Vegetationsdynamik in Buchen-Naturwäldern: Ein Vergleich aus Süd-Niedersachsen

Abstract

Fischer, C., Parth, A., Schmidt, W.: Vegetation dynamics in beech-dominated strict forest reserves. A comparison study from southern Lower-Saxony (Germany). – Hercynia N.F. 42 (2009): 45-68.Out of the one hundred and six established strict forest reserves in Lower-Saxony, only in four cases there are available data from repeated measurements of the ground vegetation. These data allow for a first overview of herb layer´s dynamics, after at least one decade of lack of forest management. As a first example, in the Totenberg strict forest reserve (Luzulo-Fagetum) in Lower-Saxony, vegetation data from 2007 were compared with records carried out a few years after forest´s abandonment in 1989. As a result, a strong decline in the mean of species’ richness is registered. While the percentage of coverage in the herb layer shows a significant reduction, the tree layer and shrub layer indicate increments in coverage. This specific case is mainly due to the strong response of European beech (Fagus sylvatica) in both layers. From the selected Ellenberg-indicator values, the light-value decreases clearly. Moreover, the proportion of both typical forest species and tree regeneration (exclusively beech) increases, whereas the mean percentage of species characterizing conditions in open landscape decreases. In addition, in the first records from 1993/1994, differences in species composition are characterized mainly by the high abundance of Carex remota, Juncus effusus, Oxalis acetosella and Rubus idaeus. The comparison between the beech-dominated strict forest-reserves of Hünstollen (Hordelymo-Fagetum; Göttinger Wald) and Großer Staufenberg (Galio-Fagetum, Luzulo-Fagetum; southern Harz-mountains) reveals a general decline of diversity within the herb-layer since cessation of the forest management. When comparing forest-reserves Totenberg and Hünstollen DCA, a shift towards conditions with lower light supply becomes obvious. However, in the Staufenberg case, this trend can not be observed due to the dieback of elm (Ulmus glabra) and spruce (Picea abies) in the tree layer, together with the absence of a shrub layer. As a conclusion, the main reasons for the assessed changes in ground vegetation are the decreasing disturbances caused by lacking effects like the opening of canopy, soil perturbations during harvesting procedure, and liming. Moreover, on sites with lower pH understorey diversity was probably influenced by increasing beech litter layer thickness following lower decomposition rates.