Neal Smith National Wildlife Refuge

Research Reporting Symposium

March 6, 2008

 

Abstracts of Presentations

 

 

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Learning and teaching with experimental watersheds: evaluation of ecosystem services in mixed annual-perennial agroecosystems

 

Heidi Asbjornsen¹, Matt Helmers¹, Nancy Grudens-Schuck¹, Cathy Kling¹, Matt Liebman¹, Matt O’Nea¹l, Lisa Schulte¹, Silvia Secchi¹, Gene Takle¹, Rick Cruse^1,  Pauline Drobney², Carl Herndl¹, Randy Kolka³,  USFS, Mark Tomer⁴

 

1.        Iowa State University, Ames, Iowa

2.        US Fish and Wildlife Service, Neal Smith National Wildlife Refuge, Prairie City, Iowa

3.        US Forest Service

4.        National Soil Tilth Laboratory, Ames, Iowa

 

We are conducting an integrated project that analyzes the economic, social, and environmental implications of mixed annual-perennial agroecosystems and creates education programs for diverse stakeholders.  Specifically, we would evaluate multifunctional agricultural production management strategies and develop curricula on ecological systems functions.  With the demand on agriculture for supplying food, feed, fiber, and fuel increasing, the resulting complex set of drivers and responses may cause enormous changes in ecological, economic, and social systems in the Midwestern U.S.  We propose to study how integration of perennial vegetation at small percentages in agricultural lands can provide ecosystem services. 

Our central hypothesis is that strategic placement of perennial cover within agricultural landscapes will have disproportionate benefits on biophysical and socioeconomic systems.  Our project has two linked components: 1) a research component, which quantifies the biophysical and socioeconomic impacts of incorporating perennial vegetation into row-crop agriculture, and 2) an education component, which promotes dialogue about perennial vegetation within agroecosystems.  We will test our hypothesis by replicating four configurations of perennial strips within corn-soybean systems.  Our education component will develop education modules that promote learning by visitors to the Neal Smith National Wildlife Refuge and course curricula and research opportunities for undergraduate Honors students.  A stakeholder committee will enable broad exchange and dissemination of knowledge. 

Project impact will be assessed by documenting treatment effects on watershed characteristics and peoples’ knowledge and perceptions. We expect to show that the project’s integrated activities influence decision making by diverse groups related to agroecosystem sustainability.

 

 

 

 

 

 

Temporal effects on soil carbon dynamics in newly established prairies

 

Jose Guzman and  Mahdi Al-Kaisi: Iowa State University, Ames, Iowa

 

In addition to its aesthetic and environmental qualities, prairie restorations can potentially act as a C sink and offset rising atmospheric CO₂. Recent research in the past ten years has repeatedly shown the benefits of prairie restorations to sequester soil organic C by measuring changes in soil C content, however, this measurement alone does not determine whether a site is a net sink or a source for CO₂. The determination of potential atmospheric CO₂ sequestration in the soil requires an assessment of the ecosystem’s metabolism. The objective of this study was to determine soil C sequestration potential of newly established prairie (prairie remnant, 1993, 1998, and 2003 sites) on previously cultivated land and soil surface CO₂-C emission using a C budgeting approach. Soil C content, vegetation type (cool and warm season grasses, forbs, and legumes), aggregate size distribution, soil surface CO₂-C emission, above and below ground plant biomass and microbial biomass were measured. Preliminary findings suggest; (i) that total C potential input differences between sites were only observed in root biomass contribution; (ii) total soil surface CO₂-C emissions were strongly related to year since establishment and vegetation type within site; (iii) the prairie remnant site had the greatest soil C content while the cropland sites and the youngest prairie had the least (iv) and soil C content increased as time since establishment increased in prairie restorations, although at a decreasing rate. Calculations of net C input show that the youngest prairie restorations had the biggest potential for sequestering C, although it took less than a decade before these sites ceased as a major net sink for CO₂-C compared to prairie remnants and cropland. Furthermore, findings suggest that root biomass and time since establishment may be the leading factors in determining the effectiveness of prairie restorations on soil C sequestering potential.

 

 

Interactions between Bison, Elk, and Plant Communities in an Ongoing Tallgrass Prairie Reconstruction Effort

 

Barbara W. Kagima and W. Sue Fairbanks; Iowa State University, Ames, Iowa

 

Strong evidence indicates that large, native herbivores and fire played profound roles in the evolution, dynamics, and maintenance of the tallgrass prairie ecosystem. Although fire is often incorporated into the reconstruction process, grazing by large, native herbivores typically is not. Little is known about how native grazers interact with plant communities during the reconstruction process, i.e. selection of plant communities in different stages of reconstruction, representation of native versus exotic plant species in the diet, and the effect of other habitat features on distribution of native grazers. Lack of this knowledge prevents prediction of the potential impacts of native herbivores on reconstruction efforts, as well as the potential impacts of reconstruction activities on the ability of native grazers to meet their energetic and nutritional requirements during the reconstruction process. In an effort to understand the impacts of native herbivores on tallgrass prairie reconstruction efforts we conducted a two-year (2006-07) diet and habitat selection study on reintroduced populations of elk and bison at the Neal Smith National Wildlife Refuge in Prairie City, Iowa. This observational study included intensive surveys of bison and elk group locations throughout the summer seasons, estimation of percent cover of plant species in habitat patches, and collection of fecal samples for diet analysis. In both summers the elk population (n=15-17) utilized mostly the treed and reed canary grass areas along the creek within the enclosure. The bison population (n=37) in summer 2006 segregated into a bull bachelor group and a mixed group, containing cows, calves, yearlings, and bulls. Both groups used different areas of the enclosure; while the mixed group utilized the recently burned half of the enclosure the bull groups used the unburned half. In November 2006, the bison herd was replaced with a new herd (n=40) containing rare alleles from the National Bison Range in Montana in an effort to establish a meta-population. The 2007 bison herd did not segregate into a mixed and bachelor group until mid-July and spent a majority of their time in the brome patches. Findings from this study will help illustrate the benefits and challenges of incorporating native herbivores in tallgrass prairie restoration and reconstruction efforts, and therefore aid in future management plans for reconstruction and restoration processes in this greatly reduced ecosystem. 

 

 

Role of planting method in success of native tallgrass prairie restorations

 

Diane L. Larson¹,, USGS, Pauline Drobney²,  Nick Palaia³, Sara Vacek⁴, Doug Wells⁵, Timothy Yager⁶, Jennifer Larson⁷

 

1.        US Geological Service, Northern Prairie Wetland Research Center, Jamestown, North Dakota

2.        US Fish and Wildlife Service, Neal Smith National Wildlife Refuge, Prairie City, Iowa

3.        US Fish and Wildlife Service, Litchfield Wetland Management District, Litchfield, Minnesota

4.        US Fish and Wildlife Service, Morris Wetland Management District, Morris, Minnesota

5.        US Fish and Wildlife Service, Upper Miss NW &FR McGregor District, McGregor, Iowa

6.        University of Minnesota, Minneapolis, Minnesota

 

Infestation by weeds of newly restored tallgrass prairies is a major problem for land managers in the upper Midwest, U.S.A.  Canada thistle (/Cirsium arvense/) is a particular problem in the early stages of these restorations because its control is mandated by local laws, thus often forcing management actions that may be detrimental to the restoration as a whole.  Few studies have addressed optimal planting methods with respect to both establishment of desired species and suppression of weeds, especially Canada thistle.  Our goal in this study was to compare the success (in terms of establishment of desired species, non-planted species, and Canada thistle) of three planting methods (dormant broadcast, spring broadcast, and spring drill) across existing soil texture and nitrogen fertility gradients in the upper Midwest.  We used structural equation models to assess effects of percent sand and nitrification rates (as a measure of soil fertility) on cover of planted and non-planted species and on Canada thistle stem counts in 2005 and 2006.  We then used multi-group analyses to determine if effects differed among the three planting methods.  We also used analysis of variance to compare mean values of our response variables among planting methods.  Our results indicate that cover of planted species was more sensitive to potential net nitrification rates than was cover of non-planted species, and this effect was strongest in the dormant broadcast planting method.  Percent sand had the largest influence on plant cover, but its effect differed between the relatively wet 2005 and the relatively dry 2006 conditions.  Under conditions present when we initiated the plantings, the dormant broadcast seeding method resulted in greater cover of planted species, less cover of non-planted species, and similar amounts of Canada thistle in 2006, compared with the spring broadcast and spring drill methods.

 

 

 

 

Temporal shifts in avian diversity and community structure through stages of restoration of a tallgrass prairie, Neal Smith National Wildlife Refuge

 

Brian F.M. Olechnowski¹, Diane M. Debinsk¹, Pauline Drobney², Karen Viste-Sparkman², William T. Reed¹

 

1.        Iowa State University, Ames, Iowa

2.        US Fish and Wildlife Service, Neal Smith National Wildlife Refuge, Prairie City, Iowa

 

We examined how individual grassland bird species respond to the amount of time a prairie restoration has been out of crop rotation, and observed how avian community composition shifts through these successional stages on a large-scale restoration of a tallgrass prairie. During 2007, both vegetation surveys and bird surveys were performed at study locations at NSNWR. Certain species become less abundant as the restored prairies age (Red-Winged Blackbirds, Horned Larks, Killdeers, Vesper Sparrows). Other species tend to peak in abundance 2-3 years after site restoration (Dickcissels and Common Yellowthroats). Henslow's Sparrows, an obligate grassland species of conservation concern in Iowa, only appear in sites that have been out of rotation for 6+ years. A number of generalist species show no trend. Overall species richness tends to increase at sites that have been out of crop rotation for 3-6+ years. Abundance of individual birds at our study sites is greatest in areas that are at least 2 years out of crop rotation. The community composition of avian species tends to shift dramatically as grassland succession proceeds. Study sites that are 1 year out of crop rotation and 6+ years out of crop rotation display the least degree of similarity in community composition. In addition, sites that are 4-6 years out of crop rotation have significantly different community composition than sites that are 6+ years out of crop rotation. Future studies will focus on identifying the particular habitat variables that most influence avian species richness and abundance in these restored prairies.

 

 

Can prairies help reduce the impact of invasive insects?

 

Matt O’Neal, Iowa State University, Ames, Iowa

 

Landscape structure can be a key factor determining the abundance, community structure and effectiveness of predator and parasitoid communities in agricultural landscapes. The current state of the Iowa agroecosystem, comprised almost entirely of corn and soybean with little natural or undisturbed habitats, may limit the potential of biological control of insect pest within crop land.  The recent invasion of the soybean aphid into the North Central US has increased the value of this ecosystem service.  The endemic community of natural enemies within soybeans can suppress this pest, but is limited by simplified agricultural landscapes that may lack potential alternate host, adult feeding sites and overwintering habitats. I will review studies done within and around the Neal Smith Wildlife refuge that reveal the extant that prairies may serve as a refuge or reservoir for key natural enemies of the soybean aphid.

 

 

Terrestrial arthropod indicators of biotic integrity for prairie ecosystems

 

Jessica M. Orlofske,  Wayne J. Ohnesorg,  Diane Debinski, Iowa State University, Ames, Iowa

 

Arthropod surveys have become a useful tool for scientists and natural resources professionals concerned with aquatic ecosystem quality. Arthropod assessments or indices of biotic integrity can provide information that would be difficult or more expensive to gather by alternative means. However, tools like these have not been developed for Iowa’s critical and vanishing prairies. By combining several broad sampling methods in a standardized protocol along a gradient of quality, or biotic integrity, we can identify potential bioindicators to develop a terrestrial index of biotic integrity. Our survey data will be used to describe how the invertebrate communities differ at remnant, restored and recreated prairies. Our analyses will allow us to determine how we can use invertebrate distribution and abundance data to create a meaningful categorization of prairie quality. This initial project is intended to provide Iowa scientists and professionals with a new and useful tool, as well as more fundamental knowledge of prairie invertebrate ecology.

 

 

An assessment of riparian land-use and channel condition impacts on streambank eroding lengths and recession rates in Walnut Creek

 

Jason Palmer, Iowa Department of Natural Resources, Des Moines, Iowa

 

Over the 150 year history of major agricultural activity in Iowa nearly all the native prairie and wetlands were converted to row-crop agriculture.  This major change was accompanied by broad scale installation of tile drainage intended to remove moisture from saturated wetland soils, increasing available crop land.  The increased removal of water by tile drainage accompanied by the increase in surface runoff, caused by the loss of permanent soil cover and compaction, resulted in an increase in the rate and amount of water entering stream systems.  The increase in discharge overtime resulted in a series of channel adjustments (deepening & widening) to accommodate the increased flow.  Sediment contributed from these channel adjustments has been shown to be a major source of sediment in many Midwestern stream systems.  The main objective of this study was to determine what impact the major land use practices in the Walnut and Squaw Creek Watersheds were having on the location and rate of severe stream bank erosion within the two channel systems.  The location and length of severe stream bank erosion was mapped along the main channels of each watershed.  Eroding lengths were divided into riparian land use categories: cool-season grass, warm-season grass, row-crop agriculture, grazed pasture, riparian forest, and grassland-forest mix.  Total stream length, sinuosity, and eroding stream bank lengths were compared among all land use categories.  To estimate stream bank recession rates, erosion pins were installed along stream banks in four major riparian land uses along the main stem of Walnut Creek.  Outcomes of this investigation indicate that areas with high sinuosity located directly downstream of channelized portions of the stream network were subject to longer eroding lengths with higher recession rates than locations higher in the watershed.  The two current major riparian land uses most frequently associated with meandered sections of the steam system were riparian forest land and grazed pasture land.  Results suggest that lengths of streams segmented by alternating patches of channelized and meandered reaches likely represent major source areas for stream bank derived sediment.

 

 

The effects of varying seeding rates of Bouteloua curtipendula and mowing on native plant establishment in a new prairie reconstruction

Ryan Welch, Daryl Smith, and Dave Williams, University of Northern Iowa, Cedar Falls, Iowa

A major problem in prairie reconstruction is weed competition.  Research has shown that mowing in the first year can increase emergence and survival of prairie plants.  The use of nurse crops (companion crops) has been suggested as an alternative to mowing for weed suppression.  The goal of this study is to examine varying seeding rates of B. curtipendula, as a nurse crop in mowed and un-mowed plots to see if it can successfully suppress weeds without reducing the establishment of seeded natives. We hypothesize that increasing the seeding rate of B curtipendula will reduce weed growth and promote an increase in native seedling numbers. In addition we hypothesize that number of the native seedlings in mowed plots with no B. curtipendula seed will be similar to un-mowed plots seeded with B. curtipendula. Seeds from 25 different species of grasses and forbs were broadcast on June 18^th at Neal Smith Wildlife Refuge at a seeding rate of 22 seeds/m². B. curtipendula was also broadcast at seeding rates of 0, 22, 43, 173, and 345 seeds/m². The site was mowed mid-August of the first growing season and approximately every three weeks of the second growing season. Sampling was done early September 2005, in June and early September 2006.  Native seedling counts, biomass clippings, basal cover, and photosynthetic light were measured. Results show no significant difference (p>0.05) between seeding rates in total native species composition or weed biomass.

 

 

Vegetation structure and plant distributions in drilled and broadcast grassland reconstructions

 

Kathryn A. Yurkonis¹, Brian J. Wilsey¹, Kirk A. Moloney¹,  and Pauline Drobney²

 

1Iowa State University, Ames, Iowa

2US Fish and Wildlife Service, Neal Smith National Wildlife Refuge, Prairie City, Iowa

 

Restoration success is typically determined based on species diversity and composition.  However, fine-scale plant distribution which may affect species turnover rates and resource use may also be important.  To determine to what extent seeding method may affect fine-scale plant distributions, we tested for quadrat-scale differences in vegetation structure within a larger reconstruction study at Neal Smith National Wildlife Refuge.  A diverse grassland seed mix was either drill seeded, which plants seeds in equally spaced rows, or broadcast seeded, which places seeds uniformly across the ground surface, into 24 plots in each of three sites in 2005.  We predicted that closer neighbors in drilled plantings would result in lower species diversity and larger conspecific patch sizes due to greater competitive exclusion during establishment.  Species abundance was measured with point-intercept sampling in a 1 m² quadrat in each plot.  Common species distributions were mapped by dividing each quadrat into 64- 12.5 x 12.5 cm cells and recording the most abundant species in each cell.  Plant distributions were then quantified using patch-based measures of landscape composition.  Quadrat-scale diversity, planted forb and exotic species abundance, and mean patch characteristics did not differ between plantings.  This suggests that planting type did not differentially affect quadrat-scale establishment or invasion and closer neighbors in drilled plantings did not result in greater competitive exclusion.  However, native warm season grasses, with similar resource requirements, were more abundant and occurred in more dispersed patches in drilled plantings.  This was likely due to more open space available for grasses to spread among rows.  The canopy in the drilled quadrats also captured more light, suggesting that fewer microsites are available for colonization in drilled over broadcast plantings.  Although these communities are similar in diversity at present, they may diverge in time due to differences in plant distribution and resource use.  The extent to which spatial relationships among plants affects maintenance of diversity and ecosystem function in restored communities needs to be further investigated and may enhance current restoration practices in our region.