Japanese Stiltgrass (Microstegium vimineum): Population Dynamics and Management for Restoration of Native Plant Communities

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Title: Japanese Stiltgrass (Microstegium vimineum): Population Dynamics and Management for Restoration of Native Plant Communities
Author: Judge, Caren Ann
Advisors: Theodore H. Shear, Committee Member
Frank A. Blazich, Committee Member
Joseph C. Neal, Committee Chair
Michael G. Burton, Committee Member
Abstract: Japanese stiltgrass is a nonnative invasive grass that occurs in many habitats and is a management concern throughout the eastern United States. Experiments were conducted to address biological and ecological considerations for effective management of Japanese stiltgrass and restoration of native plant communities. Conventional management recommendations emphasize Japanese stiltgrass removal in autumn prior to flowering. Investigations of Japanese stiltgrass reproductive biology were conducted to assess biological considerations that impact such management strategies. Japanese stiltgrass was grown in long day growth chambers (26/22 C) and plants were moved 2, 6, or 10 wk after germination to short day growth chambers (26/22 or 22/18 C). All plants exposed to short days flowered, while under long days no plants flowered. No difference in inflorescence number or shoot dry weight was observed between the two temperature regimes. Japanese stiltgrass populations from North Carolina, Pennsylvania, and Virginia flowered similarly in response short day conditions. Furthermore, inflorescences from natural stands of Japanese stiltgrass were harvested four times; one raceme branch beginning to emerge through the leaf sheath, one raceme branch fully elongated and a second branch visible, fully expanded inflorescence, and in concert with natural dispersal. Following > 90 d storage, seed germination from each harvest averaged 13, 51, 95, and 100%, respectively, suggesting management designed to prevent seed production should be implemented before flowering. In forested areas, herbicides that selectively control Japanese stiltgrass while preserving native vegetation may be desired. The efficacy of three selective postemergence herbicides (fenoxaprop-P, imazapic, and sethoxydim) applied early, mid-, or late season were compared. The herbicides, averaged across application timings, controlled Japanese stiltgrass 83 to 89% and reduced seedhead production 79 to 94%. Seedling emergence was reduced 89, 70, and 78% in spring 2004 by fenoxaprop-P, imazapic, and sethoxydim, respectively, applied in 2003. Additionally, fenoxaprop-P or sethoxydim applied twice (4 wk interval) at half-label or full labeled rates controlled Japanese stiltgrass, providing 92% reduction in biomass and 97 to 98% seedhead reduction. Experiments were conducted to determine if Japanese stiltgrass seeds possess dormancy and if so, to determine conditions required to overcome dormancy and for successful germination. Mature Japanese stiltgrass seeds were collected in autumn 2002 and 2003, cold stratified moist at 4 C or stored dry at 21 C, 0 to 90 d. After storage, seeds were incubated in petri dishes in alternating or constant temperatures and exposed to 14 h or 0 h (total dark) photoperiod. Less than 1% of seeds stored 0 or 15 d germinated while > 95% of seeds stored 90 d germinated, suggesting primary innate dormancy upon natural dispersal. A three-year experiment was conducted in two forest sites to document the ecological impacts of conventional and alternative selective management on Japanese stiltgrass populations and native flora recruitment and establishment. Conventional management treatments included hand-pulling, mowing, or glyphosate (1.1 kg ai/ha) applied in autumn compared to hand-pulling or fenoxaprop-P (0.19 kg ai/ha) applied as needed throughout the season. All management treatments significantly reduced Japanese stiltgrass cover and seed bank over time compared to no management and decreases in relative Japanese stiltgrass cover and seed bank populations were greater in 2004 than 2003, after two seasons of management. However, selective management was more suitable than nonselective management or no management for recruitment and re-establishment of native plants and increasing overall species richness. Additionally, relative cover of other exotic plants decreased 6% over time, suggesting that removal of Japanese stiltgrass did not increase invasion of other exotic plant species.
Date: 2005-07-19
Degree: PhD
Discipline: Horticultural Science
URI: http://www.lib.ncsu.edu/resolver/1840.16/3645

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