2.4 Biomes, Zonation and Succession Flashcards
Define biome
collections of ecosystems sharing similar climatic conditions that can be grouped into five major classes
Explain the distributions, structure, biodiversity, and relative productivity of deserts
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
5 major classes of biomes
aquatic, forest, grassland, desert and tundra
Explain the distributions, structure, biodiversity, and relative productivity of a tundra
distributions:
- high alt
- low temps
- seasonal sunlight
- short day length
- low percipitation
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
Explain the distributions, structure, biodiversity, and relative productivity of a tropical rainforest
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
Explain the distributions, structure, biodiversity, and relative productivity of a temperate forest
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:
- high mean NPP
- 1.20 kgm-2yr-1
define insolation
the amount of solar radiation that reaches the Earth’s surface and affects temperature.
define precipitation
when rain, snow, sleet or hail falls from the sky.
what shows how insolation, precipitation and temperature determine the distribution of the biomes
Tri Cellular model of Atmospheric Circulation
Intro how the tricellular model contributes to the distribution of biomes
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.
Discuss how climate change is impacting biomes and causing them to shift.
- increases in co2 + other greenhouse gases lead to an increase in global temperatures -> affect rainfall patterns because with more heat, there is more condensation leading to more rainfall
- these changes in climate affect the distribution of biomes
Convection Currents
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.
define zonation
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).
define succession
the long term change in the composition of a community
difference zonation versus succession
zonation is a spacial phenomenon whereas succession is a temporal phenomenon
example zonation
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.
primary succession characteristics
- Begins with no life
- No soil present
- New area (e.g., volcanic island)
- Lichen and moss come first
- Biomass is low
secondary succession characteristics
- begins after removal of existing life
- soil present
- old area
- biomass is higher
early stages versus later changes in climax community
Early Stages of Succession:
- gpp = low (low density)
- npp = high (low R)
Later Stages/Climax Community:
- GPP = high (high density)
- NPP = low (high R)
Explain how succession links to habitat, species and genetic diversity
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
r strategist characteristics
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
k strategist characteristics
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
Compare and contrast r and K strategist species including their roles in succession.
pioneer communites: suited to r-strategist
climax communities: suited to k-strategist
Distinguish the roles of r and k strategists in succession.
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
Discuss the factors that could lead to alternative stable states in an ecosystem.
1.Climatic Factors
2.Soil Properties
3.Random Events
changes in energy flow, gross productivity, and net productivity during succession
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 respiration are balanced
- NPP approaches zero
2 components of stability
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.
List the ways in which humans can disrupt the process of succession.
- agriculture
- hunting
- forest clearance
- burning
- grazing
-> divert progression of succession
-> lead to alternative stable states
-> more or less permanent depending on the resilience of the ecosystem
ecosystem resilience definition
the ability an ecosystem to recover from disturbance or withstand ongoing pressures.
case study to describe the pattern of change in the plant communities during succession
lava erupting from volcano
- secondary succession
- pioneer community = swordfern, green algae
- intermediate community = deer mouse, white-crowned sparrow
- climax community = bigleaf maple, northern goshawk
Explain the general pattern of change in communities undergoing succession
- 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.
what determines the structure, function and distribution of biomes?
rainfall, temperature and insolation rates.
how does the tricellular model of atmospheric circulation work?
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
what changes occur during succession
- 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
what is the level of productivity during succession
zero
example 4 causes of succession
- climate change
- fires
- severe flooding
- pest infestations
what is respiration ratio
relationship when GPP is low but NPP is high bc of low rates of respiration (production/respiration ratio or P/R ratio)
P/R> 1
biomass accumulates
P/R<1
biomass depletes
P/R = 1
a steady-state community results
changes in diversity during succession
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
changes in mineral cycling during succession
early stages:
- forms an open system
- carbon + nitrogen can enter and leave
later stages:
- forms more of a closed system
- carbon + nitrogen can remain and cycle
- minerals from soil -> biomass -> soil when organisms die/decay
factors of climax communities (compared to an early community)
- greater biomass
- higher species diversity
- more favourable soil conditions
- better soil structure
- taller, longer living plant species
- greater community complexity, stability
- higher habitat diversity
link between ecosystem stability, succession, diversity and human activity
- succession increases biodiversity over time
- biodiversity strengthens ecosystem stability by creating complex interactions
- human activity can:
- interrupt succession
- reduce biodiversty
= making ecosystems fragile - stability is lost -> ecosystems become vulnerable to collapse
- conservation efforts -> help restore biodiversty + stability
