xerosere

Ecological

succession on

a bare rockelk

Sere and seral community

• an intermediate stage found in an ecosystem advancing towards its climax community

• in many cases more than one seral stage evolves until climax conditions are attained

Screen clipping taken: 20-02-2013, 22:54

Bare rocks

The first form of life originates at such places which do not had life such as an island formed after a volcanic activity or a retreating glacier

Screen clipping taken: 20-02-2013, 23:45

crustose lichen stage

A lichen is an important pioneer

in primary succession

composed of a

photosynthesizing algae, and a

fungi absorbing nutrients from

rock and holds water.

Together they break down rock

Soil accumulates as dust

particles trapped in cracks in

rock

Lichens decompose providing

food for mosses

F o l i o s e l i c h e n s t a g e

They can absorb more water and

are able to accumulate more dust

particles. The shallow depressions

in the rocks become filled with sold

and topsoil layer increases further.

These autogenic changes favor

growth and establishment of

mosses.

Moss stage

As mosses develop in patches

they catch soil particles from the

air and help increase the

amount of substratum. The

changing environment leads to

migration of lichens and helps

invasion of herbaceous

vegetation that can out-compete

mosses.

Herbaceous weeds, mostly

annuals such as asters,

evening primroses, and

milk weeds, invade the

rock. Their roots penetrate

deep down, secrete acids

and enhance the process

of weathering. Leaf litter

and death of herbs add

humus to the soil

Herb stage

Shrub stageThe herb and grass mixture

is invaded by shrub

species, such as Rhus and

Phytocarpus. Early

invasion of shrub is

slow, but once a few

bushes have become

established, birds invade

the area and help disperse

scrub seeds.

Climax stageThe succession

culminates in a

climax

community, the

forest. Many

intermediate tree

stages develop

prior to

establishment of

a climax

community

thank youMade by:-Khursheed alam khan