Conifer clearing and prescribed burning effects to herbaceous layer vegetation on a Maryland serpentine “barrens.”

Indigenous plant communities are being rapidly destroyed by expanding conifer populations in remaining serpentine "barrens" of Maryland. The main purpose of this study was to determine herbacous layer effects of two restoration treatments in Soldiers Delight Natural Environmental Area near Baltimore, Maryland. The cleared-only treatment consisted of post-growing season manual removal of all conifers, and the cleared-and-burned treatment consisted of the latter followed by two consecutive post-growing season prescribed burns. Clearing occurred in November 1989, prescribed burning in November 1990 and 1991, and sampling for presence and percent cover data occurred during the growing seasons of 1989 through 1992. Analysis of covariance was used to detect significant treatment effects to the frequency, percent cover, and community importance percentage of each species. Major results included (1) the community dominant, Schizachyrium scoparium (Michx.) Nash, did not respond to either treatment, (2) each treatment affected a completely different set of species, and (3) the cleared-and-burned treatment affected more species than the cleared-only treatment. The cleared-only treatment significantly affected 3 species, and each responded positively in at least one parameter. The cleared-and-burned treatment significantly affected 6 species; three species responded positively, two negatively, and one had mixed effects. Neither treatment affected oak seedling survival. Clearing-and-burning significantly increased bare mineral soil coverage; the cleared-only treatment had no effect. Neither treatment affected frequency of exposed substrate. Based on short-term responses, these restoration treatments could lead to communities with different vegetation structures.