Karl W. J. Williard

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.

Indicators of nitrate export from forested watersheds of the mid‐Appalachians, United States of America

Soil net nitrogen mineralization and nitrification rates were studied on nine undisturbed, forested watersheds in an effort to explain large variations in nitrate export in streamflow within the mid-Appalachian region. Rates of soil net nitrogen mineralization and net nitrification were measured in the upper 10 cm of mineral soil over a 5-week summer incubation period (June–July) using nine buried bags in each of the three major soil types on each watershed. Watersheds with high, medium, and low nitrate export rates exhibited high, medium, and low mean net nitrogen mineralization and net nitrification rates, respectively. Exchangeable calcium (an index to site fertility), C/N ratios, and soil moisture content together explained 63% of the variation in soil nitrogen mineralization rates, and exchangeable calcium and soil moisture content explained 61% of the variation in soil nitrification rates using multiple regression analysis. The variation in watershed nitrate export was best explained by total nitrogen in the upper 10 cm of mineral soil (explained 46%) and the percentage of mineralization due to nitrification (explained 42%). Estimated rates of wet and dry atmospheric deposition of nitrogen were not significantly correlated with watershed nitrate export. Results from this study demonstrate that soil nitrogen pools and dynamics are the most critical factors controlling nitrate export from forested watersheds in the mid-Appalachians. Long-term changes in site fertility, C/N ratios, and soil moisture, which largely control microbial nitrogen cycling, should have a significant effect on long-term trends in nitrate leaching.

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.

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.

SOIL CHEMICAL RESPONSE TO EXPERIMENTAL ACIDIFICATION TREATMENTS

One of the conclusions reached during the Congressionally mandated National Acid Precipitation Program (NAPAP) was that, compared to ozone and other stress factors, the direct effects of acidic deposition on forest health and productivity were likely to be relatively minor. However, the report also concluded “the possibility of long-term (several decades) adverse effects on some soils appears realistic” (Barnard et al. 1990). Possible mechanisms for these long-term effects include: (1) accelerated leaching of base cations from soils and foliage, (2) increased mobilization of aluminum (Al) and other metals such as manganese (Mn), (3) inhibition of soil biological processes, including organic matter decomposition, and (4) increased bioavailability of nitrogen (N). Sulfate-induced acidification occurs as the sulfate (SO

Potential Denitrification Rates in an Agricultural Stream in Southern Illinois

ABSTRACT The influences of stream temperature, nitrate concentration, dissolved oxygen concentration, and substrata composition on potential denitrification rate (PDR) were investigated over one year in Big Creek, an agricultural watershed in southern Illinois. PDR ranged from 0 to 106 μg N g AFDM−1 hr−1 with higher rates in the early spring and late summer. The greatest PDRs were measured in April 2000 and April 2001, which both coincided with newly established periphyton communities. PDR did not correlate as expected with seasonally variable, ambient stream conditions such as temperature, dissolved oxygen or nitrate concentration; however, significant relationships did exist between PDR and dissolved oxygen within seasons. The coarse sediments from the headwater section of Big Creek had a significantly higher PDR (13.1 μg N g AFDM−1 hr−1) than the fine sediments (5.2 μg N g AFDM−1 hr−1) from the lower channelized reach, which may have been a function of lower C:N organic matter in the headwater reach. Based on the PDR measured in this stream, denitrification was not a significant sink of the stream nitrogen load.

Tree Response to Experimental Watershed Acidification

Forest ecosystems in the Eastern USA are threatened by acid deposition rates that have increased dramatically since industrialization. We utilized two watersheds at the Fernow Experimental Forest in West Virginia to examine long-term effects of acidification on ecological processes. One watershed has been treated with ammonium sulfate (approximately twice the ambient deposition rate) since 1989 to simulate elevated acidic deposition, while the other served as a control. Prior to treatment, both watersheds were similar in age and species composition. Ten dominant overstory Prunus serotina and Liriodendron tulipifera trees were selected and cored from each watershed to measure bolewood concentrations of essential elements through time. In addition, changes in tree species basal area were analyzed utilizing 50 long-term growth plots. Results of this experiment show lower calcium and magnesium concentration and increased acidic cation concentration for both species in the treated watershed, indicating a negative treatment effect. Growth response, measured through relative growth rates of cored trees and changes in basal area from growth plots, was not as conclusive and appeared to differ by species. The resulting difference in species response indicates that acidification sensitivity is something that land managers should consider when managing forests affected by acidification.