13 Jahre nach dem Sturm – Vegetationsentwicklung im Buchen- Naturwald „Königsbuche“ (südwestliches Harzvorland, Niedersachsen)

Abstract

Schmidt, W., Heinrichs, S.: 13 years after windthrow – Vegetation dynamics of the strict beech forestreserve “Königsbuche” (southwestern Harz Mountain foothills, Lower Saxony). - Hercynia N. F. 45(2012): 81 – 110.The strict forest reserve “Königsbuche” was established in 1972. In 1997, parts of the old beech stand weredestroyed by a local summer storm, which created a disturbance gradient ranging from unaffected areas tosmaller and extensively large gaps. After a first inventory during the years 1998 to 2001, flora and vegetationwere recorded again on permanent plots in 2010 in order to understand plant succession and regenerationin unmanaged windthrown beech forests (Galio odorati-Fagetum) according to the initial disturbanceintensity. 13 years after windthrow plant species diversity was higher compared to the year 1998 andwas positively correlated with the disturbance gradient unthrown stand – gap – extensively thrown stand.Contrasting the three disturbance categories, light emerged as the most important environmental factorexplaining differences in species richness. In comparison to the initial situation after windthrow changesin microclimate (temperature, water supply) seemed also to be important for plant species composition.Furthermore, the decomposition of high amounts of dead wood (mainly from twigs and brushwood), particularlyon the extensively thrown plots, favored plant species indicating a higher nutrient supply of theseoriginally mesotrophic soils. Therefore, an Urtica-Rubus-stage has been established on these plots for ashort period, which was as well characterised by a high proportion of plant species of both forests andopen sites. On the contrary, in unthrown stands and gaps species of closed forests dominated togetherwith young beech indicating a fast and secure natural regeneration of the beech forest community aftersmall-scale disturbance. However, the current vegetation survey showed that also in the extensively thrownstands beech is the dominant regenerating tree species overcrowding most parts of the Urtica-Rubus-stagenow. Pioneer tree species (Betula pendula, Salix caprea) – well-known from managed windthrown areason acidic soils – established rarely in the strict forest reserve “Königsbuche”. With increasing initial disturbanceintensity, however, shrub species (Crataegus monogyna, Sambucus nigra, S. racemosa) as well assome other deciduous tree species (Acer pseudoplatanus, Carpinus betulus, Prunus avium) became moreimportant. Nevertheless, these species can only survive on extensively thrown stands with a sufficient lightsupply and under low roe deer browsing pressure as shown by comparing fenced and unfenced plots.Key words: Strict forest reserve, permanent plot, forest succession, intensity of disturbance, windthrow,Galio-Fagetum, diversity, Ellenberg indicator value, natural regeneration, roe deer browsing