215 Final

• Ecological succession • - the sequential change in species composition of the community over time
• Primary succession-initial establishment of plant and animal communities on substrates lacking living organisms (examples: bare rock,lava, sand dunes, glacial meltwater pond, rainwater)
• • Secondary succession change of an established community, each sequential community is called a seral stage.
• Allogenic succession- abiotic disturbance
• Autogenic succession- biotic disturbance
• Rate of succession positively correlated to temperature and rainfall
• Ecological mechanisms for succession:

  • Stochastic events- largely unpredictable – who gets there first can become established.......

  • Facilitation-a species creates conditions favourable for a succeeding species but not itself Clover– nitrogen fixer Trees shade out the clover Accumulation of leaf mulch Most important in early seral stages
• Inhibition – a species inhibits the colonization of subsequent colonists (slows succession and prolongs a seral stage)• -allelopathy - plant communities, coral reefs• -competitive exclusion• -example- intertidal communities
• Tolerance- members of a seral stage are those that co-exist due to the use of different resources• -combines facilitation and inhibition into a co-evolutionary view of succession ‘the ghost of competition past’
• Trophic levels- the sequence of steps in a food chain or pyramid
• The 4 trophic levles: Primary producer, Primary consumer, Secondary consumer, Tertiary consumer
• Connectance (C) - number of links (L) in a foodweb divided by the total number of possible links(N). C=L/N. N= n(n-1)

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• Umbrella (indicator) species• a species used for conservation decisions• (Grizzly bear, Panda bear, Spotted owl)
• Keystone species• a species whose presence is essential to maintain an ecosystem • (sea otter, wolves, sea stars)
• Dominant species:• a common species with an effect on the community proportional to its biomass
• Keystone species:• a species with an effect on the community that is disproportional to its biomass
• Clear and deep mountain lakes are -oligotrophic- low productivity-nitrogen and phosphorus limited - low plankton abundance,-usually few fish
• migration of salmon from the oceans greatly increase primary productivity (phytoplankton)
• Salmon carcass remnants in riparian zone contribute 120 kg nitrogen per hectare
• Increased primary productivity and species diversity in watersheds with salmon and bears Summary: Bears are a keystone species Relative to trees, salmon are a keystone species Relative to bears, salmon are a dominant species
• Coral reefs: greatest species diversity of vertebrateson the planet -kalaidoscope of colours - highly efficient recycling of nutrients -under major global threat
• Arctic - mainly frozen ocean surrounded by land~4000 meters water depth, ice cover ~3 meters thick-upper 15m has reduced salinity from large rivers-highly complex layering of Atlantic and Pacific waters-high abundance of plankton in summer, arctic cod,seals, walrus, Beluga, Narwhal, Bowhead whale-polar bear is major terrestrial predator
• Antarctic - large frozen continent surrounded by oceans~98% ice- cover...up to 2 km in thickness-mountainous ....4500 m elevation-low species diversity – bacteria, lichens, penguins-surrounding very cold oceans with high primary productivity and species diversity - weddell seal, leopard seal, elephant seal, penguins, Orca, Humpback-no terrestrial predator
• oligotrophic - clear water lakes (low productivity)
• dystrophic –stained (tea-coloured) lakes (lowproductivity)
• mesotrophic - intermediate productivity
• eutrophic - high productivity lakes
• lake stratification: the way lakes separate into layers based on temperature.
• Tundra •3-6 months of darkness with ice and snow• permafrost- subsoil (>0.5 m depth) permanently frozen all year• all cold-hardy plants• surface soil thaws in summer•3 strata - soil, ground, low shrubs• many aquatic/terrestrial insects• shorebirds, waterfowl- seasonal migrants• hare, fox, wolves, caribou, grizzly bear, polar bear
• • Temperate Coniferous forests(Taiga or Boreal forest) -conifers (ex. spruce, hemlock,fir, cedar, pine)-few shrubs-ground layer of ferns and mosses-trees with monopodial growth 4 strata (trees, shrubs, ground ,soil)-short summers and long cold winters(slow decomposition)-Seasonal migrants-Occasional hibernation/torpor forresidents
• Temperate rainforest -ancient trees (1000 y old, 4 m diameter), 4 strata, high 3D structural complexity-multiple species of fungi, mosses, angiosperms ,high insect diversity-species-rich riparian zones,-1000 y for seral stage recovery of community structure after clear cutting• Greatest biomass/ha of all terrestrial ecosystems on the planet
• 6 strata for tropical rainforests: emergent trees over 60 m-discontinuous, sympodial growth rather than monopodial growth B- up to 20 m-discontinuous C- lowest trees-continuous canopy D- shrub layer, tall herbs and ferns E- ground layer, herbaceous plants and seedlings A and F connected by vines- Lianas-many epiphytes-high species diversity-most taxonomic groups-high biological turnover, high recycling of nutrients F- root/soil layer- shallow and poorly developed
• Tundra and Taiga has the majority of nitrogen in the soil.
• temperate deciduous forests and grasslands are pretty even with nitrogen distributions, more in above ground/roots.
• tropical biomes like savannah and rainforests have high nitrogen in above ground.
• Biomass distribution on the planet: Viruses: 0.2 Gt C, Bacteria: 70 Gt C, Protists: 4 Gt C, Fungi: 12 Gt C, Plants: 450 Gt C, Animals: 2 Gt C
• Of the animal biomass majority is arthropods at 1 Gt C and fish at 0.7 Gt C. humans at 0.06 Gt C. and live stock at 0.1 Gt C.
• Biomass distribution of earth article findings: Census of 550 Gt C is distributed among all kingdoms of life. plants are the dominant kingdom primarily terrestrial. animals are mainly marine. Bacteria and archaea are predominantly located in the deep subsurface environment.
• Terrestrial biomass is about two orders of magnitude higher than marine.
• Global marine biomass pyramid contains more consumers than producers