Text

ETD_2491

http://hdl.rutgers.edu/1782.2/rucore10001600001.ETD.000053156

theses

Japanese barberry (Berberis thunbergii DC.) is an invasive woody shrub that has invaded many different habitats throughout the northeast United States. Since its deliberate introduction as a horticultural plant and replacement shrub for common barberry, around the early 1900s, it has spread from horticultural settings into natural habitats. Its ability to flourish under various environmental conditions gives it a tremendous competitive advantage when compared to indigenous flora. As a result, many indigenous plants are being displaced, ultimately causing changes in biodiversity and ecosystem function. Although there have been considerable amounts of research involving invasive plants, including Japanese barberry, there is little information about the below ground components of invasive shrubs and their role in plant invasions. Since Japanese barberry is so prevalent under various environmental conditions I wanted to determine if Japanese barberry seedlings, first year plants, demonstrate different root growth patterns and structure based on local soil conditions. I also wanted to determine how early root development might contribute to invasiveness. My research was conducted at three locations in northeastern New Jersey, USA where all three locations were heavily invaded by Japanese barberry. The three sites selected were an upland forest site, a wetland area adjacent to a stream bed with organic soils, and a large wetland area with mineral hydric soils. I measured ten different soil components at each site to establish a soil chemistry and composition profile that I used as a baseline for comparing sites. I also wanted to determine if variations local soil chemistry and composition were possible contributors to root structure and development. I analyzed Japanese barberry seedlings by collecting 10 plants from each site during July, October, and December. Seedlings were separated into above-ground and below-ground components; I made images of the seedlings by scanning them and used digitizing software to perform analysis. The images were analyzed with WinRhizo software. Using WinRhizo, I measured the overall root length, number of forks, and number of branches. Separately, I measured the mass of the above-ground and below-ground components to determine if there were any relationships between sites and months. Results indicate that Japanese barberry seedling demonstrated very distinct growth patterns and structure at each site during their first year. The Upland and Stream Bed seedlings showed relatively linear growth with the Upland seedlings having much greater plant mass and complex root structure opposed to the Stream Bed seedlings, which appeared poorly developed. The Great Swamp seedlings demonstrated very limited change in plant mass and root growth from July to December. The Great Swamp soil lay in between the Upland and Stream Bed soils and therefore had moderate root complexity. Although Japanese barberry seedlings demonstrate different growth patterns at each site there is no indication soil composition is a key factor in my results. Soil analysis indicated slight variations in soil chemistries and composition at each site but no significant variations between sites. Further analysis using more precise instrumentation may provide a clearer depiction of soil chemistries and yield significant differences. However, the difference among the three sites in hydrology was quite apparent, and may be the most important factor. In the upland sites, the soils were never saturated, whereas in the SB and GS sites, the soils were often wet or saturated. Although I did not measure hydrologic conditions it is apparent this variable is a factor and warrants further research. I conclude that although Japanese barberry seedlings are clearly capable of germinating and surviving the first growing season in saturated or wetland soils, the conditions of these soils may help these areas avoid dense infestations because root growth is impaired compared to upland soils.

M.S.

Includes bibliographical references

by Craig M. Ruzicki

Includes abstract

doi:10.7282/T3Q81D5Z

ETD graduate

The author owns the copyright to this work.

ETD

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