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Changing ecosystem conditions and diverse socio-economical events have contributed to an ingrained presence of non-native tree species (NNTs) in the natural and cultural European landscapes. Recent research endeavors have focused on different aspects of NNTs such as legislation, benefits, and risks for forestry, emphasizing that large knowledge gaps remain. As an attempt to fulfill part of these gaps, within the PEN-CAFoRR COST Action (CA19128) network, we established an open-access questionnaire that allows both academic experts and practitioners to provide information regarding NNTs from 20 European countries. Then, we integrated the data originating from the questionnaire, related to the country-based assessment of both peer-reviewed and grey literature, with information from available datasets (EUFORGEN and EU-Forest), which gave the main structure to the study and led to a mixed approach review. Finally, our study provided important insights into the current state of knowledge regarding NNTs. In particular, we highlighted NNTs that have shown to be less commonly addressed in research, raising caution about those characterized by an invasive behavior and used for specific purposes (e.g., wood production, soil recultivation, afforestation, and reforestation). NNTs were especially explored in the context of resilient and adaptive forest management. Moreover, we emphasized the assisted and natural northward migration of NNTs as another underscored pressing issue, which needs to be addressed by joint efforts, especially in the context of the hybridization potential. This study represents an additional effort toward the knowledge enhancement of the NNTs situation in Europe, aiming for a continuously active common source deriving from interprofessional collaboration.

Background The ability of overstory tree species to regenerate successfully is important for the preservation of tree species diversity and its associated flora and fauna. This study investigated forest regeneration dynamics in the Cat Ba National Park, a biodiversity hotspot in Vietnam. Data was collected from 90 sample plots (500 m2) and 450 sub-sample plots (25 m2) in regional limestone forests. We evaluated the regeneration status of tree species by developing five ratios relating overstory and regeneration richness and diversity. By examining the effect of environmental factors on these ratios, we aimed to identify the main drivers for maintaining tree species diversity or for potential diversity gaps between the regeneration and the overstory layer. Our results can help to increase the understanding of regeneration patterns in tropical forests of Southeast Asia and to develop successful conservation strategies. Results We found 97 tree species in the regeneration layer compared to 136 species in the overstory layer. The average regeneration density was 3764 ± 1601 per ha. Around 70% of the overstory tree species generated offspring. According to the International Union for Conservation of Nature’s Red List, only 36% of threatened tree species were found in the regeneration layer. A principal component analysis provided evidence that the regeneration of tree species was slightly negatively correlated to terrain factors (percentage of rock surface, slope) and soil properties (cation exchange capacity, pH, humus content, soil moisture, soil depth). Contrary to our expectations, traces of human impact and the prevailing light conditions (total site factor, gap fraction, openness, indirect site factor, direct site factor) had no influence on regeneration density and composition, probably due to the small gradient in light availability. Conclusion We conclude that the tree species richness in Cat Ba National Park appears to be declining at present. We suggest similar investigations in other biodiversity hotspots to learn whether the observed trend is a global phenomenon. In any case, a conservation strategy for the threatened tree species in the Cat Ba National Park needs to be developed if tree species diversity is to be maintained.

1. Forest management greatly influences biodiversity across spatial scales. At the landscape scale, combining management systems that create different stand properties might promote biodiversity due to complementary species assemblages. In European beech forests, nature conservation and policy advocate a mixture of unmanaged (UNM) forests and uneven-aged (UEA) forests managed at fine spatial grain at the expense of traditionally managed even-aged shelterwood forests (EA). Evidence that such a landscape composition enhances forest biodiversity is still missing. 2. We studied the biodiversity (species richness 0D, Shannon diversity 1D, Simpson diversity 2D) of 14 taxonomic groups from bacteria to vertebrates in ‘virtual’ beech forest landscapes composed of varying shares of EA, UEA and UNM and investigated how γ-diversity responds to landscape composition. Groups were sampled in the largest contiguous beech forest in Germany, where EA and UEA management date back nearly two centuries, while management was abandoned 20–70 years ago (UNM). We used a novel resampling approach that created all compositional combinations of management systems. 3. Pure EA landscapes preserved a maximum of 97.5% γ-multidiversity (0D, 1D) across all taxa. Pure and mixed UEA/UNM landscapes reduced γ-multidiversity by up to 12.8% (1D). This effect was consistent for forest specialists (1D: −15.3%). We found only weak complementarity among management systems. 4. Landscape composition significantly affected γ-diversity of 6–9 individual taxa, depending on the weighting of species frequencies with strongest responses for spiders, beetles, vascular plants and birds. Most showed maximum diversity in pure EA landscapes. Birds benefited from UNM in EA-dominated landscapes. Deadwood fungi showed highest diversity in UNM. 5. Synthesis and applications. Our study shows that combining fine-grained forest management and management abandonment at the landscape scale will reduce, rather than enhance, regional forest biodiversity. We found an even-aged shelterwood management system alone operating at intermediate spatial scales and providing stands with high environmental heterogeneity was able to support regional biodiversity. However, some taxa require certain shares of uneven-aged and unmanaged forests, emphasizing their general importance. We encourage using the here presented resampling approach to verify our results in forest landscapes of different composition and configuration across the temperate zone., publishedVersion

Floristische und vegetationskundliche Daten aus 21 Naturwaldreservaten (NWR) in Rheinland-Pfalz wurden hinsichtlich ihres Anteils an gebietsfremden Gefäßpflanzenarten (Neophyten i. w. S.) ausgewertet und überregional verglichen, um generelle Trends in der Naturnähe und der natürlichen Waldentwicklung - unabhängig von lokal wirkenden Faktoren – aufzuzeigen. Neben überwiegend zonalen, naturnahen Buchenwäldern bodensaurer Standorte umfasst der Datensatz auch drei Auenwald-Standorte und zwei Moorbirken-Bruchwälder. Als Besonderheit im Ver-gleich zu anderen Bundesländern hat Rheinland-Pfalz zwei NWR mit hohen Douglasien-Anteilen ausgewiesen, um deren Entwicklung ohne forstliche Nutzung zu dokumentieren. Von diesen beiden NWR und zwei NWR mit besonderer Dynamik nach Windwurf sowie einem weitgehend ungestörtem NWR im Biosphärenreservat Pfälzer Wald liegen auch Wiederholungsinventuren vor, die erste Hinweise auf die langfristige Entwicklung des Neophyten-Anteils in NWR liefern. Durch einen Vergleich gezäunter und ungezäunter Flächen in NWR konnte der Schalenwildein-fluss, durch den Vergleich mit angrenzenden, weiterhin bewirtschafteten Beständen der Einfluss der forstlichen Nutzung auf den Anteil gebietsfremder Arten an der Vegetation analysiert wer-den. Gebietsfremde Arten spielen in den naturnahen, nicht mehr bewirtschafteten NWR in Rhein-land-Pfalz insgesamt eine untergeordnete Rolle. Vor allem krautige Neophyten sind ausgespro-chen gering vertreten, insbesondere in den naturnahen Buchenwald-NWR. Auch von Impatiens glandulifera, die in allen Auen-NWR am Rhein vorkommt, geht bisher weder ein Verdrängen ein-heimischer Arten noch ein Verlust an Diversität und Naturnähe aus. Den größten Anteil unter den gebietsfremden Arten bilden die nicht-autochthonen Gehölze, die in der Vergangenheit 142 forstlich angebaut wurden und von denen sich vor allem Picea abies, Larix decidua und Pseudotsuga menziesii in den NWR vielfach spontan verjüngen. Wiederholungsinventuren zeigen unterschied-liche Entwicklungen im Anteil gebietsfremder Arten, wobei vorangegangene Störungen (z. B. Windwurf) einen wesentlichen Einfluss ausüben. Im Vergleich der Aufnahmen von zwei Dougla-sien-reichen NWR kam es innerhalb eines Jahrzehnts zu einem starken Rückgang der Douglasie. Sie ist dort vor allem in der Konkurrenz zur Buche unterlegen, so dass sich ohne waldbauliche Unterstützung hier der Naturnähegrad wieder erhöht hat. Ohne Schalenwildeinfluss (hauptsäch-lich Reh- und Rotwild) sind gebietsfremde Arten tendenziell erfolgreicher. Insbesondere Picea abies und Pseudotsuga menziesii waren im Zaun in Strauchschichthöhe stärker vertreten als außer-halb. Im Vergleich mit bewirtschafteten Wäldern ist der Anteil gebietsfremder Arten in unbewirt-schafteten NWR absolut gesehen niedriger. Durch den geringen Artenreichtum an Gefäß-pflanzen und einem geringeren Deckungsgrad der Bodenvegetation im NWR gleichen sich die Unterschiede zwischen (naturnah) bewirtschafteten und nicht bewirtschafteten Wäldern jedoch weitgehend aus., Floristic data and data from vegetation surveys were compared across 21 strict forest nature reserves (SFNR) in Rhineland-Palatinate (south-west Germany) concerning the proportion of non-native plant species (alien plant species or neophytes) in order to detect general trends in the naturalness and dynamics of unmanaged forests in Central Europe. Beside the predominant zonal and close-to-nature oligotrophic beech forests the data set included three eutrophic floodplain forests and two oligotrophic bog woodlands. Apart from other German federal states Rhineland-Palatinate established two SFNR with a high proportion of the alien species Douglas fir in order to study the further development of these stands without forest management. Resurveys of these two SFNR and two further SFNR with a high dynamic after windthrow as well as an undisturbed SFNR in the biosphere reserve Palatinate Forest give the opportunity to analyze long-term trends of alien species. A comparison of fenced and unfenced plots allowed an assessment of browsing effects, a comparison of SFNR with close-by managed forests an assessment of forest manage-ment impacts on the relevance of neophytes in forest vegetation. In a regional context the proportion of non-indigenous plant species in unmanaged SFNR in Rhineland-Palatinate is low. Especially in close-to-nature beech forest SFNR alien herb layer species are rare. Even Impatiens glandulifera – well established in all of the investigated floodplain SFNR of the Rhine valley – seems not to suppress native plant species and shows no negative impact on diversity and the degree of naturalness of the riparian forests. Phanerophytes (woody species) have the highest proportion among aliens in the dataset, mainly introduced by planting in the past. Among them especially Picea abies, Larix decidua, and Pseudotsuga menziesii showed the ability to regenerate naturally in the SFNR. Resurveys of disturbed and undisturbed SFNR indi-cated a divergent development in the proportion of alien species. SFNR stands with Douglas fir Wolfgang Schmidt, Michaela Dölle, Steffi Heinrichs & Patricia Balcar: Gebietsfremde Gefäßpflanzen in Naturwaldreservaten von Rheinland-Pfalz 143 showed a strong decrease of Pseudotsuga menziesii mainly outcompeted by beech within one dec-ade. Therefore, without forest management naturalness of the stands has increased. Without deer browsing (mainly roe and red deer) alien plant species seemed to be more successful. Especially Picea abies and Pseudotsuga menziesii are limited by browsing as fencing increased species frequency and abundance of these woody species within the shrub layer. In general, forest management increased the total number of neophytes. But due to the decreasing species richness and the lower coverage of understorey vegetation in the unmanaged SFNR the differences in the propor-tion of alien species in close-to-nature managed forests and unmanaged forests are negligible, Erforschung und Erhaltung der Phytodiversität: Festschrift zum 70. Geburtstag für Prof. Dr. Dietmar Brandes, p. 141

Alien tree plantations are expanding globally with potential negative effects for native biodiversity. We investigated plant species diversity and composition in a Pinus radiata landscape in south-central Chile, a biodiversity hotspot, by sampling understory vegetation in different plantation age classes, along forest roads and in natural forest remnants in order to find effective conservation measures for native biodiversity. Plantations, including different age classes and roadsides, maintained high native species richness at the landscape scale but supported a completely different community composition than natural forests. Thus, natural forest remnants must be conserved as plantations cannot replace them. Certain natural forest species occurred frequently in mature plantations and can represent starting points for retaining natural elements in plantations. Generalist native and alien species benefited from plantation management, mainly in young plantations and along roadsides. Stand maturation and a closed canopy, though, reduced alien species occurrences within plantations. Along roads, shade-tolerant aliens should be monitored and removed as they can potentially invade natural forests. Native species conservation in plantations requires a holistic approach of the full mosaic of land uses including the protection of remaining natural forests, alien species monitoring along roadsides and patches with continuous canopy cover to reduce pressure by alien species.

Allium ursinum, a dominant herb layer species in nutrient rich, deciduous forests of Central Eu-rope, has considerably expanded in the past decades. As this species mainly relies on regeneration by seeds, we wanted to analyse if and how the timing of phenological phases, climatic factors and resource availability correlated with flowering intensity as a potential factor for its success. We rec-orded annual inflorescence numbers in a population of the Göttinger Wald from 1981 until 2017 and conducted phenological observations across the same time span. In addition, inflorescences were counted in a fertilization experiment contrasting a control with a nitrogen, a phosphorus and a nitro-gen + phosphorus fertilization variant from 2010 to 2017. To investigate the effect of disturbance, inflorescence numbers were counted two to four years after a local summer storm in the southwest-ern foothills of the Harz Mountains in different disturbance categories after windthrow. Our results demonstrate that the length of the growing period for A. ursinum was a strong predic-tor of the number of inflorescences produced in the following year from 1981 to 2017. Climatic factors that had a significant effect on inflorescence numbers were all linked to growing period length. The effect of an increasing trend in growing period length on inflorescence numbers of A. ursinum, was, however, not directly obvious through an increasing flowering intensity with time. Instead, an exceptionally long growing period in 1991 synchronized the flowering behaviour of the population leading to years with a very high flowering intensity. These recurrent high flowering years may have facilitated the expansion of A. ursinum e.g., by increasing the probability of successful seedling establishment or of an accidental dispersal by ungulates. Results of the fertilization experi-ment indicate that atmospheric nitrogen deposition alone does not lead to an increase in inflorescence numbers. Highest numbers were recorded with a combined application of nitrogen and phosphorus. Inflorescence numbers also benefited from an increase in light availability after windthrow but de-creased in the third year after disturbance. Nevertheless, the high reproductive effect after disturb-ance might enable the persistence of this closed forest specialist against other competitors. Overall our results indicate that recurrent high flowering years induced by long growing periods and a high resource availability including light, phosphorus and nitrogen may have influenced the successful expansion of A. ursinum in the past decades and can explain new occurrences and the efficient gap filling in already A. ursinum-rich stands.

Steilhänge der Mittelgebirge weisen eine kleinräumige standörtliche Vielfalt auf und wurden aufgrund ihrer exponierten Lage bereits frühzeitig durch den Menschen u. a. als Befestigungsanlage genutzt. Daraus resultierte häufig eine hohe floristische und vegetationskundliche Diversität mit hohem Naturschutzwert. Durch Umwelt- und Nutzungsveränderungen hat sich aber auch an diesen Standorten in den letzten Jahrzehnten ein starker Wandel vollzogen. Durch Auswertung alter Florenlisten und Vegetationsaufnahmen und durch aktuelle Erhebungen wollen wir die Vegetationszusammensetzung der Lengder Burg, eines Steilhangs auf Unterem Muschelkalk im südlichen Göttinger Wald (Süd-Niedersachsen, Deutschland), und ihre Veränderung aufzeigen und Rückschlüsse für die zukünftige Behandlung ziehen. Dazu wurden Angaben zur Gefäßpflanzenflora aus dem Zeitraum 1950 bis 1995 mit einer aktuellen floristischen Kartierung des Gesamtgebiets von 2016 verglichen. Die Vegetationszusammensetzung wurde anhand von 37 Vegetationsaufnahmen aus dem früheren Zeitraum harakterisiert. 29 dieser Flächen wurden 2009 bis 2016 erneut aufgenommen. Räumliche und zeitliche Unterschiede in der Diversität und Artenzusammensetzung wurden hinsichtlich verschiedener standörtlicher Parameter und ökologischer Artengruppen analysiert. Die Vegetation lässt sich zwei Gruppen zuordnen: 1. Das Carici-Fagetum und seine Kontaktgesellschaften an südlich und westlich exponierten Steilhängen. 2. Das Hordelymo-Fagetum mit verschiedenen Ausbildungen auf dem Plateau und an flacheren Süd- und Nordhangbereichen. Im Carici-Fagetum ist ein deutlicher Diversitätsverlust und eine Zunahme in der Dominanzstruktur der Krautschicht zu erkennen, der im Vergleich der Aufnahmezeiträume auf eine zunehmende Homogenisierung der Vegetation hinweist. Zurückgegangen sind dabei besonders die typischen Kenn- und Trennarten dieser Waldgesellschaft bei gleichzeitiger Zunahme der Buche in der Verjüngung. Im Hordelymo-Fagetum bewirkt neben Gehölzen in der Strauch- und Krautschicht vor allem die Zunahme von Allium ursinum eine homogenere Artenzusammensetzung, jedoch ohne Diversitätsverlust. Neben Stickstoffeinträgen, dem Klimawandel sowie einem reduzierten Rehwild-Verbiss bedingt besonders der Nutzungswandel diese Veränderungen. Vor allem im Carici-Fagetum wirkte sich der Übergang zwischen früherer Nieder- und Mittelwald-Nutzung mit Waldweide über eine fast 100jährige Hochwald-Nutzung bis zum jetzigen Schutzwald stark aus. Gleichwohl weisen die steilen Hänge weiterhin einen hohen Anteil an Rote-Liste-Arten auf und tragen wesentlich zur hohen Biodiversität des Gebiets bei. Veränderungen in der Vegetation der Lengder Burg spiegeln die Veränderungen im Göttinger Wald insgesamt wider. Kleinflächige Offenhaltungsmaßnahmen zur Erhaltung wertvoller floristischer Elemente sind teilweise erfolgreich. Kleinwüchsige, lichtbedürftige Magerkeitszeiger verschwinden jedoch zunehmend aus den sich entwickelnden, hochwüchsigen Stauden-Säumen. In den benachbarten, unbewirtschafteten Hangbuchenwäldern sorgt die fehlende Nutzung nach Jahrhunderten der Auflichtung und Aushagerung für eine Sukzession in Richtung mesophilen Kalkbuchenwalds. Steep slopes of low mountain ranges have a high small-scale heterogeneity and were early used by humans as fortification in times of danger. This caused a high floristic diversity with high conservation value. Environmental and management changes have, however, influenced these sites in the past decades. By analyzing old floristic lists and vegetation relevés and by resurveying we want to characterize the vegetation composition of the Lengder Burg, a steep slope area on Triassic limestone in the Göttinger Wald (southern Lower Saxony, Germany), demonstrate its changes, and give conclusions for its conservation. Floristic records from 1950 to 1995 were contrasted to new records of the study area from 2016. Vegetation composition was assessed using 37 vegetation relevés from the period 1950 to 1995. 29 of these relevés were resurveyed between 2009 and 2016. Spatial and temporal dynamics in species diversity and composition were analyzed regarding site conditions and ecological species groups. The vegetation can be grouped into 1) the Carici-Fagetum and adjacent communities at the southern and western exposed steep slopes and 2) the Hordelymo-Fagetum in different formations at the plateau and at flat-angled southern and northern slopes. The Carici-Fagetum shows a clear diversity loss causing a homogenization of the vegetation when contrasting both survey periods. Thereby, characteristic species decreased while beech increased in the herb layer. The increasing abundance of woody species in the understorey and of Allium ursinum led to a more homogeneous vegetation composition in the Hordelymo-Fagetum as well. There was, however, no diversity loss. Besides nitrogen depositions, climate change and a decreasing browsing intensity, land use changes are mainly responsible for these dynamics. The conversion from coppice and coppice-with-standards with wood pasture to high forest management applied for one century to todays no management seems to have especially affected the Carici-Fagetum. Despite species losses, though, the steep slopes maintained a high proportion of redlist species and determine the high biodiversity of the area. Vegetation changes at the Lengder Burg reflect the dynamics of the total Göttinger Wald area. Small-scale conservation measures by opening stands are successful in maintaining some valuable floristic elements. Small-statured, light-demanding species, indicative of nutrient poor conditions were, however, outcompeted by tall-growing forbs in these clearings. The adjacent, unmanaged Carici-Fagetum stands are developing towards mesic beech forests due to management abandonment after centuries of usage and soil impoverishment.