Ecosystems Flashcards
Structure of an ecosystem
- Autotrophs/primary producer
- Primary consumer - herbivores
- Secondary consumer - carnivore
- Top predators/tertiary consumer - omnivores
Energy pyramid
Decreases each level as 90% lost in living processes.
Only 10% available for next level, hence why number of living organisms decreases with each trophic level.
Where energy goes
Most to decomposers
- receive most plant energy and use over half for life maintenance
- rest locked in soils or taken in by organisms that feed on decomposers
- all energy captured by plants is transformed and lost as heat (not recycled)
Nutrient cycling
Nutrients stored in three components
- biomass
- soil
- litter
Illustrated in gersmehl diagrams
Tropical rainforest nutrient cycle
Large biomass - rapid plant growth
Medium/small soil - fast reuptake for growth
Small litter - broken down quickly (hot+humid)
Tropical grasslands nutrient cycle
Large litter - lacks maoisture = slow decomposition
Small biomass - grasses die in dry season (limited accum)
Small soil - plant growth seasonal
Temperate deciduous woodland nutrient cycle
Large biomass - plant growth (not as fast as rainforest)
Medium soil - nutrients from litter in here by decomposers
Medium litter - slow decomposition in lower temps
Nitrogen Cycle
for construction of plant and animal matter
- present in atmosphere
- fixed in soil by some plants (taken up by roots of other plants, passes through ecosystem)
operates:
- over land/sea/in atmosphere
includes: inputs (volcanic eruptions), outputs (deep sea sediments)
Carbon Cycle
stored in: - coal/oil/gas/peat temporary stores: -plants/animals/soil burning fossil fuels + deforestation + destroy peat deposits = release C in atmosphere = greenhouse gases = global warming + climate change
food chains
link/show energy flow
trophic pyramids from simple FCs
most FCs interconnected = food webs
succession
change in a plant community through time
climatic climax
plant species living in perfect balance/equilibrium with the surrounding environmental conditions
primary succession
occurs on surfaces that have had no previous vegetation by the gradual colonisation of a lifeless abiotic surface.
e.g. lava flows, bare rock
xeroseres
form on dry land
lithoseres: bare rock
psammoseres: sand
hydroseres and haloseres
hydrosere: form in fresh water
halosere: form in salt water
two types of primary succession
xeroseres
hydroseres
secondary succession
follows destruction/modification of an existing plant community
- occur naturally (landslide)
- occur by human activity (deforestation)
sere
entire sequence of stages of a succession
seral stages
plagioclimax
when human influences prevent the ecosystem from developing further
stages (seres) of development of a succession
invasion pioneers compete colonisation domination decline (polyclimax theory)
Invasion sere of development of a succession
plants - bare ground - group/colony - 2 or more species survive (hardy plants/pioneer species)
e.g. long rooted, salt tolerant marram grass on sand dunes
Pioneers compete stage of development of a succession
as die, add organic matter - develop soil - affect microclimate
roots help weather surface - aid soil formation
Colonisation stage of development of a succession
immature soil - change balance of species - each stage better conditions for plant growth - inc no. species
Domination stage of development of a succession
- more species - added organic matter = imp water retention and soil qualities = taller and more agg plants - more demanding of space, water, nutrients
- taller plants (dominant plants) - shelter - other plants establish
- over time - stability = climax (dominants exclude rivals less suited)
Decline stage of development of a succession
once major dominants in place = saturation
climatic climax community (CCC)
vegetation stable balance with climate and soils in area
Example of a lithosere
Surtsey, Iceland (erupted 1963)
bacteria - lichens, mosses - herbs, grasses - ferns, bracken - large shrubs/small trees - large trees (birch, pine) - oak, ash trees
Lithosere develops in UK
Seral Stages
- Colonisation
- Establishment
- Competition
- Stabilisation
Seral Climax
Temperate Deciduous Woodland Location
UK: climatic climax - 8000yrs ago
Mid latitudes
Decent moisture
Oak + ash original dominants
Temperate Deciduous Woodland Climate
- winter 2-7C / summer 13-17C
- 500-2000mm precipitation/yr (most in winter)
- on-shore W winds: mod temp + bring moisture
- low pressure weather systems
Temperate Deciduous Woodland vegetation
- broadleaved deciduous trees (oak, ash) shed leaves in autumn
- soil temps fall, roots absorb less water: growth retarded
- heat loss dec transpiration + dec demand for water in cooler months
Temperate Deciduous Woodland soil
- 1.5m deep: brownearth, fertile zone, well drained
- autumn: leaf litter accu. - quickly decomposed by organisms, supports lots of fauna
- well mixed by earthworms (no clear layers)
- nutrient recycling: annual leaf fall
- aut+winter: some leaching - acidic soil = good for plant growth
Forest Structure
- Ground layer (mosses, seedlings, fallen decaying wood)
- Field layer (woodland (+grasses) + flowers, bluebell)
- Shrub layer (small trees, hazel, rowan)
- Tall tree canopy (oak 30-40m, ash, beech)
Some woods so dense + tall =light prevented reaching lower layers = fewer species
Effects of human activity on succession
4000BC: forests cleared
500BC: 1/2 woodland cleared-rest for timber+fuelwood
1086: everyone wood dependent
13th Cent: wood plantations (protected from grazing)
18th Cent: woodland clearance = parkland
19th Cent: industrial rev = wood major source fuel+building materials
1914: War = afforestation programme
1945: 1/3 remain woods cleared= agri + urbanisation
1975: little lost = conservation groups+tax incentive to replant
Effects of human activity on succession
Example: Caledonian Forest
Remnants of post-glaciation forest still exist:
- inaccessibility
- protection from deforestation, grazing, burning
Now protected by conservation legislation:
- mix of scots pine, birch, oak
- shrub layer: rowans
- field layer: heather
Plagioclimax
Interfering factors that stop a community from reaching climatic climax.
deforestation, agri = plagioclimax comm = dec biodiversity
UK:
- wood cleared for agri + settlement, industrial = pollution = acid rain = impacts veg + aquatic ecosystems in NW Europe
Plagioclimax UK: Heather Moorland
- deforestation, soil deteriorated = hardy plants dominate
- sheep grazing prevents regen = destroy saplings
- controlled: managed burning = eliminate less fire resistant = heather dominates = conserve nutrients
(- if burning not continued: trees grow + heather degenerates)
Heather Cycle
- Pioneer Phase: 0-6 yrs, small shoots
- Building Phase: 6-15yrs, heather dominate
- Mature Phase: 12-28yrs, colonisation other plants
- Degenerate Phase: 20-30yrs, gaps enlarged, mosses + lichens
(after stages 2,3,4 burning to take back to pioneer phase)
(after 20-30 yrs natural succession= young birch = succession to woodland)
Tropical Savanna Grasslands: African Savanna
Location
5-15deg N+S Equator
Occupy 65% Africa
Savanna
areas of tropical; grasslands that can occur with/without trees + shrub
Tropical Savanna Grasslands: African Savanna
Climate
- high temps throughout yr (>20C highs:36C, 11-13hrs daylight)
- seasonal climate - sun migration
- precipitation 600-2000mm (near rainforests enough rain for tree growth/ near deserts grasses sparse, drought)