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7/30/2019 Effects of Wetland Microtopography on Hydric Soils
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Effects of Wetland Microtopography on Hydric Soils
Nicholas R. Fink
Geography 313 Lab Report 2
Abstract
Wetlands are areas that have become either saturated or inundated by the amount of water
seeping through the soil from groundwater or surface water and can support a majority of flora
adapted to those conditions. The objectives of this lab were to characterize wetland
microtopography by transit and hand leveling techniques, to experience characterization process
by working in small groups and to prepare a scientific report on the findings. The areas studied
were located at Shaver's Creek in Barree Township, Huntingdon County, Pennsylvania on the
eastern slope of Tussey Mountainn and Emerick Mitigation which is located northwest of
Cambria Township, Cambria County, Pennsylvania. Field work was excuted using transits and
stadia rods to measure microtopography and pits were dug to check for hydric soils. The results
of the comparison between the natural and manmade wetlands were closer than I would have
expected, although there were some definite differences between the two. A better option when
building a wetland would be to use heavy machinery to thoroughly rough up the soil and create
greater microtopographic variation.
IntroductionWetlands are areas that have become either saturated or inundated by the amount of water
seeping through the soil from groundwater or surface water and can support a majority of flora
adapted to those conditions. Three categories establish an area as a wetland: vegetation,
hydrology and soil type. Hydrophytes, or plants species adapted to life in an inundated or
submerged area, are one of the requirements for an area to be classified as a wetland. The
hydrology of a wetland is simply that the area is either saturated or inundated by groundwater or
surface water permanently or seasonally, but it does not exceed 2 meters in depth as that is
defined as a deepwater aquatic habitat. Soil in a wetland can only be hydric, or a soil that
developed under reduced circumstances (anaerobic) (Wilen and Bates 1995).
Microtopography is an important factor in the biodiversity of wetlands. Microtopography
is essentially the roughness of a small area of ground. In a natural wetland there is generally a
fairly rough surface that is conducive to plant and animal species variation. In a manmade
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setting there tends to be less microtopological variance (a flatter surface) and this leads to a
decrease in the biological diversity of the area (Vivian-Smith 1998). The main factors in causing
this is the difference is water table depth and water outflow, specifically the size and duration of
the outflow. Natural wetlands have higher water table depths and decreased water outflow and
increased duration of the outflow (Tweedy et all 2001).
Soil pits are often dug to characterize whether or not soils are hydric. The pits are usually
around a .3 meters wide and 30 centimeters deep. Several methods are then used to determine
whether or not the soil is hydric, including color matching using the Munsell soil chart and
looking for oxidization around plant roots and mottles. Mottles are orange-reddish brown or
dark-reddish-brown/black, depending on what mineral type, that form in soils that are seasonally
flooded. Mottles are typically found in gleyed soil, which is soil that is often flooded to the point
that the iron in the soil chemically reacts to the saturation (Mitsch et all 1993).
The objective of this lab were to characterize wetland microtopography by transit and
hand leveling techniques, to experience characterization process by working in small groups and
to prepare a scientific report on the findings. The two wetlands studied were Shaver's Creek and
a manmade wetland known as the Emerick Mitigation. Shaver's creek is located in Barree
Township, Huntingdon County, Pennsylvania on the eastern slope of Tussey Mountain. Emerick
is located northwest of Cambria Township, Cambria County, Pennsylvania.
Methods and Materials
Study Area
The natural wetland we studied was a floodplain of Shaver's Creek (40.6675 N, 77.9051 W). It
is located in Barree Township, Huntingdon County, Pennsylvania and is part of the Pennsylvania
State University's nature center. The area studied was characterized by a slope in the southeast
down to the wetland, which was a wooded area with a variety of fauna and evidence of a deer
population. Soils in the area were Atkins silt loam near the creek, indicating a floodplain, and
Ernest silt loam on the hill (Figure 1).
The manmade wetland studied was the Emerick Mitigation (40.5256 N, 78.7718 W)
located in northwest Cambria Township, Cambria County, Pennsylvania. The area around the
mitigation is mostly cleared, with some trees. The soils around Emerick are mainly Cookport
and Ernest soils, which indicate a mountaintop location (Figure 2).
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We began our field exercise to examine the microtopography of Shaver's Creek wetland
by measuring out a 50 meter transect with a tape measure at the bottom of a small hill off the
main road of Shaver's Creek. Next our group set up a transit to measure the elevation of the land
every meter using a stadia rod. At each one meter mark, the area was marked as dry, saturated or
inundated. The collected data was then inserted into a spreadsheet prepared by the course
instructor to compare the results we collected to a pre-collected data set for Emerick Mitigation.
After all 50 measurements were taken, our group moved on to examining the difference
between the soil at the top of hill near the road and at the end of the transect in the wetland. To
accomplish this, two pits were dug to a depth of 20 centimeters at each location. We then used
the Munsell soil chart to study the differences between the two locations and made notes on
whether or not they were inundated. The holes were then filled back in once all the
measurements had been taken.
The data for Emerick Mitigation was already provided by the instructor. It should be
noted that 100 measurements were taken for Emerick, instead of 50, and only one pit was dug for
the manmade wetland.
Results
The results of the comparison between the natural and manmade wetlands were closer
than I would have expected, although there were some definite differences between the two
(Figures 5 and 6). The natural wetland had higher average mound heights and lower average
depression depths, at 5.0 centimeters and -4.6 centimeters, respectively. This contrasts with
Emerick Mitigation's average mound height of 3.6 centimeters and average depression depths of
3.1 centimeters. Emerick had the lowest point of the two, with a microtopographic reading of
5.5 centimeters in one depression (Tables 1 and 2).
The pits at the natural wetland were fairly different (all numbers in parenthesis refer to
Figure 3 when noting 10 yr and Figure 4 when noting 7.5 yr). The first pit excavated at Shaver's
Creek at a higher elevation than the floodplain had a texture of silty loam (10 yr, 4/3, brown)
with 30% mottle (10 yr, 3/2, dark brown) and was moist at a depth of 5 centimeters, with no
oxidized roots. At a depth of 20 centimeters (7.5 yr, 5/6, orange-brown), the same conditions
applied except that mottle was reduced to 7%. This indicates no hydric soil. In the second low
elevation in the wetland, the pit showed saturated silty clay (10 yr, 4/1, grey), with no mottle at a
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depth of 5 centimeters with no oxidized roots, while at 20 centimeters it was saturated and had a
clay texture (10 yr, 5/4, orange-brown) with around 50% mottle (7.5 yr, 3/2, orange-brown) and
oxidized roots. This is a very good indication of hydric soil.
At the manmade wetland, only one pit was dug. At the 5 centimeter mark, the texture
was a moist silty clay (10 yr, 5/2, grey-brown) with oxidized roots and was not reduced. Mottle
began to show at around 6 centimeters (10 yr, 6/1, grey). At 20 centimeters the texture had
changed to moist clay (7.5 yr, 5/6, orange-brown) with around 40% mottle and oxidized roots
and the soil had become reduced, indicating hydric soil.
Discussion
A difference between the two types of wetlands became apparent after examining the data
for both Shaver's Creek and Emerick Mitigation. The natural wetland had more variation in its
microtopography than the manmade one. This is likely because the natural wetland was created
by sediment deposition from flooding events and the natural debris that can be found in woody
areas. Emerick Mitigation was probably created using bulldozers or other large machinery and
smoothed out because it is in a more populated area and receives more sediment from the settled,
which can lead to species reduction (Werner and Zelder 2002).
The differences in soil between high and low elevations at Shaver's Creek were stark.
The browner coloration of the higher elevation soil is most likely due to the lower amount of
water in the soil, as opposed to down the slope where the wetland keeps the soil soaked year
round, leading to oxidization of the minerals present. A similar situation is present at Emerick,
most likely due to the fact that the area is used to prevent flooding, which cause the surrounding
soils to be oxidized from excessive saturation.
If I were to construct a wetland, I would go about it differently than was done at Emerick.
The more homogenous terrain does not support the kind of species diversity that makes up a
healthy ecosystem. A better option would be to use heavy machinery to thoroughly rough up the
soil and create greater microtopographic variation. I would also seed the area with hydrophytes
and put in features such as downed trees to attract species that would help to create a healthy
ecosystem.
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Literature Cited
Mitsch, W.J. et all. 1993. Wetlands. 2: 119-121. New York.
NRCS. 2011.http://websoilsurvey.nrcs.usda.gov/app/homepage.htm . Accessed 11-10-11.
Tweedy, K.L., et all. 2001. Influence of Microtopography on Restored Hydrology and Other
Wetland Functions. 2001 ASAE Annual International Meeting. Paper 01-2061.
Vivian-Smith, G. 1997. Microtopographic Heterogeneity and Floristic Diversity in Experimental
Wetland Communities. The Journal of Ecology. 1: 78-82.
Werner, K.J. and J.B. Zedler. 2002. How Sedge Meadow Soils, Microtopography, and
Vegetation Respond to Sedimentation. Wetlands. 3: 451-466.
Wilen, B.O. and M.K. Bates. 1995. The US Fish and Wildlife Service's National Wetlands
Inventory Project. Vegetatio. 1/2: 153-169.
http://websoilsurvey.nrcs.usda.gov/app/homepage.htmhttp://websoilsurvey.nrcs.usda.gov/app/homepage.htmhttp://websoilsurvey.nrcs.usda.gov/app/homepage.htmhttp://websoilsurvey.nrcs.usda.gov/app/homepage.htm7/30/2019 Effects of Wetland Microtopography on Hydric Soils
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Figure 1. Pictured above is the area of Shavers Creek examined by our group on 10-87-11. It islocated in Barree Township, Huntingdon County, Pennsylvania on the eastern slope of Tussey
Mountain. The area is outlined in blue, with soil types noted in orange. (NCRS 2011)
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Figure 2. Pictured above is the area of Emerick Mitigation examined on 8-6-2007. Emerick is
located northwest of Cambria Township, Cambria County, Pennsylvania. The area is outline inblue with soil types noted in orange. (NCRS 2011)
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Figure 3. Pictured above is a 10 yr Munsell soil chart like the one used in our groupsexamination of Shavers Creek on 10-7-11. It is located in Barree Township, Huntingdon
County, Pennsylvania on the eastern slope of Tussey Mountain.
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Figure 4. . Pictured above is a 7.5 yr Munsell soil chart like the one used in our groups
examination of Shavers Creek on 10-7-11. It is located in Barree Township, Huntingdon
County, Pennsylvania on the eastern slope of Tussey Mountain.
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Figure 5. Pictured above is the plot of the microtopography of the transect studied at ShaversCreek on 10-7-11. It is located in Barree Township, Huntingdon County, Pennsylvania on theeastern slope of Tussey Mountain.
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Figure 6. Pictured above is the plot of the microtopography of the transect studied at Emerick
Mitigation on 10-7-11. Emerick is located northwest of Cambria Township, Cambria County,Pennsylvania.
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Microtopo Indeces
Sum of mounds (cm) 110.2
Sum of depressions (cm) -114.1
Count of mounds 22
Count of depressions 25
Avg. mound height (cm) 5.0
Avg. depression depth (cm) -4.6
Sum of absolute deviation (cm) 224.3
Std. Dev of Elevation(m) 0.140
Count of Dry mounds 8
Count of Inundated depres. 10
Max Reading (m) 1.74
Table 1. Pictured above is a table of key values for the Shavers Creek data set from 10-7-11. Itis located in Barree Township, Huntingdon County, Pennsylvania on the eastern slope of Tussey
Mountain.
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Microtopo IndecesSum of mounds (cm) 162.8
Sum of depressions (cm) -166.5
Count of mounds 45
Count of depressions 53
Avg. mound height (cm) 3.6
Avg. depression depth (cm) -3.1
Sum of absolute deviation (cm) 329.3
Std. Dev of Elevation (m) 0.169
Count of Dry mounds 12
Count of Inundated depres. 31
Max Reading (m) 2.19
Table 2. Pictured above is a table of key values for the Emerick Mitigation data set from8-6-07. Emerick is located northwest of Cambria Township, Cambria County,Pennsylvania.