A critical review of bark anatomical terms is undertaken to stimulate the discussion on bark terminology. Suggestions are made for a standardised usage of the corresponding terms for facilitating the communication between people working on bark anatomy. A tentative glossary of terms is given at the end of the paper.

Background Studying root biomass, root system distribution and belowground interactions is essential for understanding the composition of plant communities, the impact of global change, and terrestrial biogeochemistry. Most soil samples and minirhizotron pictures hold roots of more than one species or plant individual. The identification of taxa by their roots would allow species-specific questions to be posed; information about root affiliation to plant individuals could be used to determine intra-specific competition. Scope Researchers need to be able to discern plant taxa by roots as well as to quantify abundances in mixed root samples. However, roots show less distinctive features that permit identification than aboveground organs. This review discusses the primary use of available methods, outlining applications, shortcomings and future developments. Conclusion Methods are either non-destructive, e.g. visual examination of root morphological criteria in situ, or require excavated and excised root samples. Among the destructive methods are anatomical keys, chemotaxonomic approaches and molecular markers. While some methods allow for discerning the root systems of individual plants, others can distinguish roots on the functional group or plant taxa level; methods such as IR spectroscopy and qPCR allow for quantifying the root biomass proportion of species without manual sorting.

The development of bark structure of Quercus robur L., Ulmus glabra Huds., Populus tremula L. and Betula pendula Roth is being described. Profound structural changes can be observed during the first years after secondary growth has started. In all four species the epidermis is replaced by a periderm, the cortex shows intensive dilatation growth, and the groups of primary bark fibres are pushed apart. The collapse of sieve tube members starts with the second year. With proceeding secondary growth, the specific formation of sclerenchymatic tissue, especially sclereids, and the dilatation growth are processes which strongly affect the bark structure of Quercus robur, Populus tremula and Betula pendula. In addition, wide, fused phloem rays develop in Quercus robur. The structure of Ulmus glabra bark is affected by the formation of phloem fibre-/sclereid-like cells and mucilage cells and by dilatation growth. The histological pattern of Ulmus glabra bark stabilises to a great extent after the first few years, the other barks investigated show further developmental processes over many years. In all species the formation of a rhytidome is the last distinct modification of bark structure.

Quantitative changes of certain anatomical characters during bark development of Quercus robur L., Ulmus glabra Huds., Populus tremula L. and Betula pendula Roth were analysed.

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