TY - JOUR A1 - Wieczorek, Mareike A1 - Kolmogorov, Alexei A1 - Kruse, Stefan A1 - Jacobsen, Inga A1 - Nitze, Ingmar A1 - Nikolaev, Anatoly N. A1 - Heinrich, Ingo A1 - Pestryakova, Luidmila Agafyevna A1 - Herzschuh, Ulrike T1 - Disturbance-effects on treeline larch-stands in the lower Kolyma River area (NE Siberia) JF - Silva Fennica : a quarterly journal for forest science N2 - Tree stands in the boreal treeline ecotone are, in addition to climate change, impacted by disturbances such as fire, water-related disturbances and logging. We aim to understand how these disturbances affect growth, age structure, and spatial patterns of larch stands in the north-eastern Siberian treeline ecotone (lower Kolyma River region), an insufficiently researched region. Stand structure of Larix cajanderi Mayr was studied at seven sites impacted by disturbances. Maximum tree age ranged from 44 to 300 years. Young to medium-aged stands had, independent of disturbance type, the highest stand densities with over 4000 larch trees per ha. These sites also had the highest growth rates for tree height and stem diameter. Overall lowest stand densities were found in a polygonal field at the northern end of the study area, with larches growing in distinct " tree islands". At all sites, saplings are significantly clustered. Differences in fire severity led to contrasting stand structures with respect to tree, recruit, and overall stand densities. While a low severity fire resulted in low-density stands with high proportions of small and young larches, high severity fires resulted in high-density stands with high proportions of big trees. At waterdisturbed sites, stand structure varied between waterlogged and drained sites and latitude. These mixed effects of climate and disturbance make it difficult to predict future stand characteristics and the treeline position. KW - treeline KW - Larix cajanderi KW - Siberia KW - fire KW - stand structure Y1 - 2017 U6 - https://doi.org/10.14214/sf.1666 SN - 0037-5330 SN - 2242-4075 VL - 51 IS - 3 PB - The Finnish Society of Forest Science CY - Helsinki ER - TY - JOUR A1 - Glückler, Ramesh A1 - Geng, Rongwei A1 - Grimm, Lennart A1 - Baisheva, Izabella A1 - Herzschuh, Ulrike A1 - Stoof-Leichsenring, Kathleen R. A1 - Kruse, Stefan A1 - Andreev, Andrej Aleksandrovic A1 - Pestryakova, Luidmila A1 - Dietze, Elisabeth T1 - Holocene wildfire and vegetation dynamics in Central Yakutia, Siberia, reconstructed from lake-sediment proxies JF - Frontiers in Ecology and Evolution N2 - Wildfires play an essential role in the ecology of boreal forests. In eastern Siberia, fire activity has been increasing in recent years, challenging the livelihoods of local communities. Intensifying fire regimes also increase disturbance pressure on the boreal forests, which currently protect the permafrost beneath from accelerated degradation. However, long-term relationships between changes in fire regime and forest structure remain largely unknown. We assess past fire-vegetation feedbacks using sedimentary proxy records from Lake Satagay, Central Yakutia, Siberia, covering the past c. 10,800 years. Results from macroscopic and microscopic charcoal analyses indicate high amounts of burnt biomass during the Early Holocene, and that the present-day, low-severity surface fire regime has been in place since c. 4,500 years before present. A pollen-based quantitative reconstruction of vegetation cover and a terrestrial plant record based on sedimentary ancient DNA metabarcoding suggest a pronounced shift in forest structure toward the Late Holocene. Whereas the Early Holocene was characterized by postglacial open larch-birch woodlands, forest structure changed toward the modern, mixed larch-dominated closed-canopy forest during the Mid-Holocene. We propose a potential relationship between open woodlands and high amounts of burnt biomass, as well as a mediating effect of dense larch forest on the climate-driven intensification of fire regimes. Considering the anticipated increase in forest disturbances (droughts, insect invasions, and wildfires), higher tree mortality may force the modern state of the forest to shift toward an open woodland state comparable to the Early Holocene. Such a shift in forest structure may result in a positive feedback on currently intensifying wildfires. These new long-term data improve our understanding of millennial-scale fire regime changes and their relationships to changes of vegetation in Central Yakutia, where the local population is already being confronted with intensifying wildfire seasons. KW - fire KW - larch KW - boreal KW - forest KW - Russia KW - charcoal KW - pollen KW - ancient DNA Y1 - 2022 U6 - https://doi.org/10.3389/fevo.2022.962906 SN - 2296-701X VL - 10 PB - Frontiers Media CY - Lausanne ER - TY - JOUR A1 - Frommhold, Martin A1 - Heim, Arend A1 - Barabanov, Mikhail A1 - Maier, Franziska A1 - Mühle, Ralf-Udo A1 - Smirenski, Sergei M. A1 - Heim, Wieland T1 - Breeding habitat and nest-site selection by an obligatory "nest-cleptoparasite", the Amur Falcon Falco amurensis JF - Ecology and evolution N2 - The selection of a nest site is crucial for successful reproduction of birds. Animals which re-use or occupy nest sites constructed by other species often have limited choice. Little is known about the criteria of nest-stealing species to choose suitable nesting sites and habitats. Here, we analyze breeding-site selection of an obligatory "nest-cleptoparasite", the Amur Falcon Falco amurensis. We collected data on nest sites at Muraviovka Park in the Russian Far East, where the species breeds exclusively in nests of the Eurasian Magpie Pica pica. We sampled 117 Eurasian Magpie nests, 38 of which were occupied by Amur Falcons. Nest-specific variables were assessed, and a recently developed habitat classification map was used to derive landscape metrics. We found that Amur Falcons chose a wide range of nesting sites, but significantly preferred nests with a domed roof. Breeding pairs of Eurasian Hobby Falco subbuteo and Eurasian Magpie were often found to breed near the nest in about the same distance as neighboring Amur Falcon pairs. Additionally, the occurrence of the species was positively associated with bare soil cover, forest cover, and shrub patches within their home range and negatively with the distance to wetlands. Areas of wetlands and fallow land might be used for foraging since Amur Falcons mostly depend on an insect diet. Additionally, we found that rarely burned habitats were preferred. Overall, the effect of landscape variables on the choice of actual nest sites appeared to be rather small. We used different classification methods to predict the probability of occurrence, of which the Random forest method showed the highest accuracy. The areas determined as suitable habitat showed a high concordance with the actual nest locations. We conclude that Amur Falcons prefer to occupy newly built (domed) nests to ensure high nest quality, as well as nests surrounded by available feeding habitats. KW - cleptoparasitism KW - fire KW - habitat use KW - machine learning KW - magpie KW - nest-site selection KW - random forest Y1 - 2019 U6 - https://doi.org/10.1002/ece3.5878 SN - 2045-7758 VL - 9 IS - 24 SP - 14430 EP - 14441 PB - Wiley CY - Hoboken ER - TY - THES A1 - Esther, Alexandra T1 - Investigating mechanisms maintaining plant species diversity in fire prone Mediterranean-type vegetation using spatially-explicit simulation models T1 - Untersuchung von Mechanismen zum Erhalt von Pflanzenartendiversität in feuergeprägter mediterraner Vegetation durch räumlich explizite Simulationsmodelle N2 - Fire prone Mediterranean-type vegetation systems like those in the Mediterranean Basin and South-Western Australia are global hot spots for plant species diversity. To ensure management programs act to maintain these highly diverse plant communities, it is necessary to get a profound understanding of the crucial mechanisms of coexistence. In the current literature several mechanisms are discussed. The objective of my thesis is to systematically explore the importance of potential mechanisms for maintaining multi-species, fire prone vegetation by modelling. The model I developed is spatially-explicit, stochastic, rule- and individual-based. It is parameterised on data of population dynamics collected over 18 years in the Mediterranean-type shrublands of Eneabba, Western Australia. From 156 woody species of the area seven plant traits have been identified to be relevant for this study: regeneration mode, annual maximum seed production, seed size, maximum crown diameter, drought tolerance, dispersal mode and seed bank type. Trait sets are used for the definition of plant functional types (PFTs). The PFT dynamics are simulated annual by iterating life history processes. In the first part of my thesis I investigate the importance of trade-offs for the maintenance of high diversity in multi-species systems with 288 virtual PFTs. Simulation results show that the trade-off concept can be helpful to identify non-viable combinations of plant traits. However, the Shannon Diversity Index of modelled communities can be high despite of the presence of ‘supertypes’. I conclude, that trade-offs between two traits are less important to explain multi-species coexistence and high diversity than it is predicted by more conceptual models. Several studies show, that seed immigration from the regional seed pool is essential for maintaining local species diversity. However, systematical studies on the seed rain composition to multi-species communities are missing. The results of the simulation experiments, as presented in part two of this thesis, show clearly, that without seed immigration the local species community found in Eneabba drifts towards a state with few coexisting PFTs. With increasing immigration rates the number of simulated coexisting PFTs and Shannon diversity quickly approaches values as also observed in the field. Including the regional seed input in the model is suited to explain more aggregated measures of the local plant community structure such as species richness and diversity. Hence, the seed rain composition should be implemented in future studies. In the third part of my thesis I test the sensitivity of Eneabba PFTs to four different climate change scenarios, considering their impact on both local and regional processes. The results show that climate change clearly has the potential to alter the number of dispersed seeds for most of the Eneabba PFTs and therefore the source of the ‘immigrants’ at the community level. A classification tree analysis shows that, in general, the response to climate change was PFT-specific. In the Eneabba sand plains sensitivity of a PFT to climate change depends on its specific trait combination and on the scenario of environmental change i.e. development of the amount of rainfall and the fire frequency. This result emphasizes that PFT-specific responses and regional process seed immigration should not be ignored in studies dealing with the impact of climate change on future species distribution. The results of the three chapters are finally analysed in a general discussion. The model is discussed and improvements and suggestions are made for future research. My work leads to the following conclusions: i) It is necessary to support modelling with empirical work to explain coexistence in species-rich plant communities. ii) The chosen modelling approach allows considering the complexity of coexistence and improves the understanding of coexistence mechanisms. iii) Field research based assumptions in terms of environmental conditions and plant life histories can relativise the importance of more hypothetic coexistence theories in species-rich systems. In consequence, trade-offs can play a lower role than predicted by conceptual models. iv) Seed immigration is a key process for local coexistence. Its alteration because of climate change should be considered for prognosis of coexistence. Field studies should be carried out to get data on seed rain composition. N2 - Feuer geprägte, mediterrane Vegetationstypen, wie sie im Mittelmeerraum und Süd-West Australien zu finden sind, gelten als globale „hotspots“ für Pflanzendiversität. Um sicher zu stellen, dass Managementprogramme zum Erhalt dieser hoch diversen Pflanzengesellschaften zielgerichtet beitragen, ist ein profundes Verständnis der wesentlichen Koexistenzmechanismen notwendig. In der aktuellen Literatur werden verschiedene Mechanismen diskutiert. Das Ziel meiner Doktorarbeit ist es, die Bedeutung der Mechanismen für den Erhalt der artenreichen, feuergeprägten Vegetation anhand eines Modells systematisch zu untersuchen. Das von mir dafür entwickelte Modell ist räumlich-explizit, stochastisch und regel- und individuenbasiert. Es ist unter Zuhilfenahme von Daten zu Populationsdynamiken parametrisiert, die über 18 Jahre im Mediterranen Buschland von Eneabba Westaustraliens gesammelt wurden. Anhand von 156 Arten sind sieben für meine Studie relevante Pflanzeneigenschaften identifiziert wurden: Regenerationsart, jährlich maximale Samenproduktion, Samengröße, maximaler Durchmesser, Trockentoleranz, Ausbreitungsart und Samenbanktyp. Kombinationen der Eigenschaften bilden funktionelle Pflanzentypen (PFTs), deren jährliche Dynamik über Lebenszyklusprozesse im Modell simuliert wird. Der erste Teil meiner Arbeit präsentiert die Studie zur Bedeutung von „trade-offs“ für den Erhalt der hohen Diversität in artenreichen Systemen. Die Simulationsergebnisse mit 288 virtuellen PFTs zeigen, dass das „trade-offs“-Konzept für die Identifizierung nicht-lebensfähiger Kombinationen von Pflanzeneigenschaften hilfreich sein kann. Allerdings kann der Shannon-Diversitäts-Index der modellierten Pflanzengesellschaft trotz der Anwesenheit von „Supertypen“ hoch sein. Ich schlussfolgere, dass „trade-off“ zwischen zwei Eigenschaften weniger wichtig für die Erklärung der Koexistenz von vielen Arten und hoher Diversität sind, als es durch konzeptionelle Modelle vorhergesagt wird. Viele Studien zeigen, dass Sameneintrag aus dem regionalen Samenpool essenziell für den Erhalt lokaler Artendiversität ist. Es gibt allerdings noch keine systematischen Studien zur Zusammensetzung des Samenregens artenreichen Systemen. Die Ergebnisse der Simulationsexperimente im zweiten Teil meiner Arbeit machen deutlich, dass ohne Sameneintrag die lokale Pflanzengesellschaft Eneabbas sich in eine Richtung entwickelt, in der nur wenige PFTs koexistieren. Mit steigender Samenimmigrationsrate erreicht die Anzahl an koexistierenden PFTs und die Shannon-Diversität schnell die Werte, die auch im Feld gefunden werden. Der regionale Sameneintrag kann also als Erklärung zur Struktur lokaler Pflanzengesellschaften dienen. Seine Zusammensetzung sollte jedoch in zukünftigen Studien berücksichtigt werden. Im dritten Teil meiner Doktorarbeit präsentiere ich Analysen zur Sensibilität der PFTs von Eneabba vorhergesagte Klimaszenarien und der Auswirkungen auf die Samenimmigration. Die Ergebnisse zeigen deutlich, dass Klimaänderungen das Potential haben, die Anzahl an ausgebreiteten Samen der meisten Eneabba PFTs zu verändern. Die Entscheidungsbaum-Analyse veranschaulicht, dass die Reaktion auf Klimaänderung PFT-spezifisch ist. In den Eneabba hängt die Sensitivität der PFTs gegenüber klimatischen Veränderungen von den PFT-spezifischen Eigenschaftskombinationen und vom Klimaszenarium ab, d.h. von der Entwicklung der Regenfallmenge und der Feuerfrequenz. Dieses Ergebnis betont, dass PFT-spezifische Reaktionen und die klimabedingten Änderungen in der Samenimmigration in Studien zum Einfluss von Klimaänderungen auf die zukünftige Artenverteilung berücksichtigt werden sollten. Die Ergebnisse aus den drei Kapiteln werden in der allgemeinen Diskussion zusammengeführt und analysiert. Das Modell wird diskutiert und Verbesserungen und Vorschläge für weitere Forschung aufgezeigt. Meine Arbeit führt zu folgenden Schlussfolgerungen: i) Es ist notwendig, empirische Arbeit und Modellierung zu kombinieren, um Koexistenz in artenreichen Systemen zu erklären. ii) Durch den gewählten Modellansatz kann die Komplexität von Koexistenz erfasst und das Verständnis vertieft werden. iii) Auf Felddaten basierende Annahmen bezüglich Umweltbedingungen und Lebenzyklus können zur Relativierung der Bedeutsamkeit von Mechanismen führen. So können Trade-offs eine geringere Rolle spielen, als konzeptionelle Modelle nahe legen. iv) Samenimmigration ist ein Schlüsselprozess für lokale Koexistenz. Deren Änderung aufgrund von Klimawandel sollte für Prognosen zu Artenvorkommen berücksichtigt werden. Feldstudien sollten durchgeführt werden, um die Datenlücken zur Samenregenzusammensetzung zu füllen. KW - Feuer KW - Artenreichtum KW - individuelle Modellierung KW - fire KW - plant functional types KW - species richness KW - individual based modeling Y1 - 2010 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-44632 ER -