The Spring Creek Watershed is home to some of Pennsylvania’s most productive soils. These soils are a primary reason for the region’s economic success. They support agricultural and forestry operations that produce a wide variety of building materials, biofuels, and food products for humans and animals. Soils also act as engineering materials for roads, pipelines, residential and commercial buildings, and recreational opportunities like bike paths. Unfortunately, the best soils for food production are also the best soils for building homes or office parks. Finding a balance between these two needs is often a difficult challenge for any community.
The Spring Creek Watershed is a rural, suburban and urban watershed. Many of the areas' populations depend on the capability of the soil to filter wastewater, which eventually is returned as groundwater and stream recharge. For example, Penn State’s wastewater is treated at the Living Filter, one of the longest running on-site wastewater spray-irrigation experiments in the United States! Last, but not least, the watershed’s soils support the production of clean air, and a healthy and vibrant environment
The watershed’s soils have been mapped by the United States Department of Agriculture, Natural Resources Conservation Service (Figure 1). These maps are available online at the Web Soil Survey. In Centre County soil mapping was underway by the early 1900s and first completed by 1910 (Eckenrode and Ciolkosz, 1999). Since 1910, several updates to the original soil maps have been made with a stronger focus on the crop production lands than forests lands. A soil map will consist of an area with polygons (mapping units) representing different soil phases. Mapping units will typically refer to a named soil series (e.g. Hagerstown or Opequon) and additional attribute information related to the landscape slope and surface texture. Web Soil Survey allows users to highlight specific types of data describing the soil in each mapping unit as well as information on suitability or limitation ratings for soil uses. Soil mapping has helped guide land planning in the Spring Creek Watershed, which has resulted in the protection of valuable aquifer recharge areas and wetlands.
Figure 1. General soil and parent materials map of Spring Creek Watershed, Pennsylvania.
The genesis of watershed soils is the product of soil forming reactions as regulated by the soil forming factors, i.e. organisms, climate, parent material, topography, and time. The degree to which any one or combination of these factors drives soil formation is dependent upon local conditions. Due to the types of bedrock in the watershed and their response to long-term soil formation, the Spring Creek Watershed exhibits close ties between parent material and landform (Figure 2).
Figure 2. General soil-landscape relations of Nittany Valley (A is northeast and B is southwest of State College).
Modified from Ciolkosz et al. (1986).
The climate of the watershed varies more than expected primarily due to differences in topographic relief. While relief is not substantial enough to mimic climate extremes like that of the Intermountain Western US, temperature and precipitation gradients are substantial enough between the valley floor and summits to have an effect on soil formation. For example 45 inches of rain falls on the Allegheny Plateau near Black Moshannon State Park, while State College annually receives about 39 inches of rain and has about 50 more frost-free days (160 vs. 110) (Ciolkosz et al., 1995). In addition, topographic relief differences across the watershed result in substantial temperature differences, not only between the summits and valley, but also within the valley itself due to cold air drainage patterns. Within the valley, 10°F temperature differences due to local relief are not uncommon, with the coldest area in the vicinity of Gamelands 176 (the Scotia Barrens). The watershed’s past climate has varied substantially. During the last glaciation (>20,000 years ago (PADCNR, 1987)) a harsh climate, similar to today’s arctic, existed due to the close proximity of the continental ice sheet (no glaciers reached the watershed though). The evidence for this past environment is preserved in many of our soils, in our ridges in the form of sandstone block fields with little to no vegetation and in our colluviated mountain side slopes (Ciolkosz et al., 1986a). Tied to these past climate changes there have also been vegetation changes. For example, following the retreat of the glaciers, several vegetative successions occurred over time, starting with boreal forest, to coniferous forest, and most recently deciduous forest. Periods of warming and drying during the post-glacial Holocene also have resulted in some areas of prairie vegetation.
The parent material from which soils form in the Spring Creek Watershed consists of: in place bedrock (residuum), material moved down-slope due to gravity (colluvium), and sediments deposited by water (alluvium)(Ciolkosz et al., 1980, 1986b). Several dominant landforms across the watershed (ridges, valleys, floodplains) can be linked to distinct groups of soils and their parent materials. Watershed soils (Figure 2), away from streams, have largely formed in place (residuum) and from limestone (Figure 3). The most common soil series formed from these limestone rocks are Opequon and Hagerstown. Opequon is shallow (< 20 inches to bedrock), and Hagerstown is deeper to bedrock. Watershed soils formed from interbedded limestone and sandstone are the Morrison series and those from sandstone alone are the Vanderlip series; Morrison soils are by far the most extensive watershed soils influenced by sandstone. The western area of the watershed near State Gamelands 176 (Scotia Barrens), has sandstone bedrock that results in soils with very high sand contents.
Figure 3. Limestone soil (residuum) with limestone in the bottom of the pit. Photo tape scale is in feet. Photo Edward J. Ciolkosz.
Formation of the watershed limestone soils via the dissolution of the rock has taken a very long time (>1 million years). During this time these soils have also accumulated dust from distant sources, resulting in upper horizons (topsoil) having 25-50% silt (Ciolkosz, et al., 1995). However, the lower horizons (subsoils) typically have high amounts of red clay. Some areas with limestone rock close to the surface, or at the surface, are due to geochemical weathering and the development of karst topography.
Areas of shale-derived soils occur near Boalsburg, around the base of Nittany Mountain, and in the southeastern portion of the watershed (Figure 1)(Ciolkosz et al., 1986b). Shale-derived soils can vary in depth to bedrock. The thinner soil (Weikert soil series) (Figure 4) is a challenging soil for many land uses, while the thicker soil (Berks) commonly is used for pasture, hay production, forestry or development. Some of the shale around Nittany Mountain produces high pH soils while the other shale soil areas near Boalsburg and farther southeast tend to produce a more acidic soil pH.
Adjacent to streams, the soils are derived from flood sediments. Some sandstone and shale ridges occur in the watershed and their erosional materials, along with weathering products from limestone, are deposited in these areas, forming floodplains. However, in comparison to the limestone watershed soils, or sandstone soils of the Barrens, floodplain soils often have more silt and less clay due to silt being an optimal particle size for water transport. Common silty alluvial soil series forming from mostly limestone parent materials are Lindside, Nolin, and Melvin. Alluvium with more resistant sandstone or higher flows will have more sand and gravels (Chagrin or Atkins series). One interesting aspect of our floodplain soils is the legacy of European settlement preserved in them. Early land clearing for agriculture and charcoal production (Ciolkosz et al., 1980) resulted in extensive erosion and transport of sediment to low-lying areas and streams. Accumulations of these eroded materials can be as thick as 100 cm (39 inches) and have buried older soil surfaces (Figure 5).
Figure 4. Weikert soil series, shale residuum. Photo tape scale is in feet. Photo: Edward J. Ciolkosz.
Figure 5. Buried surface from local alluvial erosion created by 1800s land clearing for agriculture (off Rt. 45 near Penn State Agronomy Farm), Spring Creek Watershed, Pennsylvania. Photo tape scale is in cm on left and feet on right. Photo: Patrick J. Drohan.
Lastly, we have the soils of Nittany, Tussey, and Bald Eagle Mountains. All three are comprised in part from sandstone and shale bedrock. These rock types, coupled with their long, steep mountain slopes, result in the soils being in part residual and in part a mix of side slope sandstone and shale materials (Figure 2). Mountain top soils (Figure 6) are sandy with high rock fragment content, but like valley soils can have silt and some clay due to dust additions and weathering (Hazleton or Leetonia series) (Ciolkosz et al., 1990). The sand in these soils is derived from the prevalence of sandstone bedrock which is very resistant to long term weathering. The high rock fragment content of these soils may suggest that bedrock is close to the surface. However, excavation of such soils shows that the bedrock is deeply fractured. The side slope materials (colluvium) on the upper slopes typically have larger and less weathered rock fragments. The colluvial soils tend to have quite a bit of clay due to the shale material and dust that has been mixed into the soil over time. In addition there is a trend of increasing clay content in the soils from the upper to the lower side slope soils. The colluvial thickness on the side slopes varies with the deeper material being near the lower side slope or footslope (10 – 20+ feet thick) and the shallower material being on the upper side slope (6-15 feet thick) (Ciolkosz et al., 1990). The colluvial material on side slopes was deposited across multiple periods of time. This is evident by color differences between the deposits where the older, deeper colluvium is redder than the overlying and younger brown colluvium (Figure 7). Side slope soil series developed in colluvium include (from better to poorer drainage) Laidig, Buchanan, and Andover. Colluvial soils can extend into the valley for hundreds of feet, and cover limestone derived soils (e.g the Murrill series). Soils like that of the Murrill series will have very small, rounded and angular rock fragments suggesting a dual colluvial and alluvial transport mechanism. One thought is that late Pleistocene runoff from melting permafrost could have contributed to the rounding of rock fragments in these deposits.
Figure 6. Hazleton soil series on Tussey Mountain. Photo tape scale is in feet. Photo: Edward J. Ciolkosz.
Figure 7. Colluvial soil derived from sandstone and shale on the sideslope of Tussey Mountain. Grey colors are an indicator of wet conditions. Note the redder colored colluvium below grey zone. This suggests two different colluvial depositions with the bottom one being older. Photo tape scale is 1.3 m long. Photo: Patrick J. Drohan.
Patrick J. Drohan and Edward J. Ciolkosz.
Dept. of Ecosystem Science & Management, The Pennsylvania State University
References
Ciolkosz, E.J., Parizek, R.R., Petersen, G.W., Cunningham, R.L., Gardner, T.W., Hatch, J.W., Shipman, R.D. 1980. Soils and geology of Nittany Valley. Agronomy Series 64. Available at: Available at: http://ecosystems.psu.edu/research/labs/soilislife/pa-soils/pa-soils-information
Ciolkosz, E.J., Cronce, R.C., and Sevon, W.D. 1986a. Periglacial features in Pennsylvania. Agronomy Series 92. Available at: http://ecosystems.psu.edu/research/labs/soilislife/pa-soils/pa-soils-information
Ciolkosz, E.J., Cronce, R.C., Cunningham, R.L., and G.W. Petersen. 1986b. Geology and Soils of Nittany Valley. Agronomy Series Number 88. Available at: Available at: http://ecosystems.psu.edu/research/labs/soilislife/pa-soils/pa-soils-information
Ciolkosz, E. J., Carter, B. J., Hoover, M. T., Cronce, R. C., Waltman, W. J., Dobos, R. R. 1990. Genesis of soils and landscapes in the Ridge and Valley province of central Pennsylvania. Geomorphology, 3:245-261.
Ciolkosz, E.J., Cronce, R.C., Sevon, W.D., and Waltman, W.J. 1995. Genesis of Pennsylvania’s limestone soils. Agronomy Series Number 135. Available at: http://ecosystems.psu.edu/research/labs/soilislife/pa-soils/pa-soils-information
Eckenrode, J.J. and Ciolkosz, E.J. 1999. Pennsylvania soil survey: The first 100 years. Agronomy Series Number 144. Available at: http://ecosystems.psu.edu/research/labs/soilislife/pa-soils/pa-soils-information
To learn more about the properties of local soils, their relationship to the landscape, and the limits and potential of Pennsylvania soils, please refer to An Introduction to Soils of Pennsylvania. This document can also be found on the Atlas Resources page along with other watershed-related material. Click here for more information.