Online Prairie Data
What to Look for in Your Data
IntroductionA quadrat study can almost be thought of as a snapshot of the prairie during a particular year and at a particular time of that year. The plant population observed is influenced by how old the prairie is and what plants are blooming.
The Fermilab prairie was fairly well established when students started to take data in 1992, but the data represents a very short time in the life of a prairie. How will the prairie change in ten or fifty years? Also, most of the student data was taken in the fall from mid-September to mid-November. How might the data be different in April or June? You can look at the data for Ongoing Studies and Studies from Previous Years (starting in 1992) to see how much the prairie has changed. It was once 100% bare earth and non-native grass.
The student prairie at Fermilab was once farmland. To restore the prairie, the land was plowed and planted with a mixture of prairie grasses and seeds. At first, it did not look like a prairie. It looked like a weed field. The prairie plants were too small to be noticed. The prairie seeds sent down deep roots and grew slowly. As time went on, the prairie plants started to replace the weeds (invasives).
To imitate the natural prairie, the student prairie is safely burned every year unless weather does not allow it. Fire was a natural part of the prairie. Fire did not harm the prairie plants, in fact, it helped in several ways. Fire quickly recycles the nutrients in dead material into a form that plants can use. It removes built up layers of dead material so that young plants can grow easily, and it allows sunlight to reach the soil. Prairie plants have deep roots that are not harmed if the top of the plant is burned. The prairie plants grow again from the roots. Invasives such as weeds, and woody plants, however, do not survive fire very well. Burning helps the prairie plants replace the invasives.
In a quadrat study researchers look at certain characteristics of the prairie plant population. These include plant dominance, importance value and diversity.
Dominance and Importance Value
You can use the data to tell which prairie 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 prairie 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 prairie plant below the ground is often two or three times the size (see Prairie Plants and Their Root Systems) 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.
Value Definition Dominance = Total percent cover of a species / Total area sampled Frequency = Total # quadrats in which a species occurs / Total # quadrats Density = Total # plants of a certain species / Total area sampled Relative Dominance = 100 x Dom. of a species / Sum of the Dom. of all species Relative Frequency = 100 x Freq. of a particular species / Sum of the Freq. of all species Relative Density = 100 x Density of a particular species / Sum of the Densities of all species Importance Value = Relative Dominance + Relative Frequency + Relative Density
Note: We calculate the relative dominance, relative frequency, and relative density separately for prairie plants and for invasives. For example, we calculate the sum of the dominance of all prairie plant species to calculate the relative dominance of a prairie plant species. To calculate the relative dominance of a invasive, we calculate the sum of the dominance of all invasives. This means that you cannot compare the relative dominance of a prairie plant to the relative dominance of a invasive. Similarly for the importance value, you cannot compare the relative importance value of a prairie plant with the relative importance value of a invasive.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 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 the student prairie has changed since it was planted is to compare the data tables for 1992 and the most recent year. To see if there is an increase in plant diversity, count the number of prairie plant species for the two years. Look at the data for Ongoing Studies and Studies from Previous Years (starting in 1992). Also look at the graphs to see how diversity and dominance change through the years for different prairies and plants.
Also, the student data underestimate biological diversity because the time of year that the samples are taken. Most of the sampling is done in the fall after school has started. Some of the spring and summer flowers may be missed by student groups because the plants may have finished blooming by autumn. Students may investigate blooming times of various plants.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 nitches in a prairie, 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 animals, 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.