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A suitable external standard method which was first described by O’Connor and Raven (1988) (“Application of the Rietveld refinement procedure in assaying powdered mixtures,” Powder Diffr. 3, 2–6) was used to determine the quantitative phase composition of a commonly used Ordinary Portland Cement (OPC). The method was also applied in order to determine amorphous contents in OPC. Also investigated were the impact of atomic displacement parameters and the microstrain on the calculated amorphous content. The investigations yielded evidence that said parameters do indeed exert an influence on the calculated amorphous content. On the basis of the data produced we can conclude that the method used is entirely to be recommended for the examination of OPC. No significant amorphous content could be proven in the OPC used.

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Old-growth forests are important stores for carbon as they may accumulate C for centuries. The alteration of biomass and soil carbon pools across the development stages of a forest dynamics cycle has rarely been quantified. We studied the above-and belowground C stocks in the five forest development stages (regeneration to decay stage) of a montane spruce (Picea abies) forest of the northern German Harz Mountains, one of Central Europe's few forests where the natural forest dynamics have not been disturbed by man for several centuries. The over-mature and decay stages had the largest total (up to 480 Mg C ha -1 ) and aboveground biomass carbon pools (200 Mg C ha -1 ) with biomass C stored in dead wood in the decay stage. The soil C pool (220-275 Mg C ha -1 , 0-60 cm) was two to three times larger than in temperate lowland spruce forests and remained invariant across the forest dynamics cycle. On the landscape level, taking into account the frequency of the five forest development stages, the total carbon pool was approximately 420 Mg C ha -1 . The results evidence the high significance of over-mature and decaying stages of temperate mountain forests not only for conserving specialized forest organisms but also for their large carbon storage potential.

Question Natural forest age dynamics is often more or less cyclic, with profound temporal changes in stem density and tree size, tree age structure, deadwood frequency and the abundance of canopy gaps. We investigated the response of ground and epiphyte vegetation to the natural forest age dynamics of an old‐growth spruce forest focussing on (1) the influence of stand age‐related shifts in forest structure and related changes in soil conditions on the diversity and composition of plant communities, (2) differences in the species turnover of cryptogamic epiphytes and ground vegetation in relation to forest age development, and (3) the importance of later (advanced) forest development stages for characteristic epiphyte communities. Location High‐montane old‐growth spruce forest (Picea abies (L.) Karst.) on Mt. Brocken, Harz Mountains, Germany. Methods Five defined forest development stages (regeneration to decay) were investigated with five 100‐m² plots for each stage, in which we studied forest structure, ground vegetation and the epiphytes of living trees and dead trunks. Results The ground vegetation did not significantly change across the forest development stages. Epiphyte diversity on dead standing trees markedly increased towards later stages, with the highest diversity in the over‐mature and decay stages. Diversity of epiphytes on lying trunks was highest in early development stages. Trees in decay as well as regeneration stage included a set of characteristic epiphytes, being rare or absent in the other stages. Conclusions Deadwood, i.e. trees and lying trunks and their epiphytes, outlast the oldest individuals of the tree layer and are still present in the early stages of the following forest generation. Epiphyte diversity on lying deadwood was higher in young than late forest development stages. Habitat continuity presents a fundamental difference to managed forests; it promotes species with dispersal limitations, which are common among cryptogamic epiphytes.

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