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Understorey plant communities play a key role in the functioning of forest ecosystems. Under favourable environmental conditions, competitive understorey species may develop high abundances and influence important ecosystem processes such as tree regeneration. Thus, understanding and predicting the response of competitive understorey species as a function of changing environmental conditions is important for forest managers. In the absence of sufficient temporal data to quantify actual vegetation changes, space-for-time (SFT) substitution is often used, i.e. studies that use environmental gradients across space to infer vegetation responses to environmental change over time. Here we assess the validity of such SFT approaches and analysed 36 resurvey studies from ancient forests with low levels of recent disturbances across temperate Europe to assess how six competitive understorey plant species respond to gradients of overstorey cover, soil conditions, atmospheric N deposition and climatic conditions over space and time. The combination of historical and contemporary surveys allows (i) to test if observed contemporary patterns across space are consistent at the time of the historical survey, and, crucially, (ii) to assess whether changes in abundance over time given recorded environmental change match expectations from patterns recorded along environmental gradients in space. We found consistent spatial relationships at the two periods: local variation in soil variables and overstorey cover were the best predictors of individual species’ cover while interregional variation in coarse-scale variables, i.e. N deposition and climate, was less important. However, we found that our SFT approach could not accurately explain the large variation in abundance changes over time. We thus recommend to be cautious when using SFT substitution to infer species responses to temporal changes.
The contemporary state of functional traits and species richness in plant communities depends on legacy effects of past disturbances. Whether temporal responses of community properties to current environmental changes are altered by such legacies is, however, unknown. We expect global environmental changes to interact with land-use legacies given different community trajectories initiated by prior management, and subsequent responses to altered resources and conditions. We tested this expectation for species richness and functional traits using 1814 survey-resurvey plot pairs of understorey communities from 40 European temperate forest datasets, syntheses of management transitions since the year 1800, and a trait database. We also examined how plant community indicators of resources and conditions changed in response to management legacies and environmental change. Community trajectories were clearly influenced by interactions between management legacies from over 200 years ago and environmental change. Importantly, higher rates of nitrogen deposition led to increased species richness and plant height in forests managed less intensively in 1800 (i.e., high forests), and to decreases in forests with a more intensive historical management in 1800 (i.e., coppiced forests). There was evidence that these declines in community variables in formerly coppiced forests were ameliorated by increased rates of temperature change between surveys. Responses were generally apparent regardless of sites’ contemporary management classifications, although sometimes the management transition itself, rather than historic or contemporary management types, better explained understorey responses. Main effects of environmental change were rare, although higher rates of precipitation change increased plant height, accompanied by increases in fertility indicator values. Analysis of indicator values suggested the importance of directly characterising resources and conditions to better understand legacy and environmental change effects. Accounting for legacies of past disturbance can reconcile contradictory literature results and appears crucial to anticipating future responses to global environmental change.
Wildfires affect biodiversity at multiple levels. While vegetation is directly changed by fire events, animals are often indirectly affected through changes in habitat and food availability. Globally, fire frequency and the extent of fires are predicted to increase in the future. The impact of fire on the biodiversity of temperate wetlands has gained little attention so far. We compared species richness and abundance of plants and birds in burnt and unburnt areas in the Amur floodplain/Russian Far East in the year of fire and 1 year after. We also analysed vegetation recovery in relation to time since fire over a period of 18 years. Plant species richness was higher in burnt compared to unburnt plots in the year of the fire, but not in the year after. This suggests that fire has a positive short-term effect on plant diversity. Bird species richness and abundance were lower on burnt compared to unburnt plots in the year of the fire, but not in the year after. Over a period of 18 years, high fire frequency led to an increase in herb cover and a decrease in grass cover. We show that the effects on biodiversity are taxon- and species-specific. Fire management strategies in temperate wetlands should consider fire frequency as a key driving force of vegetation structure, with carry-over effects on higher trophic levels. Designing fire refuges, i.e., areas that do not burn annually, might locally be necessary to maintain high species richness.
Um Themen des Schutzes von Pflanzengemeinschaften wirksamer in der breiten Öffentlichkeit zu kommunizieren wird der Vorstand der „Floristisch-Soziologischen Arbeitsgemeinschaft (FlorSoz)“ ab 2019 eine „Pflanzengesellschaft des Jahres“ ausrufen. Damit sollen politische und administrative Entscheidungs- und Umsetzungsprozesse zur Erhaltung der Vielfalt von Ökosystemen und Pflanzengesellschaften in Deutschlands gezielt unterstützt werden. Für das Jahr 2019 wurde die Glatthaferwiese ausgewählt. Sie zählt aktuell zu den durch Artenverarmung und Flächenrückgang besonders bedrohten Pflanzengesellschaften Deutschlands. Es sind deshalb dringend Maßnahmen zum Schutz und zur Wiederherstellung notwendig. Dieser Artikel gibt einen kurzen Überblick zur naturschutzfachlichen Bedeutung von Glatthaferwiesen und deren Ökosystemleistungen sowie zur floristisch-soziologischen Erforschung, zu Ursachen ihres Rückgangs und zu geeigneten Gegenmaßnahmen.
In einem rund 2.200 ha großen Waldgebiet bei Magdeburgerforth (Fläming, Sachsen-Anhalt) wurden 1948 bis 1950 von Harro Passarge 120 Vegetationsaufnahmen sowie eine Vegetationskartierung erstellt. Das Gebiet zeichnet sich durch eine große Vielfalt an Waldtypen aus den Verbänden Agrostio-Quercion petraeae, Alnion glutinosae, Alnion incanae, Carpinion betuli, Dicrano-Pinion und Quercion roboris aus. Daher und weil viele der heute in Wäldern wirksamen Prozesse (z. B. Stickstoffeintrag,
Klimawandel) vor 60 Jahren noch nicht spürbar waren, bietet sich das Gebiet für eine Wiederholungsuntersuchung besonders an. Da die Aufnahmeflächen von Passarge nicht punktgenau verortet waren, wurden im Jahr 2014 in einem über die Forstabteilungen und die Vegetationskarte definierten Suchraum immer die der Erstaufnahme ähnlichsten Waldbestände erfasst. Insgesamt konnten 97 (81 %) der Aufnahmen wiederholt werden. Vegetationsveränderungen werden mithilfe einer NMDS-Ordination, der Gegenüberstellung von α -Diversität, Zeigerwerten und Waldbindungskategorien für die beiden
Aufnahmezeitpunkte sowie über die Identifikation von Gewinner- und Verlierer-Arten analysiert.
Auch wenn methodenbedingt bei der Wiederholungsuntersuchung nur die jeweils geringstmögliche
Vegetationsveränderung abgebildet wird, konnten Ergebnisse erzielt werden, die mit denen quasi permanenter Plots übereinstimmen. Die beobachteten allgemeinen Trends (Eutrophierung, Sukzession nach Nutzungswandel, Verlust lichtliebender und magerkeitszeigender Arten, Ausbreitung von stickstoffliebenden Arten und mesophilen Waldarten, Einwanderung von Neophyten, keine generelle Abnahme der Artenzahl) stimmen gut mit den in zahlreichen Studien aus mitteleuropäischen Wäldern festgestellten überein. Durch das von nassen bis trockenen sowie von bodensauer-nährstoffarmen bis zu relativ basenreichen Böden reichende Standortsspektrum innerhalb des Untersuchungsgebietes konnte aber – deutlicher als in den meisten bisherigen Fallstudien – gezeigt werden, dass sich die Resilienz der
Wälder gegenüber Vegetationsveränderung je nach Ausgangsgesellschaft stark unterscheidet und jeweils unterschiedliche Treiber wirksam sind. Stellario-Carpinetum und Luzulo-Quercetum erwiesen
sich als relativ stabil, und auch in den Feuchtwäldern des Circaeo-Alnetum gab es trotz eines Artenwechsels wenig Hinweise auf Umweltveränderungen. Dagegen wiesen die Wälder nährstoffarmer Standorte (Sphagno-Alnetum, Betulo-Quercetum, Dicrano-Pinion) viele Verliererarten und eine starke Eutrophierungstendenz auf. Die in besonderem Maße von historischen Waldnutzungsformen abhängigen thermophilen Wälder und die Flechten-Kiefernwälder gingen weitgehend verloren.
Topsoil conditions in temperate forests are influenced by several soil-forming factors, such as canopy composition (e.g. through litter quality), land-use history, atmospheric deposition, and the parent material. Many studies have evaluated the effects of single factors on physicochemical topsoil conditions, but few have assessed the simultaneous effects of multiple drivers. Here, we evaluate the combined effects of litter quality, land-use history (past land cover as well as past forest management), and atmospheric deposition on several physicochemical topsoil conditions of European temperate deciduous forest soils: bulk density, proportion of exchangeable base cations, carbon/nitrogen-ratio (C/N), litter mass, bio-available and total phosphorus, pH(KCI)and soil organic matter. We collected mineral soil and litter layer samples, and measured site characteristics for 190 20 x 20 m European mixed forest plots across gradients of litter quality (derived from the canopy species composition) and atmospheric deposition, and for different categories of past land cover and past forest management. We accounted for the effects of parent material on topsoil conditions by clustering our plots into three soil type groups based on texture and carbonate concentration. We found that litter quality was a stronger driver of topsoil conditions compared to land-use history or atmospheric deposition, while the soil type also affected several topsoil conditions here. Plots with higher litter quality had soils with a higher proportion of exchangeable base cations, and total phosphorus, and lower C/N-ratios and litter mass. Furthermore, the observed litter quality effects on the topsoil were independent from the regional nitrogen deposition or the soil type, although the soil type likely (co)-determined canopy composition and thus litter quality to some extent in the investigated plots. Litter quality effects on topsoil phosphorus concentrations did interact with past land cover, highlighting the need to consider land-use history when evaluating canopy effects on soil conditions. We conclude that forest managers can use the canopy composition as an important tool for influencing topsoil conditions, although soil type remains an important factor to consider.
Wie erstmals 2019 wird auch für das Jahr 2020 von der „Floristisch-soziologischen Arbeitsgemeinschaft“ (FlorSoz) für Deutschland die „Pflanzengesellschaft des Jahres“ vorgestellt. Damit soll wiederum für die Öffentlichkeit die Notwendigkeit des Schutzes gefährdeter Pflanzengesellschaften aufgezeigt werden. Für das Jahr 2020 wurden die Borstgrasrasen ausgewählt. Wie alle Pflanzengemeinschaften nährstoffarmer Standorte, sind auch die Borstgrasrasen stark gefährdet und regional sogar unmittelbar vom Aussterben bedroht. Wir konzentrieren uns vor allem auf die Bestände der planaren bis montanen Stufe (Unterverband Violenion caninae: Hundsveilchen-Borstgrasrasen). Die Standorte von Violenion caninae-Gesellschaften werden nicht gedüngt und sind auf extensive Beweidung, z.T. auch auf einschürige Mahd angewiesen. Für Borstgrasrasen bezeichnend sind eine Fülle gefährdeter Pflanzenarten wie z.B. Arnica montana (Arnika) und Antennaria dioica (Zweihäusiges Katzenpfötchen). Bei den Borstgrasrasen spielen für die zunehmend hohe Gefährdung nicht nur Flächenrückgänge durch Nutzungsaufgabe, Aufforstung, Sport- und Freizeitaktivitäten und Überbauung eine Rolle, sondern auch Änderungen der Struktur und Artenzusammensetzung durch direkte Düngung sowie atmogene Stickstoffeinträge sind von Bedeutung. Nährstoffanreicherungen führen zum Verlust der konkurrenzschwachen, gefährdeten Arten zugunsten einiger allgemein verbreiteter, häufig dominanter Gräser sowie konkurrenzkräftiger Kräuter. Wir skizzieren die Bedeutung der Borstgrasrasen als gefährdete Lebensgemeinschaften, geben Hinweise zur floristisch-soziologischen Erforschung und zu weiteren Naturschutz-Aspekten (Rückgang, Erhaltung, Möglichkeiten der Restitution). Ein wirksamer Schutz ist nur bei einem integrativen Naturschutzansatz mit geeigneter Nutzung möglich.
Global environmental changes are expected to alter the functional characteristics of understorey herb-layer communities, potentially affecting forest ecosystem functioning. However, little is known about what drives the variability of functional traits in forest understories. Here, we assessed the role of different environmental drivers in shaping the functional trait distribution of understorey herbs in fragmented forests across three spatial scales. We focused on 708 small, deciduous forest patches located in 16 agricultural landscape windows, spanning a 2500-km macroclimatic gradient across the temperate forest biome in Europe. We estimated the relative effect of patch-scale, landscape-scale and macroclimatic variables on the community mean and variation of plant height, specific leaf area and seed mass. Macroclimatic variables (monthly temperature and precipitation extremes) explained the largest proportion of variation in community trait means (on average 77% of the explained variation). In contrast, patch-scale factors dominated in explaining community trait variation (on average 68% of the explained variation). Notably, patch age, size and internal heterogeneity had a positive effect on the community-level variability. Landscape-scale variables explained only a minor part of the variation in both trait distribution properties. The variation explained by shared combinations of the variable groups was generally negligible. These findings highlight the importance of considering multiple spatial scales in predictions of environmental-change effects on the functionality of forest understories. We propose that forest management sustainability could benefit from conserving larger, historically continuous and internally heterogeneous forest patches to maximise ecosystem service diversity in rural landscapes. (C) 2018 Gesellschaft fur Okologie. Published by Elsevier GmbH. All rights reserved.
Habitat fragmentation is one of the most important causes for the decline of plant species. However, plants differing in phylogeny, habitat requirements and biology are likely to respond differently to habitat fragmentation. We ask whether case studies on the effects of habitat fragmentation conducted so far allow generalizations about its effects on the fitness and genetic diversity of populations of endangered plant species. We compared the characteristics of plant species endangered in Germany whose sensitivity to habitat fragmentation had been studied with those of the endangered species that had not been studied. We found strong discrepancies between the two groups with regard to their taxonomy and traits relevant to their sensitivity to habitat fragmentation. Monocots, graminoids, clonal, abiotically pollinated and self compatible species were underrepresented among the studied species, and most study species were from a few habitat types, in particular grasslands. We conclude that our current knowledge of the effects of habitat fragmentation on plant populations is not sufficient to provide widely applicable guidelines for species management. The selection of species studied so far has been biased toward species from certain habitats and species exhibiting traits that probably make them vulnerable to habitat fragmentation. Future studies should include community-wide approaches in different habitats, e.g. re-visitation studies in which the species pool is assessed at different time intervals, and population-biological studies of species from a wide range of habitats, and of different life forms and growth strategies. A more representative picture of the effects of habitat fragmentation would allow a better assessment of threats and more specific recommendations for optimally managing populations of endangered plants.
Significant effects of temperature on the reproductive output of the forest herb Anemone nemorosa L.
(2010)
Climate warming is already influencing plant migration in different parts of the world. Numerous models have been developed to forecast future plant distributions. Few studies, however, have investigated the potential effect of warming on the reproductive output of plants. Understorey forest herbs in particular, have received little attention in the debate on climate change impacts. This study focuses on the effect of temperature on sexual reproductive output (number of seeds, seed mass, germination percentage and seedling mass) of Anemone nemorosa L., a model species for slow colonizing herbaceous forest plants. We sampled seeds of A. nemorosa in populations along a 2400 km latitudinal gradient from northern France to northern Sweden during three growing seasons (2005,2006 and 2008). This study design allowed us to isolate the effects of accumulated temperature (Growing Degree Hours; GDH) from latitude and the local abiotic and biotic environment. Germination and seed sowing trials were performed in incubators, a greenhouse and under field conditions in a forest. Finally, we disentangled correlations between the different reproductive traits of A. nemorosa along the latitudinal gradient. We found a clear positive relationship between accumulated temperature and seed and seedling traits: reproductive output of A. nemorosa improved with increasing GDH along the latitudinal gradient. Seed mass and seedling mass, for instance, increased by 9.7% and 10.4%, respectively, for every 1000 degrees C h increase in GDH. We also derived strong correlations between several seed and seedling traits both under field conditions and in incubators. Our results indicate that seed mass, incubator-based germination percentage (Germ%(Inc)) and the output of germinable seeds (product of number of seeds and Germ%(Inc) divided by 100) from plants grown along a latitudinal gradient (i.e. at different temperature regimes) provide valuable proxies to parameterize key population processes in models. We conclude that (1) climate warming may have a pronounced positive impact on sexual reproduction of A. nemorosa and (2) climate models forecasting plant distributions would benefit from including the temperature sensitivity of key seed traits and population processes.