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Lecture 5

Lecture 5. Principles of Ecology: Ecosystem structure and development, and Importance of Biodiversity. We hope you come to understand Ecosystem structure and function Biological and physical aspects Trophic levels Mutualisms Ecosystem development with time Succession r-K species

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Lecture 5

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  1. Lecture 5 Principles of Ecology: Ecosystem structure and development, and Importance of Biodiversity

  2. We hope you come to understand • Ecosystem structure and function • Biological and physical aspects • Trophic levels • Mutualisms • Ecosystem development with time • Succession • r-K species • Role of Biodiversity and Strategies to Conserve it • Current extinctions • Distribution of biodiversity • Ethics • Misc. Other Concepts • Niche and habitat • Island Biogeography

  3. 1. Ecosystem structure and function Boxes – Structure Arrows - Function

  4. Ecosystem structure • Biological structure (composition) - Living species (animals – including humans, plants, fungi, bacteria) • Physical structure – coarse woody debris, standing dead trees, soil, vertical canopy structure, canopy gaps

  5. Examples of Structures in western OR, WA and BC old-growth forests • Large, old well spaced trees (DF, WRC, WH, SS, PSF and • others) – mostly conifers • 2. Biodiversity – both species and habitat diversity • 3. Lots of dead wood in different stages of decay – snags and • coarse woody debris (CWD) on the ground • 4. Multiple canopy layers – horizontal and vertical • 5. Disturbance – fire, wind, pathogens, insects, and an • occasional volcanic eruptions, etc. • 6. Canopy gaps – landscape patches containing trees of • different ages

  6. Old-growth forest – Hoh River, Olympic National Park

  7. Hoh rain forest – gaps created in storm in 1996 West Twin Creek gap

  8. West Twin Creek Gap

  9. Trophic Structure and Function Food chains and food webs Food chains and food webs and/or food networks describe the feeding relationships between species in a biotic community. They show the transfer of material and energy from one species to another within an ecosystem.

  10. Trophic levels-- In ecology, the trophic level is the position that an organism occupies in a food chain - what it eats, and what eats it.

  11. Terrestrial food chain

  12. 90% of ecosystem energy goes through the detritus (decomposer) food chain 10% through the consumer food chain

  13. Relationships within Ecosystem (competition, predation, parasitism, etc) Often we forget Mutualisms Relationships between two organisms where both benefit – can influence forest succession, biodiversity and productivity Examples Mycorrhizal fungi and tree roots N fixing bacteria and alder roots

  14. Ecosystem development with time

  15. Species Succession • Ecological succession refers to more-or-less predictable and orderly changes in the composition or structure of an ecological community with time. • Whenever an event such as a fire, clear cut, or lava flow creates an empty habitat, species arrive, interact, and assemble to form a new ecological community • Most ecologists expect change to be rapid at first and then decline as the community ages.

  16. Primary and Secondary Succession • Primary succession – on sand dunes,on lava and pyroclastic flows, after glacial retreat • Secondary succession after disturbance of already established vegetation

  17. Primary succession

  18. Secondary Succession

  19. The trajectory of ecological change can be influenced by site conditions, by the interactions of the species present, and by more stochastic factors such as availability of colonists or seeds, or weather conditions at the time of disturbance. In general, communities in early succession will be dominated by fast-growing, well-dispersed species (opportunist, fugitive, or r-selected life-histories). As succession proceeds, these species will tend to be replaced by more competitive (K-selected) species

  20. Oliver stand development stages

  21. Forest stand development stages suggested by Franklin et al. (2002) Typical stand age (years) Development stage Disturbance and legacy creation 0 Cohort establishment 20 Canopy closure 30 Biomass accumulation/competitive exclusion 80 Maturation 150 Vertical diversification 300 Horizontal diversification 800 Pioneer cohort loss 1200

  22. Classical forest succession series in the Pacific Northwest Red alder Douglas-fir western hemlock Western hemlock western hemlock Ponderosa pine grand fir/Douglas-fir

  23. Shade tolerance – ability to grow in low light Pacific Northwest Species Shade Tolerance Western hemlock Very tolerant Pacific silver fir Very tolerant Western redcedar Tolerant Sitka spruce Tolerant Engelmann spruce Tolerant Grand fir Tolerant Subalpine fir Tolerant Mountain hemlock Tolerant Western white pine Intermediate Douglas-fir Intolerant Noble fir Intolerant Ponderosa pine Intolerant Lodgepole pine Intolerant Big leaf maple Tolerant Red alder Intolerant

  24. Species competition and self thinning Plant species compete for light, water, nutrients, space Self thinning of individuals with time happens when plant compete for resources. -3/2 power law – slope of line when tree density is plotted against volume. Canopy differentiation – dominants, co-dominants, intermediate, suppressed

  25. Change in Species Traits Through Development/ Successionr and K species The theory originates from work on island biogeography by the ecologists Robert MacArthur and E. O. Wilson Selective pressures are hypothesised to drive evolution in one of two generalized directions: r- or K-selection dN/dt = rN (1-N/K) r=population growth rate of the population (N), K=carrying capacity

  26. Trait r-selected K-selected Reproduction High rate Lower rate Dispersal Widely less widely Body size small larger Competiveness less more Niche occupation new niche occupied niche Life span short long Probability of survival to adult low high Environment unstable stable Example bacteria, insects many trees, whales, weedy plants, elephants, terns small rodents

  27. Although some organisms are primarily r- or K-strategists, most display traits considered characteristic of both r and K. e.g., trees have traits such as longevity and strong competitiveness that characterize them as K-strategists. In reproduction, however, they typically produce thousands of offspring and disperse them widely, traits characteristic of r-strategists. Where do red alder, western hemlock and Douglas-fir fit in the continuum? r-selected K-selected

  28. Successional theories Relay floristics Initial floristics Monoclimax (Clementsian) versus polyclimax (many successional pathways) – now widely accepted

  29. Relay (facilitation) floristics SPECIES Initial floristics TIME

  30. MULTIPLE Successional pathways in the coast range and western Cascades of Oregon after clearcutting Coast Range Western Cascades Open Open 100% 100% Shrub/herb Shrub/Herb 3% 100% 97% Semi-closed Semi-closed 22% 7% 8 % 85% 3% 72% Closed Closed Closed Closed Closed Hard Mixed Conifer Mixed Conifer Wood Yang, Cohen and Harmon 2005. Can. J. For. Res 35:1889-1900

  31. 3. Biodiversity • The word first began to be used in mid 1980s. • Definitions: • “Variation of life at all levels of biological organization • a measure of the relative diversity among organisms present in different ecosystems. • -the "totality of genes, species, and ecosystems of a region.. • Three Levels of Biodiversity

  32. Three common metrics used to measure species-level biodiversity, encompassing attention to species richness or species evenness: Species richness - the least sophisticated of the indices available (species/area) – No. species/ha Simpson index - takes into account percent cover Shannon index –takes into account species evenness – e.g., 40 Douglas-fir and 40 hemlock

  33. Global Change and Biodiversity Continental extinction rates have increased from 10-7 to 10-4 species/species/year Nott, et al. 1995. Current Biology 5:14-17

  34. (Chapin et al 2000)

  35. Highest biodiversity is in the soil e.g., Saprophytic Fungi

  36. 44% of all vascular plants and 35% of vertebrates are confined to 25 hotspots comprising 1.4% of Earth (Myers et al. 2000)

  37. 20% of Human Population also live in the hotspots (Cincotta et al. 2000)

  38. Does it Matter? • Yes • Much is unknown, so save the parts • Leopold’s advice for intelligent tinkering is to save all the parts • How many rivets can we pop? • Ehrlich and Ehrlich 1983. Extinction: the causes and consequences of the disappearance of species. New York: Ballatine Books • Biodiversity is connected to ecosystem function • Loreau 2000; Tilman 2000; Chapin et al. 2000.

  39. (Chapin et al. 2000)

  40. (Chapin et al. 2000)

  41. (Chapin et al. 2000)

  42. Increase understanding • End Subsidies • Diverting 5% would pay the habitat bill • Global Treaties • Montreal Protocol • CFCs • Kyoto • CO2 • Rio • Biodiversity • International Peace Parks (Korean DMZ) • Incentives and compensation • Credits, premium pricing for certification • Ethics, Morals, Values What To Do? (1170 plants, 83 fish, endangered birds, 67% of Korean mammals {51 sp}; Kim 1997) (Balmford et al 2002, Wilson 2002, Ferraro and Kiss 2002)

  43. Expected Drivers of Changing Biodiversity (Sala et al. 2000)

  44. Spatial Extent of Expected Changes (Sala et al. 2000)

  45. Direct May be Better • People respond to immediate, selfish needs • Couple with long-term change in subsidies and longer-term change in morals (Ferraro and Kiss 2002)

  46. Leopold’s Land Ethic 1937 • Conservation is getting nowhere because it is incompatible with our Abrahamic concept of land. • We abuse land because we regard it as a commodity belonging to us. • That land is a community is the basic concept of ecology, but that land is to be loved and respected is an extension of ethics. 1995 (Leopold 1948)

  47. Science, Ethics, and Nature The problem for the environment is that the nearly 14 billion feet busy trampling the life out of ecosystems belong to the most uncontroversial deservers of moral value. (Nash 1990 in Agar 2001)

  48. A Strategy for Washington • Washington Biodiversity Council • Documents available here

  49. 4.Habitats and Ecological Niches Habitat - a place where a plant or animal can get the food, water, shelter and space it needs to live. Niche - is a term describing the relational position of a species or population in an ecosystem and how it responds to resources and enemies. The abiotic or physical environment is also part of the niche. The description of a niche may include descriptions of the organism's life history, habitat, and place in the food chain. No two species can occupy the same niche in the same environment for a long time.

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