Dr. Roman Saini explains about Biomes.
What is a Biome?
- It is a geographical or climatic unit and the largest sub division of terrestrial ecosystems
- each biome holds specific subcontinental species
- these division apply only to land masses
- characterized by similar climatic conditions
A biome is defined by its:
- plant structures
- leaf types
- plant spacing
- climate
Ecozones, on the other hand, are defined by similarities of the following kinds:
- genetic
- taxonomic
- historical
Further specifications include:
- annual temperature variation
- minerals available
- amount of rainfall
- availability of sunshine
Biodiversity:
- a rule of thumb, altitude mimics latitude
- a shift outward from the equator, and up from sea level, sees a decrease in biodiversity
eg: the multitude of species present in the Amazon Rain Forests, 10 to 20 times more than Temperate Forests, and thus the title 'Lungs of the Earth'
Reasons for high biodiversity in tropics areas:
- undisturbed environments, which means
- less seasonal with an environment that is more predictable
- more resources available, sunlight, increased productivity
Species Area Relationship within a region: species increase with the area, up to a certain limit
Types of Biomes: 11 total types
(1) Tropical Rainforests - also called Tropical Wet Forests, Tropical Moist Broad-leaf Forests, Lowland Equatorial Evergreen Rainforests
- Situated between between Cancer and Capricorn; 0-28 degree N and S
Eg. South America (Amazonian forests)
- Temperature: between 25-30 degree C, always above 19degreeC
- Rainfall: 175-200 cm annually, high humidity
- this means that the terms weather and climate are interchangeable
- Stratification, or layering, exists in these forests. forest floor: receives 2% of sunlight, few species and holds all the decaying matter
b. understory layer
c. canopy layer: the primary layer of the forest, casts shade on the two layers below it, 30-55 m in height
d. emergent layer: 55-80 m in height, gaps created by a disruption in this layer
- high biodiversity:
- epiphytes - plants that grow on other plants for support, not parasitic
- despite the high diversity, the species themselves have few individuals
- soil
- due to high leeching, the soil is low in nutrition
- selva soil, either ultisols or oxisols, the latter better drained
- trees are hardwood species, eg. Mahogany, Rosewood, Cinchona(2) Tropical Deciduous
(3) Temperate Deciduous
(4) Temperate Coniferous
Grasslands
(5) Tropical: savannas
(6) Temperate: steppes
(7) Desert - this is a climatic term
- deserts are not defined in terms of vegetation
- to be a desert an area must have
- rainfall less than 25 cm annually
- evapotranspiration levels higher than precipitation in terms of water loss
- adaptations in vegetation
- roots are modified to increase access to moisture
- taproots
- higher number of rootlets
- stems are fleshier and spongier to increase storage of water
- these plants are called succulents, eg. cactus
- leaves
- harden and have a waxy coating to reduce water loss
- white in color and shiny surfaces increase the reflection of light
- spines for protection
- reproductive cycle: lie dormant until there is sufficient water, when they go through an entire life cycle in a matter of days
- types of deserts
- hot: mostly subtropical
eg. Sahara, Kalahari, Thar, Great Sandy deserts
- lie between 20-30 latitude North and South in the West of continents in the trade wind belt
- high temperatures with a large daily range
- get barely any rainfall, resulting in low humidity levels and extremely high levels of evaporation
- Halophytic adaptation allows for survival
- cold: beyond the subtropics towards the poles
eg. Gobi, Karakum, Patagonian deserts
(8) Mediterranean
(9) Tundra
(10) Temperate Monsoon type
(11) Cool Temperate East Margin type
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