Describe and use suitable methods to assess the distribution and abundance of organisms in an area, limited to frame quadrats, line transects, belt transects and mark-releaserecapture using the Lincoln index (the formula for the Lincoln index will be provided, as shown in the Mathematical requirements)

SouravNovember 1, 2024

Answer

Assessing the distribution and abundance of organisms in an area is essential for understanding biodiversity and ecosystem health. Several methods can be employed for this purpose, including frame quadrats, line transects, belt transects, and mark-release-recapture techniques using the Lincoln Index. Below is a description of each method along with its application.

1. Frame Quadrats

Description: Frame quadrats are square or rectangular plots of a defined size (e.g., 1m x 1m) used to sample a specific area of habitat. Researchers randomly place these quadrats within the study area to avoid bias.Application:

• Sampling Procedure:
  • Randomly select locations within the study area using a grid system or random number generator.
  • Place the quadrat at each selected location and record the species present along with their abundance.
• Data Analysis:
  • Calculate species frequency (the likelihood of a species being present in any quadrat) and density (the number of individuals per unit area).

This method is particularly useful for assessing plant communities or stationary organisms.

2. Line Transects

Description: A line transect involves laying out a straight line (often marked with tape) across the study area and sampling organisms along that line.Application:

• Sampling Procedure:
  • Lay a tape measure across the habitat.
  • Record all species encountered at set intervals along the line (e.g., every meter).
• Data Analysis:
  • Analyze species distribution patterns along the transect to understand how different species are distributed in relation to environmental gradients.

Line transects are effective for studying changes in species composition over distance, especially in habitats with gradients.

3. Belt Transects

Description: A belt transect is similar to a line transect but involves sampling a wider strip of habitat, allowing for more comprehensive data collection.Application:

• Sampling Procedure:
  • Establish two parallel lines (usually 1m apart) along which all organisms within the belt are recorded.
• Data Analysis:
  • Assess species abundance and diversity within the belt and compare it across different belts or habitats.

Belt transects are useful for capturing more detailed information about community structure and species interactions.

4. Mark-Release-Recapture Using the Lincoln Index

Description: This method estimates population size for mobile organisms by capturing, marking, and releasing individuals, then recapturing them after some time.

Steps:

1. Capture and Mark: Capture a sample of individuals from the population, mark them using a non-toxic method, and release them back into their habitat.
2. Recapture: After allowing sufficient time for mixing, capture another sample from the population.
3. Count Individuals: Record the total number of individuals captured in the second sample and note how many of those were marked.

Lincoln Index Formula:

The population size $N$ can be estimated using the formula:

N = n1 X n2/m2

Where:

• N = estimated total population size
• n1 = number of marked individuals in the first sample
• n2 = total number of individuals captured in the second sample
• m2 = number of marked individuals recaptured in the second sample

Example:

Suppose researchers initially capture and mark 100 butterflies (n1=100n1​=100). Later, they capture a second sample of 150 butterflies (n2=150n2​=150), which includes 30 that were previously marked (m2=30m2​=30). The estimated population size would be calculated as follows:

N = 100×150​/50 = 500

This indicates an estimated population size of 500 butterflies in that area.