1. PLANT GROWTH AND MAMMALIAN DECOMPOSITION AMONG SOIL TYPES FOUND AT WILD
BASIN
June 26, 2014
ABSTRACT
Wild Basin Creative Research Center is home to six distinct and different soil communities
ranging from riparian to dry grassland. These communities offer the opportunity for many mammal and
plant species to thrive and, when these mammals die and begin the process of decomposition, their
decomposing cadavers serve as incredible sources of carbon and nutrients to the soils in which they are
decomposing. Testing whether or not: 1. Plant life experiences an increase in growth due to an
underground decomposing mammal, 2. Different soil types can sustain the same plant life, and 3.
Mammalian decomposition rates among soil types vary, can be completed by growing plants in the
presence of a cadaver,planting the same seeds within the different soils from the plant communities
found Wild Basin, and allowing different cadavers to decompose within the different soils from the plant
communities found at Wild Basin. Three soil samples were collected from six distinct sites at Wild Basin
and thirty two Brassica rapa plots were planted, eighteen with mice buried beneath the soil and eighteen
without mice (serving as a control group). Also, using the excess soils, thirty two small cups were placed
outside the greenhouse and mice were placed atop each one, eighteen being observed for a ten day study
and eighteen being observed for a twenty day study. These experimental designs resulted in an increase in
growth in plants that do not have underground decomposing mammals, failure for some Brassica rapa
seeds to germinate in certain soils, and a difference in decomposition rates among soil types, but little to
no correlation between them. Two of my original hypotheses were not supported: 1. In the presence of a
belowground decomposing mammal, plants will experience an increase in growth rate due to the nutrients
released by the cadaver,relative to a control with no mammals and 2. Exploring the null hypothesis, the
six soil types found at Wild Basin can sustain the same plant life while one of them: Due to a difference
in soil biodiversity among the six plant communities found at Wild Basin, mammalian decomposition
rates among soil types will vary, was partially supported. Knowing this information can lead to a greater
understanding of human decomposition tendencies and experimentation in attempt to create optimal
growing conditions of crops by knowing what causes them to grow faster and more efficiently.
INTRODUCTION
Background
In the summer of 2013, a research study lead by Dr. David Johnson, assistant professor at St.
Edward’s University, concluded that there exist six distinct plant communities at Wild Basin Creative
Research Center. Located in Austin, TX, Wild Basin is home to hundreds of plant species and likewise,
plant communities ranging from riparian to grassland to forest. Dozens of mammals thrive in this these
environments and when these animals die and begin the process of decomposition, their decomposing
cadavers serve as incredible sources of carbon and nutrients to the soils in which they are decomposing.

2. In a study conducted in 2007 by David O. Carter,he demonstrated that belowground mammalian
decomposition can have a greater effect on belowground ecology than the other resources (plant and
fecal) and the results of his experiment in which he buried a mouse cadaver beneath a community of plant
life was an island of high concentrated fertility. A second study that Carter conducted two years earlier in
2005 concluded that mice decomposition occurs in varying rates among the three soils of differing
textures that he collected.
Purpose/Hypothesis
In order to accurately study whether or not: 1. Plant life experiences an increase in growth due to
an underground decomposing mammal, and 2. Different soil types can sustain the same plant life, an
experiment can be conducted in which unique soil samples are collected from distinctly different soil
types and planted with both the same seed type and a decomposing mammal. To accurately study whether
or not mammalian decomposition rates among soil types vary, an experiment can be conducted in which
unique soil samples are collected from distinctly different soil types and a decomposing mammal is
placed atop each of the soils, monitored daily for its decomposition rates. The three hypotheses for this
experiment are:1. In the presence of a belowground decomposing mammal, plants will experience an
increase in growth rate due to the nutrients released by the cadaver,relative to a control with no mammals
(animal/plant relationship), 2. Exploring the null hypothesis, the six soil types found at Wild Basin can
sustain the same plant life (plant/soil relationship), and 3. Due to a difference in soil biodiversity among
the six plant communities found at Wild Basin, mammalian decomposition rates among soil types will
vary (animal/soil relationship). In a forensic setting, these results may serve the purpose of being a model
to human decomposition (i.e. if it proves to be conclusive, calculating the post mortem interval with the
knowledge that humans do not decompose at the same rates in different environments).
METHODS AND MATERIALS
Animal/Plant Hypothesis, Soil/Plant Hypothesis
Three soil samples were collected from each of the six soil communities at Wild Basin (the three
samples being collected from three different areas of the site to maximize/emphasize the potential for site
diversity). The soil was left overnight to dry and then processed,removing plant debris such as seeds,
roots, leaves, etc. In the greenhouse, each of the soils were planted in separate planting spaces along with
a dead pinky mouse (purchased frozen and pre-dead) and two Brassica rapa seeds. Twelve days later,the
experimental design was completed again. However,it did not have mice planted within the soil and
therefore,would act as a control group. The plants were watered and measured daily and after twenty
eight days from the initial set-up, the mice were unearthed, cleaned, and weighed. Using the final and
initial masses,decomposition rates were calculated.
Animal/Soil Hypothesis

3. Excess soil samples collected from the previous experiment were placed in small, labeled
containers with holes poked around the bottom for water drainage. Eighteen new mice were purchased
and, surrounded by a makeshift wire cage,were placed on the ledge outside of the greenhouse. They were
photographed daily and monitored for decomposition. After twenty days, they were removed and
weighed. Twelve days later, the experimental design was completed again for a ten day decomposition
study. Using soil from the same collection group, eighteen new mice were placed in new containers and
monitored four times a day for their decomposition status. Ten days later, they were removed and
weighed. Lastly, using the initial and final masses,the decomposition rates were calculated.
RESULTS
Figure 1.1: Plant Height after Sixteen Days in the Soil without Mice
-2
0
2
4
6
8
10
Site 4 Site 5 Site 7 Site 8 Site 10 Site 11
Height(cm)
Plant Height after SixteenDays:Soil without Mice

4. Figure 1.2: Average Decomposition Rate for Aboveground Mice (the 10 and 20 Day Studies)
Figure 1.3: Average Decomposition Rate for Belowground Mice
0
0.05
0.1
0.15
0.2
0.25
0 5 10 15 20 25
DecompositionRate
Time (Days)
Average Decomposition Rate for AbovegroundMice
4
5
7
8
10
11
Sites
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0 5 10 15 20 25 30
DecompositionRate
Time (Days)
Average DecompositionRate for BelowgroundMice
5
7
8
10
11
Sites
4

5. Figure 1.4: Total Daily Height Average:With Mice vs. Without Mice
DISCUSSION
The experiment aims to address topics within the relationships among animals, plants, and soils. The
initial hypotheses stated that 1. In the presence of a belowground decomposing mammal, plants will
experience an increase in growth rate due to the nutrients released by the cadaver,relative to a control
with no mammals, 2. Exploring the null hypothesis, the six soil types found at Wild Basin can sustain the
same plant life, and 3. Due to a difference in soil biodiversity among the six plant communities found at
Wild Basin, mammalian decomposition rates among soil types will vary. At the close of the experiment, it
was concluded that the two of my hypotheses were unsupported while only one was supported.
In regards to the hypothesis 1 (see above),the growth averages per day were calculated among
the eighteen different soil samples for both test groups: with mice and without mice (see figure 1.4).
While the line representing the soils with mice appears to start two days sooner than the line representing
the soils without mice, it appears that the plants with mice grow at a slower, more constant rate than those
without. Based on the data derived from the experiment conducted, my original hypothesis stating that
plant growth will increase with the presence of a belowground decomposing mammal was disproven; the
daily average heights of the plants without mice appeared significantly higher than that of those with
mice. To improve the experiment and to get a more accurate idea of decomposition tendencies on plant
growth, one would need to allow the plants to grow for the duration of their entire lifecycle (which did not
occur in this experiment due to time constraints).
When looking at hypothesis 2 (see above), the control plant group in experiment 1was used to
monitor accurate plant growth. In figure 1.1, the plant heights after sixteen days are modeled by site (with
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Height(cm)
Number of Days
Total Daily Height Average:WithMice vs. Without Mice
With
Mice
Without
Mice

6. an average of the three samples collected). It is evident that not all plants grew to the same height—while
site 8 grew to an average of almost 8 centimeters while site 10 failed to reach 2 centimeters. In sites that
have the largest error bars—in sites 7, 10, and 11—there existed at least one seed that failed to germinate
(resulting in such a large error margin), disproving my original hypothesis that all six soil types found at
Wild Basin can sustain the same plant life. To improve the experiment and to get a more accurate idea of
the soil’s effect on seed germination, it is essential that multiple trial runs be completed, as opposed to
just one.
For hypothesis 3 (see above), decomposition rates were calculated for all mice involved in the
experiment (see figures 1.2 and 1.3) and the values were graphed. For figure 1.2, there appears to be little
relation to the decomposition rates at day 10 and the decomposition rates at day 20. However, there does
exist two important relationships between the sites: sites 5 and 8 (the forest sites) seem to have similar
decomposition rates and likewise, sites 4 and 10 (the dry grassland sites) seem to have similar rates. This
suggests that perhaps decomposition rates are related to soil types, though related in a way other than
what was previously studied. Figure 1.3 demonstrates little correlation to figure 1.2, suggesting that
decomposition rate is not reflected by soil type, disproving my original hypothesis that due to a difference
in soil biodiversity among the six plant communities found at Wild Basin, mammalian decomposition
rates among soil types will vary. To improve the experiment and to get a more accurate idea of the role of
soil on animal decomposition, a larger test subject would be needed and also, it is important that the soil
be left in its original environment to ensure that moisture levels of the water are accurate.
REFERENCES
Carter,David O.,David Yellowlees, and Mark Tibbett. "Cadaver decomposition in terrestrial
ecosystems." Naturwissenschaften 94.1 (2007): 12-24.
Carter,David. O. Forensic taphonomy: processes associated with cadaverdecomposition in
soil.Diss. James Cook University, 2005.