Tropical Biomes Flora
Biomass
Biomass - The total amount of living organic matter that can be found in an ecosystem. Made up of flora and fauna
Primary Productivity - rate at which producers will build on the amount of biomass
Rainforest
. Net primary productivity- 2200 g/m/y
Total biomass- 765b tonnes
Very large biomass with a high productivity rate. This is due to the high rate of decay + recycling of nutrients caused by the climate
40,000 species of plant. Timber- mahogany, palm, ebony. Food - Brazil nuts, cocoa + sweet potato
Emergent layer - reach up to 50m. Narrow trucks (boles) with large crown so have exposure to sunlight. Many have shallow roots (buttress) due to nutritious surface layer. - rubber, mahogany, Brazil nut, kapok.-hardwoods + evergreen. Form a continuous veg cover blocking sunlight
Canopy Layer - many trees are covered in epiphytes such as fern, flowers + orchids which climb up the tree for support as they are unable to survive beneath the canopy with 90% of sunlight being blocked. Lianas hand down form the branches + root the ground. It also contains smaller + younger trees. Trees are branchless due to photosyn only occurring in crown
Shrub layer – Young trees with bear flower + fruit on branches.- rubber
Ground – Tall ferns + buttress roots of trees with seedlings
Climate influences
Vast productivity is caused by a climate perfect for growth.
Long hours of sun for the whole year, no annual temp variations, rainfall supplies abundant water supply.
Grasslands
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The savanna grasslands are a transition of an ecocline between rainforest and desert.
Climate influences
There is enough rainfall to support deciduous and thorn-scrub veg.
Average biomass per year is 4 kg/m2.
Plant adaptations
Deciduous trees eg Baobab will loose their leaves in the winter drought to prevent moisture loss via transpiration.
Baobab trees have thick bark and small leaves store water in their trunks
Acacia - with a deep root system (rhizome) to reach water
Many plants and trees have adapted drought-resisting features
3 m high grasses eg Napier grass which will die back in winter leaving tussocks of dry grass which protect the plants by conserving moisture. Grass blades are silver in colour to reflect light away.
This leads to a tall grass wet season as they revive and a scrubland in the dry season as they die.
Desert
Climate
Climate makes it a very challenging environment for plant growth.
Biomass is 1kg/m2
Cacti
Are in most desert regions. Conserve moisture by having a succulent water store with a thick waxy skin and fleshy stem.
Has thorns which allows photosyn with min water loss + protects plant from grazing animals.
Phreatophytes
eg tamarisk bush in N Africa, long tap roots to access groundwater.
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Some species eg salt bush in Australian desert remain dormant until rare rainfall triggers their growth + will germinate and spread flowers + grasses and for a few days until they dieback.
Time - Equatorial regions have remained stable with no interruptions by glaciations
Flora have adapted to deal with long periods of drought + high temps. Plants are slow growing and have a lasting longevity with the bio-diversity restricted.