Neophyten in Buchen- und Fichtenwäldern des Sollings

405 Neophyten in Buchen- und Fichtenwäldern des Sollings* Wolfgang Schmidt, Steffi Heinrichs, Martin Weckesser, Luise Ebrecht und Bernadett Lambertz Abstract: Non-native plant species in beech and Norway spruce forests of the Solling Hills The proportion of alien plant species in the ground vegetation of beech forests and Norway spruce stands on acidic soils was investigated by comparing vegetation relevés in the Solling Hills (Lower Saxony) obtained from different research projects during four decades. In general, the proportion of non-indigenous plant species is rather low. In species-poor closed beech stands 4.4 % (on average 1.3 %) of the maximum species number and 7.3 % (on average 1.9 %) of the maximum coverage of the sparsely covered herbaceous layer belong to alien plant species. In the Norway spruce stands with a more species-rich and more densely covered herbaceous layer, the proportion of alien species is 2.8 % (on average 1.4 %, species number) and 4.7 % (on average 1.7 %, coverage) at maximum, respectively. In 1966-1968, no alien plant species were recorded in managed beech and Norway spruce forests. In contrast, vegetation relevés recorded 30 years later on the same site showed an increase in the number of alien species up to 1.3 % of the mean number of species. The mean cover of non-native species increased to 0.2 % (beech) and 4.7 % (Norway spruce) of the total herbaceous layer coverage, respectively. Non-indigenous plant species are still lacking completely in the unmanaged beech forest nature reserve. Silvicultural treatments like group selection felling in beech stands or girth-limit felling and clear-cutting in Norway spruce stands were not followed by a significant increase of alien species according to the disturbance gradient. By the creation and use of skid trails in forests there was no shortterm increase of non-native species. Only on heavily or repeatedly disturbed parts of compacted forest roads and skid trails, such as wheel tracks or mid-line in Norway spruce stands did aliens increase significantly. The most important non-native herbs of beech and Norway spruce stands in the Solling Hills are Impatiens parviflora and Epilobium ciliatum. Until now, E. ciliatum was missing in the beech forests mainly due to the low light availability. Rare occurrences of spontaneous tree regeneration of introduced Pseudotsuga menziesii, Larix decidua and Quercus rubra result from near-by forest plantations and indicate that the most important impact on vegetation is coming from the plantation of exotic tree species rather than the spontaneous establishment of herbaceous neophytes. Other alien woody species as well as adventative ornamental plants which are fully established in the flora of the Solling Hills today, are presently not found in the herbaceous layer of the forests. Most of these species can be found in open landscapes or urban areas with gardens and parks. Accordingly the whole Solling landscape including the open and ruderal outskirts has a higher proportion of non-native plant species than the nearly completely forested central part of the research area (11.1 % versus 7.6 % of the flora)

Vascular plant species richness in forest vegetation records differs depending on surveyor

Flächenbezogene Artenzahlen sind besonders im Kontext von Monitoringprojekten grundlegend für die Beurteilung von Veränderungen der Biodiversität. Diese Studie vergleicht die von neun Bearbeitern (5 Einzelbearbeiter, 2 Zweierteams) erfasste Zahl an Gefäßpflanzenarten bei Vegetationserhebungen auf markierten Flächen von 4, 100 und 400 m2 Größe in einem artenreichen Kalkbuchenwald im Göttinger Stadtwald. Dabei wurden Bearbeiter- und Zeiteffekte untersucht, sowie artspezifische Übersehensraten, Fehlbestimmungsraten und Ungenauigkeiten bei der Zuordnung von Pflanzenindividuen zur jeweiligen Aufnahmefläche (Fehlzuordnungsraten) abgeschätzt. Protokollierte Fragen ließen keine systematischen Unterschiede bei der Vertrautheit der Bearbeiter mit der Vegetation vor Ort erkennen, so dass Ausbildung und Erfahrung für gefundene Unterschiede ausschlaggebend sein dürften. Bei den 4 m2 großen Erhebungseinheiten ergaben sich bei der Artenzahl relative Abweichungen der Bearbeiter vom Erwartungswert von 8 bis 26 % (1 bis 4 Arten absolut). Diese waren bei den 100 m2 großen Erhebungseinheiten mit 9 bis 27 % (2 bis 6 Arten absolut) höher. Mit zunehmender Flächengröße nahm der Flächenidentitätseffekt tendenziell ab und der Bearbeitereffekt signifikant zu. Bei den 100 m2 großen Flächen hatte eine längere Bearbeitungszeit einen positiven Effekt auf die Artenzahl. Mit Hilfe artbezogener Auswertungen wurden Übersehens-, Fehlbestimmungs- und Fehlzuordnungsraten ermittelt. Nicht eine Art wurde von allen Bearbeitern auf allen Flächen gefunden, auf denen sie jeweils auftrat. Schwer differenzierbare Arten sowie Arten in ungünstigen Entwicklungsstadien wiesen höhere Übersehens-, aber auch höhere Fehlbestimmungsraten auf. Bei morphologisch gut charakterisierten Arten wurde bei Einzelfunden von einer Fehlzuordnung zur Erhebungseinheit ausgegangen. Die erzielten Ergebnisse sind auch für andere Projekte zur Erfassung der Biodiversität relevant und Bemühungen zur Reduzierung entsprechender Bearbeitereffekte sollten unternommen werden. Eine organisatorische Einbindung entsprechender Bemühungen wird vorgeschlagen.Local species richness is a crucial biodiversity measure also in monitoring projects. This study was carried out in a speciesrich beech forest on limestone within the communal forest of the city of Göttingen. It compares species richness estimates from nine surveyors (five individuals and two teams of two) on plots of 4, 100, and 400 m2 size. The influence of surveyor and elapsed time on the outcome was investigated. Additionally, species-specific overlooking and misinterpretation rates were estimated. As a further source of error, wrong assignment of plant specimen to plots was considered. Analysis of recorded questions of the probates did not reveal a differentiated familiarity with the on-site vegetation on the base of their professional embedding in regional terms. Outcomes have therefore to be seen as the result of individual training and experience. On the spatial level of the 4 m2 plots relative deviances between expected values of species richness and estimates of individual surveyors varied between 8 and 26% (1 to 4 species absolutely). At the 100 m2 plots differences between surveyors were with 9 to 27% (2 to 6 species absolutely) even more pronounced. With increasing plot area effects from plot identity tend to decrease, while observer effects distinctly increase. For the 100 m2 plot level an effect of processing time was detectable. None of the species were found by all surveyors at all subplots on which they occurred. Closely related or otherwise similar species, and those which were in an unfavourable developmental stage, had a higher chance of being overlooked or misinterpreted. Species with peculiar morphological features were considered to be misallocated. For all three types of error respective rates were calculated. The relationships found have generally to be considered in monitoring projects focusing on vegetation changes; however, in large-scale cross-sectional surveys respective error rates should be considered. An organized controlling system is outlined