Changing the Scholarly Sources Landscape with Geomorphology Undergraduate Students

Science is a core discipline in academia yet the focus of most undergraduate technical writing is generally on the data and results, not the literature review. The Science, Technology, Engineering, and Math (STEM) librarian and a new geology professor at the University of Nebraska at Omaha (UNO) collaborated to develop an information literacy session for students in a geomorphology class. Here we outline the background of the campus STEM initiatives and the assignment as well as the library instruction activity, learning outcomes, and assessment components. The activity improved student use of scholarly sources and we provide suggested activity modifications for future teaching and assessment efforts

INSIGHTS INTO GROUNDWATER FLOW PATHS IN AN INTENSIVELY MANAGED CRITICAL ZONE IN NEBRASKA

Glacier Creek, a groundwater-fed stream located in Glacier Creek Preserve (GCP) near Omaha, Nebraska, flows through restored tallgrass prairie and agricultural land (corn-soy rotation) draining a 4 km2 area. The 1 km wide watershed developed on Peoria Loess that overlies Sangamon age glacial till; Glacier Creek itself flows through the glacial till. Previous work concerning land use impacts on solute fluxes indicated a distinct distribution and flux of solutes through restored prairie and agricultural land. Inputs into the subsurface on agricultural land are slow and more concentrated but are diluted by precipitation along shallow flow paths to the north fork of Glacier Creek. In contrast, subsurface flow paths through the restored prairie are more rapid and deeper, leading to less concentrated water in the south fork of Glacier Creek. However, little is known about the subsurface stratigraphy and hydrogeology of the groundwater that provides year-round flow into Glacier Creek. Here we present the initial interpretation of a series of sediment cores and aquifer tests from the ridgetop, midslope, and foot slope topographic positions of agriculture and restored prairie. Sediment cores from the southern, restored prairie portion of GCP show loess overlying glacial till (identified by the appearance of gravel-sized rock fragments). The stratigraphy of the northern, agricultural portion of GCP is much more complex: while loess does overlie glacial till, there are also a series of sandy outwash deposits that cannot be correlated across the landscape. Under both land uses, the local groundwater table lies within the glacial till as referenced by water depth measurements in monitoring wells and gleyed sediments present in cores. Slug tests conducted in ridgetop and foot slope wells indicate that the saturated hydraulic conductivity of the sediments underlying the agricultural land range from two-fold to an order of magnitude greater than those underlying restored prairie, consistent with the presence of sandy layers that conduct water at a quicker rate. Furthermore, the higher flow rates explain why the north fork of Glacier Creek (draining agriculture) produces more water despite being a smaller portion of the watershed. Given these new findings, we modify our conceptual model of subsurface flow at GCP

Natural and anthropogenic processes contributing to metal enrichment in surface soils of central Pennsylvania

Metals in soils may positively or negatively affect plants as well as soil micro-organisms and mesofauna, depending on their abundance and bioavailability. Atmospheric deposition and biological uplift commonly result in metal enrichment in surface soils, but the relative importance of these processes is not always resolved. Here, we used an integrated approach to study the cycling of phosphorus and a suite of metals from the soil to the canopy (and back) in a temperate watershed. The behavior of elements in these surface soils fell into three categories. First, Al, Fe, V, Co, and Cr showed little to no enrichment in the top soil layers, and their concentrations were determined primarily by soil production fluxes with little influence of either atmospheric inputs or biological activity. Second, P, Cu, Zn and Cd were moderately enriched in surface soils due to a combination of atmospheric deposition and biological uplift. Among the metals we studied, Cu, Zn and Cd concentrations in surface soils were the most sensitive to changes in atmospheric deposition fluxes. Finally, Mo and Mn showed strong enrichment in the top soil layer that could not be explained strictly by either current atmospheric deposition or biological recycling processes, but may reflect both their unique chemistry and remnants of past anthropogenic fluxes. Mn has a long residence time in the soil partly due to intense biological uplift that retains Mn in the top soil layer. Mo, in spite of the high solubility of molybdate, remains in the soil because of strong binding to natural organic matter. This study demonstrates the need to consider simultaneously the vegetation and the soils to understand elemental distribution within soil profiles as well as cycling within watersheds

Shale weathering rates across a continental-scale climosequence

A transect of sites has been established in North America and England as part of the Critical Zone Exploration Network (CZEN) to investigate the rates of soil formation across a climate gradient. Sites reported here are all underlain by an organic-poor, iron-rich Silurian-age shale, providing a constant parent material lithology from which soil is forming. This climosequence includes relatively cold and wet sites in Wales, New York and Pennsylvania, with temperature increasing to the south in Virginia, Tennessee and Alabama. Puerto Rico provides a warm/wet end member for the transect, although this site does not lie on the same shale formation as the Appalachian Mountain sites. Geochemical, mineralogical, and cosmogenic isotope analyses are being completed similarly at all sites to allow direct comparisons and eventual modelling of the weathering processes. Preliminary results from Wales, Pennsylvania and Virginia show soils become more sodium-depleted and the depth to bedrock is significantly deeper at the wet/warm site in Virginia. The fraction of Na lost relative to parent material composition at each site varies linearly as a function of mean annual temperature. Overall, results from the transect will promote a better understanding of how climate changes and human activities impact soil formation rates

Shale weathering rates across a continental-scale climosequence

A transect of sites has been established in North America and England as part of the Critical Zone Exploration Network (CZEN) to investigate the rates of soil formation across a climate gradient. Sites reported here are all underlain by an organic-poor, iron-rich Silurian-age shale, providing a constant parent material lithology from which soil is forming. This climosequence includes relatively cold and wet sites in Wales, New York and Pennsylvania, with temperature increasing to the south in Virginia, Tennessee and Alabama. Puerto Rico provides a warm/wet end member for the transect, although this site does not lie on the same shale formation as the Appalachian Mountain sites. Geochemical, mineralogical, and cosmogenic isotope analyses are being completed similarly at all sites to allow direct comparisons and eventual modelling of the weathering processes. Preliminary results from Wales, Pennsylvania and Virginia show soils become more sodium-depleted and the depth to bedrock is significantly deeper at the wet/warm site in Virginia. The fraction of Na lost relative to parent material composition at each site varies linearly as a function of mean annual temperature. Overall, results from the transect will promote a better understanding of how climate changes and human activities impact soil formation rates

Biotic controls on solute distribution and transport in headwater catchments

Solute concentrations in stream water vary with discharge in patterns that record complex feedbacks between hydrologic and biogeochemical processes. In a comparison of headwater catchments underlain by shale in Pennsylvania, USA (Shale Hills) 5 and Wales, UK (Plynlimon), dissimilar concentration-discharge behaviors are best explained by contrasting landscape distributions of soil solution chemistry – especially dissolved organic carbon (DOC) – that have been established by patterns of vegetation. Specifically, elements that are concentrated in organic-rich soils due to biotic cycling (Mn, Ca, K) or that form strong complexes with DOC (Fe, Al) are spatially heteroge- 10 neous in pore waters because organic matter is heterogeneously distributed across the catchments. These solutes exhibit non-chemostatic “bioactive” behavior in the streams, and solute concentrations either decrease (Shale Hills) or increase (Plynlimon) with increasing discharge. In contrast, solutes that are concentrated in soil minerals and form only weak complexes with DOC (Na, Mg, Si) are spatially homogeneous in pore waters 15 across each catchment. These solutes are chemostatic in that their stream concentrations vary little with stream discharge, likely because these solutes are released quickly from exchange sites in the soils during rainfall events. Differences in the hydrologic connectivity of organic-rich soils to the stream drive differences in concentration behavior between catchments. As such, in catchments where soil organic matter (SOM) is dom- 20 inantly in lowlands (e.g., Shale Hills), bioactive elements are released to the stream early during rainfall events, whereas in catchments where SOM is dominantly in uplands (e.g., Plynlimon), bioactive elements are released later during rainfall events. The distribution of vegetation and SOM across the landscape is thus a key component for predictive models of solute transport in headwater catchments

Designing a suite of measurements to understand the critical zone

Many scientists have begun to refer to the earth surface environment from the upper canopy to the depths of bedrock as the critical zone (CZ). Identification of the CZ as an integral object worthy of study implicitly posits that the study of the whole earth surface will provide benefits that do not arise when studying the individual parts. To study the CZ, however, requires prioritizing among the measurements that can be made – and we do not generally agree on the priorities. Currently, the Susquehanna Shale Hills Critical Zone Observatory (SSHCZO) is expanding from a small original focus area (0.08 km2 , Shale Hills catchment), to a larger watershed (164 km2 , Shavers Creek watershed) and is grappling with the prioritization. This effort is an expansion from a monolithologic first-order forested catchment to a watershed that encompasses several lithologies (shale, sandstone, limestone) and land use types (forest, agriculture). The goal of the project remains the same: to understand water, energy, gas, solute, and sediment (WEGSS) fluxes that are occurring today in the context of the record of those fluxes over geologic time as recorded in soil profiles, the sedimentary record, and landscape morphology. Given the small size of the Shale Hills catchment, the original design incorporated measurement of as many parameters as possible at high temporal and spatial density. In the larger Shavers Creek watershed, however, we must focus the measurements. We describe a strategy of data collection and modeling based on a geomorphological and land use framework that builds on the hillslope as the basic unit. Interpolation and extrapolation beyond specific sites relies on geophysical surveying, remote sensing, geomorphic analysis, the study of natural integrators such as streams, groundwaters or air, and application of a suite of CZ models. We hypothesize that measurements of a few important variables at strategic locations within a geomorphological framework will allow development of predictive models of CZ behavior. In turn, the measurements and models will reveal how the larger watershed will respond to perturbations both now and into the future

Labile and Stable Nitrogen and Carbon in Mine Soil Reclaimed with Manure-Based Amendments

Organic C and nutrients in manure can improve degraded mine soil quality if they are retained in the soil. Composting manure or mixing manure with a high C/N ratio material before application could facilitate this improvement. The effects of these manure stabilization techniques on N and C retention in mine soil were investigated in two incubation experiments with six treatments: unamended soil, lime and fertilizer (14.3 Mg ha−1), two rates of composted poultry layer manure (78 and 156 Mg ha−1), and layer manure mixed with paper-mill sludge (PMS) (50 Mg ha−1 manure, 102 and 183 Mg ha−1 PMS) to provide C/N ratios of 20 and 30. In one experiment, amendments were laboratory applied just before incubation; in the other, amendments were field applied 1 yr before incubation. Carbon dioxide evolution and labile N and C were measured during incubation and microbial biomass N was determined at the end of the incubations. In laboratory-amended soil, all treatments produced similar quantities of labile N while compost and manure + PMS treatments resulted in stable soil N pools that were 2.5 to 2.7 times larger than in the unamended soil. In field-amended soils, stable N pools were similarly increased by compost and manure + PMS treatments. Large CO2 production and microbial biomass N from manure + PMS treatments suggested that rapid microbial turnover of N was an important factor in stabilizing manure N. These results indicate that the combined manure + PMS amendment was as effective as composting in building stable N pools in mine soil

Nutrient Leaching and Switchgrass Growth in Mine Soil Columns Amended With Poultry Manure

In Pennsylvania, land disturbance from 150 years of extensive coal mining and intensive animal production that produces manure nutrients in excess of crop needs have degraded ecosystems and water quality. Excess manure could be used in mine reclamation, but the large application rates required for successful revegetation could result in significant nutrient discharge. This greenhouse experiment investigated two approaches to minimizing the potential for nutrient leaching of poultry layer manure used for mine reclamation: composting and C:N ratio adjustment. Columns of mine soil were amended with manure only, manure mixed with short-fiber paper mill sludge (C:N ratios of 20-40) and three rates of composted manure. Mine soil was planted with switchgrass (Panicum virgatum L.) to test biomass production of this potential biofuel, and columns were periodically leached and biomass was harvested during the 8-month experiment. Amendment with manure only resulted in the largest leaching of NO3--N (192 mg column−1) and P (12 mg column−1), whereas nutrient leaching from compost-amended soil was less than or equal to 1.67 mg NO3--N and 3.38 mg P column−1. Each level of compost addition increased switchgrass growth compared with unamended soil, and mine soil amended with manure and paper mill sludge further increased switchgrass growth while decreasing cumulative NO3- and P leaching compared with manure alone. Although composting manure was most effective at limiting nutrient leaching, our results demonstrate that coapplication of manure with a high carbon material could provide superior biomass production on mine soil while also controlling nutrient loss via leaching

Nutrient Leaching and Soil Retention in Mined Land Reclaimed with Stabilized Manure

Two environmental problems in Pennsylvania are degraded mined lands and excess manure nutrients from intensive animal production. Manure could be used in mine reclamation, but the large application rates required for sustained biomass production could result in significant nutrient discharge. An abandoned mine site in Schuylkill County, Pennsylvania, was used to test manure nutrient stabilization by composting and by mixing with primary paper mill sludge (PMS). Reclamation treatments were lime and fertilizer, composted poultry manure (78 and 156 Mg ha−1), and poultry manure (50 Mg ha−1) mixed with PMS (103 and 184 Mg ha−1) to achieve C-to-N ratios of 20 and 29. Leachates were collected with zero-tension lysimeters, and during 3 yr following amendment application, −1 during 3 yr, 12.4 times more N than compost treatments), mostly as pulses of NO3− in the first two fall seasons following reclamation. The manure+PMS C:N 20 treatment leached 107 kg N ha−1 during 3 yr. Three years after amendment application, most of the N and P added with the manure-based amendments was retained in the mine soil even though net immobilization of N by PMS appeared to be limited to 3 mo following application. Composting or mixing PMS with manure to achieve a C-to-N ratio of 20 can effectively minimize N leaching, retain added N in mine soil, and provide greater improvement in soil quality than lime and fertilizer amendment