Name Block Date. The Quadrat Study: An Introduction

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1 Name Block Date The Quadrat Study: An Introduction A quadrat study can almost be thought of as a snapshot of the ecosystem during a particular year and at a particular time of that year. The plant and animal populations observed are influenced by how far into succession the ecosystem is and what plants are blooming. Remember, the surface upon which we live was once 100% bare earth, followed by plants native to the area. In a quadrat study, researchers look at certain characteristics of the various populations. These include plant dominance, importance value and diversity. Dominance and Importance Value You can use the data to tell which plants are becoming dominant. Dominant plants are the plants that are the most noticeable and take up the most room. In a forest, for example, oak trees and maple trees may be the most noticeable plant. Oak trees and maple trees would be called the dominant plants. Look at the graphs that are called Total Percent Covered. Do not count the Bare Earth and Invasives bar on the graph. Which plants are becoming dominant? The dominant plants are important because they supply much of the food and living space for animals. They are also important because they not only take up the most space above the ground, but below it too. In general, the amount of a grass below the ground is often two or three times the size of the plant above the ground. Dominant plants may control some environmental conditions. They may change the amount of sunlight available to shorter plants, and their roots may change the soil chemistry. These changes may affect other species of plants that live with the dominant plants. The Importance Value is the sum of three values: the relative dominance, the relative frequency, and the relative density of a plant. We calculate these values for a species when we combine the data for all the quadrats sampled. Note: # quadrats is the same as the total area sampled because each quadrat is 1 square meter. 1

2 Value Dominance Frequency Density Relative Dominance Definition = Total percent cover of a species / Total area sampled = Total # quadrats in which a species occurs / Total # quadrats = Total # plants of a certain species / Total area sampled = 100 x Dom. of a species / Sum of the Dom. of all species Relative Frequency Relative Density = = 100 x Freq. of a particular species / Sum of the Freq. of all species 100 x Density of a particular species / Sum of the Densities of all species Importance Value = Relative Dominance + Relative Frequency + Relative Density Biological Diversity Biological diversity means that many different kinds of living things live together in the same area. Having a variety of living things in an area is important in the health of an environment. In general, the more diversity of life in an environment (the greater the biodiversity of the area, in other words), the better the environment is. Value Definition Diversity = Total number of different species for all quadrats / Total # of quadrats The total number of different species for all quadrats = Sum of the # of different species for each quadrat. The easiest way to see if the diversity of an area has changed over time is to compare the data tables for the past and the most recent year. Ecologists use this data to see how diversity and dominance change through the years for different places and species over time. Also, bear in mind that the student data may underestimate biological diversity because the time of year that the samples are taken. Your sampling is done in the fall after school has started. 2

3 Increased diversity of plants also increases the habitat for insects and other animals. Habitat is the place where particular plants and animals live. In the habitat, different living things have different niches. A niche is how a living thing earns its living. Some animals have very exact niches. The Monarch Butterfly caterpillar for example, must live on milkweed plants. The niche of the Monarch caterpillar is living on and eating milkweed. With many niches in an ecosystem, many kinds of living things can live closely together. This is because they don't compete for exactly the same living space or exactly the same food. Some scientists think that more than 50 percent of existing species will be lost in the next 100 years. Laws have been made to protect certain species, but the best way to preserve a species is to make sure that their habitat is protected. This not only helps the endangered species, but the diversity of life in that habitat is preserved as well. Quadrat Sampling Activity: Question: HOW DO ORGANISMS INTERACT WITH EACH OTHER AND THEIR ENVIRONMENT? Organisms are not isolated in their environment. Organisms must interact with other individuals of their own species, with other species, and with their physical environment. The study of the interactions between organisms and their environment is called ecology (Greek: oikos- house; logia- study). The study of ecology can encompass all aspects of biology; from physiology to behavior, because any change within an organism has the potential to affect its relationship with the environment. Likewise, ecological interactions can be studied at many different levels; between an organism and its environment, between an organism and a group of organisms, or between two groups. In this unit we will cover many of the important concepts within ecology. Procedure: As described by Mrs. McAleer Establish a 1 metre square quadrat Make observations using the quadrat tool to determine the number of organisms in your quadrat. Record your observations on the data table provided. Materials: 4 metre sticks per group Quadrat tools 3

4 Data: Category Name Description Number in quadrat % coverage Bare ground abiotic Observations: Date: Time am/pm Temperature Light / weather conditions Other Observations: 4

5 Questions for contemplation: remember our initial question. HOW DO ORGANISMS INTERACT WITH EACH OTHER AND THEIR ENVIRONMENT? 1. How do the organisms you observed interact with each other and their environment? Outline at least one possible ecological niche for each organism observed. 2. How many producers did you observe? Were there many more present? What would happen to the other species if they were reduced in number? 3. Did you see any consumers? How many? What were they? 5

6 4. Sketch a possible food web for this quadrat, based upon your observations 4. What was the diversity value for your sample based upon the number of organisms you observed? (See introduction how to do calculations. Please show your work.) 5. What was/were the dominant species in your quadrat sample? What are their density and dominance values? (See introduction how to do calculations. Please show your work.) Conclusion: write a short conclusion responding to our initial question. 6