3.3 Terrestrial biomes

Terrestrial biomes are distinct ecological communities shaped by climate, vegetation, and animal adaptations. They play crucial roles in global biodiversity patterns, ecosystem functioning, and biogeochemical cycles. Understanding these biomes provides insights into how life adapts to different environmental conditions across the planet.

From tundra to tropical rainforests, each biome has unique characteristics that influence the plants and animals living there. Climate factors, soil properties, and species interactions all contribute to shaping these diverse ecosystems. Human activities are significantly impacting biomes worldwide, making conservation efforts increasingly important.

Major terrestrial biomes

• Terrestrial biomes represent distinct ecological communities characterized by specific climate conditions, vegetation types, and animal adaptations
• Understanding major terrestrial biomes provides insights into global biodiversity patterns and ecosystem functioning
• Biomes play crucial roles in global biogeochemical cycles and climate regulation

Tundra characteristics

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• Located in Arctic and Antarctic regions with extremely cold temperatures and low precipitation
• Characterized by permafrost, a permanently frozen layer of soil beneath the surface
• Vegetation consists of low-growing plants adapted to harsh conditions (lichens, mosses, sedges)
• Short growing season limits plant growth and productivity
• Supports specialized wildlife adapted to extreme cold (caribou, arctic foxes, polar bears)

Taiga vs boreal forest

• Taiga and boreal forest often used interchangeably, but subtle differences exist
• Taiga refers to the transition zone between tundra and boreal forest
  • Sparser tree cover and more open areas
  • Dominated by cold-tolerant coniferous trees (spruce, fir, larch)
• Boreal forest extends further south with denser tree cover
  • Longer growing season allows for more diverse plant communities
  • Includes both coniferous and deciduous trees (birch, aspen)
• Both biomes experience long, cold winters and short, cool summers
• Important habitats for migratory birds and large mammals (moose, wolves)

Temperate deciduous forest

• Found in mid-latitude regions with distinct seasonal changes
• Characterized by trees that shed leaves annually in response to cold winters
• Dominant tree species include oak, maple, beech, and hickory
• Rich understory vegetation with diverse herbaceous plants and shrubs
• Supports high biodiversity of mammals, birds, and insects
• Four distinct seasons influence plant phenology and animal behavior

Temperate grasslands

• Occur in mid-latitude regions with moderate rainfall and periodic droughts
• Dominated by grasses and forbs with few trees or shrubs
• Includes prairies in North America, steppes in Eurasia, and pampas in South America
• Soil typically rich in organic matter due to extensive root systems of grasses
• Home to large grazing mammals (bison, antelope) and burrowing animals (prairie dogs)
• Historically shaped by natural fires and grazing, now heavily impacted by agriculture

Mediterranean scrub

• Found in coastal regions with Mediterranean-type climates
• Characterized by hot, dry summers and mild, wet winters
• Vegetation adapted to drought and fire (sclerophyllous leaves, fire-resistant bark)
• Includes chaparral in California, maquis in Mediterranean Basin, fynbos in South Africa
• High plant diversity with many endemic species
• Supports unique wildlife adapted to seasonal water scarcity (jackrabbits, lizards)

Tropical rainforest

• Located near the equator with consistently high temperatures and rainfall
• Characterized by dense, multi-layered canopy structure
• Extremely high biodiversity, hosting over 50% of Earth's terrestrial species
• Complex nutrient cycling with rapid decomposition and nutrient uptake
• Stratified habitat supports diverse animal life (primates, birds, insects)
• Plays crucial role in global climate regulation and carbon sequestration

Tropical savanna

• Found in tropical and subtropical regions with distinct wet and dry seasons
• Characterized by grasses interspersed with scattered trees and shrubs
• Vegetation adapted to periodic fires and grazing pressure
• Supports diverse large mammal populations (elephants, giraffes, lions)
• Complex interactions between herbivores, predators, and vegetation structure
• Highly seasonal productivity patterns influenced by rainfall distribution

Desert ecosystems

• Occur in regions with extremely low precipitation and high evaporation rates
• Characterized by sparse vegetation adapted to water scarcity and extreme temperatures
• Include hot deserts (Sahara) and cold deserts (Gobi)
• Plants exhibit adaptations like deep root systems, succulent leaves, and CAM photosynthesis
• Animals display behavioral and physiological adaptations to conserve water
• Unique geomorphological features shaped by wind erosion and occasional flash floods

Biome distribution patterns

• Global distribution of biomes reflects complex interactions between climate, topography, and biogeographic history
• Understanding biome distribution patterns provides insights into species ranges and ecosystem functioning
• Biome boundaries shift over time in response to climate change and human activities

Latitudinal gradients

• Biomes generally arranged in latitudinal bands from equator to poles
• Temperature and solar radiation decrease with increasing latitude
• Tropical biomes concentrated near equator, transitioning to temperate and polar biomes towards poles
• Species diversity generally decreases with increasing latitude
• Exceptions occur due to ocean currents, mountain ranges, and continental position

Altitudinal zonation

• Biomes change with increasing elevation, mirroring latitudinal gradients
• Temperature decreases and precipitation patterns change with altitude
• Lowland tropical forests transition to montane forests, then alpine meadows, and finally to snow-capped peaks
• Compressed biome transitions create unique ecotones and high biodiversity in mountain regions
• Altitudinal zonation varies between different mountain ranges and latitudes

Continental position effects

• Distance from oceans influences climate and biome distribution
• Coastal regions experience more moderate temperatures and higher humidity
• Continental interiors have more extreme temperature fluctuations and lower precipitation
• Rain shadow effects of mountain ranges create distinct biome patterns (deserts leeward of mountains)
• Ocean currents modify coastal climates, influencing biome distribution (Gulf Stream effect on European biomes)

Climate factors shaping biomes

• Climate serves as the primary driver of biome distribution and characteristics
• Understanding climate-biome relationships essential for predicting ecosystem responses to global change
• Complex interactions between temperature, precipitation, and seasonality determine biome boundaries

Temperature regimes

• Average annual temperature and temperature extremes influence plant and animal distributions
• Tropical biomes characterized by consistently high temperatures year-round
• Temperate biomes experience seasonal temperature fluctuations
• Polar and high-altitude biomes adapted to prolonged cold periods
• Temperature affects metabolic rates, growth patterns, and phenology of organisms
• Climate change altering temperature regimes, leading to shifts in biome boundaries

Precipitation patterns

• Total annual precipitation and its seasonal distribution shape vegetation structure
• Tropical rainforests receive high year-round rainfall, supporting lush vegetation
• Seasonal rainfall in savannas and temperate grasslands drives distinct wet and dry periods
• Deserts defined by extremely low precipitation, often less than 250 mm annually
• Precipitation type (rain, snow, fog) influences water availability for plants
• Extreme precipitation events (monsoons, hurricanes) impact ecosystem dynamics

Seasonality influence

• Seasonal variations in temperature and precipitation drive ecosystem processes
• Temperate deciduous forests exhibit distinct phenological changes with seasons
• Tropical dry forests and savannas experience alternating wet and dry seasons
• Seasonality affects animal migration patterns and reproductive cycles
• Plant adaptations to seasonality include leaf shedding, dormancy, and seed dispersal timing
• Climate change altering seasonal patterns, disrupting ecological relationships

Soil characteristics across biomes

• Soil properties vary significantly between biomes, influencing vegetation structure and ecosystem processes
• Soil-plant-climate interactions create feedback loops that shape biome characteristics
• Understanding soil variations essential for predicting ecosystem responses to environmental changes

Nutrient availability

• Tropical rainforest soils often nutrient-poor due to rapid leaching and weathering
• Temperate grassland soils rich in organic matter from extensive root systems
• Desert soils generally low in organic matter but may have mineral accumulations
• Nutrient cycling rates vary across biomes, influencing plant growth strategies
• Mycorrhizal associations play crucial roles in nutrient uptake, especially in nutrient-poor soils
• Human activities (fertilization, pollution) altering nutrient dynamics in many biomes

pH and mineral content

• Soil pH influences nutrient availability and microbial activity
• Tropical soils often acidic due to high rainfall and weathering
• Arid region soils tend to be alkaline with salt accumulations
• Temperate forest soils typically slightly acidic to neutral
• Mineral content affects soil structure, water retention, and nutrient availability
• Soil pH and mineral composition influence plant community composition and diversity

Soil formation processes

• Pedogenesis influenced by climate, parent material, topography, organisms, and time
• Tropical soils undergo intense weathering, leading to deep, highly leached profiles
• Temperate soils experience slower weathering with distinct horizons
• Permafrost in tundra regions limits soil development and organic matter decomposition
• Soil erosion and deposition processes shape soil profiles differently across biomes
• Biological activity (plant roots, soil fauna) plays vital role in soil formation and structure

Plant adaptations in biomes

• Plants exhibit diverse adaptations to survive and thrive in specific biome conditions
• Understanding plant adaptations provides insights into ecosystem functioning and resilience
• Plant adaptations influence biome structure, productivity, and responses to environmental changes

Morphological adaptations

• Leaf modifications reduce water loss in arid environments (small leaves, waxy cuticles)
• Succulence allows water storage in desert and Mediterranean plants (cacti, aloes)
• Aerenchyma tissue enables oxygen transport in wetland plants (mangroves, water lilies)
• Buttress roots provide stability for tall trees in tropical rainforests
• Thorns and spines deter herbivores in many arid and savanna plants
• Epiphytes in tropical rainforests adapt to growing on other plants without soil contact

Physiological strategies

• C4 and CAM photosynthesis increase water-use efficiency in hot, dry environments
• Deciduous strategy conserves resources during unfavorable seasons in temperate regions
• Nitrogen fixation allows plants to thrive in nutrient-poor soils (legumes, actinorhizal plants)
• Freeze tolerance mechanisms enable survival in cold climates (antifreeze proteins, supercooling)
• Halophytes manage salt stress in coastal and desert environments through ion compartmentalization
• Mycorrhizal associations enhance nutrient uptake across various biomes

Reproductive mechanisms

• Wind pollination common in grasslands and temperate forests with open canopies
• Animal pollination prevalent in tropical forests with high biodiversity
• Seed dispersal strategies vary across biomes (wind dispersal in open habitats, animal dispersal in forests)
• Fire-adapted plants in Mediterranean and savanna biomes (serotinous cones, resprouting ability)
• Clonal reproduction allows rapid spread in resource-limited environments (Arctic tundra plants)
• Mast seeding synchronizes reproductive effort in some temperate and boreal tree species

Animal adaptations in biomes

• Animals display a wide range of adaptations to survive in different biome conditions
• Adaptations involve morphological, physiological, and behavioral strategies
• Understanding animal adaptations crucial for conservation and predicting responses to environmental changes

Thermoregulation strategies

• Endothermy allows mammals and birds to maintain constant body temperature across biomes
• Ectothermic animals in cold climates use behavioral thermoregulation (basking, burrowing)
• Desert animals often nocturnal to avoid extreme daytime heat
• Insulation adaptations vary across biomes (thick fur in Arctic, sparse hair in tropical species)
• Countercurrent heat exchange systems in extremities of polar animals reduce heat loss
• Estivation allows some animals to survive hot, dry periods in arid environments

Dietary specializations

• Herbivores in different biomes adapted to specific plant types (grazing vs. browsing adaptations)
• Carnivores exhibit hunting strategies suited to their habitat (ambush predators in forests, pursuit predators in open areas)
• Omnivory common in temperate forests with seasonally variable food resources
• Specialized diets in tropical rainforests due to high plant diversity (fruit-eating bats, nectar-feeding birds)
• Desert animals often able to obtain water from food sources (kangaroo rats extracting water from dry seeds)
• Seasonal dietary shifts in many temperate and boreal animals to cope with changing food availability

Behavioral adaptations

• Migration allows animals to exploit seasonal resources across different biomes (birds, large mammals)
• Hibernation and torpor conserve energy during resource-scarce periods in temperate and polar regions
• Social behaviors vary across biomes (herding in grasslands, territoriality in forests)
• Nest building and burrow construction provide shelter from environmental extremes
• Camouflage strategies differ between biomes (cryptic coloration in forests, countershading in open habitats)
• Activity patterns synchronized with resource availability and predator avoidance (crepuscular activity in many savanna animals)

Biome productivity

• Biome productivity varies greatly across ecosystems, influencing global carbon and nutrient cycles
• Understanding productivity patterns essential for assessing ecosystem services and carbon sequestration potential
• Productivity influenced by climate, soil characteristics, and disturbance regimes

Net primary production

• Tropical rainforests have highest net primary production (NPP) due to year-round growing conditions
• Temperate deciduous forests and grasslands show moderate NPP with seasonal variations
• Desert and tundra biomes have lowest NPP due to environmental constraints
• NPP influenced by factors such as solar radiation, temperature, water availability, and nutrient supply
• Human activities altering NPP through land-use changes, fertilization, and climate change
• Remote sensing techniques allow global monitoring of NPP patterns and trends

Biomass accumulation

• Tropical rainforests store largest amount of biomass in vegetation, particularly in tree trunks and branches
• Boreal forests significant carbon sinks due to slow decomposition rates in cold climates
• Grasslands store much of their biomass below ground in extensive root systems
• Desert and tundra biomes have low above-ground biomass but may have significant below-ground storage
• Biomass accumulation rates vary with successional stage and disturbance history
• Climate change affecting biomass storage potential of different biomes

Energy flow in ecosystems

• Solar energy captured by primary producers through photosynthesis forms basis of food webs
• Energy transfer efficiency between trophic levels typically around 10%
• Detrital food webs important in many biomes, especially in forests with high litter production
• Grazing food webs dominant in grassland and savanna ecosystems
• Energy flow patterns influence ecosystem stability and resilience to disturbances
• Human activities altering energy flow through habitat modification and species introductions

Human impacts on biomes

• Human activities significantly altering structure and function of terrestrial biomes worldwide
• Understanding human impacts crucial for developing effective conservation and management strategies
• Anthropogenic changes often interact with natural processes, leading to complex ecosystem responses

Land use changes

• Deforestation in tropical regions for agriculture and resource extraction
• Urbanization expanding into natural habitats, particularly in coastal and lowland areas
• Agricultural intensification altering soil properties and hydrological cycles
• Wetland drainage for development and agriculture impacting water-dependent ecosystems
• Overgrazing in grasslands and savannas leading to soil degradation and vegetation changes
• Mining and resource extraction causing localized but severe ecosystem disturbances

Habitat fragmentation

• Forest fragmentation reducing habitat connectivity for many species
• Edge effects altering microclimate and species composition in remnant habitat patches
• Increased vulnerability of small populations to local extinction in fragmented landscapes
• Disruption of animal migration routes and plant dispersal patterns
• Genetic isolation of populations leading to reduced genetic diversity
• Creation of novel ecosystems in fragmented landscapes with altered species interactions

Climate change effects

• Shifting biome boundaries due to changes in temperature and precipitation patterns
• Phenological mismatches between plants and pollinators or predators and prey
• Increased frequency and severity of disturbances (wildfires, droughts, storms)
• Sea-level rise threatening coastal ecosystems and low-lying islands
• Thawing permafrost in tundra regions releasing stored carbon and altering hydrology
• Range shifts of species leading to novel community assemblages and ecosystem functions

Conservation of terrestrial biomes

• Conservation efforts aim to protect biodiversity and maintain ecosystem services provided by terrestrial biomes
• Integrating scientific knowledge with social and economic considerations essential for effective conservation
• Adaptive management approaches needed to address ongoing environmental changes and human pressures

Protected area networks

• Establishment of national parks, nature reserves, and wildlife sanctuaries to preserve representative ecosystems
• Connectivity between protected areas crucial for maintaining viable populations and ecological processes
• Transboundary protected areas facilitate conservation of wide-ranging species and ecosystems
• Marine protected areas safeguard coastal and marine ecosystems connected to terrestrial biomes
• Indigenous and community conserved areas recognize traditional management practices
• Challenges include inadequate funding, enforcement issues, and conflicts with local communities

Restoration ecology

• Active restoration of degraded ecosystems to recover structure, function, and biodiversity
• Reforestation and afforestation projects to increase forest cover and carbon sequestration
• Wetland restoration to improve water quality and provide habitat for aquatic species
• Grassland restoration to combat desertification and support grazing economies
• Invasive species removal to promote recovery of native plant and animal communities
• Soil remediation techniques to address contamination and improve ecosystem health

Sustainable management practices

• Agroforestry systems integrating trees with crops or livestock to enhance biodiversity and productivity
• Sustainable forestry practices maintaining forest ecosystem functions while providing timber resources
• Integrated pest management reducing reliance on chemical pesticides in agricultural systems
• Rotational grazing in rangelands to prevent overgrazing and maintain soil health
• Ecotourism promoting conservation while providing economic benefits to local communities
• Payment for ecosystem services incentivizing landowners to maintain natural habitats

Biome transitions and ecotones

• Ecotones represent transition zones between adjacent biomes or ecosystems
• Understanding ecotone dynamics crucial for predicting ecosystem responses to environmental changes
• Ecotones often hotspots of biodiversity and ecological processes

Edge effects

• Microclimate changes at ecosystem boundaries influence species composition and interactions
• Increased light availability at forest edges alters vegetation structure and species assemblages
• Edge-adapted species may thrive in fragmented landscapes
• Predation and parasitism rates often higher in edge habitats
• Altered nutrient cycling and soil properties at ecosystem boundaries
• Human activities creating novel edge habitats with unique ecological characteristics

Species interactions at boundaries

• Competitive interactions between species from adjacent biomes shape community composition
• Facilitative interactions may enhance survival of species at their range limits
• Predator-prey dynamics altered in ecotones due to changes in habitat structure and resource availability
• Pollinator behavior and plant-pollinator networks influenced by ecotone characteristics
• Seed dispersal patterns affected by changes in animal movement at biome boundaries
• Hybridization between closely related species more common in ecotone regions

Ecotone biodiversity patterns

• Ecotones often support higher species richness than adjacent ecosystems
• Unique species assemblages found in transition zones between major biomes
• Ecotones provide habitat for edge specialists and generalist species
• Importance of ecotones for maintaining regional biodiversity in fragmented landscapes
• Climate change causing shifts in ecotone positions and altering biodiversity patterns
• Conservation strategies increasingly recognizing the value of protecting ecotone habitats