In the previous two experiments, students set out to measure the biodiversity of two communities in Chattanooga: Signal Point Park and the Confederate Cemetery. This week, students aimed to analyze the data of the whole class that was collected during this time and compare the biodiversity of the two communities. To do this, students used the Shannon Diversity Index to calculate the observed biodiversity value (H’), the maximum diversity value possible (Hmax), the total species richness (S), and species evenness (J). When compared to Signal Point Park, the cemetery will have a greater Shannon Diversity Index value and thus greater biodiversity due to the greater human impact on the Signal Point Park community.
Signal Point Park is a community nestled on Signal Mountain in Chattanooga, Tennessee. The area sampled by students was a field adjacent to the parking lot, and a walking path ran through it to connect the lot to hiking trails and the mountain overlook. The Confederate Cemetery, on the other hand, is closer to the campus of the University of Tennessee at Chattanooga, nestled just across from Holt Hall. It is a cemetery, so it is maintained and visited. The occasional student may walk through the community to get to class, too.
Students used the same methods to sample biodiversity from both communities. Students broke into four groups and obtained a 1m2 quadrat. They generated a random number and walked forward that many steps. With a second random number, they walked to the right and placed the quadrat at their feet. Students recorded a description of each species found within the quadrat, and they recorded the number of individuals within each species. They repeated this until they sampled a total of ten areas. With four student groups sampling ten plots each, that came to a total of 40 areas sampled for each community. Back in the lab, students added up the number of individuals found within all their quadrants.
In order to calculate the Shannon Diversity Index values of the communities, students used the following equations:
P= (Number of individuals of one species)/(total number of individuals)
H’ = ∑ [-p (ln p)]
S= total number of species
Hmax= lnS
J= H’/Hmax
From these equations, students calculated that Community A (Signal Point Park) had an H’ value of 2.54 and an Hmax value of 3.61. It had 37 total species and a species evenness of 0.70. These values are listed in Table 1. In Community B (Confederate Cemetery), the H’ value was determined to be 2.48 and the Hmax value was 3.58. It had 36 total species and a species evenness of 0.69. The determination of these values is listed in Table 2.
Table 1. Species Abundance and Shannon Diversity Index Values of Signal Point Park
| Species | Abundance | Proportion | -p(ln p) |
| Granddaddy Long Leg Spider | 1 | 0.00070 | 0.0051 |
| Jumping Spider | 2 | 0.0014 | 0.0091 |
| Beetle | 1 | 0.00070 | 0.0051 |
| Moss | 14 | 0.0097 | 0.045 |
| Black Ants | 56 | 0.039 | 0.13 |
| Red Ants | 3 | 0.0021 | 0.013 |
| Small Red Insects | 2 | 0.0014 | 0.0091 |
| Lichen | 67 | 0.047 | 0.14 |
| Sawtoothed plant | 45 | 0.031 | 0.11 |
| Clover | 83 | 0.058 | 0.16 |
| Pine | 2 | 0.0014 | 0.0091 |
| Red Bud | 6 | 0.0047 | 0.023 |
| Wild Onion | 47 | 0.033 | 0.11 |
| Poison Oak | 1 | 0.00070 | 0.0051 |
| Heart-shaped Leaf Grass | 14 | 0.0097 | 0.045 |
| Wild Strawberry | 51 | 0.035 | 0.12 |
| Small, Woody Shrub | 18 | 0.013 | 0.055 |
| Pointed Shrub | 1 | 0.00070 | 0.0051 |
| Broad-leaf plant | 99 | 0.069 | 0.18 |
| Dandelion | 17 | 0.012 | 0.052 |
| Tear-shaped Plant | 12 | 0.0083 | 0.040 |
| Maple | 1 | 0.00070 | 0.0051 |
| Violet | 20 | 0.014 | 0.059 |
| Yellow Violet Vine | 31 | 0.022 | 0.083 |
| Flowering Vine | 18 | 0.013 | 0.055 |
| Thin Grass | 304 | 0.21 | 0.33 |
| Broad Grass | 401 | 0.28 | 0.36 |
| Short, fuzzy plant | 16 | 0.011 | 0.050 |
| Stemmed Grass | 10 | 0.0070 | 0.035 |
| Bunny Grass | 7 | 0.0049 | 0.026 |
| 3 squiggly leafed plant | 1 | 0.00070 | 00.051 |
| Oval leaf sapling | 3 | 0.0021 | 0.013 |
| Branched leaf plant | 11 | 0.0076 | 0.037 |
| Prickly grass | 16 | 0.011 | 0.050 |
| Bumpy grass | 41 | 0.029 | 0.101 |
| Broad diamond leaf plant | 8 | 0.0056 | 0.029 |
| Lobed grass | 8 | 0.0056 | 0.029 |
| Total Individuals | 1438 | H’ | 2.54 |
| Total Number of Species | 37 | ||
| J | 0.70 | ||
| Hmax | 3.61 |
Table 2. Species Abundance and Shannon Diversity Index Values of the Confederate Cemetery
| Species | Abundance | Proportion | -p(ln p) |
| Lichen | 96 | 0.034 | 0.12 |
| Wild Strawberry | 7 | 0.0025 | 0.015 |
| Pillbug | 7 | 0.0025 | 0.015 |
| Red bug | 1 | 0.00036 | 0.0028 |
| Leaf Bug | 2 | 0.00071 | 0.0052 |
| Weavel | 1 | 0.00036 | 0.0028 |
| Snails | 5 | 0.0018 | 0.011 |
| Spider | 2 | 0.0071 | 0.0052 |
| Fruit Fly | 1 | 0.00036 | 0.0028 |
| Caterpillar | 1 | 0.00036 | 0.0028 |
| Black Ants | 476 | 0.17 | 0.30 |
| Red Ants | 1 | 0.00036 | 0.0028 |
| Clover | 144 | 0.051 | 0.15 |
| Moss | 10 | 0.0036 | 0.020 |
| Poison Oak | 4 | 0.0014 | 0.0093 |
| Vines | 12 | 0.0043 | 0.023 |
| Two-leaf Vine | 55 | 0.020 | 0.077 |
| Ivy | 5 | 0.0018 | 0.011 |
| Lily pad leaves | 141 | 0.050 | 0.15 |
| Thin bladed grass | 763 | 0.27 | 0.35 |
| Broad bladed grass | 192 | 0.068 | 0.18 |
| Violets | 80 | 0.029 | 0.10 |
| Three leaf sapling | 36 | 0.013 | 0.056 |
| Broad sapling | 23 | 0.0082 | 0.039 |
| Sawtooth leaves | 87 | 0.031 | 0.11 |
| Woody stem plant | 138 | 0.049 | 0.15 |
| Long grass | 121 | 0.043 | 0.14 |
| Small leafy branch | 15 | 0.0053 | 0.028 |
| Flower shaped leaves | 2 | 0.00071 | 0.0052 |
| Fuzzy leaf | 3 | 0.0011 | 0.0073 |
| Oval leaf | 3 | 0.0011 | 0.0073 |
| Rounded leaf | 16 | 0.0057 | 0.029 |
| Ruffled leaf | 42 | 0.015 | 0.063 |
| Heart-shaped grass | 281 | 0.10 | 0.23 |
| Lobed grass | 24 | 0.0086 | 0.041 |
| Stemmed grass | 10 | 0.0036 | 0.020 |
| Total Individuals | 2807 | H’ | 2.48 |
| Total Number of Species | 36 | ||
| J | 0.69 | ||
| Hmax | 3.58 |
The relative abundances of each species in both communities is graphed as a rank abundance curve in Figure 1.
Figure 1. The Rank Abundance Curves of Signal Point Park and the Confederate Cemetery
The blue line plots the rank abundance of species in Signal Point Park. The orange line plots the rank abundance of species in the Confederate Cemetery.
The Signal Point Park community has a higher H’ value. Thus, it has higher biodiversity than the Confederate Cemetery. Both communities have a relatively moderate diversity when compared to their Hmax values. My hypothesis is disproved by the data. Signal Point Park has the greater biodiversity when calculated with the class data set. When calculated with only my group’s data, however, this was not the case. The Confederate Cemetery was found to have an H’ value of 1.92, which is higher than the H’ value of 1.87 calculated for Signal Point Park. The differences in biodiversity between the two communities is minimal, and it is likely that human impact is roughly equal in both areas. Additionally, there could have been an error in recording data from either community. One group may have had a different name for the same species, causing the total species richness to be counted higher than it actually is. Lastly, when comparing the two communities in Figure 1, students can see that both communities are dominated by a few species. Overall, though, they have highly similar species evenness
Exploring Ecology 