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.htm


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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.

Documents

Effects of Wetland Microtopography on Hydric Soils