Altitude, Latitude and Soil - Ecosystem, Class 12, biology Notes - Class 12

ALTITUDE AND LATITUDE

Altitude                                                        

Height above the sea surface of any place.

Latitude

The distance of any place from the equator

On the basis of variation in mean temperature along latitude the main climatic regions are

(1) Tropical = 00 – 200 latitude

(2) Subtropical = 200 – 400 latitude

(3) Temperate = 400 – 600 latitude

(4) Arctic and antarctic = 600 – 800 latitude

Note :

•  The temperature and light values are maximum at the equator, decreases gradually towards the pole.

Effect of altitude and latitude are almost same on temperature.

•  The types of vegetation from sea level to measuring altitudes are similar to increasing latitude (distance from equator)

SOIL OR EDAPHIC FACTOR

On the basis of the soil condition there are seven ecological group of plant w Halophytes – Plants grow in saline soils

•  Psamophytes – Plants grow in sand

•  Lithophytes – Plants grow on rock surface

•  Chasmophytes – Plants grow in rock crevices

•  Chersophytes – Plant grow in waste land

•  Eremophytes – Plant grow in dry area

•  Cryophytes or Psychrophytes – Plant grow in low temperature or cold

Soil – Soil is the uppermost layer of earths crust formed by weathering of rocks. It is the mixture of living or non living materials.

Minerals 45% + Water 25% + Air 25% + Organic matter (living + non living) 5% Soil formation is slow process 1 inch soil is formed in 500-1000 years Pedogenesis – development of soil or soil formation

Pedology(Edaphology) – study of soil

Soil mineral matter – As a result of weathering the mineral particles of different size are formed. The soil is divided into five types on the basis ofsize of soil particles.

Note : Loam Soil is thebest soil for growing of crops, it has high water holding capacity, high aeration and high root penetration.

SOIL ORGANIC MATTER

The dead organic matter present in soil is called humus, which is formed by decomposition of plant and animal remains. Freshly fallen plant and animal material called detritus or litter, partially decomposed litter is called duff. Fully decomposed litter is called humus.

Litter → Duff → Humus

Decomposition (Formation of Humas) : Decomposers break down complex organic matter into inorganic substances like carbon dioxide, water and nutrients and the process is called decomposition.Dead plant remains such as leaves, bark, flowers and dead remains of animals, including fecal matter, constitute detritus, which is the raw material for decomposition. The important steps in the process of decomposition are fragmentation, leaching, catabolism humification and mineralisation.

Detritivores (e.g.earthworm) break down detritus into smaller particles. This process is called fragmentation. By the process of leaching, water soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts. Bacterial and fungal enzymes degrade detritus into semple inorganic substances, This process is called as catabolism.

It is important to note that all the above steps in decomposition operate simultaneously on the detritus.

Humification and mineralisation occur during decomposition in the soil. Humification leads to accumulation of a dark coloured amorphous substance called humus that is highly resistant to microbial action and undergoes

decomposition at an extremely slow rate. Being colloidal in nature it serves as a reservoir of nutrients. The humus is further degraded by some microbes and release of inorganic nutrients occur by the process known as mineralisation.

Decomposition is largely an oxygen-requiring process. The rate of decomposition is controlled by chemical composition of detritus and climatic factors. In a particular climatic condition, decomposition rate is slower ifdetritus is rich in lignin and chitin, and quicker, if detritus is rich in nitrogen and water-soluble substances like sugars. Temperature and soil moisture are the most important climatic factors that regulate decomposition though their effects on the activities of soil microbes. Warm and moist enviroment favour decomposition wheres low temperature and an anaerobiosis inhibit decompositon resulting in build up of organic materials.
 

Two types of Humus –

(i) Mor (Coarse terxtured humus) – It is raw humus and is formed in acidic soil (PH - 3.8 – 4.0) in which decomposition of litter is slow because it has less number of decomposer organism.

(ii) Mull – This is completely decomposed litter i.e. humus because rate of decomposition is fast due to high PH of soil.

SOIL WATER
It is of three types Holard– The total amount of water present in the land is called holard.

• Hygroscopic water – A thin layer of water attached tightly to soil particles due to forces of cohesion or adhesion. This is non available to plant.
• Gravitational water – The water that moves downwards due to gravity, it is non available to plant.
• Capillary water – Inter particle spaces or porous spaces act as minute capillaries and some amount of water is present in these capillaries due to surface tension, This is capillary water. It is the only form of soil water which is available to.plant.
• Combined water – The water which is present as hydroxides of iron, aluminium silicon, etc. is called combined water.

Some Terminology :

1. Field capacity – When soil holds all the water except gravitational water, it is known as field capacity. It is upper limit of water availability.

Field capacity = Holard – Gravitational water,

               or

Field capacity = Capillary water   +   Hygroscopic water  +  Combined water

2. Water holding capacity  (Storage capacity) – W.H.C. = Holard – (Hygroscopic water + Combined water + Gravitational water)

3. Wilting point : The lower limit of water availability of a soil is called wilting point.

Note :

1. The water potential of soil at field capacity is (–0.01 Mpa) [Mpa = Mega pascal]
2. The water potential of soil at wilting point is (–1.5 Mpa)
3. Amount of water in soil measured by tensiometer.

SOIL PROFILE

Note : A Horizon  +  B  Horizon = Solum

Type of soil on the basis of the mode of their formation –

(1) Residual soil – The soil in which soil formation i.e., weathering and pedogenesis, occurs at same place.

(2) Transported soil – Soil in which weathering process occurs at one place and pedogenesis occurs at another place.

(a) Colluvial soil → It is brought by gravity.

(b) Alluvial soil → It is brought through water, it is highly fertile soil.

(c) Glacial soil → Soil is brought by ice.

(d) Eolian soil → This soil is brought through wind.

SOME TERMINOLOGY RELATED TO SOIL:

In thetropical area due to high temperature, high rainfall, litter is decomposed very rapidly in A layer. Due to mineralization of litterAl and Fe are liberated in the upper layer (A - layer) of soil, colour of this soil becomes redish-brown, this process is known as laterization.

PODSOLIZATION :
In temperate area temperature is low and high humidity occurs. Humus and minerals contents dissolve and percolate with water and are leached from A layer to B layer. Due to loss of chemicals the colour of soil of A layer (horizon) turns tolight ashcolour. This process is known as podsolization and soil is known as podosols.

GLEIZATION :
Intundra region due to low temperature and humid condition humus is formed in less quantity and moves slowly in B layer. So colour of B layer becomes blue – grey due to deposition of Fe salt. This process is known as gleization and soil is known as gleys.

Note :

• Best pH of the soil for cultivation of plant is 5.5 – 6.5
• Excess water produces salinity problem in soil.
• Calcifuge plants → Those plants which can grow in little amount of calcium in soil (pH – 3.8 to 4.0) e.g. Rhododendron, Rumax etc.
• Calcarious soil → Soil having excess of calcium carbonate.
• Alkaline soil can be corrected by adding gypsum (CaSO₄) and heavy irrigation whereas acidic soil can be corrected by adding lime Ca(OH)₂
• Availability of nutrients from the soil is related with pH of soil.

Note :

• Black cotton – Soil of Maharashtra are commonly known as regur soil
• Sierozen – Light coloured soil of arid region
• Bog soil – Soil of marshes and swamps
• Solnetz/Solansltz – Black alkaline soil
• Peat soil – In which 90% humus in present.
• Solonchak – White alkaline & Saline soil

OTHER ABIOTIC COMPONENT

1. Precipitation – It is a source of soil water. The hydrological cycle is the movement of water between earth, air and atmosphere.

Forms of precipitation –

(i) Drizzle – Minute drops of water floating in air
(ii) Rain – Large drops of water
(iii) Snow – Water in solid form
(iv) Sleet – Ice in minute granular from
(v) Hails – Large balls of ice

2. Humidity – Atmospheric moisture in the form of invisible vapour is known as humidity. It is expressed in terms of relative humidity.
Relative humidity – The amount of moisture in air as percentage of the amount which the air can hold at saturation at the existing temperature.
If temperature ­   RH
 

Note :

• R.H. is measured by Psychrometer
• Wind speed is measured with the help of anemometer.

3. Topography – It includes the physical features of the earth like altitude, slope, exposure, mountain chains valleys plants. It affects distribution of organism by influencing the climatic factor like light, wind, rainfall etc.