Every day you walk to class, maybe play some sports outside, and hopefully get food from somewhere. In order to do these things, I would assume you are standing on something as well, probably not majestically floating about and defying physics. Assuming you have not found a way yet to oppose gravity, you are standing on soil as you engage in any outdoor activity that involves you moving from place to place.

Have you ever wondered what specifically it is that you are walking on though? What is it that makes up our Earth?

For this blog, I intended to focus on profiling the soils of Centre County, Pennsylvania and explaining some ways that us humans can make a better footprint on our world to allow for soil and animal conservation.

First, I would like to introduce you to a helpful tool called the Web Soil Survey created by the United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS). This is an easy-to-use satellite system that has programmed in every soil in every region down to the specificity of series (Figure 1) and landscape position (Figure 2).

If you would like to follow along, I will show you step-by-step how to generate the maps I am about to explain. If not, I won’t be hurt at all, I promise!

Using NRCS Web Soil Survey Tutorial

(Totally optional!)

1. Click here to go to the NRCS Web Soil Survey page
2. Go to the Area of Interest (AOI) tab in the Web Soil Survey.
   

   Step 2

3. Find Quick Navigation and scroll to the State and County Tab. Input Pennsylvania for the state and Centre County for the county. Select view and your map should show an outline of the county.
   

   Step 3

4. Then, under Quick Navigation, you will need to select the Soil Survey Area tab and input our state and county again. Select the name that pops up below along with “Show Soil Survey Areas Layer in Map.”
   

   Step 4

5. After this, select “Set AOI.”
   

   Step 5

6. Scroll up to find the AOI Properties tab and ensure that Soil Survey Area Map Unit Symbols are selected.
   

   Step 6

7. Then, go to the very top of the page to find a Soil Map section. You will see an orange map of Centre County now.
   

   Step 7

8. From there, you will need to use the zoom-in button to actually see the map key. To do so, click the zoom-in button and the click on the screen where you want to zoom in.
   

   Step 8

9. Another faster way that you can accomplish this same goal is by going back to the AOI section and selecting “Latitude and Longitude or Current Location” to put in your coordinates.
   

   Step 9

10. If you are like me and do not want to look that up, you can also just go to “Address” under “Quick Navigation” and type in “University Park, Pennsylvania” or “Mount Nittany.” Make sure “Show Location Marker” is selected, however. Be sure to select the view button before moving on to the last step.
    

    Step 10

11. Once zoomed in enough that you can see the symbols, take note of the letters you see most frequently and then click on them for more detailed descriptions in the “Map Unit Legend” tab.
    

    Step 11

For our analysis of what we are walking on most in Centre County, I have devised two maps, one of University Park (Figure 3) and one of the transition into Mount Nittany using the method I described above.

From our University Park soil map, we can primarily see symbols of HaB, HaA, OhB, OhC, and OxB in the landscape position we will most be frequently interacting with. What do these symbols mean though? They are the Soil Survey Area Map Unit Symbols and signify a soil series. Series is essentially the soil version of species in the animal kingdom – it is as specific as you can possibly get. So, in order we have Hagerstown silt loam, 0 to 3 percent slopes (HaA), Hagerstown silt loam, 3 to 8 percent slopes (HaB), Opequon-Hagerstown complex, 3 to 8 percent slopes (OhB), Opequon-Hagerstown complex, 8 to 15 percent slopes, and Opequon-Rock outcrop complex, 0 to 8 percent slopes (OxB). Let us simplify this by finding the actual taxonomic names for these soils. The Hagerstown series is listed as “fine, mixed, semiactive, mesic Typic Hapludalfs” while the Opequon series is listed as “clayey, mixed, active, mesic Lithic Hapludalfs.” These modifiers describe the soil properties, but let us focus in on the fact that both the Hagerstown and Opequon series are Hapludalfs. I seek to do this because Hapludalfs both belong to Udalfs under the large soil order of Alfisols.

So what even is an Alfisol? Alfisols are one of 12 other soil orders characterized for being moderately leached and having a B horizon with clay accumulation (argillic, kandic, or natric), having a relatively high fertility, and being formed under forest cover in a temperate humid or subhumid region. To be distinguished from Ultisols, a soil order we talked about in the last blog (that red Georgia clay), the base saturation must be at least 35% in the subsoil. This means that Alfisols have a more basic pH than Ultisols, which are inherently more acidic. I mentioned that the specific Alfisols that we have here at The Pennsylvania State University are, in fact, Udalfs. An Udalf is an Alfisol of an Udic temperature regime, which means that the area is humid enough for the soil to not need irrigated (Figure 4). Coupled with the high fertility, Udalfs make for great farming opportunities.

Let us now take a look at Mount Nittany’s soils to see if we can find any differences (Figure 5).

Where did all the Hagerstown and Opequon series go? We instead have many orders here that seem to correlate to topography. We are going to examine only a few to avoid getting tedious. Starting from the bottom of Mount Nittany and working our way to the summit, we have AnC, LaC, LcD, LDF, HSD to name just a few. These series correspond to Andover channery silt loam, 0 to 8 percent slopes (AnC), Laidig channery loam, 8 to 15 percent slopes (LaC), Laidig extremely stony loam, 8 to 25 percent slopes (LcD), Laidig extremely stony loam, steep (LDF), and Hazleton extremely stony sandy loam, moderately steep (HSD). The Andover series is listed as “fine-loamy, mixed, active, mesic Typic Fragiaquults,” the Laidig series is listed as “fine-loamy, siliceous, active, mesic Typic Fragiudults,” and the Hazelton series is listed as “loamy-skeletal, siliceous, active, mesic Typic Dystrudepts.” From these names, we can determine that the Andover series is an Aquult and the Laidig series is an Udult, two types of Ultisols. Conversely, near the summit, we have an Udepts of order Inceptisol, which is the Hazleton series.

Let us discuss briefly what makes up our mountain, then, by examining Ultisols and Inceptisols generally. As we touched on last week, Ultisols tend to have a high clay content but are also really sandy. Like Alfisols, they will have a translocated clay B horizon (Bt) that has a natric, argillic, or kandic subsurface horizon. However, they vary from Alfisols by having a base saturation less than 35%, making them more acidic and less fertile. We mentioned that we found Aquults and Udults on Mount Nittany. Aquults have a saturated water table that is at or near the surface for most the year, while Udults are simply those found in an Udic or other humid soil moisture regime (Figure 6).

Near the summit likely on a shoulder, we also had an Udepts of order Inceptisol. Inceptisols are basically just soils with poorly developed subsurface horizons (Bw horizons) and are very common in mountainous regions. Udepts are simply Inceptisols with Udic soil moisture regimes (Figure 7).

There are some patterns here I would like you to notice. In the valleys where our university lies, we have primarily Alfisols. However, moving up Mount Nittany to the summit, we develop more Ultisols and Inceptisols. What can this tell us? One of the most major factors revealed is that properties of Alfisols versus Ultisols and Inceptisols involve sand content. Limestone predominates in our valleys, while sandstone predominates in our mountains. Further, more basic soil is found in the valleys, but more acidic soil is found in the mountains. If we think about it, there is a whole civilization in the valley, but there is a very untouched forest in the mountains. Why is that? Limestone parent material and Alfisol soils give much more productive soil worth farming, so trees were cleared out to expose the soil and a civilization was built around this industry initially (Figure 8). Meanwhile, our sandstone parent material mountains were left relatively forested and uncivilized because the soils they offer are not particularly fertile due to the high sand content and occasional oversaturation for some of our listed soil types.

Why does any of this matter? Well, first of all, it is sort of cool to know that you walk on Hagerstown series of the soil order Alfisols every day. But also, it is important to recognize that you as people are leaving a footprint on super valuable, fertile soil! To end this blog, I would like to challenge you to something. Humans are great at changing their landscapes, for better or for worse. Remember I told you this blog also involves our furry (and scaly) friends?

Every time soil is walked upon, it grows more compact, increasing something called the bulk density and decreasing porosity. What this means is that it is harder for water to enter the soil and it is incredibly hard for plants to grow. This is why campers and hikers are taught to stick to a path. You must sacrifice some land consistently for making your journey, but straying from that path can cause imminent consequences for ecological resources for animals. So I challenge you to stick to the paths on campus and not walk through the grass or any potential shortcut. It will allow more plants to grow in the untouched regions for any small mammals and foragers.