Topic 18 - Global Ecology-2025

Global Ecology: Patterns in Climate, Productivity, & Biome Location

Definition

  • Global Ecology: The study of the interactions among the Earth’s terrestrial, aquatic, sub-terrestrial, and atmospheric biomes.

  • Emergent Global Processes:

    • Biogeochemical Cycling

    • Food Webs Processes

    • Energy Flow

  • Biomes: Ecosystems of biotic communities within a large habitat defined by a particular climate (abiotic conditions) and productivity.

Biomes Defined by Climate and Productivity

Abiotic Conditions

  • Climate: The long-term pattern of weather in an area, as opposed to Weather, which refers to day-to-day temperature, precipitation, and other atmospheric conditions in an area.

  • At broad scales, abiotic conditions such as climate drive patterns of plant growth. These patterns of plant growth (Biomes) set the stage for other organisms living in the environment.

Factors Influencing Plant Growth

  1. Soil pH

  2. Soil Nutrient Levels (N)

  3. Light Availability

  4. Precipitation

  5. Temperature

Influence of Temperature on Plant Growth

  • Temperature sets the fundamental metabolic rates of all organisms.

  • Increases in temperature lead to higher rates of:

    • Photosynthesis

    • Cellular respiration

  • The balance between photosynthesis and cellular respiration in plants is determined by Net Primary Production (NPP).

Influence of Light on Plant Growth

  • Light is critical for the process of photosynthesis.

  • Individual species may be adapted to high or low light conditions.

  • Adaptations may include modifications to different wavelengths of light.

  • Generally, more light means more photosynthesis within communities.

Influence of Precipitation on Plant Growth

  • All plants need water for photosynthesis.

  • However, excess water can be detrimental.

  • NPP rates begin to drop at precipitation levels greater than 3 meters per year.

  • Some plants are adapted to survive in conditions of very low precipitation.

Global Climate Patterns Creating Biomes and Influencing NPP

  • Terrestrial areas with the most intense year-round sunlight, warm temperatures, and highest precipitation rates have the highest NPP.

  • Areas at the Equator receive the most solar radiation:

    • Solar radiation is most intense when the sun is overhead (perpendicular).

    • The Tropics (equator ± 23.5º) are characterized by sun being directly overhead, receiving highest solar radiation, and exhibiting the least seasonal variation.

  • Seasonal variation is a result of Earth's axial tilt.

Latitudinal Variation in Sunlight Intensity

  • Key latitudinal measurements:

    • 90°N (North Pole)

    • 60°N

    • 30°N

    • 23.5°N (Tropic of Cancer)

    • 0° (Equator)

    • 23.5°S (Tropic of Capricorn)

    • 30°S

    • 60°S

    • 90°S (South Pole)

Solar Radiation Initiates Global Climate Patterns

  • Global Circulation Patterns are initiated by intense solar radiation near the equator:

    1. Sun warms the surface.

    2. Air above warms and rises, creating locally lower pressure.

    3. Air expands and cools.

    4. Cool air sinks, creating locally higher pressure.

    5. Cool air replaces rising hot air.

  • Atmospheric Pressure: The sum weight of the air above an area.

  • Convection Current: The circular movement of air due to alternate heating and cooling.

a. Hot air rises
b. Surface warms the air
c. Air cools
d. Cool air sinks
e. Replaces rising hot air

Pressure Systems Influence Precipitation

  • Low-Pressure Systems:

    • Warm, moist air rises and cools as it gains altitude, forming clouds and leading to greater precipitation.

  • High-Pressure Systems:

    • Warm, moist air trapped at the surface results in less cloud formation and less precipitation.

Air Movement Patterns

  • Westerlies: Winds blowing from high-pressure to low-pressure zones.

  • Trade Winds: Northeast trades and Southeast trades are prominent near the equator.

  • Coriolis Effect: The earth's rotation influences wind direction.

Global Circulation Patterns

  • Diagram illustrating high pressure (H) and low pressure (L) zones across latitudes, influencing climate patterns and biomes.

Biomes Characterization

  • Biomes are geographically regulated by global atmospheric circulation and climate.

  • Each biome is named according to its dominant vegetation or plant communities and is characterized by the respective animal, plant, fungi, protist, bacteria, and archaea species adapted to that environment.

  • While species may vary from one biome to another, organisms often appear similar due to convergent evolution.

Terrestrial Biomes Overview

  • Amount of Rainfall primarily determines vegetation, not light or temperature.

  • Specific Biomes:

    • Tropical Rain Forest: Located near the equator with abundant year-round rainfall and multiple layers of vegetation.

    • Tropical Deciduous Forest: Leaves drop in the dry season when transpiration exceeds water availability, typically found at ~23°.

    • Savanna: Grassland with scattered trees, warmer winters, and more rainfall than temperate grasslands. Located in South America, Australia, and Africa.

    • Desert: Defined by low precipitation, characterized as the driest biome with potential seasonal fluctuations. Found around 30°N and 30°S.

    • Temperate Grasslands: Have colder winters, less rainfall, absence of trees, and rich organic matter in soil.

    • Temperate Deciduous Forest: Features moisture, seasonal temperature variation, loss of leaves annually, and diverse species.

    • Boreal Forest (Taiga): Largest terrestrial biome with long, cold winters and short, wet summers, located in high latitudes.

    • Tundra: Characterized by permanently frozen sub-soil (permafrost) limiting root depth, low species diversity, long winters with minimal light.

Local Climate Effects

  • Regional and local scales illustrate how climates differ across locations, such as the differentiation between Buffalo and NYC.

  • Annual Snow Differences:

    • Buffalo: Average snowfall of 91.3 inches (2.32m)

    • NYC: Average snowfall of 28.4 inches (0.72 m)

Influence of Large Bodies of Water

  • Water heats and cools more slowly than land, impacting regional climates.

  • Areas near water have more moderated climates while areas far from ocean have more extreme climates (higher highs and lower lows).

  • Lake effect: Warmer water results in air picking up moisture, leading to precipitation changes.

Rain Shadow Effect

  • On windward side of a mountain, warm, moist air must rise, cools, and causes precipitation.

  • On the leeward side, cool dry air descends, warms, and absorbs moisture resulting in drier conditions (e.g., the Great Basin and Mojave Deserts).

Summary of Global Ecology

  • Abiotic factors of climate influence productivity, including temperature, light, and precipitation.

  • Global climate is influenced by solar light and air circulation patterns.

  • Climate and producers define various terrestrial biomes: Tropical Forest, Savanna, Desert, Temperate Grassland, Temperate Deciduous Forest, Boreal Forest, and Tundra.

  • Regional climate effects are shaped by bodies of water, including lake effects and rain shadows