RETROGRESSIVE CHANGES, CONCEPT OF CLIMAX COMMUNITIES AND RESILIENCE OF COMMUNITIES.pptx

1. RETROGRESSIVE CHANGES, CONCEPT OF CLIMAX
COMMUNITIES AND RESILIENCE OF COMMUNITIES
SUBMITTED TO,
DR. AGHIL SOORYA
DEPARTMENT OF
BOTANY
SUBMITTED BY,
HASNIYA.K.M
ROLL NO. :09
II MSc BOTANY

2. INTRODUCTION
• Ecological succession is the steady and gradual change in a species of a given area
with respect to the changing environment.
• It is a predictable change and is an inevitable process of nature as all the biotic
components have to keep up with the changes in our environment.
• These changes lead finally to the equilibrium of the community with the
environment called a climax community. Climate community marks the endpoint
of succession.
• An intermediate stage in the successional process towards the climax community
is known as seral community and the temporary stage is called the seral stage.

3. Progressive Succession:
Progressive succession is a succession where the community becomes
complex and contains more species and biomass over time.
Retrogressive Succession:
Retrogressive succession is a succession where the community becomes
simplest and contains minimum or fewer species and less biomass over
time.

5. Retrogressive changes
• It is a type of succession in which the
community becomes more simplistic and
contains fewer species and less biomass over
time.
• In certain cases, a situation occurs in which a
community depreciate and a new simpler
community develops.
• Some retrogressive succession is allogenic in
nature.
• For example, introduction of grazing animals
into grassland resulting in degenerated
rangeland.

6. When the depletion of glaciers occurred on
the slopes and flat terrains in Alaska,
succession proceeds from the formation of
simpler community to complex communities
(herb and shrub stage) and finally reaches to
climax community, the spruce forest.
Along with spruce tree, some mosses and
small trees were also found in the forest. But
during the course of time there was sudden
invasion of sphagnum mosses. It has the
ability to hold large amount of water. As a
result it absorbed large amount of water
from the soil and leads to death of spruce
tree.
Another example:
Pedersen Glacier, Alaska, ~1930s and
2005

7. The spruce beetle is a bark beetle that attacks the White spruce trees in Interior
Alaska. Of all the insects that affect spruce in Alaska, the spruce beetle causes
the most damage.
Spruce beetle-killed trees in Alaska
Spruce trees in Alaska

8. Climax or stable community
• Climax community (Clements 1916) is the more or
less stable final stage of ecological succession. It is
almost self perpetuating, and is in equilibrium
with the physical environment so long as the
environment remains unperturbed.
• Climax community is in steady-state or dynamic
equilibrium because its net annual organic
production, energy level, and density of
populations are kept almost constant.
• The annual production and input of organic matter
will be counterbalanced by consumption and
output. So, there is no net accumulation of organic
matter and energy.

9. Forest Desert
Grassland Coral reef

10. Climax community cont..
According to Clements, climax has the following three principle characteristics:
(a) Unity:
Climax is a unit. All
the species are taken
as an organised unit
to show the climate.
In other words,
climax is a unit,
which acts as the
index of climate of
an area.
(b) Stability:
The form of the climax
community is stable with
the climate. The climax
community cannot be
replaced through
competition.
(c) Origin and Organism
Concept:
Climax community is
interpreted as a super
organism. This community takes
birth, grows and develops like
an organism. Climax
communities undergo changes
with the changes of time and
climate.

11. Characteristics of climax community
• Climax communities maintain species diversity for an extended period.
• They contain multiple specialized ecological niches.
• They maintain high levels of organism interactions.
• Climax communities recycle nutrients while maintaining a relatively constant
biomass.
• They can withstand a lot of environmental stress.
• They have a lot of species diversity, and energy is transferred through
complicated food webs rather than simple food chains.
• Organisms in the climax stage are replaced by organisms that are similar to them.
As a result, the balance of species is maintained.

12. Types of climax community
(1) Climatic climax
• A climatic climax exists when there is only one climax,
and the location’s climate influences the climax
community’s development.
• For example, the growth of a Maple-beech climax
community in moist soil.
(2) Edaphic Climax
• When a location has many climax communities, each of
which is influenced by local substrate circumstances
such as soil moisture, soil nutrients, terrain, slope
exposure, fire, and animal activity, the term “edaphic
climax” is used.

13. (3)Catastrophic Climax
• Climax vegetation is vulnerable to catastrophic occurrences,
such as wildfire Chaparral vegetation.
• For example, is the ultimate vegetation in California.
(4) Disclimax (disturbance climax) or Anthropogenic Subclimax
• When a man or his domestic animals maintain a stable
community that is not the climatic or edaphic climax for the
particular place, it is referred to as disclimax (disturbance
climax) or anthropogenic sub climax (man-generated).
• Overgrazing by livestock, for example, could result in a desert
community of bushes and cacti where the local climate would
allow grassland to thrive.

14. (5) Preclimax and post climax community
• Preclimax describes a society with life forms that are lower than those found in the
projected climatic climax. In contrast, post- climax describes one with higher life
forms than those in the expected climatic climax.
• Preclimax strips form in less moist and hotter locations than the surrounding
climate, whereas postclimax strands form in more moist and colder areas.
Pre climax Post climax

15. There are three theories about the climax community.
(a) Mono-climax theory
(b) Poly-climax theory
(c) Climax-pattern hypothesis

16. (a) Monoclimax theory
• Federic Clements created the monoclimax (or climatic climax) theory.
• According to the mono climax theory of succession, each region has a single
climax community toward which all other assemblies are progressing.
• The area climate determines the climax. Differences in topography, soil parent
material, biotic component, and other factors are overcome through succession
and environmental modification processes.
• A uniform plant community would cover the entire area.
• Subordinate communities are the communities that exist in that area in addition
to the climax community.
• Pro-climax, post-climax, pre-climax, sub-climax, and disclimax are subordinate
communities.

17. (b) Theory of Polyclimax
• Tansley (1939) proposed this theory, which was later backed up by Daubenmire
(1966).
• According to the hypothesis, a region’s climax vegetation comprises a mosaic of
vegetation climaxes influenced by soil moisture, soil nutrients, terrain, slope
exposure, fire, and animal activity.
• According to the poly climax theory, many forms of vegetation known as climax
communities can be found in a particular location, each of which is influenced by
factors other than the local climatic conditions.
• So, depending on the nature of the element in stabilization, the climax stages
may be labeled topographic climax, biotic climax, edaphic climax, fire climax so
on.

18. (c) The climax pattern theory
• The climax pattern theory, developed by R.H. Whittaker (1953), is a version of the
poly climax idea.
• A natural community is adapted to the entire pattern of environmental factors in
which it exists, according to Whittaker (1953); the significant factors are the
genetic structure of each species, climate, site, soil, biotic factors (animal
activity), fire, and wind, availability of plant and animal species, and dispersal
chances.
• According to this hypothesis, Climax communities are patterns of populations
that fluctuate depending on the overall environment.
• As a result, there is no fixed number of climax communities, and no one element
affects a climax community’s structure stability.

19. Resilience of community
• Community resilience is the sustained ability of a community to use available
resources (energy, communication, transportation, food, etc.) to respond to,
withstand, and recover from adverse situations.
• This allows for the adaptation and growth of a community after disaster strikes.
• Communities that are resilient are able to minimize any disaster, making the
return to normal life as effortless as possible.
• A stressor may be caused by natural disturbances or human impacts
(anthropogenic stressors) that affect the environment.

20. Some examples of factors like natural disturbances and human impacts that
cause disturbances to ecosystems include:

21. Key factors of community resilience:
1. Biodiversity: High species diversity tends to increase the resilience of both plant
and animal communities. In diverse ecosystems, there is a greater chance that
some species can adapt or thrive even when conditions change.
2. Keystone Species: Certain species in both plant and animal communities can
have a disproportionately large impact. These “keystone species” can significantly
influence the community’s structure and function. Their presence often enhances
resilience.
3. Habitat Connectivity: The connectivity of habitats is essential for the movement
and migration of species. It allows them to find new areas to inhabit or resources to
exploit when conditions change. This is crucial for resilience, especially in the face
of climate change.

22. 4. Ecosystem Health: The overall health of the ecosystem, including factors like
water quality, soil quality, and climate stability, affects the resilience of both plant
and animal communities. Healthy ecosystems are better at absorbing shocks.
5. Adaptive Capacity: The ability of individual species within a community to adapt
to changing conditions is vital for resilience. Some species may possess traits or
behaviors that enable them to survive and reproduce in a new environment.
6. Human Impact: Human activities, such as habitat destruction and pollution, can
reduce the resilience of plant and animal communities. Conservation efforts aim to
mitigate these impacts and increase resilience through restoration and protection.

23. Examples:
In the plant kingdom, an example of community
resilience can be observed in a forest ecosystem
after a wildfire. While individual trees may be
damaged or destroyed, the forest as a whole often
exhibits resilience. Some tree species have
adapted to survive and even thrive in fire-prone
environments.
Additionally, the remaining plants and shrubs can
help prevent soil erosion, and their seeds can
quickly germinate and regrow, gradually restoring
the forest ecosystem. This demonstrates how plant
communities adapt and recover collectively in the
face of natural disturbances.

24. Examples:
An example of community resilience in the
animal kingdom is seen in honeybee colonies.
When a hive faces. Challenges such as disease,
predators, or harsh environmental conditions,
worker bees cooperate to protect and repair the
hive. They adapt to changing circumstances by
adjusting their behavior and resources, ensuring
the survival and vitality of the entire colony. This
demonstrates how animal communities can
exhibit resilience in the face of various
challenges.

25. Examples:
One example of community resilience is how a
neighborhood comes together after a natural
disaster, such as a hurricane. Residents may
collaborate to help each other evacuate, provide
shelter, share resources, and support one
another during the recovery process. This
demonstrates the strength and resilience of the
community in the face of adversity.

26. Reference
1. Mishra, D.D. (2008). Fundamental Concepts in Environmental
Studies. S.Chand & Company Pvt Ltd.
2. Sharma, P.D., & Sharma, P.D. (2012). Ecology and Environment.
Rastogi Publications.
3. Smith, T.M., & Smith, R.L. (2006). Elements of Ecology, 6th edn.
4. https://www.turito.com/learn/biology/concept-of-climax-
community.

27. Thankyou