Currently legislated decreases in nitrogen deposition will yield only limited plant species recovery in European forests

Atmospheric nitrogen (N) pollution is considered responsible for a substantial decline in plant species richness and for altered community structures in terrestrial habitats worldwide. Nitrogen affects habitats through direct toxicity, soil acidification, and in particular by favoring fast-growing species. Pressure from N pollution is decreasing in some areas. In Europe (EU28), overall emissions of NO x declined by more than 50% while NH3 declined by less than 30% between the years 1990 and 2015, and further decreases may be achieved. The timescale over which these improvements will affect ecosystems is uncertain. Here we use 23 European forest research sites with high quality long-term data on deposition, climate, soil recovery, and understory vegetation to assess benefits of currently legislated N deposition reductions in forest understory vegetation. A dynamic soil model coupled to a statistical plant species niche model was applied with site-based climate and deposition. We use indicators of N deposition and climate warming effects such as the change in the occurrence of oligophilic, acidophilic, and cold-tolerant plant species to compare the present with projections for 2030 and 2050. The decrease in N deposition under current legislation emission (CLE) reduction targets until 2030 is not expected to result in a release from eutrophication. Albeit the model predictions show considerable uncertainty when compared with observations, they indicate that oligophilic forest understory plant species will further decrease. This result is partially due to confounding processes related to climate effects and to major decreases in sulphur deposition and consequent recovery from soil acidification, but shows that decreases in N deposition under CLE will most likely be insufficient to allow recovery from eutrophication

Rotföhren- und Spirkenwälder am Fernpaß (Tirol)

Die Wälder von Rotföhre (Pinus sylvestris) und Spirke (Pinus mugo subsp. uncinata) im Fernpaßgebiet (Tirol) wurden pflanzensoziologisch untersucht. Das Lycopodio annotini-Pinetum mugo wird als neue Gesellschaft beschrieben. Dieser Spirkenwald besiedelt steile Nordhänge über Bergsturzschutt aus Kalk- und Dolomitmaterial; seine Moosschicht wird von Sphagnum quinquefarium dominiert. Es wird außerdem der Versuch gemacht, mit Hilfe der Zeigerwerte von ELLENBERG die verschiedenen vorgefundenen Pflanzengesellschaften ökologisch zu charakterisieren.Forests of Pinus sylvestris and of Pinus mugo subsp. uncinata at the Fernpaß area of Tyrol (Austria) were investigated phytosociologically. The Lycopodio annotini-Pinetum mugo is described as a new plant association. This forest of Pinus mugo subsp. uncinata occurs on steep northern slopes on landslide debris consisting of calcareous and dolomitic material; its moss layer is dominated by Sphagnum quinquefarium. An attempt is also made to characterize the different plant communities ecologically by means of ELLENBERG's indicator values

Evaluation of different revegetation measures on mudflow deposits in the Nature Park Sölktäler (Styria, Austria)

In mountain regions, the likelihood of mudflows might increase due to climate change. Although mudflows are common worldwide and devastate agricultural land, virtually nothing is known about the revegetation of mudflow deposits for agricultural purposes. To provide recommendations for rapid revegetation of mountain pastures, 52 permanent plots (4 m × 4 m) on 20 revegetated mudflow deposits in the Nature Park Sölktäler were established. We evaluated different revegetation measures (seed addition alone or combined with application of straw, lime or cattle manure) two years after sowing using commercial clover-grass seed mixtures. Furthermore, 27 permanent plots on 15 unsown mudflow deposits were surveyed. Sowing seeds can considerably accelerate revegetation on siliceous mudflow deposits. Festuca rubra, Agrostis capillaris, Lolium perenne, Trifolium repens and Lotus corniculatus are particularly suitable for rapid grassland reestablishment, whereas Poa pratensis is not recommendable. A pure straw application should be avoided because it delays the revegetation success. Lime addition is not recommended because it can lead to an undesirable legume dominance if clover-grass seed mixtures are used for revegetation. The most effective measure for large-scale revegetation seems to be seed addition without additives. To facilitate revegetation on coarse-grained deposits, large rocks should be crushed using a stone mill

Species-rich montane grasslands on avalanche tracks in the Gesäuse National Park (Austria)

Das Ziel dieser Untersuchung war es, Erkenntnisse über die Bedeutung von Lawinenbahnen für die Biodiversität zu gewinnen. Dazu wurden im Nationalpark Gesäuse (Steiermark, Österreich) 16 Pflanzenbestände in drei ausgewählten Lawinenbahnen pflanzensoziologisch untersucht, vegetationsökologisch charakterisiert sowie mit Vegetationstabelle, bodenkundlichen Analysedaten und topographischen Parametern dokumentiert. Außerdem erfolgte eine Bestandsaufnahme der Schmetterlinge. Die Pflanzenartenvielfalt wurde mit verschiedenen Diversitäts-Indizes beurteilt. Die Ursachen für den Artenreichtum in den untersuchten Lawinenbahnen werden diskutiert. Die Pflanzenbestände wurden überwiegend zum Origano-Calamagrostietum variae gestellt; eine Einzelaufnahme wurde dem Seslerio-Caricetum sem pervirentis zugeordnet. Im Ersteren dominieren Arten mit hemikryptophytischer Lebensform; Therophyten erreichen die zweithöchste Deckung. Die Pflanzengesellschaft wird von CSR-, CS- und C-Strategen aufgebaut; alle anderen Lebensstrategietypen haben keine Bedeutung. Das Origano-Calamagrostietum variae ist eine artenreiche, natürliche Dauergesellschaft, in der mäßiger Stress und schwache Störungen die Artenzusammensetzung maßgeblich bestimmen. Aktive Lawinenbahnen auf sehr flachgründigen, steinigen, nährstoffarmen, basenreichen Rendzinen in lokalklimatisch wärmebegünstigten steilen Hanglagen der montanen Höhenstufe zählen zu den arten-, blüten- und aspektreichsten und somit ökologisch wertvollsten Vegetationsformationen im Nationalparkgebiet. In den kräuterreichen Pflanzenbeständen wurden im Durchschnitt 71 Gefäßpflanzenarten und 5 Moosarten pro 20 m2 Aufnahmefläche gefunden. Mit dieser hohen Phytodiversität und dem Blütenreichtum ist auch eine große Artenvielfalt bei den Schmetterlingen verbunden. Die untersuchten Lawinenbahnen weisen nicht nur ein hohes Maß an Naturnähe auf, sie dürften auch der ursprüngliche Lebensraum einiger Pflanzenarten des Wirtschafts- und Extensivgrünlandes der Tallagen sein. Auf Grund ihrer hohen naturschutzfachlichen Bedeutung müssen Lawinenbahnen als Ganzes geschützt werden. Periodische oder episodische Lawinenabgänge sind Voraussetzung für die Existenz dieser störungsgeprägten Ökosysteme. Unterhalb von Lawinenbahnen dürfen keine Gebäude oder Infrastrukturen errichtet werden, weil diese Bautätigkeit Schutzobjekte erzeugt. Dadurch würde ein Bedarf für Schutzmaßnahmen entstehen, vor allem in Form von Lawinenverbauungen und Aufforstungen, wodurch Lawinenabgänge verhindert werden.The aim of this study was to learn more about the importance of active avalanche tracks for biodiversity. For this purpose 16 vegetation stands on three different avalanche tracks in the national park "Gesäuse" (Styria, Austria) were examined and documented with a vegetation table, soil analysis data and topographical parameters. Additionally, butterfly species were recorded. Plant species richness was evaluated using different diversity indices. Furthermore, the reasons for the high plant-species density found on avalanche tracks are discussed. The vegetation stands investigated belong mainly to the Origano-Calamagrostietum variae; one stand is classified as Seslerio-Caricetum sempervirentis. In the former association hemicryptophytes are prevalent; therophytes exhibit the second highest vegetation cover. The plant community is dominated by CSR strategists, stress-tolerant competitors and competitors; all other life strategy types are insignificant. The Origano-Calamagrostietum variae is a species-rich disclimax community. Moderate stress and low intensity of disturbance determine species composition. On the investigated avalanche tracks the soils are very shallow, stony, nutrient-poor, base-rich rendzinas that developed over limestone debris. The sites are steep and mainly east-facing slopes located in the montane belt. Under these conditions, the vegetation is characterized by a high species density. The average number of vascular plant species within a plot size of 20 m2 is 71, and the number of bryophyte species is 5. The species-rich plant stands, colourful when in bloom, are dominated by herbs, resulting in a high aesthetic value and an increased diversity of butterflies. The avalanche tracks show not only a high naturalness but could also be considered as the original habitat for some plant species of extant grassland. Because of their great nature-conservation value active avalanche tracks have to be protected as a whole. Disturbances by periodic or occasional avalanche events are the precondition for the existence of these near-natural ecosystems. Hence the establishment of buildings and infrastructure below avalanche tracks should be prevented, because this building activity entails protective measures in the form of avalanche barriers and reforestation, leading to a suppression of avalanches

Avalanches keep habitats open and species-rich in the montane and subalpine belt. eco.mont (Journal on Protected Mountain Areas Research)|eco.mont Vol. 2 No. 1 2 1|

From a conservation point of view, avalanches are a natural ecological process. However, they can also endanger people and cause serious damage to buildings and infrastructure. From an anthropocentric point of view, protective measures in the form of avalanche barriers are necessary. Avalanche barriers in the starting zone of avalanches can prevent avalanche events. Hence there is a conflict between nature conservation and protection against natural hazards. This study aimed primarily at assessing the conservation value of active avalanche tracks. To this end we examined 16 plant stands on three different avalanche tracks in the Gesäuse National Park (Styria, Austria) and recorded butterfly species at the same time. On the investigated avalanche tracks, the soils are very shallow, stony, periodically dry, nutrient-poor, base-rich rendzinas developed over limestone debris. The sites are scree-covered, steep and mainly east-facing slopes located in the montane belt. The plant stands investigated belong mainly to the Origano-Calamagrostietum variae community. This study of biodiversity concludes that under these conditions the vegetation in active avalanche tracks is characterized by a high richness of vascular plant species. On average, a plot size of 20 m² contains 71 vascular plant species and 5 bryophyte species. The species-rich plant stands, colourful when in bloom, are dominated by herbs, resulting in a high aesthetic value and an increased diversity of butterflies. The avalanche tracks investigated have a high conservation value because natural ecological processes continue to happen, leading to near-natural and species-rich disclimax communities

Invasive alien plant species in unmanaged forest reserves, Austria

Invasive alien plant species (IAS) are one of the greatest threats to global biodiversity and the sustainable functioning of ecosystems and mitigating the threat posed by them is therefore of great importance. This study presents the results of a 15-year investigation into how IAS occur within natural forest reserves (NFR): unmanaged forest ecosystems within Austria, concluding that unmanaged forests are not resistant to plant invasions. The study comprised ground vegetation, regeneration, and stand structure surveys. The presence or absence of IAS in different forest types was assessed and the influencing variables for their presence or absence were determined. In addition, the study analysed whether the abundance of IAS has increased at the site level within the past decade. Significant differences in the probability of IAS presences between forest types (photosociological alliances) were found. The results of the study show that natural riparian and floodplain forests are among the forest types most vulnerable to biological invasions, which is reflected in elevation and soil type being determined as the main factors influencing the spread of IAS in unmanaged forests. The results of this study may be useful for persons responsible for sustainable forest management programmes or for managing forested areas within national parks. They provide a case study on non-intervention forest management policy in order to mitigate the impacts of IAS in protected areas. Forest areas, where IAS begin to spread can be identified, which in turn leads to measures in the early stages of invasion, and to optimise monitoring and control measures for relevant species in Central European forest types

Climate and air pollution impacts on habitat suitability of Austrian forest ecosystems

Climate change and excess deposition of airborne nitrogen (N) are among the main stressors to floristic biodiversity. One particular concern is the deterioration of valuable habitats such as those protected under the European Habitat Directive. In future, climate-driven shifts (and losses) in the species potential distribution, but also N driven nutrient enrichment may threaten these habitats. We applied a dynamic geochemical soil model (VSD+) together with a novel niche-based plant response model (PROPS) to 5 forest habitat types (18 forest sites) protected under the EU Directive in Austria. We assessed how future climate change and N deposition might affect habitat suitability, defined as the capacity of a site to host its typical plant species. Our evaluation indicates that climate change will be the main driver of a decrease in habitat suitability in the future in Austria. The expected climate change will increase the occurrence of thermophilic plant species while decreasing cold-tolerant species. In addition to these direct impacts, climate change scenarios caused an increase of the occurrence probability of oligotrophic species due to a higher N immobilisation in woody biomass leading to soil N depletion. As a consequence, climate change did offset eutrophication from N deposition, even when no further reduction in N emissions was assumed. Our results show that climate change may have positive side-effects in forest habitats when multiple drivers of change are considered.</p

Räumliche und zeitliche Muster von Ellenberg-Nährstoffzahlen in Wäldern Deutschlands und angrenzender Gebiete : eine Untersuchung auf Grundlage pflanzensoziologischer Datenbanken

Within the last 30 years the role of nitrogen in Central European forests has changed fundamentally from limiting resource to environmental problem. As the retrospective tracking of nutrient availability by soil chemical and biogeochemical measurements faces serious problems, bioindication based on understorey species composition is indispensable for monitoring broad-scale eutrophication. Based on a broad survey of more than 100,000 forest vegetation plots accessible in electronic data-bases from Germany and adjacent countries, we calculated unweighted average Ellenberg nutrient values (mN) as a proxy of plant-available macronutrients. Based on the quantiles of the frequency distribution of mN in a regionally stratified sample, we define five trophic classes, which can be used to compare dimensionless mN values. We studied spatial patterns of average nutrient values within 17 regions and compared the periods from 1899 to 1975 and 1976 to 2006. After 1975 eutrophic (mN > 5.67) and hypertrophic (mN > 6.28) conditions were common everywhere except in the Alps and Saxony-Anhalt, but very oligotrophic conditions (mN < 3.44) were still widespread in regions with nutrient-poor bedrock. Before 1975 mN of plots had been lower than after 1975 in all but the southeastern regions. Between the pre- and post-1975 data the proportion of hypertrophic plots increased from 5.7 to 11.8%, and that of very oligo-trophic plots decreased from 14.6 to 8.3%. To remove bias resulting from uneven distribution, the dataset was stratified by five tree layer dominance types, period and region and resampled. In pre-1975 plots medians of mN increased in the order Pinus sylvestris, Quercus spp., Picea abies, Fagus sylvatica and Alnus spp, whereas the increase of mN was highest in forest types with historically low nutrient values. Therefore, the widespread change in mN must be attributed to the pronounced vegetation changes in Quercus and Pinus stands, indicating the importance of land-use change, i.e. recovery of nutrient cycles after hundreds of years of exploitation through coppicing, grazing and litter use. The analysis confirms eutrophication as a megatrend of modern vegetation change and demonstrates the high research potential of linking vegetation plot databases across large regions.Einleitung: In den vergangenen 30 Jahren hat sich die Wahrnehmung des Stickstoffs in mitteleuropäischen Wäldern grundlegend gewandelt (Bernhardt-Römermann & Ewald 2006). Einst Minimumfaktor, wurde N zu einem der wichtigsten Umweltprobleme. Angesichts der Schwierigkeit, das gesteigerte Nährstoffangebot bodenchemisch nachzuweisen, ist die Bioindikation an Hand von Vegetationsdaten unverzichtbar für den Nachweis von Eutrophierung. Die überregionale Verknüpfung von großen Vegetationsdatenbanken stellt einen wichtigen Ansatz zum Nachweis von zeitlichen Trends und räumlichen Mustern der Artenzusammensetzung dar (Jandt et al. 2011). Material und Methoden: Auf Basis einer Datensammlung mit mehr als 100.000 Vegetationsaufnahmen aus Deutschland und angrenzenden Gebieten (Niederlande, Belgien, östliches Frankreich, Schweiz, Österreich, Tschechien) wurden ungewichtete mittlere Ellenberg-Zeigerwerte für Nährstoffe (mN) als Surrogat für pflanzenverfügbare Makronährstoffe berechnet (Ellenberg et al. 2001). Fünf Trophie-Klassen wurden auf Grundlage der Quantile von mN in einer nach Regionen stratifizierten Stichprobe berechnet, um die Vergleichbarkeit der dimensionslosen Werte zu ermöglichen. Die Verteilung von mN in Wäldern des Untersuchungsraums wurde räumlich (17 Regionen) und zeitlich (1899–1975 und 1976–2006) differenziert dargestellt. Um statistische Verzerrungen zu vermeiden, wurden die Vegetationsaufnahmen nach dominierenden Baumarten (Waldkiefer, Eiche, Fichte, Buche, Erle), Region und Periode stratifiziert. Ergebnisse: Nach 1975 waren eutrophe (mN > 5,67) und hypertrophe (mN > 6,28) Zustände in allen Regionen mit Ausnahme der Alpen und Sachsen-Anhalts verbreitet anzutreffen. Stark oligotrophe Zustände (mN < 3,44) waren in Regionen mit armen Ausgangsteinen immer noch weit verbreitet. Vor 1975 war mN mit Ausnahme der südöstlichen Regionen geringer. Zwischen den Perioden erhöhte sich der Anteil hypertropher Aufnahmen von 5,7 auf 11,8 %, während derjenige stark oligotropher Aufnahmen sich von 14,6 auf 8,3 % verringerte. Für die bis einschließlich 1975 erhobene Vegetationsaufnahmen fanden wir die tiefsten Mediane von mN in Beständen von Pinus sylvestris, gefolgt von Quercus spp., Picea abies, Fagus sylvatica und Alnus spp. In den Aufnahmen nach 1975 zeigten die Mittelwerte bei den nährstoffreichsten Waldgesellschaften den geringsten und bei den oligotrophen Gesellschaften den größten Zuwachs. Diskussion: Die Studie bestätigt Eutrophierung als Megatrend des Vegetationswandels (Verheyen et al. 2012) und streicht das hohe Forschungspotenzial heraus, das in der Verknüpfung von Vegetationsdatenbanken über Ländergrenzen hinweg liegt (Dengler et al. 2011). Die weit verbreitete Zunahme von mN ist in erster Linie durch die markante Veränderung in Quercus- und Pinus-Beständen bedingt, was auf die Bedeutung des Nutzungswandels und die Erholung der Nährstoffkreisläufe nach Jahrhunderten der Niederwald-, Waldweide- und Streunutzung verweist (Glatzel 1991)

Spatial and temporal patterns of Ellenberg nutrient values in forests of Germany and adjacent regions - a survey based on phytosociological databases

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