| Some forestry practices have short-term negative impacts on understory plants. Some of these man-made disturbances have no natural analog. Resilience of understory plant communities to the novel disturbance created by application of herbicides is the focus of this dissertation. A long-term study of vegetation recovery following partial overstory removal and herbicide application is reported in chapter two. Vegetation recovered by survival in place, from the seed bank, vegetative reproduction, dispersal, and by being browsed by white-tailed deer early in the growing season allowing the plant to act like an ephemeral. The role of the seed bank in recovery of the vegetation was further investigated in chapter three and showed that the earliest species to recover from herbicide application are those species with seed banking capability. Seed banks were unaffected by herbicides, but herbaceous vegetation cover declined temporarily. Red to far-red ratio and percent visible sky nearly doubled following understory treatment with herbicides. Other than light changes, there were no environmental variable relationships following herbicide. A study of the influence of increased temperature and nitrogen on seed bank response was conducted, showing an interaction of temperature and increased nitrate on number of seed bank germinants. In all of the studies collectively, it was shown that the herbaceous layer was resilient to the novel disturbance pattern created by herbicide application, with recovery of non-target species occurring after 3-5 years as is shown in chapters two and three. Herbicide differs from other understory disturbances like fire and periodic flooding in that both above- and below-ground plant parts are killed if the herbicide contacts the foliage. Thus, the role of the seed bank in recovery may be more critical than it is in following other disturbance in terrestrial systems. Herbicide application is a one-time event, so the ecosystem has not evolved with that kind of disturbance in its history. It will continue to be an important tool for land managers in restoration of ecosystems as invasive plants invade more areas and as long as legacy effects from long-term herbivory exist on the landscape.;Key Words: AccordRTM, ArsenalRTM, community similarity, diversity, glyphosate, interfering plants, imazapyr, nitrate, Oust XPRTM, recovery mechanisms, resilience, seed bank, shelterwood silviculture, sulfometuron methyl, vegetation management. |
