constructed or natural: what is a more suitable...
TRANSCRIPT
Constructed or Natural: What is a More Suitable
Wetland?
Phillip K. Adasczik
Geography Department,
The Pennsylvania State University, State College, PA 16801, USA
Abstract
A field experiment was performed to evaluate the similarities and or differences between two local
wetlands; Shaver’s Creek (a natural wetland) and Emerick wetland (a constructed wetland).
Wetlands can be defined as areas where the ground is inundated or saturated throughout a
majority of the year. They are normally classified through the observation of hydrology, vegetation,
and soil presence. Wetlands are of extreme importance to environments as they control water flow,
erosion, flooding, and offer shelter for various plant and animal species. Wetlands filter out
abundances’ of sediments and or nutrients through filtration thus improving water quality at a
much earlier cycle stage. A major influence of wetlands are simply other flows of water that reach
these wetlands, however the influence in alteration from human development; such as urban and
agricultural means has gradually redefined these wetlands. For both the natural and constructed
wetland locations, microtopography was recorded by utilizing a tripod transit and stadia rod. This
allotted for the reading of elevations in the study areas. The differentiation between the two study
areas were implementations of surface depressions. The natural wetland had depressions, whereas
the constructed did not.
Introduction
What exactly is a wetland? The US Fish and Wildlife Service (USFWS) states wetlands are “Lands
transitional between terrestrial and aquatic systems where the water table is usually at or near the
surface or the land is covered by shallow water. A wetland’s classification must have one or more of
three attributes: 1) at least periodically, the land supports predominantly hydrophytes; 2) the
substrate is predominantly un-drained hydric soil; 3)the substrate is non-soil and is saturated with
water or covered by shallow water at some time during the growing season of the year” (Rocco,
2013). The US Army Corps of engineers (USCOE) defines a wetland as “Areas that are inundated or
saturated by surface or ground water at a frequency and duration sufficient to support, and that
under normal circumstances do support, a prevalence of vegetation typically adapted for life in
saturated soil conditions” (Rocco, 2013).
A wetland is simply classified by its present characteristics in regards to hydrology, vegetation
and soil. Hydrology is the presence of water within an area, thus determining the driving factors
that compose a wetland. In the instance that water is of absence, then hydrophytes would struggle
to grow or establish within the wetland. This would also result in the absence of reduced soils
(Rocco, 2013)
There are various wetland types and these types are classified in correlation to how water is
delivered to the wetland. The saturation rate and frequency of hydrological processes are all taken
into consideration, hence dictating the hydrophyte and soil establishment in these areas (Rocco,
2013). Ultimately, wetlands are dependent upon the hydrology factors. In Pennsylvania, the
different wetland types are as follows: Headwater Floodplain, Mainstream Floodplain, Isolated
Depression, Riparian Depression, Fringing, and Slope wetlands. Just like wetlands in other regions,
Pennsylvania’s wetlands are dependent on the geographic structure of the land. The topography
also has an effect on the micro topography in wetlands, which influences the variance in elevation.
Variance in a wetland can range from one centimeter to one meter and the change in variance
implements micro topography heterogeneity and floristic diversity (Vivian-Smith 1997). Micro
topographic heterogeneity is considered to be a major determinant and its coexistence is thought to
be facilitated in heterogeneous environments due to interspecific differences in habitat preference.
Micro topographic heterogeneity is a major factor structuring natural freshwater wetland
communities and is thought to influence diversity (Vivian-Smith 1997).
Wetland vegetation is highly constructed of plants that are adaptive and tolerant to both inundated
and saturated soils. The vegetation dynamics and species diversity of many plant communities are
thought to be strongly influenced by soil nutrient heterogeneity. Microtopographic variation has
been strongly correlated with plant distribution and performance, for individual plant species and
for plant communities in wetlands (Vivian-Smith 1997). Explanations for such patterns include
deferential seed accumulation variation in species germination requirements; and differences in
growth and mortality at different microtopographic positions (Vivian-Smith 1997). These adaptive
and tolerant plants to inundated and saturated soils are known as hydrophytes (Rocco 2013).
Hydrophytes exhibit morphological, physiological, and reproductive adaptations. Examples of these
would include exposed roots on the surface, tree trunks, and viable seeds. To be classified as a
wetland, an area must be dominated by these hydrophytes; which would contain a minimum of
50% facultative wetland (FACW), and Obligate wetland (OBL) (Rocco 2013).
The last factor in wetland classification is soil. Soils that are established with wetlands are normally
hydric soils. Hydric soils are substrates providing reducing conditions as a result of temporary or
permanent inundation or saturation. Essentially, hydric is associated with the presence or living or
deceased organic material within the soil. All other hydric soils are mineral soils with duration of
inundation, largely determining classification (Finlayson and van der Valk 1995). Hydric soils are
often affiliated with anaerobic conditions because porous structures of the soil reduce the diffusion
of oxygen. The reduction process of removing oxygen is known as “Reducing Environment”, which
is the reduction or oxidation of electrons within the soils. Reduction is the gain of electrons in the
soil; whereas oxidation is the loss of electrons in the soil. Processes of Oxidation normally resemble
a red or brown soil color, which is a result from iron in the soil. Soils that endure processes from
reduction are usually represented by a blue or gray hue. The lowering of soil potential is the last
step in the Environment Reduction process, resulting in further decomposition elements such as
sulfur (Semeniuk and Semeniuk 1995). With high variance in soil composition, it is recommended
to utilize a Munsell Soil Color Chart to correlate which soils are closely related and or present in an
area.
The overall objective of the wetlands project was to determine if a natural wetland is a more
sustainable habitat as opposed to a wetland constructed by human beings. Is there substantial
evidence that characteristics’ of a constructed wetland could be placed in any location or does it
need support from various soil types to thrive in a particular location? Lastly, could the micro
topography of a natural wetland be replicated by a constructed wetland?
Methods
Study Area. --- The study was conducted at Shaver’s Creek in Huntington County, Pennsylvania
near Petersburg, PA. Coordinates in decimal degrees for the site are as follows: 40.66599, -
77.907852. The observed study area was located within close proximity to both Shaver’s Creek and
Lake Perez. Shaver’s creek is facilitated on the eastern slope of Tussey Mountain, which is located
just north of Route 26 (Huntington County). Shaver’s creek drains a significant portion of the Penn
State Stone Valley forest (Rocco, 2013). We can classify this wetland as a “Slope” wetland; the slope
gradient was 10 degrees and the drainage basin was 6.95 square miles. The average elevation is
412m and the average temperature is 56 0F. Vegetation covers roughly 95% of the area and the
present soil types in the location were Atkins Silt Loam (Aw) and this covered roughly 47% of the
area.
The Emerick wetland is in Cambria County, Pennsylvania in Cambria Township. Coordinates in
decimal degrees for the site are as follows: 40.5256, - 78.7718. The Emerick wetlands are also
roughly 250 meters away from Scout Dam Road, which is a part of the Williams Run Reservoir. The
slope gradient for this location was six degrees and the drainage basin was 0.08 square miles. The
average elevation is 680m and the average temperature is 550F. Present soil types in the location
were Wharton silt loam, Laidig Loam; slopes of 3-8 degrees and 8-15 degrees, Hazelton Channery
Loam; slopes of 3-8 degrees and 8-15 degrees, Ernest, and Cookport loam. Cookport and Ernest
were the dominant soils of the area at about 40% coverage. All of these soils correlate to various
slope gradients.
Upon arrival of the wetland near Shaver’s creek, the first objective was to establish a suitable area
for our transit setup. In doing so we had to factor in that the transit should be set up on the upland
side of the wetland. Setting the transit up on the upland side of the wetland eliminates error when
siting the stadia rod. Considering our group was fairly large (about 6-7 people) , half of the group
finished setting up and leveling the transit; while the others measured a 50m distance across the
swamp. This distance was measured from the center of the transit to the 50m position marked
across the swamp. Once this was done, we had to clarify that the line of sight from the transit to the
50m mark was clear from all vegetation, debris, etc. to complete the setup process. It was necessary
to leave the measuring tape laid out across the swamp because we would need reference to record
other data, such as elevation. The next step was to record elevations using the stadia rod by
transitioning it in 0.5 m until we reached the 50m designation. In doing so we would have data
collections for 100 points. Elevation recordings were conducted by glancing through the transit and
identifying the measurements on the stadia rod by referencing the center stadia line. In
collaboration with the Geo313 technician holding the stadia rod, another technician recorded
observations of ground characteristics for every 0.5m increment within the 50m baseline. These
characteristic observations included ground saturation (wet or dry), and whether there was
herbaceous or non-woody vegetation, woody vegetation, coarse or fine woody debris, and barren
or denuded soil, no vegetation present.
Half of the group that was not partaking in the elevation data inquiry began to excavate two soil pits
on both the upland terrain and on the lower wetland terrain. Each pit had to be at least 20cm deep
to register an accurate reading and identification of not only dry or saturated soils; but non-hydric
and hydric soils as well. In order to establish true soil characteristics via the Munsell Soil Color
Chart, samples were taken at both 5 and 20cm depths within the pit. This would further determine
what soils were present in each soil pit.
Upon completion of soil sampling, it was apparent that the group collecting elevation data points
still had some work to do. The Geo313 technicians that recently took the soil samples took it upon
themselves to continue the lab by identifying and recording fallen debris such as trees, branches,
and ground depressions along the 50m baseline. Fallen branch measurements ranged from (1-
12cm in length), trees from (12-40cm in length), and large trees from (40cm or > in length). This
was simply conducted by walking the baseline and recording the data while walking. The
recordings were assigned to predetermined data sets in the lab as displayed in Tables 1 and 2.
Depression recordings were also broken down into predetermined data sets as displayed in Table
3. Depression count was recorded into various size classes. After the data observations were
complete for the area within the 50m baseline, each group member was responsible for repairing
the disturbed land as a result from the lab processes to the best capability.
Results
The natural wetland for Shaver’s Creek produced some prevailing evidence in correlation to
floodplain characteristics. Considering the total of one hundred observations; there were various
categories that entailed the physical characteristics of micro topographic indices. Documentation of
hydrology and vegetation at each rod location was necessary. Points were marked in order of
saturation followed immediately by vegetation cover. Saturation classifications were Dry substrate
(D), Saturated; substrate is moist but not inundated (S), Inundated; surface is covered by water (I).
While vegetation cover was classified as Herbaceous or non – woody vegetation (Vh), Woody
Vegetation (Vw), Coarse or fin woody debris (CFWD), and Barren or denuded soil, no vegetation
(B). Herbaceous or non-woody vegetation (Vh) accounted for a total of 36 points with a frequency
of 0.36% out of the total 100 points. Woody vegetation accounted for just 3 points or 0.03%, while
Coarse or fine woody debris (CFWD) contained 57 points at a frequency of 0.57%. Barren or
denuded soil, no vegetation (B) was just 4 points or 0.04% of the overall 1oo points. The total
depressions accounted for was 61 with an average depression depth was -2.6 cm. The upland soil
pit contained both silty loam and silty clay loam; silty loam at the 5cm depth and silty clay loam at
the 20cm depth. The inland soil pit contained silty loam at both the 5 and 20cm depth. There were a
total of 11 depressions along the 50m baseline that averaged a depth of 0-15cm. Concluding the
Shaver’s creek data were 4 saplings (1-12cm) and 1 tree(12-40cm). The overall soil descriptions for
the Shaver’s Creek pit are as follows: in the 5cm depths; 10YR4/3- 0-10 in, dark brown silt loam;
weak fine granular structure; friable; 10% coarse fragments; very strongly acid; abrupt smooth
boundary. In the 20cm depths;10YR5/6- 10-19 in, yellowish brown silty clay loam; weak fine and
medium block structure; slightly sticky, non-plastic; coarse fragments at 10%; very strongly acid;
gradual wavy boundary.
For the constructed Emerick wetland, 9% of the 50m baseline was dry, 26% was saturated and
54% was inundated. The baseline was composed of 30% barren land (B), 2% was coarse fine
woody debris (CFWD), 8% woody vegetation (Vw), and 60% herbaceous vegetation (Vh). The
average depression depth was -3.1 cm with an average mound height of 3.6cm out of a total 56
depression count. The Emerick pits contained both silty loam and silty clay loam at the 5cm and
20cm depths. There were a recorded 5 branches and or saplings and 0 depressions along the 50m
baseline. The overall soil descriptions’ for the Emerick wetland are as follows: In the 5cm depth
10YR4/1- 0-4 in; dark gray silt loam; weak fine granular structure; slightly plastic; many roots;
strongly acid; clear smooth boundary .In the 20cm depth; 10YR6/1- 9-46 in; gray clay loam;
common medium distinct brown and strong brown mottles(7.5YR5/6); moderate medium
prismatic structure; firm, very sticky, very plastic; many small pores; very strongly acid; gradual
wavy boundary.
Discussion
In terms of differences between the study wetland; and that of the constructed wetland micro
topography, they were actually quite subtle. Noticeable data from the soil samples was the concrete
evidence amongst the two site locations. The soil samples taken from Shavers Creek area displayed
both gleying and redox soils. Both of these soils are indicators of inundation amongst soils for a
substantial amount of time (Ricardo and Fennessy, 2002). Water accumulation at the bottom of the
wetland pit is also an indicator of hydric soils, as mentioned earlier. Also, the presence of
hydrophytic vegetation at both Shaver’s Creek and Emerick wetlands only suggest that there is
hydric soils because this type of vegetation thrives of this particular soil contrast and it is necessary
for them to establish in an area (Werner and Zedler, 2002) . So the characteristics in hydrology,
vegetation, and soil were relatively similar as discussed earlier and the only speculation I could
distinguish was landform depressions. There was a considerable amount of landform depressions
present within the natural wetland, whereas the constructed wetland had none. We can speculate
that the depressions amongst the natural wetland are present, simply because of the fact that the
land was not disturbed in any man made processes. The constructed wetland utilized
organizational processes from machinery that most likely led to a similar and or more leveled
surface area throughout this wetland.
In fact, the average mound height for the Emerick constructed wetland was 3.2cm; while the
depression depth average was -2.9cm. This would again imply that the mounds in the wetland are a
result from the machine based disturbances. As a Wetland Constructor, I would attempt to replicate
micro topography observed in natural wetlands by simply altering the processes of machine work.
Considering the land is tilled, we could either alter the process or change how the land is regulated
all together. This altering would yield higher variance throughout the wetland, hence more
accurately replicating micro topography in natural wetlands.
References
Werner, K. J. and Zedler, J.B, 2002. How sedge Meadow Soils, Microtopography, and Vegetation
Respond to Sedimentation., No. 3, September 2002, pp. 451–466
Semeniuk, A and Semeniuk V., 1995. A Geomorphic Approach to Global Classification for Inland
Wetlands. Classification and Inventory of the World’s Wetlands, No. ½ June 1995, pp. 103-124
William M.J, and Renee W.F, 1996. Improving the Success of Wetland Creation and Restoration with
Know-How, Time, and Self-Design, No. 1, February 1996, pp. 77-83
Ricardo L.D. and Fennessy M.S. 2002. Testing the Floristic Quality Assessment Index as an Indicator
of Wetland Condition, No. 2, April 2002, pp. 487-497
Finlayson M.C. and Van der Valk G.A. 1995. Wetland Classification and Inventory of the World’s
Wetlands: A Summary, No. ½, June 1995, pp. 185-192
Vivian-Smith, G. Microtopographic Heterogeneity and Floristic Diversity in Experimental Wetland
Communities. 1997. The Journal of Ecology, Vol. 85, No. 1. (Feb., 1997), pp. 71-82.
Rocco G.L., Lecture, GEOG313: Field Geography, 2013
United State Geological Survey Stream Stat Application for Pennsylvania.
http://streamstats.usgs.gov/pennsylvania.html
United States Department of Agriculture Natural Resources Conservation Service Web Soil Survey
Tool. http://websoilsurvey.nrcs.usda.gov/app/HomePage.htm
Figure 1: This diagram depicts the different types of wetlands and where they normally are
located geographically. This diagram displays not only the occurrences of where wetlands
occur, but also the processes involved.
Figure 2: Study area of the natural wetland near Shaver’s Creek, Barre Twn. PA. Location of
microtpography experiment collaborated by the Geo313 technicians’ on October 11, 2013. This map
was constructed on October 25, 2013.
Figure 3: Depiction of the constructed Emerick wetland in Cambria Township, PA. Both microtopography
and data were collected in this location. This map was constructed on October 25, 2013.
Figure 4: The Shaver’s Creek Wetland drainage basin; constructed by utilizing the USGS stream
stat tool. This depicts the water flow amounts into the basin. The figure was created on
October 25, 2013.
Figure 5: The Emerick wetland drainage basin; constructed by utilizing the USGS stream stat
stool. This depicts the water flow amounts into the basin. The figure was created on October
25, 2013.
Figure 6: Soil map for Shaver’s Creek natural wetland accompanied by the Huntington County,
Pennsylvania soil types for this location. Figure was created by utilizing the United States
Department of Agriculture Natural Resource Conservation Service website; created on October
25th, 2013
Figure 7: Using the web soil survey on the United States Department of Agriculture Natural Resource
Conservation Service website the image displays the Emerick wetland; created on October 25th, 2013.
Figure 8: The microtopography of the natural wetland near Shaver’s Creek was created by using
Microsoft Excel and it depicts the Field Observations vs. the Predicted Microtopography of the wetland
location. This graph was created on November 3, 2013
Figure 9: The microtopography of the Emerick wetland data that was previously collected in 2007, that
was later implemented in an Excel spreadsheet . This graph depicts the microtopography of both the
predicted and field observations for this wetland. This graph was created on November 3, 2013
0
10
20
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60
70
80
1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67 70 73 76 79 82 85 88 91 94 97 100
FieldObs.
0
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1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67 70 73 76 79 82 85 88 91 94 97 100
FieldObs.
Table 1: The different sizes of woody debris and how many times a specific size class of tree
was observed along the 50 meters of wetland that the Geog313 group I participated in; was
measuring during the lab in the natural wetland near Shaver’s Creek on October 12, 2012.
Table 2: Dedifferentiation amongst woody debris and how many times a specific size class of tree was observed along the 50 meters of the Emerick wetland. The data was collected in August 6, 2007.
Size Class Midpoint Count Total
Branches and Fallen Saplings
(1-12 cm)
6 cm (2.3in) 5
Trees ( >12-40 cm) 26 cm (10.1in) 0
Large Trees ( >40 cm) N/A 0
Table 3: Counts of micro topographic depressions to see how many dips were present in the 50 m section of the wetland being observed by the Geog313 group I was in during the lab period on October 12, 2012.
Depth Class (cm) Count Total
0-15 11
15-30 0
30-45 0
>45 0
Size Class Midpoint Count Total
Branches and Fallen Saplings (1-12cm)
6 cm (2.3 in) 4
Trees (>12-40cm) 26 cm (10.1 in) 1
Large Trees (>40cm) N/A 0