Jon E. Schoonover

Nutrient Attenuation in Agricultural Surface Runoff by Riparian Buffer Zones in Southern Illinois, USA

Nutrients in overland flow from agricultural areas are a common cause of stream and lake water quality impairment. One method of reducing excess nutrient runoff from non-point sources is to restore or enhance existing riparian areas as vegetative buffers. A field scale study was conducted to assess the ability of remnant giant cane (Arundinaria gigantea (Walt.) Muhl.) and forest riparian buffer zones to attenuate nutrients in agricultural surface runoff from natural precipitation events. Two adjacent, 10.0 m wide riparian buffers were instrumented with 16 overland flow collectors to monitor surface runoff for nitrate, ammonium, and orthophosphate. Measurements were taken at 3.3 m increments within each buffer. The forest buffer significantly reduced incoming dissolved nitrate-N, dissolved ammonium-N, total ammonium-N, and total orthophosphate masses in surface runoff by 97, 74, 68, and 78 , respectively within the 10.0 m riparian buffer. Nutrient reductions within the cane buffer were 100 for all three nutrients due to relatively high infiltration rates. Significant reductions of total ammonium- N and total orthophosphate were detected by 3.3 m in the cane buffer and at 6.6 m in the forest buffer. Results suggest that both giant cane and forest vegetation are good candidates to incorporate into riparian buffer restoration designs for southern Illinois as well as in other regions within their native range with similar climatic and physiographic conditions.

Seasonal variability of landuse impacts on macroinvertebrate assemblages in streams of western Georgia, USA

Abstract We examined the influence of land use/land cover (LULC) on macroinvertebrate assemblages and environmental conditions in streams draining 18 small watersheds in the Southern Outer Piedmont ecoregion in Georgia, USA, over a 24-mo period of record. Specifically, we analyzed relationships among LULC categories (i.e., % impervious surface [IS], pasture, silviculture, and deciduous/evergreen forest) and hydrological, physicochemical, and benthic habitat variables, and macroinvertebrate metrics. Macroinvertebrate metrics were related primarily to % IS and % deciduous forest cover, with lowest biotic integrity (species diversity, taxon richness, biological stream condition index) found in high % IS watersheds. Biotic integrity declined with decreasing % forest cover throughout the seasons, and multiple regression models and partial correlation analysis revealed that physicochemical and benthic habitat variables explained more variation in macroinvertebrate metrics throughout the seasons than did hydrological variables at most sites. Based on nonmetric multidimensional scaling, heavily urbanized sites were strongly separated from all other sites in terms of assemblage structure. Total ordination distance among seasonal samples from the same sites increased as % forest cover increased. This pattern might have arisen because urbanized streams had high abundances of a few tolerant, persistent taxa and lacked many ephemeral taxa found in less disturbed systems. The influence of anthropogenic LULC on macroinvertebrate assemblages appears to be consistent throughout the year and reduces seasonal changes in assemblages. LULC-associated differences among assemblages are strongly associated with changes in physicochemistry and benthic habitat conditions that probably are mediated by hydrological alterations associated with altered LULC in the watersheds of this region.

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.

Ground Water Nitrogen Dynamics in Giant Cane and Forest Riparian Buffers

Abstract Forest and grass riparian buffers are a common conservation practice to control nonpoint source pollution. In the lower midwestern United States, there is significant interest in incorporating a once common native riparian species, giant cane (Arundinaria gigantea) in riparian restoration designs. Thus, assessing the water quality benefits of giant cane buffers is warranted. Ground water nitrate and ammonium concentrations were measured at the field edge (0 m), and 1.5, 3.0, 6.0, 9.0, and 12.0 m from the field edge through giant cane and forest riparian buffers adjacent to agricultural fields along three streams in southern Illinois. Ground water nitrate and ammonium were not different between the giant cane and forest riparian buffers, nor were there significant reductions in these nutrients through the riparian zones when all three sites were considered. However, site-specific regressions of nutrient concentration vs. distance showed significant reductions (>80%) in nitrate through two forest and one cane riparian buffers, and a significant reduction in ammonium (95%) through a cane buffer. Our results indicate that buffer effectiveness may be dependent on landscape position and water table depth.

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.

Survival and Genet Growth and Development of Field-Planted Giant Cane (Arundinaria gigantea) over Time in Southern Illinois

Abstract The drastic loss of giant cane (Arundinaria gigantea) -dominated communities (canebrakes) in southeastern North America has spurred great interest in habitat restoration. We report on two giant cane restoration studies that investigate the effects of collection source, rhizome propagule morphological characteristics and type (greenhouse-grown containerized stock plants or bare rhizomes), site, and time on genet survival and growth. Survival over the two studies (after three and five years) differed by propagule collection source, was marginally greater when planting older containerized stock, and varied between sites. Although field survival tended to be somewhat greater for greenhouse-grown containerized stock in comparison to bare rhizomes, overall survival was similar for both stock types when accounting for mortality of planted rhizomes in the greenhouse. The number of culms, their height, and spread of the genets increased over time and differed by planting stock type in each study. At Beccas Tract, cane genet growth ranged from a mean of 1.4 ± 0.1 culms that were 41.7 ± 1.8 cm tall with essentially no spread after the first growing season to a mean of 80.6 ± 7.6 culms that were 99.8 ± 2.8 cm tall with a spread of 212.1 ± 19.6 cm after five years. Giant cane rhizome sections initially grown in a greenhouse or planted directly in the field can be used to establish canebrakes in a framework that is operationally feasible for large-scale restoration.

Growing Giant Cane (Arundinaria gigantea) for Canebrake Restoration: Greenhouse Propagation and Field Trials

The environmental importance of giant cane (Arundinaria gigantea) habitat (i.e, canebrake) has spurred interest in restoration; however, restoration is hindered by a lack of available planting stock and practical establishment techniques. Rhizomes from 2 southern Illinois canebrakes (Rose and Bellrose Farms) were utilized in greenhouse propagation and field restoration trials to determine if culm, or stem, production and growth from bare rhizomes planted in containers were influenced by collection origin, growing period duration, rhizome morphology, or refrigerated storage. Culms developed (survived) from 77% of Rose Farm rhizomes versus 37% of Bellrose rhizomes after 1 month. Survival was not affected by an additional month in the greenhouse or 1 month of storage. Mean tallest culm height was similar after 1 month for both sources but increased nearly 4-fold when grown for an additional month. We also compared survival and growth of the greenhouse-grown and stored bare rhizome stock that was machine-planted in field plots receiving either pre-planting herbicide treatment or a non-herbicided control at 2 field sites (Big Creek and Perks). Mean field survival after 1 year was 62.2% at Big Creek and 38.8% at Perks. Herbicide did not affect cane survival or growth. Field survival was greatest for stock of Rose Farm origin especially if planted as in-leaf containerized plants. Rhizome length and number of buds also appeared to have an effect on survival. These data suggest that giant cane bare rhizomes, collected from tested sources, can be successfully machine-planted to produce surviving plants for the restoration of canebrakes.

Decay and Nutrient Release Patterns of Weeds Following Post-Emergent Glyphosate Control

Abstract The role of weed biomass in the nutrient balance of agro-ecosystems remains poorly understood. To measure the rate of decomposition and nutrient release of common weeds, litterbag methodology was employed using waterhemp and giant foxtail desiccated by glyphosate at heights of 10, 20, 30, and 45 cm in two southern Illinois soybean fields. Losses were then expressed as a decay constant (k) regressed over time according to the single exponential decay model. Concentrations of the recalcitrant cell wall components (cellulose, hemicellulose, and lignin) were generally greatest as weed height (maturity) increased in giant foxtail compared with waterhemp. Sixteen weeks after desiccation by glyphosate, 10-cm waterhemp and giant foxtail detritus had lost 10 and 12% more mass, respectively, compared to the 45-cm height of each species. Decomposition rates revealed mass loss was highest for 10-cm waterhemp (kD  =  0.022) and lowest for 45-cm giant foxtail (kD  =  0.011) and this process was negatively correlated to the overall amount of cell wall constituents (r  =  −0.73). Nutrient release rates followed a similar trend in that both shorter (younger) weeds and waterhemp liberated nutrients more readily. Across all tested plant material, K was the nutrient most rapidly released, whereas, Ca was the most strongly retained nutrient. Nomenclature: Glyphosate; common waterhemp, Amaranthus tuberculatus (Moq.) Sauer var. rudis (Sauer) Costea and Tardif AMATU; giant foxtail, Setaria faberi Herrm. SETFA; Soybean, Glycine max (L.) Merr.

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.

Restoration of Riparian Buffer Function in Reclaimed Surface Mine Soils

Ecosystem processes such as water infiltration and denitrification largely determine how riparian buffers function to protect surface water quality. Reclaimed mine areas offer a unique opportunity to study the restoration of riparian function without the confounding influence of past land use. Between 1980 and 2000 in southern Illinois, agricultural fields with forest buffers were established along three restored stream reaches in reclaimed mine land. Our research objective was to compare common indicators of soil quality (infiltration, soil C and N, bulk density, and soil moisture) between forest and cultivated riparian zones to determine if riparian function was being restored. Soil bulk density was significantly lower in the forest buffers compared to the agricultural fields. The forest buffers had greater soil total C, total N, and moisture levels than agricultural fields likely due to greater organic matter inputs. Soil total C and N levels in forest buffers were positively related to age of restoration, indicating soil quality is gradually being restored in the buffers. Restoration success of riparian buffers should not be estimated by the return of structure alone; it also includes reestablishment of functions such as nutrient cycling and water retention that largely determine water quality benefits. Watershed planning efforts can expect a lag time on the order of decades between riparian restoration activities and surface water quality improvement.