2.4: Biomes, Zonation, and Succession

Significant ideas

1) Climate determines the type of biome in a given area, although individual ecosystems may vary due to many local abiotic and biotic factors.

2) Succession leads to climax communities that may vary due to random events and interactions over time. This leads to a pattern of alternative stable steady states for a given ecosystem.

3) Ecosystem stability, succession and biodiversity are intrinsically linked.

Explain how the angle of insolation affects the temperature at different latitudes referring to the diagram.

→as you move away from the equator, you get more moderate climates

→the more direct the angle of sunlight, the more energy, heat, and productivity

→the less direct, the more the radiation is spread out

insolation

the amount of sun’s energy reaching the surface

How does precipitation determine the type of biome?

→measured in mm/m²/year

→the more precipitation a biome has, the more productivity it will have

↑ rain = ↑ productivity

How does temperature determine the type of biome?

→measured in °C

→extremely high or low temp. = lower productivity

→moderate temp. = higher productivity

generally: ↑ temp. = ↑ productivity

How does latitude determine the type of biome?

def: distance north + south from the equator

→as you move away from the equator, it gets colder, which means lower productivity

(distance from equator has inverse relationship w/ productivity)

How does altitude determine the type of biome?

def: height above sea level

→air is less dense, temps are lower, less water availability, soil is less rich, so productivity is lower

How do ocean currents determine the type of biome?

→regulates climates/biomes by distributing water around the globe

→distributes heat from the equator to the poles (increase in productivity)

How do winds determine the type of biome?

→move air masses from one place to the next, affecting daily and seasonal weather

→Warm, moist air converging near the equator causes heavy precipitation → higher productivity

How does rain shadow determine the type of biome?

def: a dry area on the leeward side of a mountainous area

→the mountains block the passage of rain-producing weather systems and cast a “shadow’ of dryness behind them → lower productivity

Identify the 5 major biomes.

1. Aquatic (freshwater and marine)

2. Forest (tropical, coniferous, deciduous)

3. Grassland (tropical, savanna, temperate)

4. Desert (cold, hot)

5. Tundra (alpine, arctic)

Tri-cellular model of atmospheric circulation

ITCS = Intertropical convergence zone

Include:

y-axis: pole degrees

equator 0 degreees

polar cell

polar front

ferrel cell

Hadley cell

Trends/similarities/differences between biomes

Desert: warm or hot temps, doesn’t fluctuate, little or no rainfall

grassland: little rain in winter, fair amount in summer (4 seasons)

savanna: steady temps between warm + hot w/ rainy + dry season

rainforest: very little change in temp, a lot of rainfall

deciduous forest: bitter winters, a little more rain than grassland, 4 seasons

tundra: coldest temps, up to 10-15 degrees C in summer, steady rain in summer but pretty low precipation

Limiting factors of aquatic biomes

water absorbs some light → limits photosynthesis

deep oceans = no light

freshwater may freeze in temperate/polar winters

Limiting factors of forest biomes

nutrients in biomass, not soil

high rainfall leeches from nutrients in the soil

Limiting factors of grassland biomes

low precipitation

extreme temps limit productivity

low decomposition → low nutrient cycling

Limiting factors of desert biomes

little precip.

high evaporation

extreme day/night temp differences

photosynthesis limited by lack of H2O

Limiting factors of tundra biomes

short days = less sunlight = decrease in productivity

frozen water in winter and saturated soils post-thaw limit photosynthesis and slow nutrient cycles

productivity of aquatic biomes

coral reefs: high

deep ocean: low

temperate freshwater: moderate

productivity of forest biomes

tropical: high

temperate: high, but lower in fall and winter

productivity of grassland biomes

moderate to low

productivity limited by seasonal extremes, slow nutrient cycles

productivity of desert biomes

low

H2O needed

soils may have good nutrients from nutrient cycling

productivity of tundra biomes

low: short days, low temps

photosynthesis limited

biodiveristy of aquatic biomes

coral reefs: high

deep ocean: low

temperate freshwater: moderate

biodiveristy of forest biomes

tropical: highest on earth

temperate: 2nd highest

biodiveristy of grassland biomes

high

diverse plants, nutrient-rich soils → extensive food webs

biodiveristy of desert biomes

low

extremes of precip. + temp. = not optimal

biodiveristy of tundra biomes

limited

too cold for reptiles, amphibians, and invertebrates (cold-blooded)

Evaluate graph suggest reasons for differences

Biomes w/ warmer weather + higher precip. are more productive. Also, higher nutrient availability →more productivity. Levels of these factors will influence graph

Outline the changes to biomes that are occurring worldwide as a consequence of global climate change; include species movement and limitations.

Increase in mean temps and decreases in precip. means biomes are migrating. Also, evolution is a slow process so they will mostly have to adapt. This means northward migration when possible, or else declining populations. Also some species are moving toward the equator for more precipitation.

→ plants migrate slowly (animals faster)

r-strategist

grow and mature more quickly + produce many small offspring (most don’t make it to adulthood)

K-strategist

slow-growing, produce few, large offspring (more make it to adulthood)

annotate survivorship curve

type I = k-strategists

type II - organisms w/ constant loss

type III = r-strategists

List features of r-strategists and k-strategists:

offspring, parental care, mortality, body size, onset of maturity, reproduction, favored environment, type of species, population size

Define zonation + describe factors that can cause it

def: change in a vegetation community along an envt’l gradient

caused by changes in altitude, depth of water, tidal level, distance from the shore, etc.

→spatial change

How do the temp, precip., solar insolation, soil type, and species interactions lead to zonation in a montane environment?

1. decreases w/ increase in altitude

2. moist @ middle altitudes

3. more intense @ higher altitudes

4. decomp. = faster in warmer zones (decrease in altitude = increase in fertility)

5. competition may crowd out some species

   grazing may alter plant competition

Explain how a kite diagram measures zonation

graphically shows amount of species in different zones

→width of kite corresponds to how many species there are

→shows # of animals (or % cover for plants) against distancee along transect

→distribution of organisms affected by abiotic factors (ex: cliff into ocean)

define succession

the predictable change in a vegetation community over time

starts with a pioneer community

distinguish between primary and secondary succession

primary - occurs on bare abiotic surfaces. the colonization of newly created/available land by organisms

secondary = occurs when established ecosytem is destroyed

Explain the stages of primary succession

start w/ bare surface

1. colonization

2. establishment

3. competition

4. stabilization

   climax community

define stage 1: colonization

terrain/soil: bare inorganic surface

biota: r-select species/pioneer species: short life cycles, rapid production of new offspring/seeds

define stage 2: establishment

terrain/soil: weathering of rock enriches soil w/ nutrients →decomp. enriches topsoil

biota: invertebrates appear →increase in humus (organic material) + water-holding capacity

define stage 3: competition

soil/terrain: grasses grow, displacing pioneer species

biota: larger plants allow k-selected species to establish themselves →outcompete r-select

define stage 4: stablization

terrain/soil: more soil nutrients allow for shrub growth

biota: fewer new species b/c late colonizers are competitive, complex food web develops, k-selected specialize

define climax community

terrain soil: increase in soil depth allows for growth of trees

biota: steady-state dynamic equilibrium → max possible development

Outline how NPP, GPPP, Diversity, Soil depth, energy flow, and avg. organisms size change throughout succession

avg organism size goes from small to large, and it goes from r-select to k-select

energy flow goes from simple to complex

critical aspects of resilience

threshold, resistance (biodiversity), and precariousness

Why do secondary forests display denser growth and contain species not found in the original primary forest?

No competition, lots of fertilizer sunlight, seeds blowing to new places

Factors that could lead to alternative stable states in an ecosystem

multiple disturbances throughout the stage of secondary succession

Ways in which humans can disrupt process of succession

→ cutting for timber

→clearing for farming

→construction

→forest fires

→overgrazing

→overfishing