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Terrestrial Ecosystem


A terrestrial ecosystem is a land-based ecological system where biotic components (living organisms) interact with abiotic components (non-living physical and chemical factors).

  • Covers approximately 28–29% of Earth's surface (land area).

  • Organized into large ecological regions called biomes.

  • Distribution is mainly controlled by:

    • Temperature

    • Precipitation

    • Latitude

    • Altitude

 Components

A. Biotic Components

  1. Producers (Autotrophs)

    • Green plants and photosynthetic organisms.

    • Convert solar energy into chemical energy through photosynthesis.

    • Form the primary productivity base.

  2. Consumers (Heterotrophs)

    • Primary consumers (herbivores)

    • Secondary/Tertiary consumers (carnivores, omnivores)

  3. Decomposers (Detritivores & Saprotrophs)

    • Bacteria and fungi.

    • Responsible for nutrient cycling and mineralization.

B. Abiotic Components

  • Soil (edaphic factors)

  • Climate (temperature, precipitation, humidity)

  • Solar radiation

  • Topography

  • Wind patterns

These factors regulate primary productivity, species distribution, and ecosystem functioning.

3. Functional Processes

  • Energy flow (unidirectional)

  • Biogeochemical cycles (carbon, nitrogen, phosphorus cycles)

  • Carbon sequestration

  • Ecological succession

  • Trophic dynamics

Forest Ecosystems

A forest ecosystem is a terrestrial biome characterized by high tree density, vertical stratification, and high biomass.

Classification Basis:

  • Latitude

  • Climate (temperature + rainfall)

  • Vegetation type (leaf morphology)

A. Tropical Forests

Location:

Near the equator (0°–10° latitude).

Climate:

  • High temperature (25–30°C average)

  • Annual rainfall > 200 cm

  • No distinct winter

Key Features:

  • High Net Primary Productivity (NPP)

  • Multi-layered canopy structure:

    • Emergent layer

    • Canopy

    • Understory

    • Forest floor

  • Extremely high species richness and endemism

  • Rapid nutrient cycling but nutrient-poor soils

Ecological Importance:

  • Major global carbon sink

  • High biodiversity reservoir

B. Temperate Forests

Location:

Mid-latitudes (30°–50°).

Climate:

  • Moderate rainfall

  • Distinct seasons

Types:

  1. Deciduous forests

    • Broad-leaved trees

    • Seasonal leaf shedding (adaptation to cold/drought)

  2. Temperate coniferous forests

    • Needle-leaved evergreen trees

Soil:

Relatively fertile compared to tropical forests.

C. Boreal Forest (Taiga)

Location:

High latitudes (50°–70° N).

Climate:

  • Long, severe winters

  • Short growing season

  • Moderate precipitation (mostly snow)

Vegetation:

  • Coniferous species (needle-leaved)

  • Adapted to cold and low evaporation

Ecological Role:

  • Stores large amounts of carbon in biomass and soils

  • Lower species diversity but large geographic extent

Specialized Forest Types

1. Mediterranean Forests

  • Hot, dry summers

  • Sclerophyllous vegetation (thick leaves)

2. Montane Forests

  • Altitudinal zonation

  • Temperature decreases with elevation

3. Mangrove Forests

  • Coastal intertidal zones

  • Salt-tolerant (halophytic) vegetation

  • Shoreline stabilization and storm buffering

2. Grassland Ecosystems

Grasslands are terrestrial ecosystems dominated by grasses and herbaceous vegetation, with insufficient rainfall to support dense forests.

Coverage:

~20% of global land surface.

Climate Control:

  • Moderate to low precipitation

  • Seasonal rainfall

  • Periodic fires and grazing

A. Tropical Grasslands (Savanna)

Features:

  • Wet and dry seasons

  • Scattered trees

  • High grazing pressure

Ecological Traits:

  • Fire-adapted vegetation

  • Large herbivore populations

B. Temperate Grasslands

Climate:

  • Cold winters

  • Hot summers

Soil:

  • Deep, fertile chernozem soils

  • High organic matter

Examples:

  • Prairies

  • Steppes

  • Pampas

C. Montane Grasslands

  • Occur at high altitudes

  • Short growing season

  • Alpine meadows

D. Flooded Grasslands

  • Seasonally inundated

  • High productivity

  • Important wetlands

E. Desert/Xeric Grasslands

  • Transition zones between grassland and desert

  • Sparse vegetation

3. Desert Ecosystems

Deserts are terrestrial ecosystems characterized by extremely low precipitation (<25 cm annually) and high evapotranspiration rates.

Key Characteristics

  • Large diurnal temperature variation

  • Low primary productivity

  • Sandy or rocky soils

  • Low organic matter

Types of Deserts

  1. Hot and dry

  2. Semi-arid

  3. Coastal

  4. Cold deserts

Adaptations

Plants:

  • Xerophytes

  • Succulents

  • Reduced leaf surface area

  • CAM photosynthesis

Animals:

  • Nocturnal behavior

  • Water conservation mechanisms

4. Mountain Ecosystems

Mountain ecosystems are characterized by altitudinal zonation, where climate and vegetation change with elevation.

Key Concepts

  • Environmental lapse rate (temperature decreases with altitude)

  • "Water towers of the world" (source of rivers)

  • High endemism

Zonation

  1. Foothill forests

  2. Montane forests

  3. Subalpine zone

  4. Alpine tundra

  5. Permanent snow

5. Tundra Ecosystems

Tundra is a treeless biome with extremely low temperatures and the presence of permafrost (permanently frozen subsoil).

Types

  1. Arctic tundra (high latitude)

  2. Alpine tundra (high altitude)

Characteristics

  • Short growing season (6–10 weeks)

  • Low precipitation (but low evaporation)

  • Poorly developed soil

Vegetation

  • Mosses

  • Lichens

  • Dwarf shrubs

  • Sedges

Faunal Adaptations

  • Thick fur/insulation

  • Migration

  • Hibernation

Comparative Analysis

FeatureDesertTundraGrasslandForest
Water availabilityVery lowFrozen waterModerate seasonalHigh (varies by type)
BiodiversityLowLow–moderateModerateVery high (tropical)
Soil fertilityPoorPoorHigh (temperate)Variable
TemperatureExtreme heat/coldPersistently coldSeasonalClimate dependent

Ecological Importance of Terrestrial Ecosystems

  1. Carbon sequestration

  2. Oxygen production

  3. Climate regulation

  4. Biodiversity conservation

  5. Soil formation

  6. Water cycle regulation

  7. Provisioning services (food, timber, fiber)

Core Controlling Factors

  • Latitude

  • Altitude

  • Precipitation

  • Temperature

  • Soil type

  • Disturbance regimes (fire, grazing, storms)


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