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Ecological niches of organisms vary across geographical space, but niche shift patterns between regions and the underlying mechanisms remain largely unexplored. We studied shifts in the pH niche of 42 temperate forest plant species across a latitudinal gradient from northern France to boreo-nemoral Sweden. We asked 1) whether species restrict their niches with increasing latitude as they reach their northern range margin (environmental constraints); 2) whether species expand their niches with increasing latitude as regional plant species richness decreases (competitive release); and 3) whether species shift their niche position toward more acidic sites with increasing latitude as the relative proportion of acidic soils increases (local adaptation). Based on 1458 vegetation plots and corresponding soil pH values, we modelled species response curves using Huisman-Olff-Fresco models. Four niche measures (width, position, left and right border) were compared among regions by randomization tests. We found that with increasing latitude, neutrophilic species tended to retreat from acidic sites, indicating that these species retreat to more favorable sites when approaching their range margin. Alternatively, these species might benefit from enhanced nitrogen deposition on formerly nutrient-poor, acidic sites in southern regions or lag behind in post-glacial recolonization of potential habitats in northern regions. Most acidophilic species extended their niche toward more base-rich sites with increasing latitude, indicating competitive release from neutrophilic species. Alternatively, acidophilic species might benefit from optimal climatic conditions in the north where some have their core distribution area. Shifts in the niche position suggested that local adaptation is of minor importance. We conclude that shifts in the pH niche of temperate forest plants are the rule, but the directions of the niche shifts and possible explanations vary. Our study demonstrates that differentiating between acidophilic and neutrophilic species is crucial to identify general patterns and underlying mechanisms.
Aim - Plant reintroductions and other forms of targeted species translocations will in the future gain growing importance for nature conservation. In fragmented habitats, species reintroductions offer one of the most efficient tools for preserving or restoring plant diversity. In our study, we have compiled available data about plant reintroduction projects in Germany to answer the following questions: (1) What are the characteristics, habitat preferences and ecological strategies of species considered in plant reintroduction trials, and are these representative of the entire class of threatened species in Germany? (2) Is the judgment of the success or failure of plant reintroductions biased by the choice of species used in the experiments? (3) Do reintroduction efforts focus on those species for which Germany has a particularly high responsibility for conservation?
Methods - Information about reintroduction projects in Germany were obtained from published and internet sources as well as unpublished reports. In our search we focused on single-species trials in the framework of scientific or conservation projects. For all threatened species included in our database, we compiled information on their systematics, life form, ecological strategies and habitat preferences. A list of all species being threatened nationally or regionally, comprising both reintroduced and not reintroduced species, served as a reference for statistical analysis.
Results - The list of vascular plants used in conservation-oriented reintroductions consisted of 196 taxa. Species of families with large and conspicuous, mostly insect-pollinated flowers (for example, Orchidaceae) were over-represented among the reintroduced species compared to those threatened species not included in reintroduction trials. Species considered were also more often than expected found in semi-natural open habitats such as heathlands and grasslands. Notably, many projects focused on calcareous grasslands, characterized by dry, high-pH and infertile soils. In contrast, species of more near-natural vegetation (alpine and rocky formations, forests) were under-represented. About 25% of the species that were reintroduced are not threatened on the national scale. Out of 150 species for which Germany has a particularly high responsibility for conservation, only 14 (9.3%) were reintroduced. For only about 1/3 of all reintroduction attempts, success or failure were documented; whereas the success rate appears to be relatively low in nutrient-poor environments, trials with nutrient-demanding and competitive species were more successful.
Conclusions - We conclude that conservation-oriented reintroduction attempts should focus more on species for which the country or a region has a particular high responsibility. Reintroductions, to a larger extent than at present, also need to consider the different chances of success in different habitat types and environments.
Climate change is acting on several aspects of plant life cycles, including the sexual reproductive stage, which is considered amongst the most sensitive life-cycle phases. In temperate forests, it is expected that climate change will lead to a compositional change in community structure due to changes in the dominance of currently more abundant forest tree species. Increasing our understanding of the effects of climate change on currently secondary tree species recruitment is therefore important to better understand and forecast population and community dynamics in forests. Here, we analyse the interactive effects of rising temperatures and soil moisture reduction on germination, seedling survival and early growth of two important secondary European tree species, Acer pseudoplatanus and A.platanoides. Additionally, we analyse the effect of the temperature experienced by the mother tree during seed production by collecting seeds of both species along a 2200-km long latitudinal gradient. For most of the responses, A.platanoides showed higher sensitivity to the treatments applied, and especially to its joint manipulation, which for some variables resulted in additive effects while for others only partial compensation. In both species, germination and survival decreased with rising temperatures and/or soil moisture reduction while early growth decreased with declining soil moisture content. We conclude that although A.platanoides germination and survival were more affected after the applied treatments, its initial higher germination and larger seedlings might allow this species to be relatively more successful than A.pseudoplatanus in the face of climate change.
Impacts of warming and changes in precipitation frequency on the regeneration of two Acer species
(2015)
Meta‐communities of habitat islands may be essential to maintain biodiversity in anthropogenic landscapes allowing rescue effects in local habitat patches. To understand the species‐assembly mechanisms and dynamics of such ecosystems, it is important to test how local plant‐community diversity and composition is affected by spatial isolation and hence by dispersal limitation and local environmental conditions acting as filters for local species sorting. We used a system of 46 small wetlands (kettle holes)—natural small‐scale freshwater habitats rarely considered in nature conservation policies—embedded in an intensively managed agricultural matrix in northern Germany. We compared two types of kettle holes with distinct topographies (flatsloped, ephemeral, frequently plowed kettle holes vs. steep‐sloped, more permanent ones) and determined 254 vascular plant species within these ecosystems, as well as plant functional traits and nearest neighbor distances to other kettle holes. Differences in alpha and beta diversity between steep permanent compared with ephemeral flat kettle holes were mainly explained by species sorting and niche processes and mass effect processes in ephemeral flat kettle holes. The plant‐community composition as well as the community trait distribution in terms of life span, breeding system, dispersal ability, and longevity of seed banks significantly differed between the two habitat types. Flat ephemeral kettle holes held a higher percentage of non‐perennial plants with a more persistent seed bank, less obligate outbreeders and more species with seed dispersal abilities via animal vectors compared with steep‐sloped, more permanent kettle holes that had a higher percentage of wind‐dispersed species. In the flat kettle holes, plant‐species richness was negatively correlated with the degree of isolation, whereas no such pattern was found for the permanent kettle holes. Synthesis: Environment acts as filter shaping plant diversity (alpha and beta) and plant‐community trait distribution between steep permanent compared with ephemeral flat kettle holes supporting species sorting and niche mechanisms as expected, but we identified a mass effect in ephemeral kettle holes only. Flat ephemeral kettle holes can be regarded as meta‐ecosystems that strongly depend on seed dispersal and recruitment from a seed bank, whereas neighboring permanent kettle holes have a more stable local species diversity.
Meta‐communities of habitat islands may be essential to maintain biodiversity in anthropogenic landscapes allowing rescue effects in local habitat patches. To understand the species‐assembly mechanisms and dynamics of such ecosystems, it is important to test how local plant‐community diversity and composition is affected by spatial isolation and hence by dispersal limitation and local environmental conditions acting as filters for local species sorting. We used a system of 46 small wetlands (kettle holes)—natural small‐scale freshwater habitats rarely considered in nature conservation policies—embedded in an intensively managed agricultural matrix in northern Germany. We compared two types of kettle holes with distinct topographies (flatsloped, ephemeral, frequently plowed kettle holes vs. steep‐sloped, more permanent ones) and determined 254 vascular plant species within these ecosystems, as well as plant functional traits and nearest neighbor distances to other kettle holes. Differences in alpha and beta diversity between steep permanent compared with ephemeral flat kettle holes were mainly explained by species sorting and niche processes and mass effect processes in ephemeral flat kettle holes. The plant‐community composition as well as the community trait distribution in terms of life span, breeding system, dispersal ability, and longevity of seed banks significantly differed between the two habitat types. Flat ephemeral kettle holes held a higher percentage of non‐perennial plants with a more persistent seed bank, less obligate outbreeders and more species with seed dispersal abilities via animal vectors compared with steep‐sloped, more permanent kettle holes that had a higher percentage of wind‐dispersed species. In the flat kettle holes, plant‐species richness was negatively correlated with the degree of isolation, whereas no such pattern was found for the permanent kettle holes. Synthesis: Environment acts as filter shaping plant diversity (alpha and beta) and plant‐community trait distribution between steep permanent compared with ephemeral flat kettle holes supporting species sorting and niche mechanisms as expected, but we identified a mass effect in ephemeral kettle holes only. Flat ephemeral kettle holes can be regarded as meta‐ecosystems that strongly depend on seed dispersal and recruitment from a seed bank, whereas neighboring permanent kettle holes have a more stable local species diversity.
Meta-communities of habitat islands may be essential to maintain biodiversity in anthropogenic landscapes allowing rescue effects in local habitat patches. To understand the species-assembly mechanisms and dynamics of such ecosystems, it is important to test how local plant-community diversity and composition is affected by spatial isolation and hence by dispersal limitation and local environmental conditions acting as filters for local species sorting.We used a system of 46 small wetlands (kettle holes)natural small-scale freshwater habitats rarely considered in nature conservation policiesembedded in an intensively managed agricultural matrix in northern Germany. We compared two types of kettle holes with distinct topographies (flat-sloped, ephemeral, frequently plowed kettle holes vs. steep-sloped, more permanent ones) and determined 254 vascular plant species within these ecosystems, as well as plant functional traits and nearest neighbor distances to other kettle holes.Differences in alpha and beta diversity between steep permanent compared with ephemeral flat kettle holes were mainly explained by species sorting and niche processes and mass effect processes in ephemeral flat kettle holes. The plant-community composition as well as the community trait distribution in terms of life span, breeding system, dispersal ability, and longevity of seed banks significantly differed between the two habitat types. Flat ephemeral kettle holes held a higher percentage of non-perennial plants with a more persistent seed bank, less obligate outbreeders and more species with seed dispersal abilities via animal vectors compared with steep-sloped, more permanent kettle holes that had a higher percentage of wind-dispersed species. In the flat kettle holes, plant-species richness was negatively correlated with the degree of isolation, whereas no such pattern was found for the permanent kettle holes.Synthesis: Environment acts as filter shaping plant diversity (alpha and beta) and plant-community trait distribution between steep permanent compared with ephemeral flat kettle holes supporting species sorting and niche mechanisms as expected, but we identified a mass effect in ephemeral kettle holes only. Flat ephemeral kettle holes can be regarded as meta-ecosystems that strongly depend on seed dispersal and recruitment from a seed bank, whereas neighboring permanent kettle holes have a more stable local species diversity.
In einem rund 2.200 ha großen Waldgebiet bei Magdeburgerforth (Fläming, Sachsen-Anhalt) wur-den 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 Wiederholungs-untersuchung besonders an. Da die Aufnahmeflächen von Passarge nicht punktgenau verortet waren, wurden im Jahr 2014 in einem über die Forstabteilungen und die Vegetationskarte definierten Such-raum 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 stick-stoffliebenden Arten und mesophilen Waldarten, Einwanderung von Neophyten, keine generelle Ab-nahme 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 Arten-wechsels 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 abhängi-gen thermophilen Wälder und die Flechten-Kiefernwälder gingen weitgehend verloren.
Waldökosysteme unterliegen vielfältigen Einflüssen wie forstlicher Bewirtschaftung, Stickstoffdeposition, Veränderung des Grundwasserspiegels oder der Einwanderung invasiver Arten. Die Wiederholung historischer Vegetationsaufnahmen ist ein wichtiges Mittel, um Veränderungen der Pflanzengesellschaften zu dokumentieren und mögliche Hauptursachen (Treiber) zu bestimmen. Wir haben 2015 den Vegetationswandel auf 140 semi-permanenten Plots in Wirtschaftswäldern der Elbtalniederung im Nordostdeutschen Tiefland (Sachsen-Anhalt, Brandenburg) untersucht. Die Erstaufnahme erfolgte von 1956 bis 1963. Die Vegetationsaufnahmen decken ein fast einzigartig breites Spektrum unterschiedlicher Waldstandorte ab, das von Feuchtwäldern (Au-, Bruch- und Moorwäldern des Alnion incanae, Alnion glutinosae und Betulion pubescentis) über bodensaure Eichen-Mischwälder (Quercion roboris) bis hin zu bodensauren, meist trockenen Kiefernwäldern mit unterschiedlicher Nährstoffausstattung (Dicrano-Pinion) reicht.
Die Veränderungen der Vegetation haben wir mit Hilfe von Bestandesdaten, Gewinner- und Verliererarten, der α- und β -Diversität sowie der Ellenberg-Zeigerwerte für Stickstoff, Reaktion, Feuchte und Licht analysiert. Dabei wurden, anders als in den meisten bisherigen Wiederholungsuntersuchungen, auch Flächen berücksichtigt, auf denen bis zur Zweitaufnahme ein vollständiger Bestandeswechsel stattgefunden hatte.
Insbesondere in den Feuchtwäldern und den bodensauren Wäldern mit mäßig guter Nährstoffversorgung sind Wechsel der Hauptbaumarten zu verzeichnen; außerdem wurden viele Kiefernbestände zwischenzeitlich neu begründet. Die Artenzahl hat insgesamt und in fast allen Waldtypen abgenommen, die β-Diversität ist jedoch unverändert geblieben bzw. hat sich erhöht. Die Zeigerwerte deuten auf eine Abnahme der Bodenfeuchte in den Au-, Bruch-, und Moorwäldern hin, während insbesondere die bodensauren Kiefernwälder dunkler, nährstoffreicher und feuchter geworden sind. Die Anzahl der Verlierer-Arten ist mehr als doppelt so hoch wie die der Gewinner-Arten, jedoch mit unterschiedlicher Entwicklung in den einzelnen Waldtypen. Insbesondere die nassen und feuchten Wälder, die bodensauren Eichen-Mischwälder und die Flechten-Kiefernwälder haben die meisten ihrer charakteristischen Arten verloren.
Veränderungen der Vegetation in den Feuchtwäldern gehen v. a. auf lokal gesunkene Grundwasserspiegel und eine dadurch gestiegene Nährstoffverfügbarkeit zurück; die Artenzusammensetzung der Auwälder wurde zudem sehr stark durch forstliche Eingriffe beeinflusst. Ursachen für den Trend zu feuchteren und nährstoffreicheren Bedingungen in ehemals trockenen bodensauren Kiefern- und Eichenwäldern sind Stickstoffeinträge sowie eine Sukzession nach Aufgabe historischer Waldnutzungs-formen (Streunutzung, Waldweide). Obwohl sich die einzelnen Waldtypen unterschiedlich entwickelt haben, sind Eutrophierung, sinkende Grundwasserspiegel und Waldbaumaßnahmen insgesamt die wichtigsten Ursachen für die beobachteten Vegetationsveränderungen. Forstliche Eingriffe wie Kahlschlag und Bestandesumbau mit Baumartenwechsel sind zugleich die Hauptursache dafür, dass es trotz Nivellierung des Standortsgradienten, gemessen an der β-Diversität, nicht zu einer Homogenisierung der Vegetation gekommen ist.