What is an example of a high-energy biome?
Tropical rainforests and temperate deciduous forests.
Own distinctive vegetation.
What is an example of a low-energy biome?
High altitude - tundra.
Low altitude - desert.
Scant vegetation.
Low NPP.
What is a biome considered to be in its natural state?
In dynamic equilibrium with its environment.
The vegetation exists in perfect balance with the climate and soils and that any change would alter the balance between the components of the biome.
What are the characteristics of a temperate deciduous forest? FIRST SIX FACTS:1/2.
- NPP – 1,200g dry organic matter per m squared per year.
- Taller trees - dominant species e.g. Oak – 30/40m, followed by elm, beech, sycamore, ash and chestnut.
- Large crowns and broad but thin leaves.
- Deciduous trees shed leaves in winter – reduces transpiration.
- Few dominant species – some woodlands are only dominated by one tree species.
- Oak - 20m, mosses - 2cm, bramble - 1.5m.
What are the characteristics of a temperate deciduous forest? SECOND SIX FACTS: 2/2.
- Stratification.
- Below the canopy - shrub layer with smaller trees e.g. holly and hawthorn.
- Herb layer - dense if enough light filters through the shrub layer e.g. grass and bluebells.
- Epiphytes grow on trunks/branches e.g. mosses.
- Thick leaf litter layer - broken down by soil microbes/animals.
- 10C, 30-60 inches of rainfall per year.
What human activity creates plagioclimaxes? 3
- Deforestation/afforestation.
- Animal grazing/trampling.
- Fire clearance.
When does a secondary succession occur?
Previously vegetated land.
E.g. area cleared for farming, but later abandoned.
More rapid stages than primary succession - organic matter already present.
Pioneer stage is short/absent altogether.
Climatic climax - reached sooner.
Occur due to a climate change, disease etc.
What is an example of a UK plagioclimax and how has it developed into a plagioclimax?
Heather moorland.
Once covered by climax vegetation - removed by deforestation.
Heather - originally featured in tiny amounts.
Soil deteriorated - heather became dominant.
Sheep grazing major agriculture form - prevents climax woodland regeneration - destroys young saplings.
What are the 4 BASIC stages within a heather cycle?
Pioneer phase (0-6 years). Building phase (6-15 years). Mature phase (12-28 years). Degenerate phase (20-30 years).
Explain the pioneer phase of a heather plagioclimax.
0-6 years.
Small shoots among dead heather stems.
Other plants present - mosses and lichens.
Explain the building phase of a heather plagioclimax.
6-15 years. Dense dome-shaped plant. Flowers profusely. Little light penetrating to ground. Heather dominant. Few other plants.
Explain the mature phase of a heather plagioclimax.
12-28 years. Reduction in vigor. Stems tough/woody, Some light penetrating to ground. Colonisation of other plants.
Explain the degenerate phase of a heather plagioclimax.
20-30 years.
Gaps enlarged.
Few new shoots.
Mosses, lichens and grasses in gaps.
How has the UK heather plagioclimax been controlled?
Managed burning - encourages new heather shoots.
Eliminates less fire-resistant species - heather dominates.
Burnt every 15 years.
Left any longer - too much woody tissues - fires burn too hot - lost nutrients.
What would happen if heather burning didn’t occur?
Heather moorland degenerates.
Climatic climax regeneration.
Majority present UK - plagioclimax - clearance of the Roman/Ango-Saxon periods.
Why does vegetation grow quickest in a tropical rainforest biome?
Constant high temperature and rainfall.
Greatest amount of organic matter (NPP).
What is the NPP for:
Tropical rainforest.
Monsoon forest.
Savanna grassland.
2,200 g m-2 year-1.
1,600 g m-2 year-1.
900 g m-2 year-1.
Where is the world’s greatest biodiversity found?
Tropical rainforests - contains half the world’s gene pool.
Stable ecosystems - 100 million years.
Undisturbed state - gained new species.
