| Shrub community development and management were studied on powerline corridors in central New York State to improve understanding and management of shrublands, which have high conservation value, yet continue to decline regionally as abandoned agricultural lands revert to forest. Maintaining shrub communities often requires vegetation management restricting tree invasion and growth. Regular, intensive vegetation management to control tall-growing trees using both mechanical and chemical treatments on powerline corridors allows managers to potentially, strongly affect the development of shrub communities. While mechanical treatments are generally understood as being useful in tending and regenerating shrubs due to the resprouting capacity of many deciduous woody species, they are not often used to directly culture shrub communities. It is not clear how important vegetation management treatments are to shrub community development relative to other factors in the environmental complex. I hypothesized that the use of mechanical treatments on powerlines would increase shrub abundance.; I used an observational-analytical approach to study site- and disturbance-related factors, coupled with species life histories and community dynamics, to explore how and why shrub communities differed along a 23-km section of corridor on two adjacent 20- to 30-year old powerlines with contrasting vegetation management treatment histories. Observed shrub distributions were consistent with known life history characteristics and generally varied more as a function of past land use and soil-site factors than vegetation management. Interacting land-use history, site, and vegetation management treatments variably affected species distributions, resulting in complex vegetation states.; A concurrent, manipulative field experiment was conducted to evaluate the potential of coppicing with a mechanical brush saw to stimulate lateral expansion and rejuvenation of two shrub species: Cornus racemosa and Viburnum dentatum. Results of the study indicated that this coppicing method was not effective at increasing the rate of shrub expansion of either species into areas previously unoccupied by shrub stems, but was effective at rejuvenating both shrubs by stimulating basal sprouting and root suckering within previously occupied areas.; Collectively, my two studies generally did not support the hypothesis that mechanical treatments lead directly to an increase in the abundance of shrubs. Investigation of treatments that disturb roots and soil seems warranted as it may be needed to stimulate expansion and colonization by some shrub species. Furthermore, a holistic perspective is needed in vegetation science that recognizes the importance of both contemporary and historic human influences in the environmental complex as a basis for vegetation management. |
