Collaborators:
David Delgado, Brandon Garff, Sona George, and Hailey Hendriks.
David Delgado, Brandon Garff, Sona George, and Hailey Hendriks.
Introduction & Problem:
Have you ever wondered if leaves were good for anything else but making a fun chore in the fall? Although it may appear to be the most static component of any habitat, leaf litter plays a central role in habitats. It is tasked with preserving the diversity of an ecosystem, and it does this by inhabiting several invertebrates. The combination of leaf litter and organisms that inhabit it are good indicators of an ecosystems overall health. Thus, the problem that will be addressed through this lab is, "What is the biodiversity of a sample of leaf litter?" According to the background information, the biodiversity of a habitat can be quantified using Simpson's Diversity Indices. These indices take into account two important components of biodiversity: species richness and species evenness. Although counterintuitive, these measurements are helpful in understanding how current environmental problems affect the biodiversity and sustainability of habitats. “Forest floor litter invertebrates provide an ideal system in which to investigate the effects of urbanization and disturbance because of their abundance and diversity"(Schneider, Anna). For example, if certain ecosystem functions are not taking place in a habitat, it is possible that deforestation, the introduction of invasive species and pollution threaten the abundance of these invertebrates and therefore the overall health of the ecosystem. Therefore, by determining the biodiversity of our leaf litter samples, we are also acquiring a better understanding of why the biodiversity of leaf litter is important to the health and resilience of an ecosystem.
Hypothesis:
If the biological diversity of a leaf litter sample from the trail at Heritage High School is quantified, then the sample will yield a Simpson's Index (D) below 0.25 due to the abundance of life that exists in this habitat and its proximity to a water source.
Parts of the Experiment:
Materials & Methods:
a) Materials:
b) Method:
Data & Data Analysis:
Have you ever wondered if leaves were good for anything else but making a fun chore in the fall? Although it may appear to be the most static component of any habitat, leaf litter plays a central role in habitats. It is tasked with preserving the diversity of an ecosystem, and it does this by inhabiting several invertebrates. The combination of leaf litter and organisms that inhabit it are good indicators of an ecosystems overall health. Thus, the problem that will be addressed through this lab is, "What is the biodiversity of a sample of leaf litter?" According to the background information, the biodiversity of a habitat can be quantified using Simpson's Diversity Indices. These indices take into account two important components of biodiversity: species richness and species evenness. Although counterintuitive, these measurements are helpful in understanding how current environmental problems affect the biodiversity and sustainability of habitats. “Forest floor litter invertebrates provide an ideal system in which to investigate the effects of urbanization and disturbance because of their abundance and diversity"(Schneider, Anna). For example, if certain ecosystem functions are not taking place in a habitat, it is possible that deforestation, the introduction of invasive species and pollution threaten the abundance of these invertebrates and therefore the overall health of the ecosystem. Therefore, by determining the biodiversity of our leaf litter samples, we are also acquiring a better understanding of why the biodiversity of leaf litter is important to the health and resilience of an ecosystem.
Hypothesis:
If the biological diversity of a leaf litter sample from the trail at Heritage High School is quantified, then the sample will yield a Simpson's Index (D) below 0.25 due to the abundance of life that exists in this habitat and its proximity to a water source.
Parts of the Experiment:
- There is no control group in this experiment.
- The experimental group consists of the sample of leaf litter collected from the outdoor trail at Heritage High School.
- The independent variable is the location from which the leaf litter sample is collected.
- The dependent variable is the level of biodiversity of the sample.
- The controlled variables include the materials, the amount of leaf litter collected and the amount of light that each sample was exposed to,
Materials & Methods:
a) Materials:
- Leaf litter
- Compound microscope
- Alcohol
- Beaker
- Petri dish
- Berlese funnel
- Source of light
- Invertebrate identification page
b) Method:
- Using an empty milk jug, collect a sample of leaf litter. Be sure to collect the entire layer down to the soil.
- Examine the sample and classify what you see the layer is composed of.
- 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.
- After a week, collect your beaker and examine the organisms you have collected under the microscopes.
- 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.
- Use the Simpson's Diversity Indices explained in the background information to calculate the diversity indices for your sample.
Data & Data Analysis:
a) Data: (Photos taken by Sona George)
|
Observations
Location: Heritage High School Trail Type of community: Climax community; deciduous forest Date: September 25, 2014 Time: 7:40 - 8:10 AM Weather description: Cloudy, foggy and humid Air temp: 63 degrees Fahrenheit Relative Humidity: 90% |
Calculations:
|
Simpson's Index (D) = 0.16
Simpson's Index of Diversity (1-D) = 0.84 Simpson's Reciprocal Index (1/D) = 6.44 |
b) Data Analysis:
At first, looking into the the bag containing the leaf litter sample gave no indication as to the biodiversity that composed it. However, a compound microscope enabled groups to notice that the samples contained several microscopic invertebrates. Among these, the two most abundant species found in the sample were Predaceous mites and Springtails (picture #4). Nevertheless, the fact that these two species dominated the sample was not detrimental to the evenness that was noted in the sample. There were not outliers in the data, which means that the evenness was quite high. In addition, the fact that more species were found in leaf litter sample than expected indicates a decent species richness. The fact that a total of seven different species were found in a small sample of the habitat being examined indicates that there is an abundance of species along Heritage's outdoor trail. With this in mind, the Simpson's Diversity Indices that were acquired from the collected data were nothing short of predictable. With a Simpson's Index of 0.16, a Simpson's Index of Diversity of 0.84 and a Simpson's Reciprocal Index of 6.44, the consensus among the group was that the leaf litter sample collected from the outdoor trail of Heritage High School had a high biodiversity.
Conclusions:
The results of this experiment cannot be defined as conclusive. First of all, the background information for this lab emphasizes the importance of taking multiple samples of leaf litter in order to poole the data and get a better estimate of overall diversity. In spite of that, the results of this experiment corroborated the hypothesis that if the biological diversity of a leaf litter sample from the trail at Heritage High School is quantified, then the sample will yield a Simpson's Index (D) below 0.25. The calculated Simpson's Index was 0.16 for the sample of leaf litter, which means that it is even more diverse than predicted. However, it should be noted that the time of day, season, weather, humidity, and temperature all impacted the calculated biodiversity for that specific leaf litter sample, and therefore it cannot be used to estimate the diversity of the forest as a whole. For example, the time of day could have skewed the results in that detritivores have the tendency to crawl under leaf litter whenever they are exposed to sunlight. This is done in order to maintain cool during the day, and to hide from predators. When exposed to the light from the lamps, these organisms adhered to this behavioral adaptation by moving away from the light and into the beaker of alcohol. Still, these indices can add to the understanding of how the biodiversity of leaf litter impacts such environmental factors as soil health (Schneider, Anna).
With a Simpson's Index of 0.16, it can be concluded that the sample of leaf litter from the outdoor trail had a high level of biodiversity. Furthermore, succession is evident in this habitat in that the trail was full of vegetation. This plant growth is supported by nutrients that are provided by soil dwelling organisms. These organisms include the detritivorous invertebrates that inhabit leaf litter. This is where leaf litter comes in, for "decomposing leaf litter releases nutrients into the soil and also keeps it moist"(Lin, Kevin). If the leaf litter were diverse, then it would have an abundance of invertebrates that would in turn decompose the leaf litter and release nutrients back into the soil. Indeed, the habitat displayed the biodiversity of leaf litter in that the plants seemed to be thriving. This relationship further supports the fact that organisms in an ecosystem are interconnected, which creates a need to preserve biodiversity if sustainability is to be an achievable goal. "If we want to sustain our environment, we have to preserve the fine natural balance of interconnected webs of life"(Shneider, Anna). Part of this natural balance relies on the biodiversity of leaf litter, and that is why it is such an important part of any habitat. Not only that, but humans also need to understand that they play an important role in maintaining this natural balance. Humans have the ability to threaten the biodiversity of leaf litter and therefore the overall health of habitats. Thus, as members of this interconnected system, we must all play a proactive role, starting with the realization that the biodiversity of leaf litter is important to the health and resilience of an ecosystem.
At first, looking into the the bag containing the leaf litter sample gave no indication as to the biodiversity that composed it. However, a compound microscope enabled groups to notice that the samples contained several microscopic invertebrates. Among these, the two most abundant species found in the sample were Predaceous mites and Springtails (picture #4). Nevertheless, the fact that these two species dominated the sample was not detrimental to the evenness that was noted in the sample. There were not outliers in the data, which means that the evenness was quite high. In addition, the fact that more species were found in leaf litter sample than expected indicates a decent species richness. The fact that a total of seven different species were found in a small sample of the habitat being examined indicates that there is an abundance of species along Heritage's outdoor trail. With this in mind, the Simpson's Diversity Indices that were acquired from the collected data were nothing short of predictable. With a Simpson's Index of 0.16, a Simpson's Index of Diversity of 0.84 and a Simpson's Reciprocal Index of 6.44, the consensus among the group was that the leaf litter sample collected from the outdoor trail of Heritage High School had a high biodiversity.
Conclusions:
The results of this experiment cannot be defined as conclusive. First of all, the background information for this lab emphasizes the importance of taking multiple samples of leaf litter in order to poole the data and get a better estimate of overall diversity. In spite of that, the results of this experiment corroborated the hypothesis that if the biological diversity of a leaf litter sample from the trail at Heritage High School is quantified, then the sample will yield a Simpson's Index (D) below 0.25. The calculated Simpson's Index was 0.16 for the sample of leaf litter, which means that it is even more diverse than predicted. However, it should be noted that the time of day, season, weather, humidity, and temperature all impacted the calculated biodiversity for that specific leaf litter sample, and therefore it cannot be used to estimate the diversity of the forest as a whole. For example, the time of day could have skewed the results in that detritivores have the tendency to crawl under leaf litter whenever they are exposed to sunlight. This is done in order to maintain cool during the day, and to hide from predators. When exposed to the light from the lamps, these organisms adhered to this behavioral adaptation by moving away from the light and into the beaker of alcohol. Still, these indices can add to the understanding of how the biodiversity of leaf litter impacts such environmental factors as soil health (Schneider, Anna).
With a Simpson's Index of 0.16, it can be concluded that the sample of leaf litter from the outdoor trail had a high level of biodiversity. Furthermore, succession is evident in this habitat in that the trail was full of vegetation. This plant growth is supported by nutrients that are provided by soil dwelling organisms. These organisms include the detritivorous invertebrates that inhabit leaf litter. This is where leaf litter comes in, for "decomposing leaf litter releases nutrients into the soil and also keeps it moist"(Lin, Kevin). If the leaf litter were diverse, then it would have an abundance of invertebrates that would in turn decompose the leaf litter and release nutrients back into the soil. Indeed, the habitat displayed the biodiversity of leaf litter in that the plants seemed to be thriving. This relationship further supports the fact that organisms in an ecosystem are interconnected, which creates a need to preserve biodiversity if sustainability is to be an achievable goal. "If we want to sustain our environment, we have to preserve the fine natural balance of interconnected webs of life"(Shneider, Anna). Part of this natural balance relies on the biodiversity of leaf litter, and that is why it is such an important part of any habitat. Not only that, but humans also need to understand that they play an important role in maintaining this natural balance. Humans have the ability to threaten the biodiversity of leaf litter and therefore the overall health of habitats. Thus, as members of this interconnected system, we must all play a proactive role, starting with the realization that the biodiversity of leaf litter is important to the health and resilience of an ecosystem.
Citations:
Lin, Kevin. "Seasonal Science: What Lurks in the Leaf Litter?" Scientific American Global RSS. N.p., 18 Oct. 2012. Web. 02 Oct. 2014. <http://www.scientificamerican.com/article/bring-science-home-leaf-litter-biodiversity/>.
Norris, Kara. Biodiversity of Leaf Litter. N.p.: Web. 02 Oct. 2014. PDF.
Shneider, Anna. "Grounds and Landscaping." Seattle University, n.d. Web. 02 Oct. 2014. PDF. <http://www.seattleu.edu/WorkArea/DownloadAsset.aspx?id=120512>.
Lin, Kevin. "Seasonal Science: What Lurks in the Leaf Litter?" Scientific American Global RSS. N.p., 18 Oct. 2012. Web. 02 Oct. 2014. <http://www.scientificamerican.com/article/bring-science-home-leaf-litter-biodiversity/>.
Norris, Kara. Biodiversity of Leaf Litter. N.p.: Web. 02 Oct. 2014. PDF.
Shneider, Anna. "Grounds and Landscaping." Seattle University, n.d. Web. 02 Oct. 2014. PDF. <http://www.seattleu.edu/WorkArea/DownloadAsset.aspx?id=120512>.