Biodiversity of Leaf Litter
Collaborators: Maggie and Amber
Introduction
In this observational lab, we studied the biodiversity of species/organisms that exist in the leaf litter in the forest behind Heritage High School. In ecology, Simpson’s Diversity Index is used to determine the biodiversity of a habitat. Biological diversity can be quantified taking into account two main factors when measuring diversity are richness and evenness. Richness is a measure of the number of different kinds of organisms present in a particular area. For example, species richness is the number of different species present. However, diversity depends not only on richness, but also on evenness. Evenness compares the similarity of the population size of each of the species present. Biodiversity is important for all species' survival and balance of competition between them. Healthier ecosystems consist of a large variety of habitats and available resources for all the different species as each species is adapts to a certain set of environmental conditions. Thus, creating opportunities for natural selection and evolution to affect organisms in an ecosystem. Today, harmful threats to species is at an accelerated and dangerous rate, because of non-natural environmental changes caused by invasive species and human activities, including habitat loss, which have had direct effects on levels of biodiversity within an ecosystem. By the use of a berlese funnel to extract critters from the soil and leaf litter, this lab helped determine the biodiversity in our own backyard of Heritage High School
Problem
What is the biodiversity of the leaf litter in the woods behind HHS?
Hypothesis: The leaf litter collected from the woods of Heritage High School will have a greater biodiversity than that of the standard soil.
Parts of the Experiment
• Independent variable: location of the collected leaf litter
• Dependent variable: biodiversity level in each sample
• Control Group: soil samples
• Experimental Group: samples of leaf litter collected from the trail behind HHS
• Controlled variables: time under the light source
Materials
Materials for this lab are:
• Microscope
• Berlese Funnel
• Leaf Litter
• Alcohol
• Source of Light
• Beaker
Methods
1. Collect a sample of leaf litter. Be sure to collect the entire layer down to the soil.
2. Examine the sample and classify what you see the layer is composed of.
3. Place your sample into the Berlese Funnel under the light source. Place a small beaker of alcohol under the funnel. The hope is that small invertebrates will travel away from the light and fall into your alcohol.
4. The next day, collect your beaker and examine the organisms you have collected under the microscopes. You will need to calculate the number of each species you have, and identify them. Each person may work on a portion of the sample and put your numbers together. Use the Identification pages to name each species.
5. Use the information to calculate the diversity indices for your sample.
Data
We began the lab by gathering leaf litter, then pouring our leaf litter into an upside-down empty gallon milk jug with the bottom cut off of it, and we placed a Berlese Funnel at the bottom. This that separates and preserves small insects found in ground litter and consists of a sieve placed over a funnel connected at the bottom to a preserving bottle. After this, we put the jug onto a ring stand with a 100 mL beaker of alcohol sitting under it. Lastly, we attached an artificial light above our leaf "aquarium". We did this because the organisms on the bottom of the forest are not accustomed to a lot of light. Therefore, they have a tendency to dig farther down into the jug and eventually pass through the bottom screen into the beaker. The beaker of alcohol was used for capturing and killing the critters. We left the lights on for a week and then returned to see the organisms that ended up in the beaker. We used a microscope to observe this. We completed this entire lab to test the biodiversity of the leaf litter behind the school. It shows us how sustainable and balanced the ecosystem is.
Weather: 34 degrees F
Humidity: 70%
Leaf Litter:
Simpsons Index: .083
Simpsons Index of Diversity: .917
Simpsons Reciprocal Index: 12.05
Soil:
NONE
Simpsons Index- 0
Simpsons Index of Diversity- 0
Simpsons Reciprocal Index- 0
DATA TABLE
Species
Leaf Litter (first row)
Soil (second row)
Isopods
2
0
Mite
14
0
Ant
1
0
Predaceas
5
0
Thrip
2
0
Psocid
3
0
Springtail
7
0
Harvestman
2
0
True Bug
1
0
Aphid
4
0
Protura
5
0
Nematoda
1
0
Diplura
4
0
Beetle Mite
6
0
Paurapoda
1
0
Spider
2
0
Japygid
2
0
Roach
2
0
Data Analysis :
The information collected from both the leaf litter and the soil samples was organized into a table, showing each species discovered. The results support the hypothesis which states that the leaf litter has a greater biodiversity than that of the soil. The leaf litter collected from the Heritage High School trail had a higher amount of species richness and a decently high level of species evenness. The species evenness is elatively high because the largest population is 14 while the lowest is 1. The species richness is large as well due to the 18 different species found in the leaf litter. The control group of soil had no species richness because there were no organisms living in the soil, which was tested.
After the diversity was calculated, it could be concluded that the leaf litter had a greater biodiversity than the soil. The Simpsons index of the leaf litter is .083 while the Simpsons index of soil is 0 because there were no organisms discovered. The Simpsons index of diversity of leaf litter was .917 while the reciprocal index was 12.05. The Simpsons index of diversity and the reciprocal index of soil were each 0. These results support the correct hypothesis that leaf litter has a greater biodiversity. This is because the leaf litter has a higher species richness of 14 different species compared to 0.
Conclusions
It can be concluded that the organisms instinctively moved away from the light and later fall into the beaker of alcohol because they are accustomed to move away from light. It is a natural reaction. They are used to living on the bottom of the forest floor which does not receive very much sunlight, and they have evolved to move away from light. Also, the light was a source of heat. I thought that the biodiversity of our leaf litter was low to medium, but after calculating the biodiversity level through Simpson's Index, it made me reevaluate my opinion. Simpson's Index is the probability that two organisms randomly selected from a sample will belong to the same species. Although we didn't find lots of organisms, we did find a good amount of organisms within our microscope.
An environmental scientist would need to make more than one measurement if he was calculating the biodiversity because one sample of the biodiversity in one location is not a valid representation of the biodiversity of the entire forest. In order to take samples of a large forest, I would take a large number of samples throughout many random locations in the forest, samples that included the same amount of litter and have the testing be over a period of time for a more reliable result.
Our results, along with others I assume I think that the overall outcome could be more accurate because there were many groups who found little organisms or none at all. We only did a small area of testing that may contained less organisms than other areas and the variations of the lab with it's applications could change. The lab applications go along with the course of Environmental Science that are very important, showing us the sustainability and balance of our ecosystems and how important it is. Humans are a huge influence in the disturbance of the environment then not only will biodiversity be affected but also the health of the entire environment.
Citations:
"Kylla M. Benes - Biodiversity, Ecology, & Evolution." Kylla M. Benes - Biodiversity, Ecology, & Evolution. N.p., n.d. Web. 03 Mar. 2015.