Transcript BIOLOGY 154: ECOLOGY and ENVIRONMENTAL ISSUES

BIOLOGY 403:
PRINCIPLES OF ECOLOGY
(Regulatory / Limiting Factors)
LIMITING / REGULATING
FACTORS
• 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)
LIEBIG’S LAW OF THE MINIMUM
• Justus Liebig (1830’s-1840’s, agronomist)
• From his work we get what some call Liebig’s
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
WEAKNESSES IN LIEBIG’S 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
SHELFORD’S 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 Liebig’s ideas ???
• lower limit, optimum, upper limit
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 stage
of the life cycle (age)
• when conditions are not optimal for one factor this
may influence other factors (? domino effect ?)
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 ?????)
SOME IMPORTANT PREFIXES
• Steno
• (narrow range)
• Meso
• (middle or a bit wider range)
• Eury
• (wide range)
SOME IMPORTANT SUFFIXES
• thermal
• hydric
• haline
• phagic
• oecious or ecious
STENO ORGANISMS
• They are specialists.
• Advantage ???
• Disadvantage ???
EURY ORGANISMS
• They are generalists (“jack of all trades”)
• Advantage ???
• Disadvantage ???
WHICH REGUALTORY FACTOR
IS HAVING THE EFFECT ????
• shrub genus Emmeranthe
• species A grows on ‘normal’ soils
species B grows on serpentine soils (high in
Mg, Fe and low in Ca, P, N)
• transplant them to the other’s habitat and
they die?
• Why ?????
WHICH REGUALTORY FACTOR
IS HAVING THE EFFECT ????
• Sp. A cannot tolerate the unusual nutrient
conditions in the serpentine soils
• Sp. B doesn’t 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
NUTRIENTS
• most material covered previously
• too much of a nutrient as well as too little can be harmful
• Too little (???)
• Too much (???)
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Synergisms and extrapolation (fertilizer experiment)
+ NaNO3 --- 10% increase in yield
+ K2SO4 --- 10% increase in yield
+ both --- doubled the yield
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?
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
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.)
TEMPERATURE (IV)
(Is it altitude and latitude?)
TEMPERATURE (V)
• North / South temp. cline similar to the Altitudinal
temp. cline
• Limiting effect of temp. --- Sequoia sempervirens
(the coast redwood)
pacific coast fogbelt
to s. Oregon (temp.) --- freezing of seedlings
c. coastal California (moisture)
• Pedicularis groenlandica (Colorado rockies)
not above 10,000 ft.
not altitude directly
temp. --- but not directly on the plant
obligate outcrosser --- temp. on its pollinator (bee)
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
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?
WATER (III)
• ‘EFFECTIVE PRECIPITATION’ depends on:
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Total precipitation
Seasonal distribution
Temp.
Wind
Relative humidity
Soil
• Precipitation may become more effective with
increasing elevation and then less effective
WHY?
LIGHT (I)
• Important for animals as well as plants
• Can have too much as well as too little
• Light and temp. often related
WHY / HOW ?
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3 factors / aspects we are concerned with:
Quality (= wavelength)
Intensity
Duration
LIGHT (II)
• Quality (= wavelength) effects:
• photosynthesis
• Flowering initiation (red/far red light in socalled short or long day plants)
• Some plant and animal tropisms
• Some organism processes / activities
LIGHT (III)
• Intensity effects:
• Plant (auxin responses) and animal tropisms
• Photosynthesis
compensation point (~100 fc)
saturation point (~2,000 fc, about 1/5 of full
sunlight)
• Humans (SAD)
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)
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)
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)
CURRENTS & PRESSURES (I)
• Especially important in aquatic situations
WHY?
• Directly on organisms in aquatic situations
- HOW?
• Indirectly on aquatic organisms
- HOW?
• Winds (direct and indirect), more often important
at higher elevations
CURRENTS & PRESSURES (II)
• Especially important in aquatic situations
WHY?
• Generally not very important in terrestrial
situations
WHY?
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
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
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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
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• Clay --- less than 0.002 mm (colloidal size particles)
SOIL (III)
• Soil particle size influences:
• Moisture holding capacity
• Aeration
• Fertility
• Root and animal penetration / burrowing ability
• Freezing and thawing patterns
SOIL (V)
SOIL (VI)
FIRE
• Helps maintain some grasslands
• Helps maintain some pine forests
• Surface fires often temporarily increase
productivity
BIOTIC FACTORS
• Some animals may help maintain vegetation in an
area
• Pollinator specificity
• Seed dissemination by animals
• Effects of humans
• Other interactions (predation, etc.)