Download 7 Principles

Post Graduate Diploma in Environment Education
Unit 7 Principles pertaining to limiting factors and
ecological assessment for sustainability
1.Liebig’s law of the minimum
2.Shelfords’s law of tolerance
3.Regulatory factors
4.Ecological indicators
Subodh Sharma Dr.nat.tech.; Aquatic Ecology Centre, P.O. Box: 6250, [email protected].
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Post Graduate Diploma in Environment Education
Unit 7 Principles pertaining to limiting factors and
ecological assessment for sustainability
Liebig’s law of the minimum: Growth of a plant is
dependent on the amount of foodstuff which is
presented to it in minimum quantity.
This law of the minimum was first expressed by Justus Liebig in
1840.
This law of the minimum is less applicable under ‘transientstate’ conditions when the amounts, and hence the effects, of
many constituents are rapidly changing.
Subodh Sharma Dr.nat.tech.; Aquatic Ecology Centre, P.O. Box: 6250, [email protected].
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Post Graduate Diploma in Environment Education
Unit 7 Principles pertaining to limiting factors and
ecological assessment for sustainability
Shelfords’s law of tolerance: The existence, abundance,
and distribution of a species in an ecosystem are
determined by whether the levels of one or more physical
or chemical factors fall within the range tolerated by that
species.
In other words, there are minimum and maximum limits for
physical conditions (such as temperature) and
concentrations of chemical substances-called tolerance
limits-beyond which no members of a particular species
can survive.
Subodh Sharma Dr.nat.tech.; Aquatic Ecology Centre, P.O. Box: 6250, [email protected].
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Post Graduate Diploma in Environment Education
Unit 7 Principles pertaining to limiting factors and ecological
assessment for sustainability
Shelfords’s law of tolerance
This concept of the limiting effect of maximum as
well as minimum was incorporated into the ‘law’
of tolerance by V. E. Shelford in 1913.
Subodh Sharma Dr.nat.tech.; Aquatic Ecology Centre, P.O. Box: 6250, [email protected].
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Post Graduate Diploma in Environment Education
Unit 7 Principles pertaining to limiting factors
and ecological assessment for sustainability
Limiting Factors
The presence and success
of an organism or a group
of organisms depends upon
a complex of conditions.
Any condition which
approaches or exceeds the
limits of tolerance is said to
be a limiting condition or a
limiting factor.
Fig: A Model summarizing general
principles of limiting factors (source
Odum, 1971)
Subodh Sharma Dr.nat.tech.; Aquatic Ecology Centre, P.O. Box: 6250, [email protected].
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Post Graduate Diploma in Environment Education
Unit 7 Principles pertaining to limiting factors
and ecological assessment for sustainability
Physical Factors of Importance as Limiting Factors
TEMPERATURE:
1. Life can exist only within
-200deg to 100 deg C.
2. Most species are
restricted to a narrower
range of temperature
3. Aquatic organisms have
narrower range of
tolerance than
equivalent land animals
4. Organisms which are subjected to temperature variations tend to
be depressed, inhibited or slowed down by constant temperature
Subodh Sharma Dr.nat.tech.; Aquatic Ecology Centre, P.O. Box: 6250, [email protected].
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Post Graduate Diploma in Environment Education
Unit 7 Principles pertaining to limiting factors
and ecological assessment for sustainability
Physical Factors of Importance as Limiting Factors
LIGHT:
The quality of light, the
intensity, and the duration
are known to be important
factors of light.
Both plants and animals
respond to different
quality of light.
Individual plants as well as
communities adapt to
different light intensities
by becoming ‘shadeadapted’. Or ‘sun adapted’.
Subodh Sharma Dr.nat.tech.; Aquatic Ecology Centre, P.O. Box: 6250, [email protected].
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Post Graduate Diploma in Environment Education
Unit 7 Principles pertaining to limiting factors
and ecological assessment for sustainability
Physical Factors of Importance as Limiting Factors
WATER:
Rainfall distribution over the year is an extremely important
limiting factor for organisms.
Humidity has a daily rhythm (high at night, low during the day),
and has special role in modifying the effects of temperature, hence
regulates the activities of organisms and in limiting their
distribution.
Evapo-transpiration is also an important limiting factor. Desert
plants expose only green buds or stems.
Dew , in areas of low rainfall, is a vital contributor to precipitation.
Subodh Sharma Dr.nat.tech.; Aquatic Ecology Centre, P.O. Box: 6250, [email protected].
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Post Graduate Diploma in Environment Education
Unit 7 Principles pertaining to limiting factors
and ecological assessment for sustainability
Physical Factors of Importance as Limiting Factors
ATMOSPHERIC GASES:
The concentration of carbon di-oxide an oxygen is limiting to
many higher plants.
BIOGENIC SALTS (MACRONUTRIENTS & MICRONUTRIENTS:
Nitrogen and phosphorous salts are of major importance to
ecologists as limiting factors.
CURRENTS & PRESSURES
Currents in water not only influence the concentration of gases
and nutrients, but act directly as limiting factors.
Subodh Sharma Dr.nat.tech.; Aquatic Ecology Centre, P.O. Box: 6250, [email protected].
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Characteristics of ecological
indicators
1. In general, steno species make much better indicators
than eury species.
Such species are often not the most abundant ones in the
community.
2. Large species usually make better indicators than small
species.
A large and more stable biomass and standing crop can be
supported with a given energy flow.
The turnover rate of small organisms may be so great that
the particular species present at any time may not be very
instructive as an ecological indicator.
Subodh Sharma Dr.nat.tech.; Aquatic Ecology Centre, P.O. Box: 6250, [email protected].
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Characteristics of ecological
indicators
3. Before relying on as single species or groups of species as
indicators, there should be abundant field evidence.
4. Numerical relationships between species, populations, and
whole communities often provide more reliable indicators
than single species.
Subodh Sharma Dr.nat.tech.; Aquatic Ecology Centre, P.O. Box: 6250, [email protected].
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If we love our children, we must love the country with tender care and pass it on, diverse
and beautiful, so that our children can hear a Danphe call in the Himal, feel peace in hills
and mountains with forest of Rhododendron, can watch a one horned Rhinoceros in Terai
and can find joy in being alive.
-Subodh Sharma
Subodh Sharma Dr.nat.tech.; Aquatic Ecology Centre, P.O. Box: 6250, [email protected].
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