2.4 Biomes, Zonation and Succession

Question 1

Define biome

Answer 1

collections of ecosystems sharing similar climatic conditions that can be grouped into five major classes

Question 2

Explain the distributions, structure, biodiversity, and relative productivity of deserts

Answer 2

distribution:
- covers 20-30 percent of the land surface
- dry air
- high temperatures (45-49 C in day)
- low precipitation (250 mm yr-1)

structure:
- vegetation scarce (absence of trees).
- soil has low water holding capacity, low fertility

relative productivity:
- low rates of photosynthesis
- low NPP rates

Question 3

5 major classes of biomes

Answer 3

aquatic, forest, grassland, desert and tundra

Question 4

Explain the distributions, structure, biodiversity, and relative productivity of a tundra

Answer 4

distributions:
- high alt
- high temps
- seasonal sunlight
- short day length

structure:
- simple
- vegetation = low, single layer
- abscence of tall trees
- frozen permafrost = soil limit productivity

relative productivity:
- low mean NPP
- 0.14 kgm-2yr-1

Question 5

Explain the distributions, structure, biodiversity, and relative productivity of a tropical rainforest

Answer 5

distribution:
- found between tropics of cancer and capricorn
- high rainfall
- high sunlight
- high temperatures
- no seasons = consistent light keeps temperatures

structure:
- complex structure
- emergent trees (up to 50m)
- dense canopy
- only 1% of light reaches floor
- soil = thin -> nutrients = poor

relative productivity:
- low mean NPP
- 2.2 kgm-2yr-1

Question 6

Explain the distributions, structure, biodiversity, and relative productivity of a temperate forest

Answer 6

distribution:
- seasonal weather (hot summers/cold winters)
- mild climate, lower average temperature / lower rainfall

structure:
- 2 types of tree types in forests; Evergreen + deciduous could be in one forest or contain both trees
- rainfall average between 500-1500 mm yr-1

relative productivity:
- lower than rainforest

Question 7

define insolation

Answer 7

the amount of solar radiation that reaches the Earth’s surface and affects temperature.

Question 8

define precipitation

Answer 8

when rain, snow, sleet or hail falls from the sky.

Question 9

​what shows how insolation, precipitation and temperature determine the distribution of the biomes

Answer 9

Tri Cellular model of Atmospheric Circulation

Question 10

Intro how the tricellular model contributes to the distribution of biomes

Answer 10

The tricellular model explains the distribution of precipitation and temperature and how they influence structure and relative productivity of different terrestrial biomes. The tricellular model is made up of three different air masses, these control atmospheric movements and the redistribution of heat energy. The three air masses, starting from the equator, are called the Hadley cell, Ferrel cell and the polar cell.

Question 11

Discuss how climate change is impacting biomes and causing them to shift.

Answer 11

• increases in co2 + other greenhouse gases lead to an increase in global temperatures -> affect rainfall patterns
• these changes in climate affect the distribution of biomes

Question 12

Convection Currents

Answer 12

Warm air rises as it heats and becomes less dense, cools at higher altitudes, increases in density, and descends, driving atmospheric and oceanic circulation patterns that influence global climate and biome distribution.

Question 13

define zonation

Answer 13

refers to changes in community along an environmental gradient due to factors such as changes in altitude, latitude, tidal level or distance from shore (coverage by water).

Question 14

define succession

Answer 14

the long term change in the composition of a community

Question 15

difference zonation versus succession

Answer 15

zonation is a spacial phenomenon whereas succession is a temporal phenomenon

Question 16

example zonation

Answer 16

rocky seashore:
The distinct vertical layers experience particular abiotic conditions. This is particularly clear in the distribution of plants and animals on a rocky seashore, where different species inhabit a series of horizontal strips or belts of the shore, approximately parallel to the water’s edge. In many places the strips (zones) are sharply bounded by the differently coloured seaweeds that populate them.

Question 17

primary succession

Answer 17

• Begins with no life
• No soil present
• New area (e.g., volcanic island)
• Lichen and moss come first
• Biomass is low

Question 18

secondary succession

Answer 18

• begins after removal of existing life
• soil present
• old area
• biomass is higher

Question 19

early stages versus later changes in climax community

Answer 19

Early Stages of Succession:
- gpp = low (low density)
- npp = high (low R)

Later Stages/Climax Community:
- GPP = high (high density)
- NPP = low (high R)

Question 20

Explain how succession links to habitat, species and genetic diversity​

Answer 20

Succession increases species diversity as there are new habitats been formed and a more complex ecosystem had been formed. An increased species diversity causes an increased genetic diversity

Question 21

r strategist characteristics

Answer 21

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

Question 22

k strategist characteristics

Answer 22

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

Question 23

Compare and contrast r and K strategist species including their roles in succession.

Answer 23

pioneer communites: suited to r-strategist

climax communities: suited to k-strategist

Question 24

Distinguish the roles of r and k strategists in succession.

Answer 24

As succession proceeds, r strategists will tend to be replaced by more competitive (k-selected) species. They tend to inhabit relatively stable biological communities, such as late-successional or climax forests

Question 25

Discuss the factors that could lead to alternative stable states in an ecosystem.

Answer 25

Ecosystems can shift from one state to another due to changes in the ecosystem. These changes are quantities that change quickly in response to feedbacks from the system. This means tht different states can exist simultaneously under equal environmental conditions. These will be dependent:
1.Climatic Factors
2.Soil Properties
3.Random Events

Question 26

changes in energy flow, gross productivity, and net productivity during succession

Answer 26

early stages:
- Gross Productivity low bc low density of producers
- Net Productivity high bc low levels of community respiration

later stages:
- Gross Productivity high in climax community
- GP and NP balanced

Question 27

2 components of stability

Answer 27

Resistance - the ability of the ecosystem to continue to function without change when stressed by disturbance.
Resilience - the ability of the ecosystem to recover after disturbance.

Question 28

factors affecting stability

Answer 28

• Disturbance frequency and intensity (how often and what kind of tillage)
• Species diversity (intercropping or rotations), interactions (competition for water and nutrients from weed species), and life history strategies (do the species grow fast and produce many seeds or slow with few seeds)
• Trophic complexity (how many functions are represented), redundancy (how many populations perform each function), food web structure (how do all of these groups interact)
• Rate of nutrient or energy flux (how fast are nutrients and energy moving in and out of the system or input:output efficiency)

Question 29

List the ways in which humans can disrupt the process of succession.

Answer 29

by modifying the ecosystem, for agriculture, grazing pressure, or resource use such as deforestation. This diversion may be more or less permanent depending upon the resilience of the ecosystem.

Question 30

ecosystem resilience definition

Answer 30

the capacity of an ecosystem to recover from disturbance or withstand ongoing pressures.

Question 31

Coral reefs and resiliance

Answer 31

Coral reefs and other tropical marine ecosystems face disturbances such as cyclones, crown-of-thorns starfish outbreaks, freshwater influxes, and various human activities

These disturbances can damage, stress, or kill components of the ecosystem, impacting its overall health and biodiversity.

A resilient ecosystem can fully recover from disturbances over time, returning to its original state of biodiversity and health. It may also absorb stresses with little or no sign of degradation, demonstrating its resilience against environmental challenges.

Question 32

Discuss the impact of climate change on biomes.

Answer 32

• changes in patterns of rainfall
• alterations in land and sea surface temps → shift in distribution of biomes

Question 33

case study to describe the pattern of change in the plant communities during succession

Answer 33

Lava from an erupting volcano incinerates everything in its path and forms new land that is made from inorganic material. While it is rich in minerals, the land cannot support a varied and complex ecosystem. Its capacity to sustain a stable ecosystem is limited. Pioneer species that colonize areas after volcanic eruptions include swordfern and green algae. A few small invertebrate animals may also venture into this territory, followed by crickets and spiders.

Question 34

Explain the general pattern of change in communities undergoing succession

Answer 34

• The size of the organisms increases with trees, creating a more hospitable environment.
• Energy flow becomes more complex as simple food chains become complex food webs.
• Soil depth, humus, water-holding capacity, mineral content, and cycling all increase.
• Biodiversity increases because more niches (lifestyle opportunities) appear and then falls as the climax community is reached.
• NPP and GPP rise and then fall.
• Productivity: Respiration ration falls.

Question 35

what determines the structure, function and distribution of biomes?

Answer 35

rainfall, temperature and insolation rates.

Question 36

how does the tricellular model of atmospheric circulation work?

Answer 36

winds meet from the N and S hemisphere:
- as substance gains heat energy, density decreases and particles rise
- as you go up, air cools, density increases + falls back toward earths surface
- these convection currents drive wind patterns -> affects biomes

Question 37

what changes occur during succession

Answer 37

• size of organisms increase
• energy flows become more complex
• soil depth, humus, water holding capacity, mineral content, cycling -> increase
• biodiversity increases and falls with climax community
• NPP+ GPP rise/fall
• production: R rise

Question 38

what changes in species diversity occur during succession

Answer 38

• early stages: few species
• increases w/ succession
• balance is reached in amount of species

Question 39

what is the level of productivity during succession

Answer 39

zero

Question 40

example 4 causes of succession

Answer 40

• climate change
• fires
• severe flooding
• pest infestations

Question 41

what is respiration ratio

Answer 41

relationship when GPP is low but NPP is high bc of low rates of respiration (production/respiration ratio or P/R ratio)

Question 42

P/R> 1

Answer 42

biomass accumulates

Question 43

P/R<1

Answer 43

biomass depletes

Question 44

P/R = 1

Answer 44

a steady-state community results

Question 45

changes in diversity during succession

Answer 45

early stages:
- low biomass
- few niches

plant community:
- changes in every state
- leads to larger plants and greater complexity

later stages:
-> number of niches increases
-> food webs become more complex
-> habitat/species diversity increases