Succession of abandoned coppice woodlands weakens tolerance of ground-layer vegetation to ungulate herbivory: A test involving a field experiment

Abstract Ground-layer vegetation of abandoned woodlands is threatened by excessive shading and increasing pressure from ungulate herbivores. Although these issues are studied separately, they are presumed to be interactive because decreasing energy input into ground layer seems to limit herbivory tolerance in plants. To separately estimate impacts of succession, herbivory, and their interactions, I conducted a 2-by-2 factorial experiment (creating canopy gaps, setting deer exclosures, their combinations and controls) in abandoned woodlands, where ground-layer vegetation had nearly vanished from deer herbivory. Changes of plant community were monitored three times since half a year before the start of experiment. Rapid increases in foliar cover, plant height, and species richness were found in plots under gaps within half a year from the beginning of the experiment. The major cause of this rapid increase was reestablishment of light-demanding and fast-growing species, whose compensation growth exceeded consumption by deer. In contrast, no significant change was found in ground-layer vegetation under a closed canopy, where only shade-tolerant and slow-growing species existed. These results suggested that limits in light resulting from the progress of forest succession is a primary factor inhibiting recovery of ground-layer vegetation from herbivory damage. In the short term, a combination of gap creation and the removal of herbivores is necessary to restore ground-layer plants in abandoned woodlands.