Lecture 21:

Biogeographic Realms

  • A biogeographic realm is a geographic region where a group of plant and animal species evolved.
  • Traditionally used as a basis for establishing terrestrial ecosystem regions.

Biomes

  • Definition: A biome is a large, stable, terrestrial ecosystem characterized by specific plant and animal communities.
  • Components:
    • A self-sustaining association of land-based plants and animals and their abiotic environment.
  • Six groups of vegetation:
    • Forest
    • Savanna
    • Shrubland
    • Grassland
    • Desert
    • Tundra

Vegetation Types

  • Biomes are determined based on identifiable vegetation characteristics such as:
    • Winter-deciduous trees
    • Drought-deciduous shrubs
    • Annual herbs
    • Bryophytes
    • Lianas
    • Epiphytes

Earth’s Physical Systems Impact on Vegetation

  • Key Factors:
    • Energy patterns
    • Atmospheric composition
    • Temperature and winds
    • Precipitation (quantity, quality, seasonal timing)
    • Soils and nutrients
    • Chemical pathways
    • Geomorphic processes

Ecotones

  • Definition: Zones of gradual transition in species composition between ecosystems.
  • As human impact causes ecosystem fragmentation, ecotones are increasing in number.
  • Characteristics of Ecotones:
    • Areas of high biodiversity
    • Large population densities
    • “Edge” species utilize territory within ecotones

Major Terrestrial Biomes

  • List of Earth's Major Biomes:
    • Equatorial and tropical rain forest
    • Tropical seasonal forest and scrub
    • Tropical savanna
    • Midlatitude broadleaf and mixed forest
    • Needleleaf forest and montane forest
    • Temperate rain forest
    • Mediterranean shrubland
    • Midlatitude grasslands
    • Deserts
    • Arctic and alpine tundra

Tropical Rain Forest

  • Characteristics:
    • Thick and continuous leaf canopy
    • Broadleaf evergreen trees
    • Annual precipitation: 180–400 cm
    • Temperature: 21°–30°C (avg. 25°C)
    • Water surpluses year-round

Tropical Seasonal Forest and Scrub

  • Characteristics:
    • Fewer than 40 rainy days
    • Includes tropical monsoon and savanna climates
    • Transition from wet to dry seasons
    • Average forest height: 15 m
    • Scrub vegetation of low shrubs and grasses

Tropical Savanna

  • Characteristics:
    • Grasslands interrupted by trees and shrubs
    • Transitional biome between tropical forests and desert
    • Seasonal precipitation correlated with ITCZ
    • Annual wildfires are common

Midlatitude Broadleaf and Mixed Forest

  • Characteristics:
    • Rich biodiversity including mammals, birds, reptiles, and amphibians
    • Adjacent to grassland regions and northern boreal forests

Boreal and Montane Forest

  • Characteristics:
    • Known as the northern needleleaf forest
    • Taiga: transitional to arctic tundra biome
    • Montane forests occur at high elevations globally

Temperate Rain Forest

  • Characteristics:
    • Wet, humid regions with lush forests
    • Broadleaf and needleleaf trees present
    • Average precipitation: ~400 cm
    • Moderate air temperatures

Mediterranean Shrubland

  • Also known as temperate shrubland
  • Dry summers typical of Mediterranean climates
  • Comprised of low-growing shrub formations

Midlatitude Grasslands

  • Highly modified by human activity
  • Known as “breadbaskets” for grain, soybeans, and livestock production

Desert

  • Occupies 1/3 of land surface
  • Two types: warm and cold deserts
  • Vegetation adaptations include:
    1. Long deep taproots
    2. Spreading root systems
    3. Waxy coatings on leaves
    4. Reflective surfaces to reduce temperatures

Arctic Tundra

  • Located in extreme northern regions near the Arctic Ocean
  • Vegetation is slow-growing, low productivity, easily disturbed

Alpine Tundra

  • Similar to arctic tundra but at lower latitudes
  • Associated with high elevations, occurs above treeline

Conservation and Management

  • Conservation biogeography applies biogeographic principles to biodiversity conservation.
  • Research focuses on:
    • Distribution and effects of invasive species
    • Impacts of climate change on biodiversity
    • Conservation planning and protected areas

Invasive Species

  • Species introduced by human activity, either intentionally or accidentally.
  • 90% of non-native species fail; 10% become invasive.
  • Example: Zebra mussels in the Great Lakes

Aquatic Ecosystem Management

  • Large marine ecosystems (LMEs) are distinctive ocean regions based on various ecological factors.

Anthropogenic Biomes

  • Result from human interaction with ecosystems linked to land-use practices such as agriculture and urbanization.
  • Impacting environmental factors include:
    • Temperature changes
    • Altered precipitation patterns
    • Changes in soil chemistry
    • Nutrient redistribution