Ecosystems and Tropical Rainforests

Ecosystem Function

• An ecosystem is a community of plants, animals, and their environment.
• Plants are producers, obtaining energy from the sun through photosynthesis to create food (leaves, seeds, fruits).
• Consumers (caterpillars, insects, birds, mice) eat the plants.
• Energy is recycled via nutrient cycling.

Nutrient Cycle

• Dead leaves and branches fall.
• Beetles and earthworms break down the leaves.
• Decomposers (bacteria and fungi) release nutrients into the soil.
• Water dissolves the nutrients.
• Plants absorb water and nutrients through their roots.
• Weathering breaks down rocks, releasing nutrients into the soil.
• Rapid nutrient cycles occur in hot climates due to high temperatures and abundant water, encouraging rotting and bacterial activity.
• Slow nutrient cycles occur in cold climates due to little heat and water, discouraging rotting and bacterial activity.

Tropical Rainforest Biome

• Located between 5 degrees north and 5 degrees south of the equator.
• Examples: Amazon Basin (Brazil), West Africa (Southern Nigeria, Congo, Ghana), Southeast Asia (Indonesia, Thailand, Northeastern Australia).
• Climate is hot due to the sun being directly overhead, concentrating solar rays.

Global Patterns of Ecosystems

• Climate influences natural vegetation and wildlife; large-scale ecosystems match climate zones.
• Large ecosystems are known as biomes (e.g., tropical rainforest, savanna, tundra).
• Latitude affects heat energy: at the Arctic Circle, solar energy strikes at a low angle and is spread over a large area; at 0 degrees latitude, solar energy strikes at almost a right angle, concentrating energy.

Climate of the Tropical Rainforest

• Hot throughout the year with high annual rainfall.
• Average temperature: 27^{\circ}C
• Rapid plant growth, trees can reach heights of 40m or more.
• Plant growth is controlled by sunlight, warmth, and water.

Rainforest Water Cycle

• Plant roots take up water.
• Rain is intercepted at the canopy level.
• Water evaporates and forms clouds, leading to convectional rainfall.

Rainforest Nutrient Cycle

• Rapid due to hot, damp conditions on the forest floor, allowing for rapid decomposition of dead plant material.
• Provides plentiful nutrients that are easily absorbed by plant roots.
• Nutrients are quickly absorbed by fast-growing plants and do not remain in the soil for long, staying close to the surface.

Nutrient Cycle in the Rainforest (Detailed Breakdown)

• Soil: Heat and high humidity allow rapid chemical weathering of bedrock, adding nutrients to the soil.
• Biomass: The number of plants and continual growing season results in high nutrient uptake from the soil to the biomass.
• Litter: Some leaves drop during the year; hot, humid conditions allow rapid decomposition, returning lots of nutrients quickly to the soil (leaves can rot in 6 weeks).
• High levels of runoff wash nutrients from the system.
• High precipitation causes leaching of nutrients from the soil.
• High precipitation adds nutrients to the system.
• Plants are always growing, with no dormant season, so a large amount of nutrients are stored in the biomass.