Habitat design

• Habitat area -

  • the habitat area must be large enough to support viable populations
  • the breeding population must not drop so low that the reproduction rate is too low to maintain the population and the gene pool must not be so small as to cause inbreeding
  • how large this area actually is depends upon the species
  • in general species that are higher up food chains have lower population densities, so a larger habitat area may be needed to support a viable population
• Habitat area continued -

  • an area that is too small to support populations of less abundant species may eventually become unsuitable for other species
  • some species benefit from small habitats: frogs, newts and toads breed more successfully in ponds that are too small to support the predatory fish that would eat their eggs and tadpoles
• Biological corridors -

  • linking isolated areas of the same habitat type allows the dispersal of young animals if there is local breeding surplus and the mixing of different populations and gene pools which reduces the risk of inbreeding
  • if a species dies out in one area then recolonisation from other areas is possible
  • They can also be used to allow animals to avoid hazards when moving between habitats
• Habitat shape -

  • the perimeter of a habitat will have a strip where the conditions ar a combination of two neighbouring habitats
  • some species benefit form these conditions for example higher light levels at the edge of a wood but they may not be suitable for the species that require the core habitat conditions
• Habitat diversity -

  • natural habitats are rarely uniform and usually have local variations in conditions producing a greater range of possible niches
  • this increases biodiversity as different species colonise the areas to which each is best adapted
• Light levels -

  • the shading effect of dense tree cover inhibits the growth of plants on the woodland floor
  • this can be reduced by selectively felling individual trees to create suitable conditions for smaller plants that need more light
• Water depth -

  • many of the plants and animals that live in aquatic habitats will colonise areas with particular water depths
  • dominant plants are those that can absorb most sunlight often by being taller
  • plants with emergent vegetation above the water level can only support their weight in shallow water where the roots can get a firm hold in the sediments
  • as the water depth increases the plant community changes as root anchorage and nutrient absorption from the sediments becomes more difficult
  • explains the plant community changes that happen in a hydrosere during ecological succession
• Vegetation age structure -

  • some habitats are dominated by plant species with individuals that can live for a long time such as woodlands where trees may live for a hundred years
  • a natural woodland will have trees of all ages with younger trees growing to fill the clearings created by the death of older trees
  • in recently planted woodland there will be few clearings until trees start to die of old age which could take over 200 years
  • during this time the canopy will become very dense, light levels on the ground will drop and biodiversity will decline, reducing the wildlife value of woodland