Unit 2.4 Biomes, zonation and succession Flashcards
Biome
a collection of ecosystems sharing similar climatic
conditions.
- Aquatic: Fresh water and Marine
- Desert
- Forest: Mediterranean forest (chaparral), Temperate forest, Boreal/coniferous forest (taiga) and Tropical forest
- Grassland: Temperate grasslands (steppes) and Tropical grasslands (savanna)
- Tundra: Arctic tundra and Alpine tundra
key factors that define a biome
Climate: rainfall, temperature and insolation (sunlight)
The impact of climate change on biomes
- Changes in temperature and rainfall patterns will likely shift biomes towards the poles (poleward shift).
- Models predict biomes will shift both north/south of the equator (latitudinal) and upwards on mountain slopes (altitudinal).
- Mangroves and other low-lying biomes are at risk due to sea-level changes.
- Up to one billion people live in areas vulnerable to biome shifts, which could affect livelihoods but also present new resource exploitation opportunities.
- Melting sea ice is opening up possibilities for oil drilling in the Arctic Ocean and creating navigable routes like the North-West Passage.
CASE STUDY Tropical Rainforest vs Desert
Climate and Water Availability:
- Tropical rainforests receive high annual rainfall and maintain warm temperatures year-round, supporting lush vegetation and high productivity.
- Deserts are characterized by low precipitation and extreme temperature variations, resulting in sparse vegetation and lower productivity.
Biodiversity:
- Tropical rainforests have one of the highest biodiversity levels on Earth
- Deserts have unique adaptations, and support fewer species.
Structural Complexity:
- the structural complexity of tropical rainforests is with multiple layers of vegetation
- deserts have a more simple, open structure
Adaptations to Environment:
- plants and animals in tropical rainforests are adapted to high humidity and relatively stable temperatures.
- Desert flora and fauna exhibit adaptations to conserve water and withstand temperature extremes.
Zonation
Zonation is the change of an ecosystem along an environmental gradient (altitude, etc.)
Succession
Succession is the change in species composition in an ecosystem over time.
Primary succession
where soil formation starts the process
Secondary succession
where soil already exists but the vegetation has been removed
Process of succession
Bare Surface: Initial lifeless state with minimal soil composed of mineral particles, poor in nutrients and with erratic water supply.
Stage 1: Colonization
- Pioneer species, adapted ( r-selected species )
Stage 2: Establishment
- Invertebrates populate the developing soil, adding organic material.
- Soil enriches.
Stage 3: Competition
- Ecosystem evolves to support new species ( K-selected species ) r-selected species are outcompeted and may decline.
Stage 4: Stabilization
- The food web becomes more complex. K-selected species dominate
Climax Community: The ecosystem reaches a stable climax community that self-regulates. Maximum sustainable development for the given conditions.
CASE STUDY: the new island of Surtsey
- Surtsey Island Formation erupted from 1963-1967, located 32 km off Iceland’s south coast, a newly formed volcanic island.
- Since its formation, protected site for studying ecological succession.
- provides valuable data on how plant and animal life colonize newly formed land without human impact.
Pioneer species
- Diatoms: First colonizers
- Marine larvae: via ocean currents
- Moss, lichens, fungi
Intermediate Species:
- Vascular plants: sea rocket and oyster plant.
- Birds: fulmars and guillemots, puffins
Climax Species: early development stages with no climax community yet.
Gross Productivity and Succession
Diversity and Complexity: Starts low, increases with time as plants and niches diversify, leading to complex food webs and greater ecosystem stability in climax communities.
Secondary Succession: Faster than primary as soil is pre-existing; follows disturbances like fires or landslides, leading to quicker recovery and rebuilding of the ecosystem.
- initially low due to scarce producers
- increases as succession progresses
- reaches high levels in climax communities
K selected species
- Long lifespan
- Slower growth
- Late maturity
- Fewer but larger offspring
- High parental care
- Significant investment in individual offspring
- Thrives in later stages of succession
- Miche specialists
- Predators
- Regulation by internal factors
- Higher trophic levels
Examples are trees, albatrosses, and humans.
R selected species
- Short lifespan
- Rapid growth
- Rarely maturity
- Many small offspring
- Little parental care
- Minimal investment in individual offspring, adaptable
- Acts as pioneers or colonizers
- Mostly regulated by external factors
- Lower trophic levels
Examples: annual plants, flour beetles, and bacteria.
Net Productivity Dynamics
- Starts high in early succession as respiration is low, allowing biomass accumulation
- In climax ecosystems, net productivity nears zero as respiration balances gross productivity
P:R Ratio
production to respiration
P: R > 1 in early succession
P: R < 1 biomass is lost
P: R = the community is said to be in a state of steady equilibrium
