Geography revision 2.B

Definitions:

  1. Nutrients are chemical compounds which plants need to survive and grow.
  2. Litter is the dead organic matter on the surface from which humus forms.
  3. Biomass is the total weight of organic matter at a point in an area.
  4. Ecosystem is a concept used to illustrate how plants and animals interact with their physical surroundings and habitat.
  5. Biotic is the living organisms and vegetation of an ecosystem.
  6. Abiotic is the non-living physical environment in which these organisms live.
  7. Trophic pyramid is a food chain where chemical plant energy is passed through the ecosystem.
  8. Heterotrophs cannot make their own food and therefore must rely on autotrophs for nutrition.
  9. Photosynthesis is the conversion of light energy into food energy which is stored as carbs in the biomass.
    1. Soil is a naturally occurring thin layer of material on the surface that is affected by the parent rock, climate, chemical and biological factors.
    2. Uptake is when nutrients are absorbed by plant roots and due to photosynthesis turned into living matter known as biomass.
    3. Fallout is when leaves shed or organisms die and this material falls to the ground as litter.
    4. Decay is when litter is decomposed by detrivores/fungi/bacteria and the nutrients are returned to the soil layer where they are available to be taken up by plants.

Remember that the width of the arrows in an ecosystems, nutrient cycle diagram indicate the rate and the size of the circles indicate the proportion of nutrients held within the particular store.

outputs of the nutrient cycle include nutrients in water lost from the litter as surface runoff and also by leaching the nutrients are lost from the soil.

The rate of transfer is affected by…climate, soils and vegetation type. (think sr for soil)

  1. Plant succession is a series of changes which takes place within a plant community.
  2. Colonisation is the process in which plants invade and begin to grow on bare rock or soil they are known as the pioneer species.
  3. The climatic climax vegetation is a balanced community of plants formed in the final stage of a plant succession. They are those best adjusted to the climatic factors.

Abiotic factors affecting which plants thrive include the sunlight(its duration affects when flowers bloom, its quality affects growth and photosynthesis. Think height of sun in sky!) availability of water(water is needed by plants for germination, growth and reproduction) and soil/nutrients(its presence/depth and nutrients available will determine different plants ability to grow).

Explain how plant succession occurs:

As colonisation begins pioneer species and each successive seral stage changes the environment in which they live. Pioneer species help to stabilise the soil, their roots bind it and dead leaves and roots add organic matter to the soil which help it retain moisture and nutrients. Overtime this mean that the soil becomes deeper, the environment less harsh and eventually the pioneer species dies out as they are shaded by larger vegetation. With each seral stage there is an increase in biomass, layering of plants and biodiversity.

Pioneers will also provide shade and shelter from the wind making more favourable conditions for plants.

Changes to the soil:

Soil depth will increase

Increase in humus/organic matter

Increase in soil moisture-dense root mat and organic content retains moisture.

Increase in Soil stability

Changes in soil PH - during decomposition humic acids are released.

Changes to the plants:

stratification

biomass increases- deeper fertile soils can support larger plants such as trees.

  1. Primary succession is if a succession is uninterrupted by natural events or human activity, from pioneer to climax veg.
  2. Lithosere is a succession based on bare rock, psammosere on sanddunes, hydrosere in fresh water and halosere in salt water.
  3. Secondary succession is one which has been disturbed by natural events.
  4. Plagioclimax is a climatic climax or succession which has been disturbed/changed by human activity.

A plagioclimax may result from burning, deforestation, draining or grazing.

eg. the heather moorlands in the british isles. These should have developed into a deciduous woodland but due to grazing tree saplings cannot survive and also burning to improve the pasture as this returns the nutrients to the soil allowing heather to grow. This prevents succession.