erosion by wind and water is most severe when crops have been lifted and soils have little protective cover
      • Changes to the carbon cycle are less apparent on pasture land or where farming replaces natural grasslands.
      • WATER: Crop irrigation diverts surface water from rivers and groundwater to cultivated land. Some of this water is extracted by crops from soil stprage and released by transpiration; bt most is lost to evaporation and in soil drainage
      • WATER: Interception and evaporation and transpiration from leaf surfaces by annual crops is less than in forest or grassland ecosystems
        • Ploughing increases evaporation and soil moisture loss
        • Furrows ploughed downslope act as drainage channels, accelerating run-off and soil erosion
        • Infiltration due to ploughing is greater in farming ecosystems, while artificial underdrainage increases the rate of water transfer to streams and rivers
        • Surface run off increases where heavy machinery compacts soils. Thus peak flow on streams draining farmland are generally higher than natural ecosystems
    • Forestry
      • Forestry management in plantations modifies the local water and carbon cycles. Changes to the water cycle include:
        • Higher rates of rainfall interception in plantations in natural forests
        • Increased evaporation
        • Reduced run-off and stream discharge
        • Compared to farmland and moorland, transpiration rates increase
        • Clear felling to harvest timber creates sudden but temporary changes to the local water cycle, increasing run off, reducing evapotranspiration and increasing stream discharge

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