Chapter 6 Practical 2
Aim:
To determine the presence and location of plant species in a given study area using the quadrat sampling method.
Principle:
To study an entire ecosystem is often impractical due to its size. Therefore, ecologists use sampling techniques to estimate species distribution and abundance. A quadrat is a square frame of a known area (e.g., 1m x 1m) that is placed randomly on the ground. By counting the individuals of a target species within multiple quadrats, we can estimate its presence and location across the larger study area. This method is particularly effective for sessile (non-moving) organisms like plants, grasses, and lichens.
Materials Required:
Quadrats: Four 1-meter-long sticks or pre-made square frames (1m² area).
Measuring Tape: A long tape (at least 20m) to measure the study area and plot transects.
Rope & Stakes: To mark the boundaries of the study area (optional but recommended).
Notebook and Pencil: For recording data.
Camera or Smartphone: To photograph species for identification (optional).
Field Guide: A local plant identification guide or a mobile app like iNaturalist/Google Lens.
Data Sheet: Pre-prepared for efficient recording.
Procedure:
Step 1: Define the Study Area and Objective
Select a clearly defined area (e.g., a 20m x 20m grassland patch, a section of the college lawn, or a forest floor).
Define your objective: For this practical, our objective is to determine the presence and location of a common species, e.g., "White Clover" (Trifolium repens) or "Dandelion" (Taraxacum officinale). Choose a species that is easily identifiable and present in the area.
Step 2: Lay Out a Transect
To ensure systematic sampling across the entire area, we will use a "Line Transect" method.
Use the measuring tape and stakes to stretch a long rope in a straight line across the longest part of your study area (e.g., 20m). This is your transect line.
Step 3: Quadrat Placement (Systematic Sampling)
Place your quadrat (1m² frame) at regular intervals along the transect line (e.g., every 5 meters). This ensures you sample different potential micro-habitats (shaded, sunny, wet, dry).
For a 20m transect, you will have 4 sampling points: at 0m, 5m, 10m, and 15m.
Step 4: Data Collection
At each quadrat placement (Q1, Q2, Q3, Q4), record the following:
Quadrat Number/Location (e.g., Q1 at 0m)
Presence/Absence: Does the target species (e.g., White Clover) exist within the quadrat? (Yes/No)
Abundance (Count): If present, count the number of individual plants of the target species.
% Cover: Estimate the percentage of the quadrat area covered by the target species. This is useful for grasses and clovers that spread.
Environmental Notes: Briefly note the conditions (e.g., "full sun," "shaded under tree," "near water puddle," "compact soil"). This helps explain the species' location.
Step 5: Mapping the Location
On a blank page in your notebook, draw a simple map of your study area.
Mark the transect line and the points where you placed your quadrats (Q1 to Q4).
For each point, mark:
A green dot if the species was present.
A red dot if the species was absent.
This visual map clearly shows the locations where the species is found.
Observations:
1. Study Area Details:
Date: 12-10-2023
Time: 11:00 AM
Location: College North Lawn
Weather Conditions: Sunny, slight breeze
Target Species: White Clover (Trifolium repens)
Size of Study Area: 20m x 20m
Transect Length: 20m
Quadrat Size: 1m x 1m (1m²)
Number of Quadrats Sampled: 4
2. Data Table:
| Quadrat | Position on Transect | Presence/Absence of Target Species | Number of Individuals | % Cover | Environmental Notes |
|---|---|---|---|---|---|
| Q1 | 0m (Edge) | Present ✅ | 8 | 15% | Full sun, well-drained soil |
| Q2 | 5m | Absent ❌ | 0 | 0% | Shaded by large tree, dry soil |
| Q3 | 10m | Present ✅ | 12 | 25% | Full sun, moist soil |
| Q4 | 15m | Present ✅ | 5 | 10% | Partial sun, slightly compact soil |
3. Map of Species Location:
(A simple hand-drawn sketch would go here)
[North]
Q4 (P)
|
Q1 (P)---Transect Line---Q2 (A)
|
Q3 (P) P = Present, A = Absent
Calculations:
Frequency of Occurrence: (Number of quadrats where species is present / Total number of quadrats) x 100
= (3 / 4) x 100 = 75%
This means White Clover was found in 75% of the samples, indicating it is widespread in this area.
Result:
The target species, White Clover (Trifolium repens), was found to be present in 3 out of 4 quadrats sampled, giving a frequency of occurrence of 75%. Its location is primarily in sunny, open areas of the lawn and is absent in the deeply shaded, dry area under the large tree (Q2).
Discussion:
The results show that White Clover is not randomly distributed but is located in areas with sufficient sunlight and moisture.
Its absence in Q2 is likely due to shade and competition from tree roots, which create a different micro-habitat.
Limitations:
The sample size (4 quadrats) is small. A more accurate study would use 10+ quadrats.
The results are for one point in time. Seasonal changes would affect the presence and abundance of the species.
This method is a simple yet powerful tool for ecologists to quickly assess the distribution of a species without surveying the entire area.
Conclusion:
The quadrat method along a transect is an effective way to determine and map the location of a plant species in a given study area. It revealed that the distribution of White Clover in the college lawn is influenced by sunlight availability and soil conditions.
Viva Voce Questions:
- Why did we use a quadrat?
- To obtain a quantitative, representative sample of a large area efficiently.
- What does 'frequency of occurrence' tell us?
- It indicates how common or widespread a species is within the study area.
3. How would you study the location of animal species?
For mobile animals, different methods are used, such as point counts for birds, pitfall traps for insects, or camera traps for mammals
4. What is a micro-habitat
A small, specific habitat within a larger one that has unique conditions (e.g., under a rock, a rotting log, or at the base of a tree)
5.Name one other method to study species distribution.
1. Direct Field Surveys:
These involve physically searching for and recording species. They are hands-on
and provide immediate, verifiable data.
- Transects: A straight line is drawn through the study area. The observer walks along this line and records all occurrences of the target species. This is excellent for estimating population density and distribution patterns across an environmental gradient.
- Quadrat Sampling: A square frame of a known area (e.g., 1m x 1m) is placed at random or systematic points. All species within the frame are counted and identified. This is the gold standard for studying sessile organisms like plants, lichens, and corals.
- Camera Traps: Motion-sensor cameras are placed strategically. They provide passive, 24/7 monitoring without human disturbance, making them ideal for documenting elusive, nocturnal, or wary mammal species.
2. Remote Sensing & Tracking Technology:
These methods are used for studying mobile species over large areas.
- GPS Tracking: A GPS collar or tag is attached to an animal. It records location coordinates at pre-set intervals, providing highly accurate data on movement, home range, and migration routes. Data can be retrieved via satellite (remote download) or by recapturing the animal.
- VHF Radio Telemetry: An animal is fitted with a radio transmitter that emits a unique signal. A researcher uses a handheld receiver and antenna to "triangulate" the animal's location by finding the direction of the strongest signal. It is reliable and often has a longer battery life than GPS but requires more field effort.
- Geographic Information Systems (GIS): This is a software-based tool for analyzing spatial data. Species location points (from GPS, transects, etc.) are plotted on digital maps layered with other information (elevation, vegetation, water sources) to create species distribution models and analyze habitat preferences.
3. Environmental DNA (eDNA):
This is a cutting-edge, non-invasive method that detects species from the
genetic material they shed into their environment (e.g., skin cells, mucus,
waste in water, soil, or air).
- Sampling: Environmental samples (e.g., water from a lake) are collected.
- Analysis: In a laboratory, DNA is extracted and amplified using polymerase chain reaction (PCR) to check for the unique genetic signature of the target species.
- Application: eDNA is incredibly sensitive and is revolutionizing the detection of rare, cryptic, or invasive aquatic species without the need for direct observation or capture.
Materials Required:
- For Direct Surveys: Measuring tape, quadrat frame, compass, notebook, pencil, field guide, camera trap.
- For Tracking: GPS collar, VHF transmitter, receiver and antenna.
- For eDNA: Sterile sample bottles, gloves, cooler, filter paper, lab access for PCR analysis.
- For GIS: Computer with GIS software (e.g., QGIS).
Procedure (Overview of Methods):
A. Using the Quadrat Method (For Plants):
- Define the study area boundaries.
- Generate random coordinates within the area for sampling.
- Place the quadrat at each coordinate.
- Identify, count, and record all individuals of the target plant species within the frame.
- Map the locations where the species is present/absent.
B. Using a Camera Trap (For Animals):
- Identify animal signs (tracks, scat, paths) to select a suitable location.
- Secure the camera trap to a tree or post, ensuring a clear field of view.
- Set the sensitivity and interval for photos.
- Leave the trap for a predetermined period (e.g., one week).
- Retrieve the camera and analyze the images for species identification and activity.
C. Using eDNA (For Aquatic Species):
- Wear gloves to prevent contamination.
- Collect multiple water samples from different points in the water body.
- Filter the water through a fine filter to capture DNA material.
- Preserve the filter in ethanol or a sterile container.
- Transport samples to a lab for DNA extraction and PCR analysis.
Observations & Expected Results:
- Quadrat Method: Will yield a map of species presence/absence and data to calculate frequency and density (e.g., "Species X was found in 4 out of 10 quadrats, indicating a patchy distribution").
- Camera Trap: Will provide visual proof of species presence, time of activity, and sometimes population estimates (e.g., "The leopard cat (Prionailurus bengalensis) was confirmed to be nocturnal, with 5 sightings between 8 PM and 4 AM").
- eDNA Analysis: Will provide a simple "yes/no" result for the presence of a specific species in the water body (e.g., "eDNA analysis confirmed the presence of the endangered Mahseer fish (Tor tor) in the river").
A wide array of methods exists to determine species location, each with its own advantages and limitations. The choice of method is critical and depends entirely on the research question, the organism being studied, and the available resources. Modern approaches often combine traditional field methods with advanced technology like GPS and eDNA for a more comprehensive understanding of species distribution.
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