Topic 2 4 Biomes zonation and succession Starter

Topic 2. 4: Biomes, zonation and succession Starter: Using the world map outline try break the world up into its different biomes. Shade them in different colours. E. g. Tropical rainforest, Desert, Tundra, Savana, Deciduous forest.

Biomes: • A collection of ecosystems sharing similar climatic conditions, e. g. tundra, tropical rainforest, desert. • Although opinions vary we will focus on 5 major types of biome: • • • Aquatic (may split this into freshwater and marine) Forest Grassland Desert Tundra

Aquatic

Different factors govern the distribution of biomes. • Insolation (the amount of suns energy reaching the surface) • It is measured by the amount of solar energy received per square centimeter per minute. • Precipitation • Usually measured in mm per meter squared. • Temperature • Usually measure in degrees Celsius.

For Homework: 1. 2. 3. Have a shaded world map with the major biomes labelled. Find a city in each biome (except polar) and draw its location on your map, and write down the mean annual temp and precipitation. Choose 2 pairs of contrasting biomes. Possibilities include… 1. 2. 3. 4. 5. 6. 4. Temperate forest and Topical forest Tundra and desert Tropical coral reefs and Hydrothermal vents Temperate bogs and tropical mangrove forests Grasslands and temperate forest ? ? ? Compare and contrast including information on 1. 2. 3. Characteristic limitation Productivity Biodiversity

Why do the biomes form in these areas?

The tri-cellular model of atmospheric circulation. • The distribution of biomes can be understood by looking at patters of atmospheric air circulation.

1 • The ITCZ (Inter Tropical Convergence Zone) • Due to the high insolation the air is heated up and becomes less dense. • High heat also causes high amounts of evaporation, this condenses to form large cumulonimbus clouds. This causes a lot of precipitation.

2 • At around 30 o North (and South) the air cools and forms an area of high pressure. • This means little cloud formation, therefore low amount of precipitation. • The air is still relatively hot here.

3 • As the air move more North it meets cooler air from the polar regions. • The polar air is colder and more dense and this pushes up the relatively warmer air of the Ferrell cell upwards. • This again causes a large amount of cloud formation, and therefore precipitation

Limitations: • Ignores other major transfers of energy e. g. El Nino and La Nina. • Ignores geomorphological factors such as mountains. • Ignores the redistribution of heat and energy via our oceans.

How will climate change alter the distribution of the biomes? Prediction: Explanation:

Changing biomes • Deserts are expanding • Grasslands are increasing

Zonation • Each species has an ecological niche. • The niches change as we increase the altitude. • Temperature • Precipitation • Solar insolation • Soil type • Species interactions

Before we move on to succession, you need to understand the concept of: K and r reproductive strategies • We saw these population growth curves before. • S-shape curve represents a population that is at carrying capacity (Kstrategy species) • J-shape curve represents a population existing in an exponential phase of growth (r-strategy species)

What are K and r? • The two variables that define a population curve. • r = growth rate • K = carrying capacity

K-strategist • Later stages of succession • Long life • Niche specialist • Slower growth • Predators • Late maturity • Fewer, but large offspring • Regulated mainly by internal factors • High parental care and • Higher trophic level protection • High investment in individual offspring • Adapted to stable environment

r-strategist • Short life • Rapid growth • Early maturity • Numerous and small offspring • Little parental care or protection • Little investment in individual offspring • Adapted to unstable environment. • Pioneers, colonizers • Niche generalists • Prey • Regulated mainly by external factors • Lower trophic level

Succession

Succession

Types of succession • Primary succession – colonisation of bare inorganic surfaces • Occurs on new land e. g. after volcanic eruptions and sand dunes Time

• Secondary succession – when an already established community is suddenly destroyed • Soils are already developed • E. g. Forest fire, abandoned crop fields

Stages of Succession Bare, inorganic surface Stage 2 – Establishment Stage 1 – Colonization Stage 4 – Stabilization Stage 3 Competition Climax community

Activity: • Using sand dunes as an case study create a poster outlining the stages of succession. Oldest • For each of the 5 stages outline how the following change: • Size and diversity of organisms • Complexity of energy flows • Soil • NPP and GPP (explain why they change) • Productivity : respiration ratio Youngest

Disturbance in succession

Climax communities • Not necessarily dense forest. • There is no one climax community. • Many stable alternatives • Dependant on: • Climatic factors • Soil properties • Random events • Complex ecosystems are more stable due to the variety of nutrient and energy pathways. • If one collapses its overall effect is low as there are many others to takes its place.

Human interference • Humans can have a huge effect on succession and influence what becomes the most stable state. • E. g. Grazing, deforestation, fires