ecological processes n.
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  1. ECOLOGICAL PROCESSES • Learning objectives • understand important ecological processes • describe ecosystem processes of energy, nutrient and material flows • describe spatial and temporal ecological processes • understand how humans influence spatial and temporal ecological processes

  2. Ecology = ‘the study of the relationships of plants and animals to each other and to their environment’ (Whittaker,1992)

  3. The functions and characteristics of ecology 1. Ecosystems = communities together with the physical environment that sustains them • Characteristics of and the • Interrelationships between the environment and living inhabitants. • Flows of materials • Open systems with inputs and outputs

  4. HOWEVER - in reality the inputs and outputs may be far more complex making realistic modelling problematic. Figure 10.1

  5. 2. The habitat • The physical environment provides the distinctive habitat/habitats of the ecosystem. • The living area for a species or group of species – may be very small or large. • the branch of a tree for lichen • entire tropical grasslands for predators of grazing animals • An ecosystem may contain a range of habitats at a variety of scales.

  6. 3. Populations • Populations vary over time • response to changing environmental conditions • chain reactions • e.g. decrease in predator = increase in prey species. • indirect changes due to loss of one important species • Population is limited due to: • Limited resources • Balance between births and deaths • Population curves • help environmental management

  7. Figure 10.2a,b

  8. Figure 10.2c,d

  9. 4. Ecological communities • Groups of individuals of any living organism. • Mostly plants/animals occupying a specific area • Characterised by its interactions • Sharp OR gradual boundary between communities • Characterised by core community • usually a specific species • all others are called differentials • May be competition and change over time (due to internal or external change)

  10. 5. Ecological functions useful to humans • A carrier = local ecology provides space and surface for humans • Production = supplier of matter and energy resources • Information = for orientation, aesthetics, education, philosophical identification • Regulation – ecosystem stabilisation e.g. damping climatic changes.


  12. Energy and nutrient flows • Autotrophs – 1st trophic level • Energy from sun by photosynthesis • Range of vegetation types and certain bacteria and algae • Heterotrophs • Feed on autotrophs (usually herbivores) • Carnivore and omnivore • Consumes herbivore • Higher level carnivore • Saprovore • Decomposers e.g. maggots • Detritus based rather than vegetation based food chain. • Releases last energy and recycles inorganic nutrients

  13. Figure 10.4 Source: After Murray, 1968

  14. Food chains and webs • Species often operate at a variety of levels in a food web • Energy • Used for digestion, movement, reproduction, respiration • Only 10% of energy is passed on to next level • Consumer therefore require large amount of biomass from lower trophic levels • rabbit spend most of their time grazing • Biomass pyramids (see previous slide) • Not all biomass of a trophic level is eaten • Some die of old age • Some species are rapid reproducers and very nutritious • Therefore form the diet of larger biomass than exists in their own trophic level e.g. some algae

  15. Materials in ecosystems follow complex pathways e.g. The biochemical cycle of Phosphate Figure 10.6

  16. Local winds spread soil and water pollution Long term bioaccumulation in vegetation Consumed by grazing animals the following year Effects spread to the wider ecosystem Bioaccumulation • Less desirable materials are taken up and stored by organisms if they become locally bioavailable. • Toxins then accumulate in specific parts of the ecosystem, usually in higher levels of food webs. • Must be stored in parts of the individual that will be consumed e.g. meat rather than bone. • Cause severe health effects once threshold is exceeded. • e.g. Chernobyl nuclear explosion

  17. Figure 10.7


  19. 1. The ecological niche ‘The position of a species in a community in relation to its specific requirement of habitat resources and micro-climatic conditions (i.e. climate, shelter, food, water)’ • No two species with identical resource requirements can occupy the same niche (competitive exclusion applies). • Different parts of a resource such as a tree are often used by different species • Fundamental niche • ideal conditions for the species requirements • only realised in simple situations with no other competitors • Realised niche • more commonly utilized • competitive interaction inhibits the idealized niche

  20. Figure 10.8

  21. 2. Competition • Important in determining ecological distributions • Inter-specific competition • share the same spatial distribution of resources but at different times • e.g. use of a waterhole. • Intra-specific competition • directly share the same resource • causes exclusion of weaker individuals • creates territorial boundaries. • e.g. squirrels collecting acorns from a small copse

  22. 3. Life strategies • Explains patterns and distributions found in ecology • Relates to elements of species life-cycles • 2 types: • ‘r’ strategists • high reproductive rates and rapid development • good colonisers - common on new/disturbed sites • out-compete others in high disturbance conditions • ‘K’ strategists • low reproductive rates and better competitive ability • will out-compete in conditions of low stress

  23. 4. Biodiversity: patterns of species richness • Some areas have more species than others • tropical forests provide habitat for 40% of Earth’s species • Need to identify biodiversity ‘hotspots’ -concern over extinctions • Large species-rich regions result from many factors including • Lack of major disturbance • Tropical areas - lack of major climatic disturbance during the ice ages causing local extinctions • Lack of isolation • species invasion allowed • Wide range of habitats within a local area • e.g. the range of light and shelter conditions in a woodlands • Short-term disturbance • may cause a mosaic of differing age since disturbance patterns with distinctive communities

  24. Figure 10.9 Source: After ‘A biodiversity concept map’ A biodiversity concept map’, Michael J. Robinson, from the Web Site of the 1999 Summer Biology Institute on Diversity, produced by the Leadership Program for Teachers at the Woodrow Wilson National Fellowship Foundation (Princeton, NJ, USA: Woodrow Wilson National Fellowship Foundation, 1999). Used by permission of the Woodrow Wilson National Fellowship Foundation 2004.


  26. 1. Succession The directional change in the complexity, composition and biomass of an ecological unit over time • Relay floristics • the process of one plant species being replaced by another invading species until a stable state is achieved • A plants vital attributes determine the place of a species in the replacement series • Succession mechanisms 1. Facilitation 2. Tolerance 3. Inhibition

  27. Human influence: Agricultural • Agroecosystems = 70% of developed areas • Managed inputs and outputs of energy and nutrients • Controlled species diversity (usually reduced) • Many successful agroecosystems mimic natural landscape • E.g. prairie grassland replaced by cereal cropping • Increasing technical abilities allows landscape change • E.g. Agricultural area in Bolivia • suffer severe wind erosion. Solution = circular farm units • Numerous Environmental problems • E.g. Nutritional Eutrophication • Fertiliser enrichment of water bodies • phytoplankton bloom. • Slash and burn agricultural systems • Population pressures cause early clearance (nutrient/seed bank loss)

  28. Figure 10.11 Source: Landsat image courtesy USGS EROS Data Center and Landsat 7 science team, NASA

  29. Figure 10.12 Source: Photo courtesy of Charles Hartley

  30. Human influence: Urban ecology • Urban areas often regarded as ecologically destructive • Distinctive features • Urban climate • Air flow • Air pollution • Increased humidity • Water quality reduced • Lower soil water and groundwater • Encapsulated countryside • an urban ecosystem that requires human management to survive • Either ancient habitats or previously managed land • Often unique communities • Urban wildlife • Some found the new resources advantageous e.g. urban fox • Gardens have increased local plant biodiversity

  31. Ecosystem fragility • Complexity of many ecosystems makes them robust under a range of conditions e.g. species removal • However highly connected KEYSTONE SPECIES removal makes them vulnerable • Secondary extinction • Food web fragmentation • Possible ecosystem collapse • e.g. Elephants are regarded as keystone species in tropical Africa since their browsing deters succession into shrubland/forest • Systems with networks intermediated level of regular and random distributions of connections withstand the most change

  32. Figure 10.13 Source: After Solé and Montoya, 1001


  34. Conservation and sustainability • Conservation implies intervention and value-judgements on what to conserve and what to ignore – objective • Management is often required to increase local diversity • E.g. maintaining networks of reserve corridors in fragmented landscapes • Should we strive to maintain ecological communities that are no longer self-sufficient? Or instead concentrate on changing our unsustainable use? • United Nations Educational Scientific and Cultural Organisation (UNESCO) • Terrestrial and coastal ecosystems promoting solutions to reconcile biodiversity conservation with sustainable human use • Emphasis is conservation rather than preservation • Social ecology • Addresses conflicts between social values and ecological sustainability • Brunkhorst (1995) – Bioregional theory

  35. Ecological footprint • Recently developed sustainability index • Provides estimates of the amount of ecological resources in hectares per person than are used by individuals, industries, activities etc • Reflects intensity of landuse and population density as well as resource use • Australia and Canada are the only countries below capacity • All others use more resources than they can sustain • Annual consumption of resources requires 14 months to be renewed – running at an ecological deficit • Goals can be set for decreasing consumption or increasing productivity • New technologies (e.g. solar panels) • Farming methods (e.g. multiple harvesting) • Recycled materials • Efficient energy use (e.g. public not private transport) • You can calculate your own ecological footprint •

  36. Climate change • Roots et al (2003) used phenological data from around the world and shown a consistent temperature-related shift in ecosystem behaviour • Species have moved poleward in the last century • Predictions: • Change in composition and structure to become weedier and structurally simpler • Biomes will not shift as intact entities • Terrestrial biosphere will become carbon source not sink

  37. Biosecurity • Isolated regions are vulnerable to the arrival and establishment of alien species e.g. Australia and New Zealand • Biosecurity is a response to this • 1997 New Zealand Minister of Biosecurity introduced • Reactive measures • Quarantine services (all ships, aircraft, mail searched and sanitised) • Proactive measures • Requiring ships between Australia and New Zealand to empty their water ballast tanks mid-voyage

  38. Figure 10.15 Source: After Wodzicki, 1950

  39. Summary • Ecosystems in constant state of change • transfers of energy and matter between plants, animals and soil • Often not simple linear processes • Biogeochemical cycles – nutrient reservoirs • Bioaccumulation • Keystone species – loss may cause ecosystem collapse • Some ecosystems are more fragile than others • Human disturbance to ecosystems is complex • Loss of various habitats • However also gain of new different habitats e.g. urban areas • Important to consider socio-economic factors within environmental management