Ecosystems

Ecosystems

1. Trophic Level Pyramids

   • 1% sunlight turned into usable energy
   • 60% energy lost by heat, 30% by daily activity and 10% stored as biomass
   • 90% energy lost at each level

2. Gersmehl diagram

   • Biomas=large (large diversity of animals and plants, favorable conditions for plant growth, consistent temps-warm & high rainfall)
   • Litter=small (favorable conditions for decomposition and growth of fungi- breaks down nutrients in litter layer, humid warm conditions)
   • Soil=small (large amount of trees and plants-high uptake, high amount of leaching)

3. Succession

   • Succession = the change in plant communities over time
   • As succession develops, it passes through a series of stages called SERES.
     • A SERE is an individual stage in plant succession. Over time, plant communities usually become more complex. It can also be called seral progression.
   • PRIMARY SUCCESSION
     • Occurs on surfaces that have had no previous vegetation e.g. bare rock, salt water, fresh water and sand dunes.
     • Development of succession
       • The first species to colonize an area are referred to as the pioneer species. These help to modify the physical environment (soil, climate etc), making it more favorable for further species to take hold. The final stage in succession is the climatic climax community. This is the plant community which is best adapted to the environmental conditions.
     • Polyclimax theory
       • Some biogeographers believe that within one climate, local factors such as drainage, geology, relief and even microclimates can create variations in the climatic climax community. This is knows as the polyclimax theory.
     • Alternatives to the climax vegetation model
       • It is rare for a community to progress from bare surface to climax community in a series of progressive stages.
         • If the succession follows this pattern it is called a PRISERE (the uninterrupted, progressive development from the pioneer species to the climatic climax.
           • However, there are normally many interruptions, which can lead to plagioclimax or subclimax community.
     • Natural Interuptions
       • Edaphic subclimax (soil characteristics limit plant growth)
       • Biotic sublclimax (grazing of land prevents growth)
   • SECONDARY SUCCESSION
     • Succession taking place on land that was formerly vegetated but has undergone loss of alteration of that vegetation.
     • Natural factors that can cause a subclimax = plate tectonics, fire, landslides, overgrazing, flooding
     • Human factors that can cause a subclimax = deforestation, animal grazing, ploughing, burning, draining, flooding, climate change.

4. Temperate deciduous woodland biome

   • Location
     • 40-60 degrees north and south of equator
     • 3 major areas: eastern N.America, E.Asia and Europe
   • Climate
     • Cool temperate maritime climate (originate from the oceans)
     • Rainfall = high (1000,1500mm per year)
     • Temps above 0 degrees celcius. Summer temps average between 20-25 degrees celcius
   • Soil
     • Zonal soil - brown earth (deep and fertile)
     • Supply of organic material from autumn leaf fall is high and decomposes fairly quickly due to humidity levels beneath the canopy
     • The soil is well mixed - rich variety of organisms e.g. worms help to incorporate humus.
     • O horizon: litter layer (layer of dead material), fermentation layer (started to decompose), humus layer (black amorphous mass of organic material)
     • A horizon: mineral rich, some humus carried downwards by water percolating down into the soil, worms carry humus down
     • B horizon: precipitation exceeds evaporation, net downwards movement of water, leaches minerals downwards (forms reddish layer - iron oxides)
   • Vegetation species
     • Tall trees e.g. Oak most common (30-40m), elm, beech, sycamore etc.
     • Other vegetation: scrubs (hawthorn, bramble), herbs (fern, wild garlic, bluebells) and mosses
   • Vegetation layers
     • Tree layer (Oak), shrub layer (bramble, rose, rowan), herb layer (nardus grass, fern bracken etc), ground layer (mosses_
   • Seasonality
     • Spring/Summer
       • until late spring there is lots of light entering (canopy hasn't fully grown. Flowers grow on ground layer
       • by June and July, the canopy is dense so it become dark - photosynthesis hard.
       • Plants grow by different methods e.g. saprophytic plants lack leaves but have a fungal association with roots - utilise organic matter in soil
     • Autumn/Winter
       • large amount of dead and decaying matter found on forest floor
       • broad leaved trees shed their leave and canopy becomes bare
   • Adaptations
     • Trees
       • broad, thin leaves - absorb max sunlight with smallest expenditure of energy
       • deciduous trees shed leaves in winter - reduces transpiration, stops them drying out, cannot photosynthesise in winter anyway.
     • Other vegetation
       • many plants grow early in Spring to avoid dense canopy
       • food reserved- manufactured in previous year e.g. daffodills and bluebells
     • Animals
       • hibernate in winter when food supply is short e.g. squirrels, hedgehogs
       • fur to keep warm e.g. skunks
       • shed fur when temps rise in Spring e.g. red squirrels

5. Ancient Woodlands in the UK

   • Ancient Woodlands are areas that are believed to have had a continuous woodland cover for at least 400 years
   • 6,000 years ago it covered 90% of the UK. Now, only 2% of Britain is covered by Ancient Woodland
   • Past Threats
     • Settlement and fuel: this is why only 15% remained by the time of the Domesday Book in 1086
     • WW1: there were timber shortages during WW1, which meant a lot of exotic species were grown e.g. Sitka spruce, Douglas fur, as they grew much faster than native species. As a result, large areas of ancient woodland were cleared and replaced.
   • Current threats
     • No legal protection: 85% of woodland not protected by any legislation
     • Legal loopholes: areas that are protected can still be developed on.
     • Prolonged neglect: practices such as coppicing etc have to take place to encourage new growth
     • Development: growth of population and urban areas
     • Agriculture: e.g. overgrazing by cattle. Hedges have also been removed which helped to link woodlands together - over 110,000km gone 1984-1993
     • Overgrazing
     • Conversion to conifer plantations
     • Fragmentation: only 501 ancient woodlands exceed 1km2. Woodlands smaller and more isolated. Pesticides and pollution
     • Planting stock: 70-85% of native trees planted in the Uk over the last 40yrs imported from other parts of Europe
     • Climate change: higher temps etc
     • Ash dieback disease
   • The future
     • Close legal loopholes
     • Increase SSSI protection
     • Reconnect ancient woodlands
     • Refuse development plans
     • Promote value of woodland

6. Tropical equatorial rainforest biome

   • Location
     • The tropical rainforest biome circle the earth, mainly between latitudes 10 degrees north and 10 degrees south of the equator
     • Amazon basin in S.America, in the Democratic Republic of Congo and the Guinea coast of Africa, parts of SE Asia, Indonesia and N.Australia
   • Soil
     • Latosol
     • Can be over 40m deep
     • Nutrient poor as plant uptake is as quick as decomposition
     • The constant hot wet climate provides perfect conditions for chemical weathering of the bedrock and there is constant supply of minerals from the parent rock to the soil
     • Moisture surplus - downward movement of water through the soil which leaches silica minerals out of the A horizon. Iron and aluminium compounds are less soluble and are left behind --> iron gives the soil the red colour
     • Soil moisture budget: Cameroon- precipitation is greater than potential evapotranspiration for at least 8 months of the year (causes moisture surplus)
   • Biodiversity
     • Tropical forests cover 7% of the earth's surface area and contain almost 50% of the world's species
   • Climate
     • hot, humid environments
     • occurs in the equatorial zone between the tropic of cancer and the tropic of capricorn
     • Virtually rains every day
     • The highest monthly rainfall is in March with over 300mm and the lowest is in August with less than 50mm
     • Night time temps- fall below 18degrees and day time can rise to 35degrees
     • The climate tropical rainforests is controlled by a band of clouds called the Intertropical Convergence Zone, a band of low pressure, located near the equator and created by the convergence of the trade winds from the Northern and Southern Hemispheres
       • Control the wet and dry seasons in the tropic
     • In a downpour, only 1/3 of the rain that falls hits the forest floor. Humidity is high at around 80% during the day and 95% at night
   • Vegetation layers
     • Emergent
       • tallest trees up to 45m
       • the canopy absorbs most of the sunlight and intercepts most precipitation
       • Plants: ephiphytes, woody climbers
       • Animals: birds and insects
     • Canopy
       • Nearly all rain intercepted
       • 15% sunlight
     • Under canopy
       • 15% sunlight
       • rain drips through the canopy
       • Plants: short, young trees and herbaceous plants that tolerate low light
     • Shrub layer
       • 10% sunlight
       • Plants: buttress roots, shrubs, herbs, mosses, ferns
       • Decomposing animals and insects
   • Vegetation adaptations
     • Trees have wide buttress roots - support them to grow tall as there is great competition for light
     • Leaves are waxy and have drip tips so water does gather on them and cause them to rot
     • thick bark - limit moisture evaporation
     • Lianas- roots in the ground and climb high to reach sunlight
     • Prop and stil roots - give support
     • epiphytes- grow on trees to take advantage of sunlight in the canopy
   • Animal adaptations
     • camoflage e.g. South American three-toes sloth
     • Brightly coloured poison arrow frog- warn predators not to eat them
     • parrots-strong beaks to crack shells of nuts
     • Monkeys and birds in canopy as there are many tangled tree branches
     • Bats in under canopy-dark

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