Succession in deciduous swamp communities of southeastern Michigan formerly dominated by American elm

Abstract

Fifty-six permanent sample plots were established in deciduous swamp communities of SE Michigan [USA] where Ulmus americana was dominant before introduction of the Dutch elm disease. Plots were also established in old fields where elm seedlings were present. The purpose of the study was to determine the composition of the overstory, understory and seedling layers in deciduous swamp forests and to provide a base line for determining the fate of young seedling and sapling elms and the rate and nature of succession in the deciduous swamp communities. The major overstory species in the 3 swamps studied were Fraxinus nigra, Acer rubrum, and Betula alleghaniensis. These species were also dominant in the understory along with smaller numbers of Carpinus caroliniana, U. americana, Tilia americana and Fraxinus pennsylvanica. In the next generation the communities will be much as they are today. The overstory dominants are also strongly represented in the seedling layer. U. americana was more abundant in this layer than in the understory. Ulmus has not been eliminated from the deciduous swamps but makes up about 10-15% of the understory and seedling layers. Old fields and other open upland areas are much more important habitats for regeneration of Ulmus than swamp communities. Indications are that unlike Castanea dentata, U. americana will be perpetuated for generations by seeds from young elm trees; however, the average life span of the species will be drastically reduced.