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Tropical Rainforests
Climate, Soils, Vegetation, Human Impact
Author:
Syed Ali
Edu Level: Unit2
Date: Aug 8 2025 - 8:44 PM
⏱️Read Time: 2 min
Tropical Rainforests
Location
- 5° N and S of the Equator
- Found in the Amazon Basin, Congo Basin, coastal Ecuador, West Africa, Southeast Asia
Climate: Equatorial
- High, consistent temperatures year-round (~3°C range)
- No distinct seasons; 12 hours daylight and 12 hours night
- Rainfall: 2,000–4,000 mm/year, evenly distributed
- Heavy rainfall when the ITCZ is overhead during equinoxes
- Very high humidity
Vegetation
- Produces ~40% of global terrestrial Net Primary Productivity (NPP)
- NPP = biomass accumulation = GPP – energy lost through respiration
- Four layers:
-
- Emergent (up to 50 m): tall, sun-exposed trees
- Canopy (~30 m): continuous layer, absorbs 70% sunlight, intercepts 80% rainfall
- Understory: smaller trees, ferns, shade-tolerant species
- Forest Floor: dark, humid, mosses and decomposing organic matter
- Tree adaptations: smooth bark, shallow buttress roots, drip tips, crown leaf growth
- Lianas (climbing vines), epiphytes (e.g. bromeliads, non-parasitic), and parasitic plants are common
- Thick layer of leaf litter feeds the nutrient cycle
Soil: Latosol (Ferralitic)
- Deep, red soils formed by leaching and eluviation
- Iron & aluminium oxides dominate upper layers
- Infertile when forest is removed (loss of humus from leaf litter)
- Laterisation creates hard clay layers; unsuitable for agriculture without cover
- Native groups practice shifting cultivation—fallow periods restore fertility
Human Impact
- Deforestation:
-
- 13.2% of the Amazon lost (2022) to agriculture, ranching, logging, mining, and urbanization
- Causes soil erosion, loss of biodiversity, climate change
- In Trinidad, illegal clearing by squatters, quarrying and logging occurs
- Example: Fondes Amandes community reforestation project in Northern Range – promotes fire prevention, youth education, and tree planting
- Mining:
-
- Forests cleared for mineral extraction
- Infrastructure (roads, equipment) fragments habitats
- Example: Gold mining in Amazon uses mercury → river pollution, toxic bioaccumulation
- Climate Change:
-
- Alters rainfall patterns, increases dry periods
- Affects tree and animal species (e.g. Panama – tree decline from prolonged dry periods)
- Agriculture & Ranching:
-
- Cattle ranching (Amazon) clears vast areas
- Fire used to clear land damages soil and spreads uncontrollably
- Oil palm plantations (Asia, Latin America, West Africa) drive large-scale deforestation
