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Pinus rotundata dominated peatbog (Žofinka Nature Reserve) in the Třeboň Basin, Czech Republic, was affected by “natural” disturbances: wind damage (1984), followed by a bark beetle attack, and fire (1994, 2000). Phytosociological relevés were used to document vegetation. Soil water chemistry was compared in three differently affected stands: (1) an undisturbed Pinus rotundata bog forest, (2) a windthrow – bark beetle affected stand and (3) a site burned by wildfire in 2000. The species composition of the windthrow – bark beetle affected sites and the undisturbed P. rotundata bog forest differed mainly in the shrub and tree layers. Burned sites were partly colonized by anemochorous species (e.g. Taraxacum sp. div .) that disappeared within two or three years after colonization. Bare peat was colonized by bryophytes (e.g. Marchantia polymorpha and Funaria hygrometrica) typical of the disturbed sites, and by Polytrichum sp. div. and Aulacomnium palustre. Most plant species characteristic of the P. rotundata bog forest occurred at the burned sites eight years after the fire, but in different abundances. The edificator of the former community— P. rotundata—was mostly absent. Compared with windthrow followed by the bark beetle attack, fire promoted rapid expansion of Molinia caerulea. Soil water in both the undisturbed P. rotundata bog forest and the windthrow – bark beetle affected sites had a similar composition: very low pH values, high P concentrations, low concentrations of cations (Ca2+, Mg2+and K+) and inorganic nitrogen. The concentrations of soluble reactive phosphorus (SRP) and $${\text{NH}}_4^ + - {\text{N}}$$ were negatively correlated with the groundwater table. Total P, SRP and $${\text{NH}}_4^ + - {\text{N}}$$ concentrations in the soil water at the burned site were by one order of magnitude higher than those in the P. rotundata bog forest, while concentrations of K+, Mg2+ and Ca2+ were only about two times higher. High concentrations of P and N in the soil water found three years after the fire indicated a long-term elevated nutrient content in the soil water. [ABSTRACT FROM AUTHOR]

Species composition of the understory of spruce (Picea abies (L.) Karsten) and beech (Fagus sylvatica L.) forests subjected to intense air pollution stress in the Krkonoše Mts., Czech Republic, showed directional changes over the last 15 years. The changes were documented with repeated observations of 29 permanent plots, initiated in 1980 and analysed with constrained ordination methods (Canonical Correspondence Analysis). Ground layer changes were mainly associated with the loss of canopy foliage from air pollution stress. The increased amount of the light at ground level resulted in increased herb cover. The initially dominant species (e.g., Calamagrostis villosa (Chaix) J. F. Gmelin, Deschampsia flexuosa (L.) P. B., Vaccinium myrtillus L., Athyrium distentifolium Tausch) were those that increased in cover. Moss cover, and moss and herb richness, declined over the course of the study. Thus, the changes in tree canopy are accompanied with changes in the forest understory, which in turn can affect the dynamics of these forests. [ABSTRACT FROM AUTHOR]