powerpointthe natural vegetation of the earth

8/12/2019 POWERPOINTThe Natural Vegetation of the Earth

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The Natural

Vegetation of

the Earth


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The Ecology of Vegetation

1. Plant communities

Ecosystem - which is a set of biotic and abiotic

elements so related that together they form acomplex whole.

Plant community - is an assemblage of plantspecies in an area, existing in a systematicinteraction with one another and with theanimal life in the area.


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- Objective of Ecology

Is the study of life communities and theirinterrelationships with one another and with the

other components of the abiotic environment

- Plant species in a community or plant association

do not usually compete for energy and moisture

because each species has its own special niche orlevel in the community with its own energy and

moisture requirements.


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examples:

Low shrubs and herbs

mosses


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Steady state or stable ecosystem - in theprocess of arriving this state, should two

species compete for essential sustenance

in the same niche in a plant community.


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2. Biotic succession

- Are specifically called pl nt succession- Is a gradual sequence of changes of

phases in biotic communities in a certain

area over a period of time, even if climate

remains unchanged.


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- One plant community appears andthen gives way to another until a series of

replacements a stable community

predominates and there is no furtheralternation in its composition


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Pioneer community - a plant community(grass) that started the succession which is able

to colonize and inhabit a bare surface

Climax community

- the end product in the succession (oaky-

hickory forest)

- Most complex type of community which a

particular natural environment will support


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- Stable and able to maintain itself over

a long period of time

- It is also the efficient user of solar

energy and soil nutrients in the area


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The general trend in plant succession

Taller plants

More densityGreater stability


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Two (2) kinds of vegetative succession

Primary succession- occurs in places

that have not previously supported life

Secondary succession - Takes place on

areas where the original climax vegetation has

been destroyed or disturbed but where thesoil has been retained


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3. Formation types

- Another way of describing plant

communities over the earths surface is to

characterize them in terms of the form

elements of their assemblage


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The classification elements

a. Plant type - such as trees, shrubs, herbs and

grasses

b. Size such as tall or short trees and grasses

c. Leaf shape such as broadleaf or needle

leaf

d. Branching character such as high-

branching (like many trees) or low- branching

(like shrubs)


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e. Leaf behavior such as evergreen (with leaves

throughout the year) or deciduous (with leaves

falling off during dry period)

f. Horizontal density such as closely spaced or

widely spaced

g. Vertical alignment such as canopy- producing

tree crowns, or a second- story growth below the

tree crown, or undergrowth (on the ground)


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Factors Affecting the Distribution

of Vegetation

1.Climatic factors

- Is the most important environmental

element influencing the distribution of plantcommunities over the earths surface

Precipitation moisture is againthe most important influence in the

distributed of vegetation


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The three great formations of natural

vegetation

Forests Grassland

Desert

- Copious rainfall often gives rise to

forests

- Moderate rainfall or summer season

rainfall to grassland

- Scanty rainfall to desert plants


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Osmosis a process where water is taken is

mainly by plants at the roots

High temperature and low humidity favor

rapid loss of plant moisture

Low temperature and high humidity

inhibit its loss


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Xerophytes(Greek xeros = dry, phytos = plant)

- Plants that is structurallyadapted to very limited moisture budgets

Hydrophytes

( Greek hydro = water)- Vegetation that are adapted to very

humid environmental and have rarely any

defense against evaporation and moistureinsufficiency


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Mesophytesplant types that haveintermediate needs and tolerances for water

Halophytes(Greek halos = salt)

- Plants that have adapted to salty water

conditions, such as beach and mangrovevegetation

Temperature - ranks next toprecipitation in importance as aninfluencing factor in vegetativerowth


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Three (3) critical temperatures

1. Minimum or lower temperature below

which it will die

2. Maximum or upper temperature above which it will likely wilt or die

3. Optimum temperature at which it

thrives best


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Species that survived prolonged low

temperatures periods through seed

carryover

Annuals complete their life cycle

during warm season and their vegetativestructure perishes completely during the

cold season

Biennials species that need more thanone year to complete their cycle


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Perennialssurvive through contrastingtemperature regimes year after year

Temperature fall below 20 degreesCelsius throughout the year

- All of the above plants cannot

survived


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Solar energy plays a major role in the

regulation of the life cycle of plants

2. Topographic factors (landform)

- Specifically in terms of elevation and

slope, also affect the growth and distributionof plant communities


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3. Edaphic factors (soil)

- Do not have much influence as climate

in influencing regional plant distribution butthey may be significant locally

4. Biotic factors

- Lower forms of organisms have a

profound and pervasive effect on vegetativecommunities

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