The significance of deadwood for total bryophyte, lichen, and vascular plant diversity in an old-growth spruce forest

Modern silviculture has led to a reduction in deadwood, especially that of large diameter, and thus the loss of an important habitat niche in most European forests. We analyzed the significance of deadwood for the total species diversity in three plant groups (bryophytes, lichens, and vascular plants) in one of Central Europe's few remnants of unmanaged old-growth forest. The site is a montane forest of Picea abies on Mt. Brocken, Harz Mountains, Germany, which has not been managed for at least several centuries, undergoes natural forest dynamics, and thus harbors large amounts of standing and downed deadwood. Epiphyte vegetation of live trees and the ground vegetation were studied for comparison. We did not find any obligate deadwood species. Nevertheless, 84 % (70 species) of the total species were found on standing or downed deadwood. One-third of these species, or 28 % of the total species in the forest, were only sampled on deadwood, whereas the remaining species were also found on live trees and/or the ground. Bryophytes were the largest group of species on deadwood (47 % of the deadwood-inhabiting species), followed by lichens (37 %) and vascular plants (16 %). Large-diameter deadwood in an advanced stage of decay harbored more species than smaller fragments in the early stages of decay. Despite the lack of obligate deadwood colonizers, deadwood apparently plays a key role for forest plant diversity, mainly by providing an environment with low competition and thus facilitating the establishment of species.