Study the plant population density by quadrat method

Aim: To study the population density of plants by quadrat method.

Material/Apparatus Required:

• Fields
• Nails
• Meter scale
• Paper
• Thread
• Hammer

Principle:

Population: Population is defined as a group of individuals of the same species which inhabit a particular space at a particular time. The number of individuals in a population never remains constant. It may change (increase or decrease) due to many factors like birth rate, death rate and migration. Population density: It represent the number of individuals of the species in any unit area at specific time. The unit area may be small or large, depending on the size and nature of the plant community under study. Population density is calculated by counting all the individuals present at a given time in a given space, divided by the number of unit area of space.

It is calculated as follows:

Density (D) = Total no. of individuals of species in all the sampling unit(s) / Total no. of sampling unit studied(Q)

Quadrat method: Counting all the individuals in a population is the most accurate method to determine its size. However, this approach is not usually feasible, especially for large population or extensive habitats. Usually, plant population is calculated by quadrat method. A quadrat is a square that encloses an area within a habitat. For herbaceous plants, a meter square (1 m × 1 m) quadrat is normally used.

Procedure:

1. Select a field to study the population density of the plants.
2. Measure 1 meter x 1 meter area with the help of the meter scale in the field to make a quadrat.
3. Fix four nails at the corner of the quadrat and tie each end of the nail using a thread.
4. Similarly, make nine more quadrats randomly in the field of the study.
5. To make the counting easy, divide the quadrat further to make smaller squares.
6. Count and mention the number of plants of a particular species in a square and similarly mention the number of plants of another species if present.
7. Now, count and add the total number of a particular plant species of all the square to get the total number of a particular plant species of the quadrat.
8. Repeat the same experiment for the other quadrats also.
9. Record the data in the observation table.

Observation Table:

Result:

The population density of a plant species in a given fields can be calculated as:

Population density = Total number of plants in ten quadrats (1 m x 1 m) / 10

Precautions:

1. Measure the quadrant accurately.
2. Mark the quadrant close to each other from one field only
3. Do not damage the vegetation while laying the quadrants