Patrick J. Drohan

The Use of LiDAR Terrain Data in Characterizing Surface Roughness and Microtopography

The availability of light detection and ranging data (LiDAR) has resulted in a new era of landscape analysis. For example, improvements in LiDAR data resolution may make it possible to accurately model microtopography over a large geographic area; however, data resolution and processing costs versus resulting accuracy may be too costly. We examined two LiDAR datasets of differing resolutions, a low point density (0.714 points/m2 spacing) 1 m DEM available statewide in Pennsylvania and a high point density (10.28 points/m2 spacing) 1 m DEM research-grade DEM, and compared the calculated roughness between both resulting DEMs using standard deviation of slope, standard deviation of curvature, a pit fill index, and the difference between a smoothed splined surface and the original DEM. These results were then compared to field-surveyed plots and transects of microterrain. Using both datasets, patterns of roughness were identified, which were associated with different landforms derived from hydrogeomorphic features such as stream channels, gullies, and depressions. Lowland areas tended to have the highest roughness values for all methods, with other areas showing distinctive patterns of roughness values across metrics. However, our results suggest that the high-resolution research-grade LiDAR did not improve roughness modeling in comparison to the coarser statewide LiDAR. We conclude that resolution and initial point density may not be as important as the algorithm and methodology used to generate a LiDAR-derived DEM for roughness modeling purposes.

Biochar amendment of soil improves resilience to climate change.

Because of climate change, insufficient soil moisture may increasingly limit crop productivity in certain regions of the world. This may be particularly consequential for biofuel crops, many of which will likely be grown in drought‐prone soils to avoid competition with food crops. Biochar is the byproduct of a biofuel production method called pyrolysis. If pyrolysis becomes more common as some scientists predict, biochar will become more widely available. We asked, therefore, whether the addition of biochar to soils could significantly increase the availability of water to a crop. Biochar made from switchgrass (Panicum virgatum L.) shoots was added at the rate of 1% of dry weight to four soils of varying texture, and available water contents were calculated as the difference between field capacity and permanent wilting point water contents. Biochar addition significantly increased the available water contents of the soils by both increasing the amount of water held at field capacity and allowing plants to draw the soil to a lower water content before wilting. Among the four soils tested, biochar amendment resulted in an additional 0.8–2.7 d of transpiration, which could increase productivity in drought‐prone regions or reduce the frequency of irrigation. Biochar amendment of soils may thus be a viable means of mitigating some of the predicted decrease in water availability accompanying climate change that could limit the future productivity of biofuel crops.

Forecasting runoff from Pennsylvania landscapes

Identifying sites prone to surface runoff has been a cornerstone of conservation and nutrient management programs, relying upon site assessment tools that support strategic, as opposed to operational, decision making. We sought to develop simple, empirical models to represent two highly different mechanisms of surface runoff generation—saturation excess runoff and infiltration excess runoff—using variables available from short-term weather forecasts. Logistic regression models were developed from runoff monitoring studies in Pennsylvania, fitting saturation excess runoff potential to rainfall depth, rainfall intensity, and soil moisture, and infiltration excess runoff potential to rainfall depth and intensity. Testing of the models in daily hindcasting mode over periods of time and at sites separate from where they were developed confirmed a high degree of skill, with Brier Skill Scores ranging from 0.61 to 0.65 and Gilbert Skill Scores ranging from 0.39 to 0.59. These skill scores are as good as models used in weather forecasting. Results point to the capability to forecast site-specific surface runoff potential for diverse soil conditions, with advances in weather forecasting likely to further improve the predictive ability of runoff models of this type.

Oil and gas impacts on forest ecosystems: findings gleaned from the 2012 Goddard Forum at Penn State University

Energy production presents numerous challenges to both industry and land managers across the globe. The recent development of unconventional (shale gas) plays around the world [US Energy Information Administration (USEIA), 2011] has brought attention to the potential for rapid change in affected landscapes and associated ecosystem services. While shale-gas development specifically has been the focus of recent research on how landscapes are changing, continued scientific investigation can lessen the resulting ecosystem disturbance across all energy infrastructure. In April 2012, the Pennsylvania State University hosted the 2012 Goddard Forum Oil and Gas Development Impacts on Forested Ecosystems--Research and Management Challenges.

Linear infrastructure drives habitat conversion and forest fragmentation associated with Marcellus shale gas development in a forested landscape

Large, continuous forest provides critical habitat for some species of forest dependent wildlife. The rapid expansion of shale gas development within the northern Appalachians results in direct loss of such habitat at well sites, pipelines, and access roads; however the resulting habitat fragmentation surrounding such areas may be of greater importance. Previous research has suggested that infrastructure supporting gas development is the driver for habitat loss, but knowledge of what specific infrastructure affects habitat is limited by a lack of spatial tracking of infrastructure development in different land uses. We used high-resolution aerial imagery, land cover data, and well point data to quantify shale gas development across four time periods (2010, 2012, 2014, 2016), including: the number of wells permitted, drilled, and producing gas (a measure of pipeline development); land use change; and forest fragmentation on both private and public land. As of April 2016, the majority of shale gas development was located on private land (74% of constructed well pads); however, the number of wells drilled per pad was lower on private compared to public land (3.5 and 5.4, respectively). Loss of core forest was more than double on private than public land (4.3 and 2.0%, respectively), which likely results from better management practices implemented on public land. Pipelines were by far the largest contributor to the fragmentation of core forest due to shale gas development. Forecasting future land use change resulting from gas development suggests that the greatest loss of core forest will occur with pads constructed farthest from pre-existing pipelines (new pipelines must be built to connect pads) and in areas with greater amounts of core forest. To reduce future fragmentation, our results suggest new pads should be placed near pre-existing pipelines and methods to consolidate pipelines with other infrastructure should be used. Without these mitigation practices, we will continue to lose core forest as a result of new pipelines and infrastructure particularly on private land.

Defoliation and Atmospheric Deposition Influences on Spring Baseflow Chemistry in 56 Pennsylvania Mixed Land-Use Watersheds

Using samples of spring baseflow chemistry on 56Pennsylvania watersheds with predominantly forested to mixedland-uses and widely varying geology/physiography, weattempted to determine spatial patterns in stream chemistrydue to insect defoliation and atmospheric deposition. Landuse and land form relations to stream chemistry wereexamined as well. Defoliation effects on stream chemistrydue to repeated, and sometimes intense, insect defoliationover the past several years were seen as reduced streamnitrate concentrations in a watershed data set (n = 11) thatincluded 100% forested lands only. Basins in regions withhigher atmospheric sulfate deposition loads had higherstream concentrations of sulfate in 100% forested basins.Significant positive correlations of stream nitrogen andpotassium with agricultural land use indicated possiblecontamination of stream waters by excess fertilizers and/oranimal wastes. Weak positive correlations were also foundwith many of the stream chemistry parameters and percentageurban/barren land use. Ridge-top versus valley bottomwatersheds also showed differences in baseflow chemistry dueto changing surficial geology and/or land use. Overall, thestudy showed that agricultural, urban, geologic, andphysiographic influences on spring baseflow chemistry maskthe effects of insect defoliation and atmospheric depositionon mixed land-use basins (<100% forest). Regionaldifferences in atmospheric deposition on 100% forestedbasins were directly reflected in spring baseflow SO4concentrations. When restricted to 100% forested basinswith relatively uniform geology, insect defoliation appearedto reduce stream nitrogen concentrations in the long term.This is believed to be due in part to nitrogen bound invegetative growth and a dilution of nitrogen from increasedflows as a result of defoliation and tree mortality bringingabout reduced evapotranspiration.

Unconventional gas development facilitates plant invasions

Vegetation removal and soil disturbance from natural resource development, combined with invasive plant propagule pressure, can increase vulnerability to plant invasions. Unconventional oil and gas development produces surface disturbance by way of well pad, road, and pipeline construction, and increased traffic. Little is known about the resulting impacts on plant community assembly, including the spread of invasive plants. Our work was conducted in Pennsylvania forests that overlay the Marcellus and Utica shale formations to determine if invasive plants have spread to edge habitat created by unconventional gas development and to investigate factors associated with their presence. A piecewise structural equation model was used to determine the direct and indirect factors associated with invasive plant establishment on well pads. The model included the following measured or calculated variables: current propagule pressure on local access roads, the spatial extent of the pre-development road network (potential source of invasive propagules), the number of wells per pad (indicator of traffic density), and pad age. Sixty-one percent of the 127 well pads surveyed had at least one invasive plant species present. Invasive plant presence on well pads was positively correlated with local propagule pressure on access roads and indirectly with road density pre-development, the number of wells, and age of the well pad. The vast reserves of unconventional oil and gas are in the early stages of development in the US. Continued development of this underground resource must be paired with careful monitoring and management of surface ecological impacts, including the spread of invasive plants. Prioritizing invasive plant monitoring in unconventional oil and gas development areas with existing roads and multi-well pads could improve early detection and control of invasive plants.

Future Challenges for Soil Science Research, Education, and Soil Survey in the USA

Soils across the USA are under extensive pressure to support the needs of society under an uncertain climate future. While our management of soils is far better than 100 years ago, chronic erosion in excess of soil building is common and human behavior frequently results in soil degradation. At odds with a need for improved soil management is a two-decade trend in the closure or downsizing of soil science academic programs and federal soil scientist positions, all of which threaten our capability to manage soils. Regardless, soil scientists must lead efforts to greatly minimize land degradation (especially erosion) and reshape American agriculture to adapt to climate change so that we secure current achievements in land management, food supply, and quality of life. New models of soil science education and training must be embraced in order to maintain and build the profession. An extensive and ubiquitous public education effort, much greater than that which ended the “Dust Bowl,” is needed to help correct harmful human behavior resulting in unsustainable soil use and degradation of ecosystem services. These are the achievements that must be realized during the next 50 years of soil science.

Hydric Soils Across Pennsylvania Reference, Disturbed, and Mitigated Wetlands

Soils were compared among natural HGM wetland types, contrasting reference standard wetlands to disturbed wetlands of that type. These latter sites were disturbed to some extent, from stressors occurring on site, within the buffer, and/or from the surrounding landscape. As expected the soils affected by glaciation in the northeastern and northwestern corners of Pennsylvania were wetter than soils from other ecoregions, and the number and density of wetlands was higher. Soil texture was coarser where hydraulic energies were greater, such as in riverine wetlands. Disturbed wetlands tended to have finer textured soils composed of more silt and clay, suggesting that they receive inputs of eroded sediments from the surrounding landscapes. Organic matter was higher in some HGM types, such as fringing and riparian depressions where soils are more saturated or inundated. Soils data from Riparia’s set of reference wetlands is available through a searchable web interface at their website. A review of the literature comparing reference wetlands to mitigation projects continues to indicate the latter are not reaching the functional performance of natural wetlands.

Short-term Forecasting Tools for Agricultural Nutrient Management

The advent of real-time, short-term farm management tools is motivated by the need to protect water quality above and beyond the general guidance offered by existing nutrient management plans. Advances in high-performance computing and hydrologic or climate modeling have enabled rapid dissemination of real-time information that can assist landowners and conservation personnel with short-term management planning. This paper reviews short-term decision support tools for agriculture that are under various stages of development and implementation in the United States: (i) Wisconsins Runoff Risk Advisory Forecast (RRAF) System, (ii) New Yorks Hydrologically Sensitive Area Prediction Tool, (iii) Virginias Saturated Area Forecast Model, (iv) Pennsylvanias Fertilizer Forecaster, (v) Washingtons Application Risk Management (ARM) System, and (vi) Missouris Design Storm Notification System. Although these decision support tools differ in their underlying model structure, the resolution at which they are applied, and the hydroclimates to which they are relevant, all provide forecasts (range 24-120 h) of runoff risk or soil moisture saturation derived from National Weather Service Forecast models. Although this review highlights the need for further development of robust and well-supported short-term nutrient management tools, their potential for adoption and ultimate utility requires an understanding of the appropriate context of application, the strategic and operational needs of managers, access to weather forecasts, scales of application (e.g., regional vs. field level), data requirements, and outreach communication structure.