BIOLOGY 403: PRINCIPLES OF ECOLOGY (Regulatory / Limiting Factors)

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BIOLOGY 403 PRINCIPLES OF ECOLOGY
(Regulatory / Limiting Factors)
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LIMITING / REGULATINGFACTORS

• Limiting Factor ???Is Regulatory Factor a better
  term?
• Virtually anything can be Limiting / Regulating .
• Nutrients (or other minerals), Temperature,
  Light, Water, Atmospheric Gases, Currents and
  Pressures, Soil, Fire, Biotic Factors (just to
  name some)

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LIEBIGS LAW OF THE MINIMUM

• Justus Liebig (1830s-1840s, agronomist)
• From his work we get what some call Liebigs Law
  of the Minimum
• The size of a crop is determined by the essential
  nutrient that is present in minimal amount.
• PARAPHRASED the weakest link determines the
  strength of the chain

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WEAKNESSES IN LIEBIGS LAW

• he was only interested in nutrients
• interested only in the effects from nutrient
  deficiency
• did not take into account and synergisms
• SYNERGISM -- result of an interaction of two or
  more factors so that the combined effect is
  greater ( or -) than the sum of their separate
  effects

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SHELFORDS LAW OF TOLERANCE

• the absence or poor performance of a species may
  be controlled by the qualitative or quantitative
  deficiency or excess of any factor that
  approaches the limit of tolerance
• much more general
• just an extension of Liebigs ideas ???
• lower limit, optimum, upper limit

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SOME RIDERS / AFTERTHOUGHTS

• relatively large variations in factor intensity
  are of relatively small consequence in the region
  of the optimum
• a particular organism may have narrow ranges of
  tolerance for some factors, medium for others and
  wide for yet others
• these ranges / limits may vary seasonally,
  geographically (ecotypes), and/or with the
  stageof the life cycle (age)
• when conditions are not optimal for one factor
  this may influence other factors (? domino effect
  ?)

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MORE RIDERS / AFTERTHOUGHTS

• organisms rarely (IF EVER!) live under optimal
  conditions for all (or even most) factors
• organisms live where an acceptable ecologic sum
  exists, that is, where a multitude of factors are
  at their relative best
• an acceptable ecologic sum can be arrived at in
  more than one way
• in real systems it is often difficult (and
  unrealistic) to single out ONE thing as the major
  regulatory factor (WHY ?????)

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SOME IMPORTANT PREFIXES

• Steno
• (narrow range)
• Meso
• (middle or a bit wider range)
• Eury
• (wide range)

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SOME IMPORTANT SUFFIXES

• thermal
• hydric
• haline
• phagic
• oecious or ecious

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STENO ORGANISMS

• They are specialists.
• Advantage ???
• Disadvantage ???

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EURY ORGANISMS

• They are generalists (jack of all trades)
• Advantage ???
• Disadvantage ???

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WHICH REGUALTORY FACTOR IS HAVING THE EFFECT ????

• shrub genus Emmeranthe
• species A grows on normal soilsspecies B grows
  on serpentine soils (high in Mg, Fe and low in
  Ca, P, N)
• transplant them to the others habitat and they
  die?
• Why ?????

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WHICH REGUALTORY FACTOR IS HAVING THE EFFECT ????

• Sp. A cannot tolerate the unusual nutrient
  conditions in the serpentine soils
• Sp. B doesnt need (as such) the unusual nutrient
  conditions in the serpentine soils
• Sp. B does well in normal soils that have been
  autoclaved
• bacterial toxins from bacteria that live only in
  the normal soils inhibit Sp. B

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NUTRIENTS

• most material covered previously
• too much of a nutrient as well as too little can
  be harmful
• Too little (???)
• Too much (???)
• Synergisms and extrapolation (fertilizer
  experiment)
• NaNO3 --- 10 increase in yield
• K2SO4 --- 10 increase in yield
• both --- doubled the yield

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TEMPERATURE (I)

• Sometimes difficult to determine if this is the
  major factor --- WHY?
• Often interacts with moisture
• Temps on the earth (oC) -70 to 100 or more
• Some spores can tolerate these conditions (and
  even worse in laboratory studies)
• Some living organisms can be active at the upper
  natural extremes but few anywhere near the lower
• Majority are found active between 0 o and 40o.
  WHY?

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TEMPERATURE (II)

• Highest temp. in some ecosystems
• 36o in normal seawater
• Land shade temp. often reaches 46o for a month or
  more sometimes 55o
• High or low temp. may be regulating but seasonal
  fluctuations are often regulating
  Midcontinental areas (Minnesota) may have 35o
  (some areas of Tibet reported to be 80o)
• Maritime equatorial area may be as little as 0.5o

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TEMPERATURE (III)

• Regulating temp. may vary depending on other
  abiotic environmental factors or with the stage
  in the life cycle
• Temp. varies with altitude and latitude it is
  temp. rather than these factors which is REALLY
  regulating
• Temp. decreases 5.5oC for every 1,000 m (3oF for
  every 1,000 ft.)

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TEMPERATURE (IV)(Is it altitude and latitude?)
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TEMPERATURE (V)

• North / South temp. cline similar to the
  Altitudinal temp. cline
• Limiting effect of temp. --- Sequoia sempervirens
  (the coast redwood)pacific coast fogbeltto s.
  Oregon (temp.) --- freezing of seedlingsc.
  coastal California (moisture)
• Pedicularis groenlandica (Colorado rockies)not
  above 10,000 ft.not altitude directlytemp. ---
  but not directly on the plantobligate outcrosser
  --- temp. on its pollinator (bee)

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WATER (I)

• Essential for all life forms
• Some organisms never ingest free water
• Too little water (drought) directly regulating
• Too much water more of an indirect effect
• Leaching of nutrients
• Too little O2 in waterlogged soils

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WATER (II)

• Total yearly precipitation not as important as
  EFFECTIVE PRECIPITATION
• One area with 45 in. (114 cm.) could support
  deciduous forest while another at the same
  latitude could be grassland or even desert
• WHY?

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WATER (III)

• EFFECTIVE PRECIPITATION depends on
• Total precipitation
• Seasonal distribution
• Temp.
• Wind
• Relative humidity
• Soil
• Precipitation may become more effective with
  increasing elevation and then less effectiveWHY?

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LIGHT (I)

• Important for animals as well as plants
• Can have too much as well as too little
• Light and temp. often relatedWHY / HOW ?
• 3 factors / aspects we are concerned with
• Quality ( wavelength)
• Intensity
• Duration

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LIGHT (II)

• Quality ( wavelength) effects
• photosynthesis
• Flowering initiation (red/far red light in
  so-called short or long day plants)
• Some plant and animal tropisms
• Some organism processes / activities

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LIGHT (III)

• Intensity effects
• Plant (auxin responses) and animal tropisms
• Photosynthesiscompensation point (100
  fc)saturation point (2,000 fc, about 1/5 of
  full sunlight)
• Humans (SAD)

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LIGHT (IV)

• Duration effects
• May interact with quality and/or intensity
• Plant flowering
• Metamorphosis in some insects resting stages in
  many plants and animals
• Humans (SAD)

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ATMOSPHERIC GASES (I)

• Already discussed water vapor
• Already discussed nitrogen as a nutrient
• NOX --- important in acid precipitation
• SO2 --- important in acid precipitation
• O2 and CO2 are the main gases
• Rarely are O2 and CO2 overly regulating in
  terrestrial situations (sometimes in very highly
  organic soils, waterlogged soils or at high
  elevations)

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ATMOSPHERIC GASES (II)

• O2 and CO2 often regulating in aquatic systems
• Water holds only about 5 the amount of O2 found
  in an equal volume of air
• CO2 is quite soluble and can alter pH (currently
  affecting marine ecosystems)

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CURRENTS PRESSURES (I)

• Especially important in aquatic situationsWHY?
• Directly on organisms in aquatic situations -
  HOW?
• Indirectly on aquatic organisms - HOW?
• Winds (direct and indirect), more often important
  at higher elevations

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CURRENTS PRESSURES (II)

• Especially important in aquatic situationsWHY?
• Generally not very important in terrestrial
  situations WHY?

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SOIL (I)

• More concerned with texture, structure and mode
  of formation
• Terrestrial soils can be delimited on mode of
  formation
• Residual (in place)
• Colluvial (talus)
• Alluvial (deltas, etc.)
• Glacial (till)
• Wind (eolian) --- dune and loess

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SOIL (II)

• Soil texture
• Parent material usually 90 or more of the soil
  solids texture usually refers to this
  constituent
• One system of classification
• Coarse gravel --- 5.0 mm and larger
• Fine gravel --- 2.0 mm to 5.0- mm
• Coarse sand --- 0.2 mm to 2.0- mm
• Fine sand --- 0.02 mm to 0.2- mm
• Silt --- 0.002 mm to 0.02- mm
• Clay --- less than 0.002 mm (colloidal size
  particles)

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SOIL (III)

• Soil particle size influences
• Moisture holding capacity
• Aeration
• Fertility
• Root and animal penetration / burrowing ability
• Freezing and thawing patterns

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SOIL (V)
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SOIL (VI)
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FIRE

• Helps maintain some grasslands
• Helps maintain some pine forests
• Surface fires often temporarily increase
  productivity

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BIOTIC FACTORS

• Some animals may help maintain vegetation in an
  area
• Pollinator specificity
• Seed dissemination by animals
• Effects of humans
• Other interactions (predation, etc.)