The Dryopteris Affinis Complex (Dryopteridaceae) In The Harz Mountains - Identification, Distribution, Ecology

In Germany, the Dryopteris affinis complex has its main distribution in southern parts of the country, but also occurs in the Harz Mountains, the northernmost German low mountain range. From 2008 to 2018, the authors made a series of excursions into the Harz Mountains to study this group. To correctly identify the taxa, samples were collected for flow cytometric analyses as well as micro- and macromorphological examinations. The following taxa and cytotypes were detected: D. affinis (diploid), D. borreri, D. cambrensis subsp. insubrica, and D. lacunosa (triploid), D. xcomplexa nothosubsp. complexa, and "D. affinis s. l." (taxon from the Rehberger Graben), which could not be assigned to any of the Central European taxa (tetraploid), and D. xcritica (pentaploid).The lengths and widths of spores and stomata were measured and their suitability for plant determination tested. The relationship between these parameters are illustrated in scatter diagrams, which also show the 95% reference range for three cytotypes (di-, tri- and tetraploid). A clear overlap of the reference range exists for the spores of the di- and triploid taxa, while this was not observed for the stomata. However, a comparison with plants from Bavaria shows that regional differences in the stomata sizes occur resulting in a shift of the reference range and causing overlapping.Macromorphological features are shown using scans of the upper and lower side of the frond. Information about the occurrences in the Harz Mountains comes from our own site surveys, the literature, and databases of Lower Saxony and Saxony-Anhalt. The occurrences are concentrated in the west, which is more oceanic and characterized by high rainfall. Members of the D. affinis group were recorded in 14 of the 40 ordnance survey maps screened. Overall, 209 individuals of all taxa were found, but the real number is likely to be several times higher. D. borreri is the most common taxon, followed by the tetraploid D. affinis s. l., D. lacunosa, and D. affinis s. str. The rarities include the two primary hybrids D. xcomplexa nothosubsp. complexa and D. xcritica, and also D. cambrensis subsp. insubrica. All recorded plants grow on soils on silicate rock in the submontane and montane zone (between 280 and 733 m), with northwestern and especially northeastern exposures dominating. The average annual precipitation is usually around 900 to 1400 mm; the annual mean temperature ranges between about 7 degrees C in the Lower Harz Mountains and 5-6 degrees C in the Upper Harz Mountains. Narrow brook valleys, forested or semi-open steep slopes, block heaps as well as hems and embankments of forest roads are the habitats colonized in the Harz Mountains.Many of the examined occurrences of the D. affinis group lie in or in the marginal area of spruce forests or mixed spruce forests, more rarely in pure beech stands. With the help of the Ellenberg indicator values, the growing sites can be classified as semi-shady (L 4.9), moderately warm (T 4.7), suboceanic (K 3.5), fresh to moist (F 6.1), moderately acidic (R 5.0), and as rather nitrogen-rich (N 5.7). There were no clear differences in the ecological behaviour between the taxa of the D. affinis group.