Xerosere: Plant Succession in Dry Environments
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Xerarch succession of ecological communities
originated in extremely dry situation such as sand
deserts
, sand dunes, salt deserts, rock deserts etc
B
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k
s
Bare rocks are produced
when
glaciers
recede or
volcanoes
erupt. Erosion
of these rocks is brought
by rain water and wind
loaded with soil particles.
lichen
, which act as
pioneer species of bare
rocks.
Crustose lichen stage
A bare rock consists of solid surface or very large
boulders and there is no place for rooting plants to
colonize. The
thalli
of
crustose
lichens
can adhere
to the surface of rock and absorb moisture from
atmosphere; therefore, these colonize the bare
surfaces of rocks first
These lichens produce acids which corrode
the rock
When these lichens die their thalli are
decomposed to add humus. This promotes
soil building and the environment becomes
suitable for growth of foliose and fruticose
type of lichens.
Foliose and fruticose lichen stage
Foliose
lichens
have leaf-like
thalli, while the
fruticose
lichens
are like small
bushes. They are
attached to the
substratum at one
point only,
therefore, do not
cover the soil
completely.
They can absorb and retain more water and are able to
accumulate more dust particles.
Their dead remains are decomposed to humus which
mixes with soil particles and help building substratum
and improving soil moisture contents further.
These autogenic changes favor growth and
establishment of mosses.
Moss stage
The
spores
of xerophytic mosses, such as
Polytrichum
,
Tortula
, and
Grimmia
, are brought to the rock where they
succeed lichens.
Their
rhizoids
penetrate soil among the crevices, secrete
acids and corrode the rocks.
The bodies of mosses are rich in organic and inorganic
compounds.
The changing environment leads to migration of lichens and
helps invasion of herbaceous vegetation that can out-
compete mosses.
Herb stage
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.
xeric conditions begin to change and
biennial
and
perennial
herbs and xeric
grasses such as
Aristida
,
Festuca
, and
Poa
,
begin to inhabit.
These climatic conditions favor growth of
bacterial and fungal populations, resulting in
increase in decomposition activity.
Shrub stage
The 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.
This results in dense scrub growth shading
the soil and making conditions unfavorable
for the growth of herbs,
Tree stage
Change in environment favors colonization of
tree species. The tree saplings begin to grow
among the scrubs and establish themselves.
The kind of tree species inhabiting the area
depends upon the nature of the soil.
The trees form canopy and shade the area.
Shade-loving scrubs continue to grow as
secondary vegetation.
Leaf litter and decaying roots weather the
soil further and add humus to it making the
habitat more favorable for growth to trees.
Climax stage
The succession culminates in a climax community, the forest.
Many intermediate tree stages develop prior to establishment
of a climax community.
The forest type depends upon climatic conditions.
Xerosere is a plant succession process limited by water availability, starting from bare rocks and advancing through stages of lichen colonization to moss growth. This ecological progression, initiated in dry environments like deserts and rock formations, demonstrates how plant communities establish and evolve over time in challenging conditions.
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Presentation Transcript
XEROSERE XEROSERE
Xerosere Xerosere Xerosere is a plant succession which is limited by water availability. Xerarch succession of originated in extremely dry situation such as sand deserts, sand dunes, salt deserts, rock deserts etc ecological communities
Bare rocks Bare rocks are produced when glaciers recede or volcanoes erupt. Erosion of these rocks is brought by rain water and wind loaded with soil particles. lichen, pioneer species of bare rocks. which act as
Crustose Crustose lichen stage lichen stage A bare rock consists of solid surface or very large boulders and there is no place for rooting plants to colonize. The thalli of crustose lichens can adhere to the surface of rock and absorb moisture from atmosphere; therefore, these colonize the bare surfaces of rocks first
These lichens produce acids which corrode the rock When these lichens die their thalli are decomposed to add humus. This promotes soil building and the environment becomes suitable for growth of foliose and fruticose type of lichens.
Foliose and Foliose and fruticose fruticose lichen stage lichen stage Foliose have thalli, fruticose are bushes. They are attached substratum at one point therefore, do not cover completely. lichens leaf-like while lichens like the small to the only, the soil
They can absorb and retain more water and are able to accumulate more dust particles. Their dead remains are decomposed to humus which mixes with soil particles and help building substratum and improving soil moisture contents further. These autogenic changes establishment of mosses. favor growth and
Moss stage Moss stage The spores of xerophytic mosses, such as Polytrichum, Tortula, and Grimmia, are brought to the rock where they succeed lichens. Their rhizoids penetrate soil among the crevices, secrete acids and corrode the rocks. The bodies of mosses are rich in organic and inorganic compounds. The changing environment leads to migration of lichens and helps invasion of herbaceous vegetation that can out- compete mosses.
Herb stage Herb stage 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.
xeric conditions begin to change and biennial and perennial herbs and xeric grasses such as Aristida, Festuca, and Poa, begin to inhabit. These climatic conditions favor growth of bacterial and fungal populations, resulting in increase in decomposition activity.
Shrub stage Shrub stage The herb and grass mixture is invaded by shrub species, such Phytocarpus. Early invasion of shrub is slow, but once a few bushes have become established, birds invade the area and help disperse scrub seeds. This results in dense scrub growth shading the soil and making conditions unfavorable for the growth of herbs, as Rhus and
Tree stage Tree stage Change in environment favors colonization of tree species. The tree saplings begin to grow among the scrubs and establish themselves.
The kind of tree species inhabiting the area depends upon the nature of the soil. The trees form canopy and shade the area. Shade-loving scrubs continue to grow as secondary vegetation. Leaf litter and decaying roots weather the soil further and add humus to it making the habitat more favorable for growth to trees.
Climax stage Climax stage The succession culminates in a climax community, the forest. Many intermediate tree stages develop prior to establishment of a climax community. The forest type depends upon climatic conditions.
