Lecture 2: slide 1

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BIOS 3010 EcologyLecture 2 Habitat Resources

• Lecture summary
• Resources
• Definition
• Abiotic
• Biotic
• Space
• Classification
• The niche

Albrecht Dürer A Young Hare 1502, The Large Turf
1503 (GSA, Vienna)
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2. What is a resource?

• All things consumed by an organism (Tilman, 1982)
  
• But, space is also a resource - therefore
• Resources are quantities that can be reduced by
  the activity of an organism
• Or, in the glossary to Begon et al. (1996) a
  resource is defined as
• that which may be consumed by an organism and,
  as a result, becomes unavailable to another
• e.g. food, water, nesting sites, etc.
• Thus CO2, O2, and light can be either resources
  or conditions - and are more likely to be
  resources at high population densities and small
  scales.
• Note like conditions, resources can also act as
  constraints and cues.

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3. Contrast with conditions

• A condition is an abiotic environmental factor
  which varies in space and time. Conditions are
  not consumed or used up by organisms or made less
  available to others.
• e.g. temperature, moisture or humidity, light,
  chemistry (e.g. O2, pH, salinity), gravity,
  pressure, sound, fire, wind, stream or current
  flow velocity, pollutants.

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4. Abiotic Resources

• Solar radiation is a resource and not a condition
  when the supply can be influenced by other
  organisms
• Resource supply can vary
• Systematically
• Unsystematically
• Systematic Variation - e.g. globally, seasonally
  or diurnally when solar radiation operates more
  like a condition.
• Fig. 3.1, solar radiation with latitude
• Fig. 3.3, annual and diurnal variation in solar
  radiation with latitude
• Figs. 3.6 3.8 of strategic responses (rigid
  responses with little tactical maneuverability)
  to predictable variation in the
  Photosynthetically Active Radiation spectrum (PAR
  of 380-710 nm) for plants that vary strategically
  in abilities to photosynthesize under different
  light regimes.

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5. Abiotic Resources

• Unsystematic Variation - e.g. local, plastic or
  tactical responses resulting in resource
  depletion zones (RDZ)
• e.g. the leaves in a forest (Fig. 3.2) or plant
  roots responding tactically to resource
  concentration with more root hairs (e.g. wheat
  grown in sand clay - more roots respond to
  available water and minerals in clay, see Figs.
  3.20 3.21).
• Resource depletion zones vary according to
  physical characteristics, e.g. nitrates are
  soluble but phosphates are not - hence
  mycorrhizae are used by all plants to aid in
  foraging.
• Note read the text (Begon et al. chapter 3) for
  accounts of CO2, water, mineral nutrients and O2
  as resources

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6. Biotic Resources

• The product of autotrophic fixation of energy by
  plants and used by heterotrophs as consumers.
• Produces decomposers, parasites, and predators
  (and grazers/herbivores).
• Nutritional content of these resources varies
• Fig. 3.23 - nutritional composition of plants
  versus animals nutritional variation among and
  within plants (plants have much higher CN ratios
  than animals).
• Fig. 3.17 - the complex of herbivores on
  raspberry plant partition resources in space and
  time (considered later under competition).

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7. Space as a resource

• e.g. lizards basking on a rock compete for
  microsite space to bask.
• or monarch butterflies overwintering on trees
  require space to avoid freezing mortality or
  mouse predation on the ground.
• or testosterone-manipulated red grouse
  territories in Fig. 3.23 (3rd ed.).

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8. Tilmans Classification of resources

• after Tilman 1982.
• Distinction between essential and substitutable
  resources to give the 5 sets of performance
  (growth) isoclines between 2 resources in Fig.
  3.27
• Essential
• Perfectly substitutable
• Complementary
• Antagonistic
• Inhibitory

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9. The ecological niche

• G. Evelyn Hutchinson (1957) defined the niche as
  an
• n-dimensional hypervolume
• Ecologically the niche is an abstract concept and
  not a fixed position in space
• (a neesh and not a nitch! Dr. Seuss.)
• n-dimensions define the limits within which a
  species can survive and reproduce, for n
  environmental factors that will include both
  conditions and resources.

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10. Fundamental Realized niche

• Fundamental niche
• So the zero growth isoclines of Fig. 3.27 define
  niche boundaries in 2 dimensions and this can be
  done for both lower and upper limits of either
  conditions or resources to define the fundamental
  niche of a species (the space that it could
  occupy - its overall potential).
• These niche boundaries can be easily drawn in 1,
  2 or 3-dimensions as inFig. 2.26, for dimensions
  such as those shown in Fig. 2.2, or dimensions
  that include resources and ecological processes.
  But it is difficult to visualize the niche in
  more dimensions and so the n-dimensional
  hypervolume is the best simple description of
  niche space.
• Realized niche
• The realized niche represents the actual niche
  dimensions of a species after various ecological
  processes such as movement, competition and
  natural enemy attack have reduced the fundamental
  niche dimensions.

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Fig. 3.1
Global solar radiation absorbed annually
(Jcm-2min-1)
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Fig. 3.3
Annual diurnal variation in solar
radiation with latitude
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Fig. 3.6
Photosynthetic CO2 uptake in response to
radiation intensity
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Fig. 3.8

• Annual variation in (a) PAR (?) and leaf
  photosynthesis (?) and (b) CO2 exchange in the
  day (?) and at night (?)

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Fig. 3.2

• Reflection (R) and attenuation of solar radiation
  in
• (a) mixed boreal forest, (b) pine forest, (c)
  sunflowers, (d) corn field

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Fig. 3.20

• (a) shortgrass prairie plant roots (b) wheat
  roots in sand and clay layers

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Fig. 3.21

• Radioautographs of mustard seedlings to show
  depletionof 32PO4- in soil

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Fig. 3.23

• Composition of different plant and animal
  resources

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Fig. 3.17 (3rd ed)

• Life cycle and phenology of raspberry plant
  (Rubus idaeus) parts as resources for animal
  consumers

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Fig. 2.26 (3rd ed. - see Fig 2.2)

• Ecological niche in 1 (a), 2 (b) 3 (c)
  dimensions

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Fig. 2.2

• Various niches in (a) 1 dimension and (b) 2
  dimensions

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Niche theory according toDr. Seuss

• And NUH is the letter I use to spell Nutches,Who
  live in small caves, known as Nitches, for
  hutches. These Nutches have troubles, the biggest
  of which isThe fact there are many more Nutches
  than Nitches.Each Nutch in a Nitch knows that
  some other NutchWould like to move into his
  Nitch very much.So each Nutch in a Nitch has to
  watch that small NitchOr Nutches who havent got
  Nitches will snitch.
• Geisel, T.S. (Dr. Seuss) 1955. On beyond Zebra.
  Random House Publishing, New York.
• http//shade.grove.iup.edu/rgendron/Seuss.htmlx