Ecology: Biomes, Tundra, and Deserts

• Biomes are large geographic areas defined by specific climate conditions, animal populations, and plant species.

Tundra

• The tundra is the coldest of all biomes, characterized by frost-molded landscapes and extremely low temperatures.
• It has little precipitation, poor nutrients, a short growing season, and large population oscillations.

Arctic Tundra

• The arctic tundra is located around the North Pole.
• The growing season lasts 50–60 days.
• Permafrost, a permanently frozen subsoil layer, is present.
• Average winter temperature is -34°C; average summer temperature is 3° - 12°C.
• Sweeping winds are common.

Alpine Tundra

• Alpine Tundra exists on mountains worldwide at high altitudes.
• It has no trees.
• The growing period is about 180 days.
• Night temperatures usually fall below 0°C.

Deserts

• Deserts cover about 1/5 of the Earth’s surface.
• Rainfall is less than 50 cm per year.
• Deserts contain specialized flora and fauna, such as reptiles, but few large mammals.
• Soils are often rich in nutrients.

Hot and Dry Desert

• Temperatures are very hot during the summer.
• There is little rainfall in the winter.
• Temperature experiences extreme changes throughout the day.
• Vegetation includes ground-hugging shrubs and short woody trees.
• Carnivores are typically nocturnal.

Semiarid Desert

• Summers are moderately long and dry.
• There is little rainfall in the winter.
• The temperature is not as extreme as in hot and dry deserts.
• Plants have spines for protection from water loss and herbivores.
• Inhabitants include insects, small mammals, and reptiles.

Coastal Desert

• Winters are cool and summers are moderately warm.
• The soil has a high salt content.
• Plants store water in fleshy leaves or stems.
• Many animals remain inactive until conditions become suitable.

Cold Deserts

• Winters are long and cold, while summers are short and fairly warm.
• There is high overall rainfall, with snow in winter.
• Some areas have high salt concentrations.
• Plants are widely scattered.
• Lots of smaller mammals populate cold deserts.

Grassland

• Grasslands are dominated by grasses rather than large shrubs or trees.
• Continental climates are favorable for grasslands.
• Frequent fires prevent them from transforming into forests.

Savanna

• Savannas are tropical with warm temperatures and scattered trees.
• Rainfall is concentrated in a wet period followed by a dry period.
• The soil is porous, leading to high water drainage.
• A thin layer of humus is present.
• Fires occur frequently.

Temperate Grassland

• These grasslands have lower temperatures and less rain than savannas.
• Seasonal droughts and frequent fires occur.
• Soils are nutrient-rich and fertile.

Forests

• Forests occupy approximately 1/3 of the Earth’s land mass.
• Dominated by trees and other woody vegetation.

Tropical Forests

• There is no winter, but instead two seasons: wet and dry.
• The length of day (12h) varies little due to proximity to the equator.
• Temperature averages 20–25°C with little variation.
• There are lots of precipitations leading to high humidity.
• Soil is nutrient-poor and acidic.
• The flora is extremely diverse with a multi-layered canopy.
• Fauna is diverse, including mammals, birds, amphibians, and insects.

Temperate Forests

• These forests have well-defined seasons with a distinct winter.
• The climate is moderate with 4–6 months frost-free.
• Precipitation is distributed evenly throughout the year.
• The soil is fertile.
• Flora: 3–4 tree species per km2.

Boreal Forests

• Temperatures are very low
• Short, moist, and moderately warm summers, and long, cold, and dry winters

Aquatic Biomes

• These biomes are filled with water.
• Oxygen distribution may vary drastically.
• Light is limited by water depth and clarity.

Freshwater Regions

Ponds and Lakes

• Temperature varies seasonally.
• Usually 4°C near the bottom.

Streams and Rivers

• Bodies of flowing water moving in one direction.
• Characteristics change along the river's course.

Wetlands

• Areas of standing water that support aquatic plants.
• Some wetlands have high salt concentrations.

Marine Regions

Oceans

• The largest of all ecosystems.

Coral Reefs

• Barriers along continents, islands, and atolls.
• Corals are the predominant fauna.

Estuaries

• Locations where freshwater streams or rivers mix with oceans.