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4 Cards in this Set

  • Front
  • Back

Commercial Farming

The North American Prairies.

Problems that occurred-

*increase salinity

*soil erosion

*limit of water

How to solve-

*Leaving bare soil for long periods were stopped or reduced.

*Snow fences or barriers enabled snowdrifts to pile up which provide water then they melt in.

*contour ploughing and strip cropping.

Mount St Helens!!!!! <3 CASE STUDY

In 1980, Mt St Helens volcano exploded violently, causing the worst volcanic disaster in the recorded history of US.

Secondary succession is how an environment recovers after a major disturbance.

Some plants and animals survive, and plants such as WILLOW and VINE MAPLE were able to re-sprout from roots protected in moist soil. These plants are called survivors and are very important to the re-initiation of plants on the barren landscape.

Despite surviving the eruption, many of those plants and animals were unable to live in the harsh new environment - but some were able to tolerate the extreme conditions and helped to pave the way for new colonisers. Winds brought light seeds and insects to the are, enabling them to enter and become established. These were r-strategists following J population growth curves. Wind played a key role in initiating early-succession.

Plants and insects attracted birds and deer from nearby areas.

Today many areas around the volcano still have a desert-like appearance, but the vast majority of plant and animal species have returned, such as the Roosevelt Elk (in this case the numbers far accede pre-1980 populations).

Now 15-25 feet tall late-successional species

2.3 - Describe and evaluate a method for the estimation of the changes in plant biomass in an ecosystem over a period of a year (5)

Select random quadrats using random number generators;

Collect plant material from quadrat;

Dry material in oven (to remove water);

Repeat at regular intervals throughout the year;

Problems occur with underground biomass such as roots which is not accounted for;


In the 19th century rabbits were introduced to Australia by European settlers. They were bred for food but many escaped into the wild. Australia has its own unique flare and fauna and there were no natural predators for rabbits, which meant that they flourished as there were plentiful supplies (space and food), little competition from other species and their only predators were humans. Australia hence has ideal conditions for a rabbit population explosion. Its mild winters enabled rabbits to breed throughout the year, and, as agriculture developed, wooded areas which might have halted their progress were turned into grassy habitats where rabbits could thrive.

Today rabbits are considered by many to be the most significant factor in the reduction in the native species of Australia, by killing young trees by chewing away their bark, and by causing serious erosion as they eat native plants and leave the soil exposed to wind and rain.

Most successful attempts to control the rabbit population have been the deliberate increase of rabbi-borne diseases, but so far they have become resistant to the diseases and any population reduction was folioed by a recovery.