Download Succession

Ecological Succession
Ecological Succession
• Ecological Secession – is a process in which
communities of an ecosystem change over
time.
– Ex. - A farms pasture if let unmaintained can over
years turn into wildflowers, weeds and small
shrubs.
– After more years it may become a lot full of young tress and
shrubs
Stages of Succession
• Primary Succession – occurs in places where an
ecosystem has never existed.
– Ex. Barren volcanic island, seeds washed ashore or carried by the wind
reached the island and resulted in the the first plants taking root on
the island.
Succession
• The stages of succession follow a certain pattern.
– Species that appear in the earliest stages ( pioneer
species) are tend to be smaller, grow faster, require
fewer resources and thrive in an environment where
these is little competition from other species.
• Pioneer species
– Hardy species
– First to establish itself at the start of the
process of succession
– Often include mosses and lichens
Bryum capillare
Lichens
• Pioneer Species prepare the way for others
species to come.
– Pioneer community colonizes as area on a bare
rock, then will break down the rock to form soil.
• Then other new species begin to take hold in the area
– This causes the new species to compete with and push out
the pioneer species. This continues the process of succession.
• Each stages causes competition among species causing
a change in the dominant community in the area.
Stage 1
Later Stages
• Larger, slower growing species replace the earlier, faster
growing species.
• These species live longer, reproduce many times during their
lifetime.
– This gives them an advantage over species that were dominant in earlier
stages.
Climax Community
• Climax Community
• Last stage of Succession
• If undisturbed by natural disasters (floods, fire) or by
human activity it will stay the same.
Secondary Succession
• Secondary Succession – is the process that
begins in an ecosystem when something has
disturbed or destroyed the natural
community.
– Examples
•
•
•
•
•
Abandon farmlands
Burned or cut forests
Heavily polluted streams
Areas that have been flooded
Heavily mined areas ( Occurs in many areas in PA)
Stage 1 of Secondary Succession
• Stage 1 – After the area has been destroyed
quick growing annual weeds cover the area
Annual Weed
and plants
Stage 1
Stage 2 of Succession
• Stage 2 – Perennial weeds and grasses take
hold among the annual weeds, eventually
crowding most of them out.
• Perennials are plants that die in winter and grow back in spring
Perennials
weeds and
grasses
Stage 3 of Succession
• Stage 3 – Shrubs dominate the ecosystem. The
perennials paved the way for the shrubs,
which were able to out compete the smaller
plants.
Stage 4 of Succession
• Stage 4 – is dominated by pine. Pine dominated because
they shade and deprive the shrubs of sunlight. Also, they
spread their seeds more effectively then shrubs.
Young pine
forest
Stage 5 of Succession
• Stage 5 – pines are crowed out and oak-hickory forest is dominant. These
trees make up the dominant species of the climax community and will
remain dominate unless some natural or human disturbances disrupts the
ecosystem.
Mature
Oak-hickory forest
(Climax Community)
Annual Weed
and plants
1
Perennials
weeds and
grasses
2
3
Young pine
forest
Mature
Oak-hickory forest
(Climax Community)
4
5