Natural changes occur in organisms

1. Ecological Succession

2. What is Ecological Succession?
• Natural, gradual changes in the
types of species that live in an
area
• Can be primary or secondary
• The gradual replacement of one
plant community by another
through natural processes over
time

15. CAUSES OF SUCCESSION
1. Initial or Initiating causes
2. Ecesis or Continuing causes
3. Stabilizing causes

16. TRENDS OF SUCCESSION
• A continuous change occurs in the kinds of
plants and animals
• An increase in the diversity of species takes
place
• There is a progressive increase in the amount of
living biomass and dead organic matter
• Green pigment (Chlorophyll) go on increasing
during the early phase of primary succession
• The community respiration increases

17. • The food chain relationships become more
complex as succession proceeds
• The quality of the habitat gets progressively
modified to a more mesic condition
• The niche specialization increases
• The life cycle of mature community species
are longer and more complex

36. • 3. Autogenic succession
• 4. Allogenic succession
• 5. Autotrophic succession
• 6. Heterotrophic succession
• 7. Induced succession

37. • 1. Nudation: Development of a bare area
without any form of life.
• (i) Topographic. Due to soil erosion by gravity, water
or wind, the existing community may disappear.
Other topographic causes include deposition of sand,
landslide, volcanic activity and other factors.
• (ii) Climatic. Glaciers, dry period, hails and storm,
frost, fire, etc., may also destroy the community.
• (iii) Biotic. Man forms a most important biotic
factor; he is responsible for destruction of forests,
grasslands for industry, agriculture, housing, etc.
Other factors are disease epidemics due to fungi,
viruses, etc., which destroy the whole population.

38. 2. Invasion: Invasion is the successful
establishment of a species in a bare area
• (i) Migration (dispersal).
• (ii) Ecesis (establishment).
• (iii) Aggregation:
• Plants or autotrophic organisms which are the first
to colonize and aggregate are called pioneers. The
pioneer
• communities are likely to be more dynamic and
have low-nutrient requirements and to take
minerals in comparatively more complex forms.
They are small-sized and make less demand from
environment.

39. 3. Competition and Coaction
• Due to aggregation of a large number of
individuals of the species at the limited
place, there develops competition (i.e.,
interspecific and intraspecific competition)
for space and nutrition.
• Individuals of a species affect each other’s
life in various ways and this is called
coaction.

40. Climax Community
• A stable group of plants and animals that
is the end result of the succession process
• Does not always mean big trees
– Grasses in prairies
– Cacti in deserts

41. • Insects
• Nationwide, 70 million acres of public and private lands are
at serious risk from insects and diseases
• Across the South, one of the biggest forest management
challenges is the Southern Pine Beetle. Attacking timber
stands throughout the region, it is estimated that 57 million
acres are at risk of infestation. From 1999 to the present,
the Southern Pine Beetle outbreak has caused timber value
losses of over $1.5 billion.
Gypsy Moth, Lymantria dispar
(Linnaeus) female
Photo from USDA APHIS PPQ archives

42. • Diseases
• Forest pests and disease have seriously harmed the environment and have imposed
significant cost to the U.S. economy. Exotic pests and pathogens, such as the
chestnut blight, Dutch elm disease, and beech bark disease have had a profound
effect on Eastern forests.
• Management of these pests and diseases has been impacted by a variety of factors
such as forest fragmentation, increasing human population, and the expansion of
invasive species.
• Prompt identification and treatment of forest diseases often means the difference
between losing or saving a valuable forest stand.
Annosum Root Disease

43. • Invasive Plants
• Invasive species have been characterized as a “catastrophic wildfire
in slow motion.” Thousands of nonnative invasive plants have
infested millions of acres of land and water across the Nation.
• These invaders cause massive disruptions in ecosystems by
reducing biodiversity and degrading the health of our nation’s
forests, prairies, mountains, wetlands, rivers, and oceans. They
have the capacity to dominate, overwhelm, or wipe out native
species.
• The financial impact from invasive species infestations in the United
States has been estimated at $138 billion per year in total economic
damages and associated control costs.
Congongrass Kudzu

55. Thank You