Saturated buffers: Improvements and issues.

Saturated buffers are a newly developed agricultural best management practice used to redirect tile flow away from waterways, thereby mitigating nutrient losses and downstream eutrophication. This study evaluated the potential benefits of a novel saturated buffer design, which included pitchfork-shaped (PF) dispersion lines and a backflow check valve, that was installed alongside a traditional or standard (ST) buffer on a field in Moultrie County, Illinois, in the spring of 2019. Daily flow measurements and routine water samples were used to monitor the movement of water through both buffers and estimate nutrient loads. During observation days in 2020 and 2021, the PF buffer diverted 35% and 1.9% of incoming tile flow, respectively, while the ST buffer increased effluent rates by 116% and 137% over the same period. Both the PF and ST buffers experienced backflow from 30% to 47% of the monitoring period, well above the often reported 5%. Ultimately, the efficacy of saturated buffers could be improved with minimal, low-cost additions to their designs. Check valves are a simple supplement to saturated buffer design that can enhance flow diversion and potential nutrient removal. Added dispersion lines provide more opportunity for diversion of tile flow; however, they require more land to be removed from agricultural production and could increase backflow volumes, so the costs and benefits should be weighed.

Watershed Vulnerability to Invasive N2-Fixing Autumn Olive and Consequences for Stream Nitrogen Concentrations.

Autumn olive ( Thunb.) is an invasive and exotic N-fixing plant species found throughout the United States. Proliferation and spread of autumn olive have displaced native plants and raised concerns about the effects of N fixation and cycling on water quality in invaded areas. This study investigated the relationship between autumn olive cover and stream N concentrations. Twelve forested watersheds were selected and classified into edge, mid-distance, and interior-of-the-forest watersheds based on autumn olive density and distance from the permanent edge of invasion point along a major road corridor. For the 2012 vegetation survey, autumn olive cover in edge, mid, and interior watersheds ranged from 37 to 61%, 18 to 37%, and 4 to 10%, respectively. From 2006 to 2012, mean stream water NO-N concentration in the edge watersheds was significantly higher (1.39 mg L, < 0.0001) than mid (0.37 mg L) and interior (0.27 mg L) watersheds. A linear relationship was found between NO-N concentration and autumn olive cover ( = 0.72, = 0.0001). Mean stream water NH-N, specific conductivity, and pH were significantly less in the interior watersheds than in the edge watersheds. Additionally, peak specific conductivity and NO-N from edge watersheds coincided with peak stage for these watersheds, demonstrating that N flushing events were driven by surface and shallow subsurface flow pathways proximal to the stream. Results from this study demonstrate how encroachment of autumn olive can influence water quality and transform biogeochemical cycles in natural systems, which points to the need for effective management of autumn olive in the edge watersheds and riparian zones that are vulnerable to invasion and increased N export.

Giant Cane Vegetative Buffer for Improving Soil and Surface Water Quality.

Over the past four decades, riparian buffers have proven effective in retaining nutrients and sediment from agricultural runoff. Many grass species have been used with variable success in riparian buffers to improve the water quality of runoff. However, limited information is available on the effectiveness of giant cane [ (Walt.) Muhl] in improving surface water quality compared with grass species such as Kentucky bluegrass ( L.) and orchardgrass ( L.). Therefore, the objective of our study was to determine the quality of runoff leaving vegetative buffer plots planted with giant cane, Kentucky bluegrass, and orchardgrass. Additionally, a bare-ground control and continuous corn ( L.) was also monitored for comparison of runoff with vegetative buffers. The giant cane treatment had significantly greater infiltration rates (38.18 mm h, < 0.05) than bare ground (1.61 mm h), corn (5.75 mm h), Kentucky bluegrass (12.30 mm h), and orchardgrass (4.21 mm h) treatments. Dissolved reactive P in runoff was ranked as follows: corn > giant cane = Kentucky bluegrass = orchardgrass > bare ground. The total P from the corn treatment (1.70 mg L, < 0.05) was significantly higher than for bare ground (1.22 mg L), giant cane (0.69 mg L), Kentucky bluegrass (0.86 mg L), and orchardgrass (0.54 mg L). Giant cane, Kentucky bluegrass, and orchardgrass significantly reduced the total P concentration more than bare ground and corn. Results from this study demonstrate the utility of giant cane as a vegetated buffer to reduce nutrient and sediment concentrations in agricultural runoff.

Unprocessed Atmospheric Nitrate in Waters of the Northern Forest Region in the U.S. and Canada.

Little is known about the regional extent and variability of nitrate from atmospheric deposition that is transported to streams without biological processing in forests. We measured water chemistry and isotopic tracers (δ18O and δ15N) of nitrate sources across the Northern Forest Region of the U.S. and Canada and reanalyzed data from other studies to determine when, where, and how unprocessed atmospheric nitrate was transported in catchments. These inputs were more widespread and numerous than commonly recognized, but with high spatial and temporal variability. Only 6 of 32 streams had high fractions (>20%) of unprocessed atmospheric nitrate during baseflow. Seventeen had high fractions during stormflow or snowmelt, which corresponded to large fractions in near-surface soil waters or groundwaters, but not deep groundwater. The remaining 10 streams occasionally had some (<20%) unprocessed atmospheric nitrate during stormflow or baseflow. Large, sporadic events may continue to be cryptic due to atmospheric deposition variation among storms and a near complete lack of monitoring for these events. A general lack of observance may bias perceptions of occurrence; sustained monitoring of chronic nitrogen pollution effects on forests with nitrate source apportionments may offer insights needed to advance the science as well as assess regulatory and management schemes.

Sediment Dynamics Within Buffer Zone and Sinkhole Splay Areas Under Extreme Soil Disturbance Conditions.

Sedimentation dynamics were assessed in sinkholes within training areas at Ft. Knox Military Installation, a karst landscape subjected to decades of tracked vehicle use and extreme soil disturbance. Sinkholes sampled were sediment-laden and behaved as intermittent ponds. Dendrogeomorphic analyses were conducted using willow trees (Salix spp.) located around the edge of 18 sinkholes to estimate historical sedimentation rates, and buried bottles were installed in 20 sinkholes at the center, outer edge, and at the midpoint between the center and edge to estimate annual sedimentation rates. Sedimentation data were coupled with vegetation characteristics of sinkhole buffers to determine relationships among these variables. The dendrogeomorphic method estimated an average accumulation rate of 1.27 cm year(-1) translating to a sediment loss rate of 46.1 metric ton year(-1) from the training areas. However, sediment export to sinkholes was estimated to be much greater (118.6 metric ton year(-1)) via the bottle method. These data suggest that the latter method provided a more accurate estimate since accumulation was greater in the center of sinkholes compared to the periphery where dendrogeomorphic data were collected. Vegetation data were not tightly correlated with sedimentation rates, suggesting that further research is needed to identify a viable proxy for direct measures of sediment accumulation in this extreme deposition environment. Mitigation activities for the sinkholes at Ft. Knox's tank training area, and other heavily disturbed karst environments where extreme sedimentation exists, should consider focusing on flow path and splay area management.

Assessing the fate and effects of an insecticidal formulation.

A 3-yr study was conducted on a corn field in central Illinois, USA, to understand the fate and effects of an insecticidal formulation containing the active ingredients phostebupirim and cyfluthrin. The objectives were to determine the best tillage practice (conventional vs conservation tillage) in terms of grain yields and potential environmental risk, to assess insecticidal exposure using concentrations measured in soil and runoff water and sediments, to compare measured insecticidal concentrations with predicted concentrations from selected risk assessment exposure models, and to calculate toxicity benchmarks from laboratory bioassays performed on reference aquatic and terrestrial nontarget organisms, using individual active ingredients and the formulation. Corn grain yields were not significantly different based on tillage treatment. Similarly, field concentrations of insecticides were not significantly (p > 0.05) different in strip tillage versus conventional tillage, suggesting that neither of the tillage systems would enable greater environmental risk from the insecticidal formulation. Risk quotients were calculated from field concentrations and toxicity data to determine potential risk to nontarget species. The insecticidal formulation used at the recommended rate resulted in soil, sediment, and water concentrations that were potentially harmful to aquatic and terrestrial invertebrates, if exposure occurred, with risk quotients up to 34.

Soil and groundwater nitrogen response to invasion by an exotic nitrogen-fixing shrub.

Autumn-olive (Elaeagnus umbellata Thunb.) is an invasive, exotic shrub that has become naturalized in the eastern United States and can fix nitrogen (N) via a symbiotic relationship with the actinomycete Frankia. Fixed N could potentially influence nutrient cycling rates and N leaching into soil water and groundwater. In situ net N mineralization, net nitrification, and net ammonification rates, as well as soil water and groundwater nitrate N (NO(3)-N) and ammonium N (NH(4)-N) concentrations, were measured under autumn-olive-dominated and herbaceous open field areas in southern Illinois. Soil net N mineralization and net nitrification rates were higher under autumn-olive compared with open field (p < 0.05) and could be driven, in part, by the relatively low C/N ratio (11.41 +/- 0.29) of autumn-olive foliage and subsequent litter. Autumn-olive stands also had greater soil water NO(3)-N (p = 0.003), but soil water NH(4)-N concentrations were similar between autumn-olive and open field. Groundwater NO(3)-N and NH(4)-N concentrations were similar beneath both types of vegetation. Groundwater NO(3)-N concentrations did not reflect patterns in soil N mineralization and soil water NO(3)-N most likely due to a weak hydrologic connection between soil water and groundwater. The increased N levels in soil and soil water indicate that abandoned agroecosystems invaded by autumn-olive may be net sources of N to adjacent terrestrial and aquatic systems rather than net sinks.

Building local community commitment to wetlands restoration: a case study of the Cache River Wetlands in southern Illinois, USA.

Natural resource professionals are increasingly faced with the challenges of cultivating community-based support for wetland ecosystem restoration. While extensive research efforts have been directed toward understanding the biophysical dimensions of wetland conservation, the literature provides less guidance on how to successfully integrate community stakeholders into restoration planning. Therefore, this study explores the social construction of wetlands locally, and community members' perceptions of the wetland restoration project in the Cache River Watershed of southern Illinois, where public and private agencies have partnered together to implement a large-scale wetlands restoration project. Findings illustrate that the wetlands hold diverse and significant meanings to community members and that community members' criteria for project success may vary from those identified by project managers. The case study provides managers with strategies for building community commitment such as engaging local citizens in project planning, minimizing local burdens, maximizing local benefits, and reducing uncertainty.

Using photographic image analysis to assess ground cover: a case study of forest road cutbanks.

Road prisms, including cutbanks, road surfaces, and fillslopes, can be important contributors of sediment to streams in forested watersheds. Following road construction, cutbanks and fillslopes are often seeded, mulched, and sometimes fertilized to limit erosion and sedimentation. Assessing the success of vegetation establishment on cutbanks and fillslopes is a common task of forested land managers. This study developed and applied a photographic image analysis method to assess percent ground cover along an entire cutbank of a cut-and-fill haul road in the Monongahela National Forest in Tucker County, West Virginia. Variable-sized sections were employed to quantify the vegetative cover. Measurements obtained by this technique were similar to more commonly applied fixed-area plots, and it proved to be a useful tool for land managers who require a more repeatable quantification of ground cover than is possible through visual assessments. Cutbank slope and aspect also were analyzed to determine their potential impact on cutbank vegetation establishment. Slope was not a significant variable in explaining differences in vegetation cover; however, aspect did affect vegetation establishment. South-facing aspects had significantly lower percent vegetation cover than northeast, east, northwest, and north northwest aspects after the first year following seeding and throughout the entire study. Mean percent cover on the south-facing cutbanks was 32% over all time periods, compared to 60% to 73% for the other represented aspects. This result was expected since south-facing slopes generally are drier in the growing season and are subject to more freeze-thaw cycles in the winter. Timber felled onto the cutbank also decreased vegetative cover in the short term on north and north northwest aspects, but vegetation quickly became reestablished on these aspects with their favorable growing conditions.

Macroinvertebrate communities in agriculturally impacted southern Illinois streams: patterns with riparian vegetation, water quality, and in-stream habitat quality.

Relationships between riparian land cover, in-stream habitat, water chemistry, and macroinvertebrates were examined in headwater streams draining an agricultural region of Illinois. Macroinvertebrates and organic matter were collected monthly for one year from three intensively monitored streams with a gradient of riparian forest cover (6, 22, and 31% of riparian area). Bioassessments and physical habitat analyses were also performed in these three streams and 12 other nearby headwater streams. The intensively monitored site with the least riparian forest cover had significantly greater percent silt substrates than the sites with medium and high forest cover, and significantly higher very fine organics in substrates than the medium and high forested sites. Macroinvertebrates were abundant in all streams, but communities reflected degraded conditions; noninsect groups, mostly oligochaetes and copepods, dominated density and oligochaetes and mollusks, mostly Sphaerium and Physella, dominated biomass. Of insects, dipterans, mostly Chironomidae, dominated density and dipterans and coleopterans were important contributors to biomass. Collector-gatherers dominated functional structure in all three intensively monitored sites, indicating that functional structure metrics may not be appropriate for assessing these systems. The intensively monitored site with lowest riparian forest cover had significantly greater macroinvertebrate density and biomass, but lowest insect density and biomass. Density and biomass of active collector-filterers (mostly Sphaerium) decreased with increasing riparian forest. Hilsenhoff scores from all 15 sites were significantly correlated with in-stream habitat scores, percent riparian forest, and orthophosphate concentrations, and multiple regression indicated that in-stream habitat was the primary factor influencing biotic integrity. Our results show that these "drainage ditches" harbor abundant macroinvertebrates that are typical of degraded conditions, but that they can reflect gradients of conditions in and around these streams.

Sampling considerations for establishment of baseline loadings from forested watersheds for TMDL application.

Five methods for estimating maximum daily and annual nitrate (NO3) and suspended sediment loads using periodic sampling of varying intensities were compared to actual loads calculated from intensive stormflow and baseflow sampling from small, forested watersheds in north central West Virginia to determine if the less intensive sampling methods were accurate and could be utilized in TMDL development. There were no significant differences between the annual NO3 load estimates using non-intensive sampling methods and the actual NO3 loads. However, maximum daily NO3 loads were estimated less accurately than annual loads. The ability to estimate baseline NO3 loads fairly accurately with non-intensive concentration data is attributed to the small fluctuation in NO3 concentrations over flow and time, particularly during storms. By contrast, suspended sediment exports determined by any of the non-intensive methods varied significantly and widely from and compared poorly to the actual exports for both daily and annual methods. Weekly sampling better approximated actual annual exports, but there were no significant statistical differences among weekly, monthly, and quarterly estimates. Suspended sediment concentrations varied widely within and among storm events, so that accurate estimates of total annual or maximum daily loads could not be obtained from infrequent sampling.