Final Report: Methods for Increasing Biodiversity in Tallgrass Prairie Reconstructions

EPA Grant Number: R825796
Title: Methods for Increasing Biodiversity in Tallgrass Prairie Reconstructions
Investigators: Jurik, Thomas W. , Moloney, Kirk
Institution: Iowa State University
EPA Project Officer: Manty, Dale
Project Period: January 1, 1998 through December 31, 2000 (Extended to September 30, 2001)
Project Amount: $243,019
RFA: Ecosystem Restoration (1997) RFA Text |  Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , Hazardous Waste/Remediation , Land and Waste Management , Ecosystems

Objective:

The prairies of the midwestern United States have largely been destroyed and replaced by agricultural fields. However, we now are much more aware of the value of the prairie ecosystem as an environmentally stable landscape that provides a variety of environmental, economic, and aesthetic benefits. Thus, there is widespread interest in reconstructing prairie vegetation, both in large tracts and along roadsides. However, many prairie species, particularly broad-leaf species (forbs), are relatively difficult to establish from seed, which is usually the only feasible method of planting. This research project investigated methods of increasing plant diversity in prairie reconstructions, with emphases on seeding and management techniques and incorporation of minor disturbances and natural spatial patterns into the reconstruction process.

Summary/Accomplishments (Outputs/Outcomes):

The impact of several factors on species diversity during prairie reconstructions was investigated, including: (1) different methods of planting seeds; (2) plant height at mowing (to reduce competition from weeds) during the first three seasons after planting; (3) the introduction of minor disturbances as sites for establishment of forb seedlings in grass-dominated areas; and (4) introduction of spatial patterns found in natural prairies. Field studies were conducted at several native prairies in Iowa, at Neal Smith National Wildlife Refuge-Prairie Learning Center (NSNWR-PLC) near Prairie City, IA, where reconstruction of an extensive (3500 ha) prairie is underway, and at Lime Creek Nature Center (LCNC) near Mason City, IA, where about 100 ha of prairie is being reconstructed.

In four seeding/mowing experiments conducted at NSNWR-PLC, diversity and floristic quality (i.e., abundance of desirable prairie "indicator" species) were lowest in the "deep" (5 cm) and "surface" seeding treatments, and highest in the "shallow" (3 cm) seeding treatment. Shorter and more frequent mowing had little effect on floristic quality, but had the universal effect of increasing richness and diversity. Each site was affected by mowing somewhat differently, depending on its age and the dominant weedy cover present. On a 2-year-old site, the shortest and most frequent mowing (mowed to 6 cm) resulted in the greatest increase in both desirable and undesirable species. On a first-year site dominated by a variety of broad-leaf weeds, increases in diversity with short and frequent mowing were primarily due to increases in weedy annuals. On a first-year site dominated by foxtail, increases in diversity and floristic quality with frequent mowing were due to increases in desirable planted species. The overall results suggest that an intermediate seeding depth (e.g., 2-3 cm) followed by frequent mowing (canopy maintained between 10 and 30 cm in height) are the most effective strategies for fostering high diversity of native species. In a mowing/fertilization experiment at LCNC, there was no significant interaction between fertilization and mowing on any community composition measure, and fertilization had no significant effect on any of the measures, whereas mowing did have significant effects. In the first year, mowing significantly increased total and desirable richness and desirable diversity. In the second year, mowing significantly decreased desirable diversity.

The effects of small-scale disturbance was evaluated using artificial gopher mounds at NSNWR-PLC. Seedling recruitment was greater for all species on mounds than off mounds. However, there was no evidence that the spatial or temporal patterns in the production of mounds had an effect on seedling recruitment. Selective foraging by small mammals reduced diversity of recruited seedlings, but seedling abundance was not affected by herbivory. Herbivore pressure was only weakly affected by the mound treatments and was unaffected by the spatial pattern treatments, possibly because of overall low numbers of small mammalian herbivores and the physical structure of the heavily grass-dominated canopy.

In native prairies of southern Iowa, 71 percent of the 85 taxa identified were present in 20 percent or less of the 0.25 m2 sample quadrats along 50-m transects, while only two taxa were present in 80 percent or more of the quadrats. Simpson's index and the Shannon-Weiner index of diversity were high, indicating high species richness and evenness with no dominant species, and dissimilarity of quadrats was only slightly related to physical distance apart. Very few species co-occurred more or less frequently than expected by chance. Thus, the general pattern that emerges is that species essentially are randomly distributed at the scale studied here and that very few, if any, species are closely associated with other species, with respect to their spatial distributions.

Conclusions:

The seeding/mowing/fertilization experiments suggest that an intermediate seeding depth (e.g., 2-3 cm) followed by frequent mowing (canopy maintained between 10 and 30 cm in height) in the first 1 or 2 years after planting are the most effective strategies for fostering high diversity of native species. The benefits of short and frequent mowing can be obtained even in the third year of a reconstruction, and a cover crop such as foxtail may be beneficial in some reconstruction situations. Based on more limited testing, we do not recommend fertilization of reconstruction sites.

Small-scale disturbances are undoubtedly important for seedling recruitment into established and reconstructed prairie, but the importance of the temporal and spatial patterns of such disturbance in reconstructed prairie is not clear. Small-scale disturbances did not provide seedlings with much protection from mammalian herbivory, nor did the spatial autocorrelation of the disturbance regime interact with mammalian herbivory to influence seedling recruitment on a reconstructed prairie. However, one should not necessarily infer from our results that mounds do not function as seedling safe sites in native prairies, because of differences in canopy structure and availability of more litter as protective cover for small mammals.

Because of the high heterogeneity of species distributions at the local scale in native prairies, it does not seem feasible that reconstructed prairies be seeded to create specific patterns on a small spatial scale. Rather, planting a highly diverse seed mix over a relatively uniform site or part of a site may be the best method to reconstruct highly diverse prairies.


Journal Articles on this Report : 4 Displayed | Download in RIS Format

Other project views: All 16 publications 4 publications in selected types All 4 journal articles
Type Citation Project Document Sources
Journal Article Jeltsch, F, Moloney K. Spatially explicit vegetation models: what have we learned? In: Esser K, Luttge U, Beyschlag W, Hellwig F, eds. Progress in Botany. Berlin, Germany: Springer, 2002, pp. 326-343. R825796 (Final)
not available
Journal Article Jurik TW, Kliebenstein H. Canopy architecture, light extinction and self-shading of a prairie grass, Andropogon gerardii. The American Midland Naturalist 2000;144(1):51-65. R825796 (1999)
R825796 (2000)
R825796 (Final)
  • Abstract: BIOONE Abstract
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  • Journal Article Klaas BA, Moloney KA, Danielson BJ. The tempo and mode of gopher mound production in a tallgrass prairie remnant. Ecography 2000;23(2):246-256 R825796 (Final)
  • Abstract: InterScience Abstract
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  • Other: InterScience PDF
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  • Journal Article Wolfe-Bellin KS, Moloney KA. The effect of gopher mounds and fire on the spatial distribution and demography of a short-lived legume in tallgrass prairie. Canadian Journal of Botany 2000;78(10):1299-1308. R825796 (Final)
  • Abstract: NRC Abstract
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  • Other: IASTATE PDF
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  • Supplemental Keywords:

    grassland, plant community structure, pattern analysis, demography, seedling recruitment, restoration ecology., RFA, Ecosystem Protection, Scientific Discipline, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Midwest, Restoration, Monitoring/Modeling, Ecological Effects - Environmental Exposure & Risk, Environmental Monitoring, ecological exposure, biodiversity, ecology, diversity, wildlife, regional species diversity, prairie reconstruction, ecosystem effects, Tallgrass Prairie reconstruction, conservation, plant diversity, Iowa (IA), ecological recovery, terrestrial, ecosystem, economic, prairie vegetation

    Progress and Final Reports:

    Original Abstract
    1999 Progress Report
    2000 Progress Report