TY  - JOUR
A1  - Schwarzer, Christian
A1  - Joshi, Jasmin Radha
T1  - Ecotypic differentiation, hybridization and clonality facilitate the persistence of a cold-adapted sedge in European bogs
JF  - Biological journal of the Linnean Society : a journal of evolution
N2  - Recent research has shown that many cold-adapted species survived the last glacial maximum (LGM) in northern refugia. Whether this evolutionary history has had consequences for their genetic diversity and adaptive potential remains unknown. We sampled 14 populations of Carex limosa, a sedge specialized to bog ecosystems, along a latitudinal gradient from its Scandinavian core to the southern lowland range-margin in Germany. Using microsatellite and experimental common-garden data, we evaluated the impacts of global climate change along this gradient and assessed the conservation status of the southern marginal populations. Microsatellite data revealed two highly distinct genetic groups and hybrid individuals. In our common-garden experiment, the two groups showed divergent responses to increased nitrogen/phosphorus (N/P) availability, suggesting ecotypic differentiation. Each group formed genetically uniform populations at both northern and southern sampling areas. Mixed populations occurred throughout our sampling area, an area that was entirely glaciated during the LGM. The fragmented distribution implies allopatric divergence at geographically separated refugia that putatively differed in N/P availability. Molecular data and an observed low hybrid fecundity indicate the importance of clonal reproduction for hybrid populations. At the southern range-margin, however, all populations showed effects of clonality, lowered fecundity and low competitiveness, suggesting abiotic and biotic constraints to population persistence.
KW  - biogeography
KW  - bog/mire plants
KW  - Carex limosa
KW  - climate change
KW  - glacial divergence
KW  - global change
KW  - leading/trailing edge
KW  - population differentiation
KW  - sexual/asexual reproduction
Y1  - 2019
U6  - https://doi.org/10.1093/biolinnean/blz141
SN  - 0024-4066
SN  - 1095-8312
VL  - 128
IS  - 4
SP  - 909
EP  - 925
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - THES
A1  - Schwager, Monika
T1  - Climate change, variable colony sizes and temporal autocorrelation : consequences of living in changing environments
T1  - Klimawandel, variable Koloniegrößen und zeitliche Autokorrelation : Leben in einer variablen Umwelt
N2  - Natural and human induced environmental changes affect populations at different time scales. If they occur in a spatial heterogeneous way, they cause spatial variation in abundance. In this thesis I addressed three topics, all related to the question, how environmental changes influence population dynamics. In the first part, I analysed the effect of positive temporal autocorrelation in environmental noise on the extinction risk of a population, using a simple population model. The effect of autocorrelation depended on the magnitude of the effect of single catastrophic events of bad environmental conditions on a population. If a population was threatened by extinction only, when bad conditions occurred repeatedly, positive autocorrelation increased extinction risk. If a population could become extinct, even if bad conditions occurred only once, positive autocorrelation decreased extinction risk. These opposing effects could be explained by two features of an autocorrelated time series. On the one hand, positive autocorrelation increased the probability of series of bad environmental conditions, implying a negative effect on populations. On the other hand, aggregation of bad years also implied longer periods with relatively good conditions. Therefore, for a given time period, the overall probability of occurrence of at least one extremely bad year was reduced in autocorrelated noise. This can imply a positive effect on populations. The results could solve a contradiction in the literature, where opposing effects of autocorrelated noise were found in very similar population models. In the second part, I compared two approaches, which are commonly used for predicting effects of climate change on future abundance and distribution of species: a "space for time approach", where predictions are based on the geographic pattern of current abundance in relation to climate, and a "population modelling approach" which is based on correlations between demographic parameters and the inter-annual variation of climate. In this case study, I compared the two approaches for predicting the effect of a shift in mean precipitation on a population of the sociable weaver Philetairus socius, a common colonially living passerine bird of semiarid savannahs of southern Africa. In the space for time approach, I compared abundance and population structure of the sociable weaver in two areas with highly different mean annual precipitation. The analysis showed no difference between the two populations. This result, as well as the wide distribution range of the species, would lead to the prediction of no sensitive response of the species to a slight shift in mean precipitation. In contrast, the population modelling approach, based on a correlation between reproductive success and rainfall, predicted a sensitive response in most model types. The inconsistency of predictions was confirmed in a cross-validation between the two approaches. I concluded that the inconsistency was caused, because the two approaches reflect different time scales. On a short time scale, the population may respond sensitively to rainfall. However, on a long time scale, or in a regional comparison, the response may be compensated or buffered by a variety of mechanisms. These may include behavioural or life history adaptations, shifts in the interactions with other species, or differences in the physical environment. The study implies that understanding, how such mechanisms work, and at what time scale they would follow climate change, is a crucial precondition for predicting ecological consequences of climate change. In the third part of the thesis, I tested why colony sizes of the sociable weaver are highly variable. The high variation of colony sizes is surprising, as in studies on coloniality it is often assumed that an optimal colony size exists, in which individual bird fitness is maximized. Following this assumption, the pattern of bird dispersal should keep colony sizes near an optimum. However, I showed by analysing data on reproductive success and survival that for the sociable weaver fitness in relation to colony size did not follow an optimum curve. Instead, positive and negative effects of living in large colonies overlaid each other in a way that fitness was generally close to one, and density dependence was low. I showed in a population model, which included an evolutionary optimisation process of dispersal that this specific shape of the fitness function could lead to a dispersal strategy, where the variation of colony sizes was maintained.
N2  - Änderungen in der Umwelt - sowohl natürliche Variabilität als auch anthropogene Änderungen - beeinflussen Populationen auf verschiedenen Zeitskalen. Wenn sie räumlich heterogen wirken, verursachen sie räumliche Variabilität in der Abundanz. In dieser Dissertation habe ich drei Themen bearbeitet, die sich auf den Effekt von Änderungen in der Umwelt auf Populationsdynamiken beziehen. Im ersten Teil untersuchte ich an einem einfachen Populationsmodell den Effekt von positiver zeitlicher Autokorrelation im Umweltrauschen auf das Extinktionsrisiko einer Population. Der Effekt der Autokorrelation hing davon ab, wie empfindlich eine Population gegenüber singulären, katastrophenähnlichen Ereignissen schlechter Umweltbedingungen war. War die Population nur dann direkt bedroht, wenn eine Serie von schlechten Umweltbedingungen auftrat, erhöhte positive Autokorrelation das Extinktionsrisiko. Konnte eine Population auch dann aussterben, wenn schlechte Umweltbedingungen einzeln auftraten, verringerte positive Autokorrelation das Extinktionsrisiko. Diese unterschiedlichen Effekte konnten durch zwei Eigenschaften autokorrelierter Zeitreihen erklärt werden. Einerseits erhöht positive Autokorrelation die Wahrscheinlichkeit, daß in einer Zeitreihe Serien von schlechten Bedingungen auftreten. Andererseits führt die Aggregation von schlechten Jahren auch zu langen Zeiträumen mit relativ guten Bedingungen. Deshalb ist die Wahrscheinlichkeit, daß innerhalb eines bestimmten Zeitraums zumindest ein extrem schlechtes Jahr auftritt, geringer unter positiver Autokorrelation. Die Ergebnisse konnten einen Widerspruch in der Literatur aufklären, in dem unterschiedliche Effekte von autokorreliertem Umweltrauschen auf das Extinktionsrisiko gefunden wurden, obwohl sehr ähnliche Modelle verwendet wurden. Im zweiten Teil, verglich ich zwei Methoden, die häufig verwendet werden, um den Effekt von Klimawandel auf die zukünftige Verbreitung und Abundanz von Arten vorauszusagen: Ein "Raum-ersetzt-Zeit-Ansatz" ("space for time approach"), in dem Voraussagen aufgrund der aktuellen geographischen Verbreitung und Abundanz einer Art in Relation zum Klima getroffen werden, und ein "Populationsmodell-Ansatz", der auf Korrelationen zwischen demographischen Parametern und der jährlichen Variabilität im Klimas beruht. In einer Fallstudie verglich ich die beiden Methoden, um den Effekt einer Änderung im mittleren Niederschlag auf eine Population des Siedelwebers Philetairus socius vorauszusagen. Der Siedelweber ist eine häufige, koloniale Vogelart in semiariden Savannen im südlichen Afrika. Im "space for time approach" verglich ich zwei Populationen des Siedelwebers in Gebieten mit stark unterschiedlichem mittleren Niederschlag. Die Untersuchung zeigte keinen Unterschied zwischen den beiden Populationen. Sowohl dieses Ergebnis als auch das weite Verbreitungsgebiet des Siedelwebers implizieren keine sensitive Reaktion der Art auf eine geringfügige Änderung im mittleren Niederschlag. Im Unterschied dazu zeigte der "Populationsmodell-Ansatz", der auf einer Korrelation zwischen Niederschlag und dem Reproduktionserfolg des Siedlerwebers beruhte, eine sensitive Reaktion in den meisten der untersuchten Modelltypen. Die Inkonsistenz der Ergebnisse wurde in einer Kreuz-Validierung der beiden Ansätze bestätigt. Aus der Untersuchung folgerte ich, daß die unterschiedlichen Ergebnisse dadurch verursacht wurden, daß die beiden Methoden unterschiedliche Zeitskalen widerspiegeln. Auf einer kurzen Zeitskala reagiert die Population sensitiv auf Änderungen im Niederschlag. Auf einer großen Zeitskala oder im räumlichen Vergleich kann die sensitive Reaktion jedoch durch eine Reihe von Mechanismen gepuffert oder kompensiert werden. Diese Mechanismen können Anpassungen im Verhalten oder in der Lebensgeschichte ("life history"), Änderungen in den Interaktionen mit andern Arten oder Unterschiede in der physikalischen Umgebung beinhalten. Diese Studie zeigt, daß ein Verständnis, wie solche Mechanismen funktionieren, und auf welcher Zeitskala sie wirken, eine wesentliche Voraussetzung ist, um Prognosen über ökologische Effekte des Klimawandels treffen zu können. Im dritten Teil untersuchte ich, warum Kolonien des Siedelwebers so stark in ihrer Größe variieren. Die Variabilität der Koloniegrößen ist erstaunlich, da man in Untersuchungen zur Kolonialität bei Tieren oft davon ausgeht, daß eine optimale Koloniegröße besteht, bei der die individuelle Fitneß maximiert ist. Aufgrund dieser Annahme sollten Vögel sich so im Raum ausbreiten, daß die Koloniegrößen möglicht nahe am Optimum liegen. In dieser Arbeit konnte ich jedoch anhand von Daten zum Reproduktionserfolg und zur Überlebensrate in Relation zur Koloniegröße zeigen, daß die Funktion der Fitneß in Abhängigkeit von der Koloniegröße nicht einer Optimumskurve folgt. Statt dessen überlagern sich positive und negative Effekte der Koloniegröße so, daß die Populationswachstumsrate generell nahe eins ist, und die Dichteabhängigkeit gering ist. Auf diesen Ergebnissen aufbauend zeigte ich in einem Populationsmodell, das einen evolutionären Optimierungsprozeß der Dispersal-Strategie beinhaltet, daß die spezifische Form der Fitneßfunktion zu einer Dispersal-Strategie führen kann, bei der die hohe Variabilität der Koloniegrößen aufrecht erhalten wird.
T2  - Climate change, variable colony sizes and temporal autocorrelation : consequences of living in changing environments
KW  - Populationsbiologie
KW  - Ökologie
KW  - Theoretische Ökologie
KW  - Ökologische Modelle
KW  - Klimawandel
KW  - Umweltrauschen
KW  - Extinktionsrisko
KW  - Kolonialität
KW  - ecological modelling
KW  - red noise
KW  - extinction risk
KW  - coloniality
KW  - climate change
Y1  - 2005
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-5744
ER  - 
TY  - JOUR
A1  - Sarmento, Juliano Sarmento
A1  - Jeltsch, Florian
A1  - Thuiller, Wilfried
A1  - Higgins, Steven
A1  - Midgley, Guy F.
A1  - Rebelo, Anthony G.
A1  - Rouget, Mathieu
A1  - Schurr, Frank Martin
T1  - Impacts of past habitat loss and future climate change on the range dynamics of South African Proteaceae
JF  - Diversity & distributions : a journal of biological invasions and biodiversity
N2  - Aim To assess how habitat loss and climate change interact in affecting the range dynamics of species and to quantify how predicted range dynamics depend on demographic properties of species and the severity of environmental change. Location South African Cape Floristic Region. Methods We use data-driven demographic models to assess the impacts of past habitat loss and future climate change on range size, range filing and abundances of eight species of woody plants (Proteaceae). The species-specific models employ a hybrid approach that simulates population dynamics and long-distance dispersal on top of expected spatio-temporal dynamics of suitable habitat. Results Climate change was mainly predicted to reduce range size and range filling (because of a combination of strong habitat shifts with low migration ability). In contrast, habitat loss mostly decreased mean local abundance. For most species and response measures, the combination of habitat loss and climate change had the most severe effect. Yet, this combined effect was mostly smaller than expected from adding or multiplying effects of the individual environmental drivers. This seems to be because climate change shifts suitable habitats to regions less affected by habitat loss. Interspecific variation in range size responses depended mostly on the severity of environmental change, whereas responses in range filling and local abundance depended mostly on demographic properties of species. While most surviving populations concentrated in areas that remain climatically suitable, refugia for multiple species were overestimated by simply overlying habitat models and ignoring demography. Main conclusions Demographic models of range dynamics can simultaneously predict the response of range size, abundance and range filling to multiple drivers of environmental change. Demographic knowledge is particularly needed to predict abundance responses and to identify areas that can serve as biodiversity refugia under climate change. These findings highlight the need for data-driven, demographic assessments in conservation biogeography.
KW  - biodiversity refugia
KW  - CFR Proteaceae
KW  - climate change
KW  - demographic properties
KW  - habitat loss
KW  - local abundances
KW  - process-based range models
KW  - range filling
KW  - range size
KW  - species distribution models
Y1  - 2013
U6  - https://doi.org/10.1111/ddi.12011
SN  - 1366-9516
VL  - 19
IS  - 4
SP  - 363
EP  - 376
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - THES
A1  - Romero Mujalli, Daniel
T1  - Ecological modeling of adaptive evolutionary responses to rapid climate change
T1  - Ökologische Modellierung anpassungsfähiger evolutionärer Reaktionen auf schnellen Klimawandel
N2  - A contemporary challenge in Ecology and Evolutionary Biology is to anticipate the fate of populations of organisms in the context of a changing world. Climate change and landscape changes due to anthropic activities have been of major concern in the contemporary history. Organisms facing these threats are expected to respond by local adaptation (i.e., genetic changes or phenotypic plasticity) or by shifting their distributional range (migration). However, there are limits to their responses. For example, isolated populations will have more difficulties in developing adaptive innovations by means of genetic changes than interconnected metapopulations. Similarly, the topography of the environment can limit dispersal opportunities for crawling organisms as compared to those that rely on wind. Thus, populations of species with different life history strategy may differ in their ability to cope with changing environmental conditions. However, depending on the taxon, empirical studies investigating organisms’ responses to environmental change may become too complex, long and expensive; plus, complications arising from dealing with endangered species. In consequence, eco-evolutionary modeling offers an opportunity to overcome these limitations and complement empirical studies, understand the action and limitations of underlying mechanisms, and project into possible future scenarios. In this work I take a modeling approach and investigate the effect and relative importance of evolutionary mechanisms (including phenotypic plasticity) on the ability for local adaptation of populations with different life strategy experiencing climate change scenarios. For this, I performed a review on the state of the art of eco-evolutionary Individual-Based Models (IBMs) and identify gaps for future research. Then, I used the results from the review to develop an eco-evolutionary individual-based modeling tool to study the role of genetic and plastic mechanisms in promoting local adaption of populations of organisms with different life strategies experiencing scenarios of climate change and environmental stochasticity. The environment was simulated through a climate variable (e.g., temperature) defining a phenotypic optimum moving at a given rate of change. The rate of change was changed to simulate different scenarios of climate change (no change, slow, medium, rapid climate change). Several scenarios of stochastic noise color resembling different climatic conditions were explored. Results show that populations of sexual species will rely mainly on standing genetic variation and phenotypic plasticity for local adaptation. Population of species with relatively slow growth rate (e.g., large mammals) – especially those of small size – are the most vulnerable, particularly if their plasticity is limited (i.e., specialist species). In addition, whenever organisms from these populations are capable of adaptive plasticity, they can buffer fitness losses in reddish climatic conditions. Likewise, whenever they can adjust their plastic response (e.g., bed-hedging strategy) they will cope with bluish environmental conditions as well. In contrast, life strategies of high fecundity can rely on non-adaptive plasticity for their local adaptation to novel environmental conditions, unless the rate of change is too rapid. A recommended management measure is to guarantee interconnection of isolated populations into metapopulations, such that the supply of useful genetic variation can be increased, and, at the same time, provide them with movement opportunities to follow their preferred niche, when local adaptation becomes problematic. This is particularly important for bluish and reddish climatic conditions, when the rate of change is slow, or for any climatic condition when the level of stress (rate of change) is relatively high.
N2  - Eine aktuelle Herausforderung in der Ökologie und Evolutionsbiologie besteht darin, das Schicksal von Populationen verschiedener Lebewesen im Kontext einer sich verändernden Welt zu antizipieren. Der Klimawandel und die durch anthropologische Aktivitäten verursachten Landschaftsveränderungen sind im Laufe der Geschichte von großer Bedeutung geworden. Von den Organismen, die sich diesen Veränderungen stellen, wird erwartet, dass sie durch lokale Anpassung (d.h. genetische Veränderungen oder phänotypische Plastizität) oder durch Verschiebung ihres Verbreitungsgebietes (Migration) darauf reagieren. Allerdings sind diese Reaktionen begrenzt. So werden beispielsweise isolierte Populationen mehr Schwierigkeiten bei der Entwicklung adaptiver Neuheiten mittels genetischer Variation haben als vernetzte Metapopulationen. Ebenso kann die Topographie der Umgebung die Ausbreitungsmöglichkeiten für zum Beispiel kriechende Organismen im Vergleich zu denen, die auf Wind angewiesen sind, einschränken. So können Populationen von Arten mit unterschiedlichen Lebensstrategien verschiedene Fähigkeiten haben, mit den sich ändernden Umweltbedingungen umzugehen. Empirische Studien, die die Reaktionen von Organismen auf Umweltveränderungen untersuchen, können jedoch, je nach Taxon, zu komplex, langwierig und teuer werden. Ebenso sollten Komplikationen im Umgang mit gefährdeten Arten nicht außer Acht gelassen werden. Die ökoevolutionäre Modellierung bietet jedoch die Möglichkeit, diese Einschränkungen zu überwinden und empirische Studien zu ergänzen, die Wirkung und Grenzen der zugrunde liegenden Mechanismen zu verstehen und mögliche Zukunftsszenarien zu erstellen. In dieser Arbeit untersuche ich mittels einer Modellierungsmethode die Wirkung und relative Bedeutung evolutionärer Mechanismen (einschließlich phänotypischer Plastizität) auf die Fähigkeit zur lokalen Anpassung von Populationen mit unterschiedlichen Lebensstrategien, die Szenarien des Klimawandels durchleben. Dazu habe ich in einem Review den Stand der Technik ökoevolutionärer individuenbasierender Modelle (Individual-Based Models; IBMs) zusammengefasst und Ansätze für eine zukünftige Forschung identifiziert. Die Erkenntnisse des Reviews nutzte ich, um ein ökoevolutionäres, individuelles Modellierungsprogramm zu entwickeln. Dieses analysiert die Rolle genetischer und plastischer Mechanismen zur Förderung der lokalen Anpassung organismischer Populationen mit unterschiedlichen Lebensstrategien, welche Szenarien des Klimawandels und der ökologischen Stochastik erfahren. Die Umweltbedingungen wurden durch eine klimatische Variable (z.B. Temperatur) simuliert, die ein phänotypisches Optimum definiert, das sich mit einer bestimmten Änderungsrate bewegt. Verschiedene Änderungsraten wurden angewandt, um unterschiedliche Szenarien des Klimawandels darzustellen (keine Veränderung, langsamer, mittlerer, schneller Klimawandel). Es wurden mehrere Szenarien stochastischen Farbrauschens untersucht, die verschiedene klimatische Bedingungen widerspiegeln. Die Ergebnisse zeigen, dass Populationen sexueller Arten hauptsächlich auf genetische Variation und phänotypische Plastizität hinsichtlich lokalen Anpassung angewiesen sind. Populationen von Arten mit relativ langsamer Wachstumsrate (z.B. große Säugetiere), und insbesondere die mit kleiner Populationsgröße, sind am anfälligsten, vor allem wenn ihre Plastizität begrenzt ist (d.h. spezialisierte Arten). Wenn Individuen dieser Populationen zu adaptiver Plastizität fähig sind, können sie Fitnessverluste unter „rötlichen“ Klimabedingungen ausgleichen. Zugleich können diese Populationen durch Anpassung der Plastizität auch unter bläulichen Umweltbedingungen zurecht kommen (z.B. Bed-Hedging-Strategie). Im Gegensatz dazu können sich Lebensstrategen mit hoher Reproduktionszahl auf nicht-adaptive Plastizität zur lokalen Anpassung an neue Umweltbedingungen verlassen, es sei denn, die Änderungsrate ist zu schnell. Eine empfohlene Handlungsmaßnahme ist es, die Eingliederung von isolierten Populationen in Metapopulationen zu gewährleisten, so dass die genetische Variation erhöht werden kann. Wenn eine lokale Anpassung problematisch wird, sollte ihnen gleichzeitig Migrationsfreiraum gegeben werden, um ihrer bevorzugten Nische zu folgen. Dies ist besonders wichtig für „bläuliche“ und „rötliche“ Klimabedingungen, bei denen die Änderungsrate langsam ist, oder für jede klimatische Bedingung, wenn die Belastung (Änderungsrate) relativ hoch ist.
KW  - climate change
KW  - local adaptation
KW  - plasticity
KW  - evolution
KW  - individual-based model
KW  - Klimawandel
KW  - lokale Anpassung
KW  - Plastizität
KW  - Evolution
KW  - Individuen-basierende Modelle
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-430627
ER  - 
TY  - THES
A1  - Popp, Alexander
T1  - An integrated modelling approach for sustainable management of semi-arid and arid rangelands
T1  - Ein integrativer Modellierungsansatz für ein nachhaltiges Management semi-arider und arider Beweidungsgebiete
N2  - The need to develop sustainable resource management strategies for semi-arid and arid rangelands is acute as non-adapted grazing strategies lead to irreversible environmental problems such as desertification and associated loss of economic support to society. In such vulnerable ecosystems, successful implementation of sustainable management strategies depends on well-founded under-standing of processes at different scales that underlay the complex system dynamic. There is ample evidence that, in contrast to traditional sectoral approaches, only interdisciplinary research does work for resolving problems in conservation and natural resource management. In this thesis I combined a range of modeling approaches that integrate different disciplines and spatial scales in order to contribute to basic guidelines for sustainable management of semi-arid and arid range-lands. Since water availability and livestock management are seen as most potent determinants for the dynamics of semi-arid and arid ecosystems I focused on (i) the interaction of ecological and hydro-logical processes and (ii) the effect of farming strategies. First, I developed a grid-based and small-scaled model simulating vegetation dynamics and inter-linked hydrological processes. The simulation results suggest that ecohydrological interactions gain importance in rangelands with ascending slope where vegetation cover serves to obstruct run-off and decreases evaporation from the soil. Disturbances like overgrazing influence these positive feedback mechanisms by affecting vegetation cover and composition. In the second part, I present a modeling approach that has the power to transfer and integrate ecological information from the small scale vegetation model to the landscape scale, most relevant for the conservation of biodiversity and sustainable management of natural resources. I combined techniques of stochastic modeling with remotely sensed data and GIS to investigate to which ex-tent spatial interactions, like the movement of surface water by run-off in water limited environments, affect ecosystem functioning at the landscape scale. My simulation experiments show that overgrazing decreases the number of vegetation patches that act as hydrological sinks and run-off increases. The results of both simulation models implicate that different vegetation types should not only be regarded as provider of forage production but also as regulator of ecosystem functioning. Vegetation patches with good cover of perennial vegetation are capable to catch and conserve surface run-off from degraded surrounding areas. Therefore, downstream out of the simulated system is prevented and efficient use of water resources is guaranteed at all times. This consequence also applies to commercial rotational grazing strategies for semi-arid and arid rangelands with ascending slope where non-degraded paddocks act as hydrological sinks. Finally, by the help of an integrated ecological-economic modeling approach, I analyzed the relevance of farmers’ ecological knowledge for longterm functioning of semi-arid and arid grazing systems under current and future climatic conditions. The modeling approach consists of an ecological and an economic module and combines relevant processes on either level. Again, vegetation dynamics and forage productivity is derived by the small-scaled vegetation model. I showed that sustainable management of semi-arid and arid rangelands relies strongly on the farmers’ knowledge on how the ecosystem works. Furthermore, my simulation results indicate that the projected lower annual rainfall due to climate change in combination with non-adapted grazing strategies adds an additional layer of risk to these ecosystems that are already prone to land degradation. All simulation models focus on the most essential factors and ignore specific details. Therefore, even though all simulation models are parameterized for a specific dwarf shrub savanna in arid southern Namibia, the conclusions drawn are applicable for semi-arid and arid rangelands in general.
N2  - Nachhaltige Managementstrategien für semi-aride und aride Beweidungsgebiete sind äusserst bedeutend, da ein nicht nachhaltiges Management sehr schnell zu irreversiblen Umweltproblemen und damit verbundenem Verlust der ökonomischen Prosperität führt. Obwohl Wasserverfügbarkeit und Viehmanagement als die bedeutendsten Faktoren für die Dynamik semi-arider und arider Ökosysteme angesehen werden, ist deren Einfluss und Interaktion nicht genügend erforscht. Ziel der Dissertation war, das Wissen über diese Prozesse zu erweitern, um grundsätzliche Richtlinien für die nachhaltige Nutzung semi-arider und arider Beweidungsgebiete zu erstellen. Hierfür habe ich in dieser Arbeit, die aus drei aufeinander aufbauenden Teilen besteht, mehrere Modellierungstechniken kombiniert. Für den ersten Teil meiner Arbeit habe ich ein gitterbasiertes und kleinskaliges Modell entwickelt, welches die Vegetationsdynamik und damit verbundene hydrologische Prozesse wie Oberflächenabfluss und Evaporation simuliert. Da Entscheidungen zur nachhaltigen Nutzung von Resourcen auf der Landschaftsebene getroffen werden, stelle ich im zweiten Teil der Arbeit eine neue Methode vor, mit deren Hilfe man diese kleinskaligen ökologischen Informationen auf die Landschaftsebene übertragen kann. Um zu untersuchen wie Oberflächenabfluss das Funktionieren von Ökosystemen auf Landschaftsebene beeinflusst, habe ich Techniken der stochastischen Modellierung mit Techniken der Fernerkundung und GIS kombiniert.. Die Ergebnisse beider Simulationsmodelle implizieren, dass öko-hydrologische Interaktionen in Beweidungsgebieten mit ausgeprägter Topographie von Bedeutung sind. Verschiedene Vegetationstypen sollten nicht nur als Futterquelle für die Weidetiere betrachtet werden, sondern auch bezüglich ihrer Bedeutung als Regler der Ökosystemfunktion. Vegetationsbestände mit einem hohen Bedeckungsgrad an perennierender Vegetation können Oberflächenabfluss aus degradierten benachbarten Gebieten abfangen. Störungen wie Überweidung beeinflussen diesen positiven Rückkopplungsmechanismus negativ, indem sie Vegetationsbedeckung und -zusammensetzung verändern. Im letzten Teil der Arbeit habe ich mit Hilfe eines ökologisch-ökonomischen Simulationsmodells die Bedeutung des ökologischen Verständnisses der Farmer für ein langfristiges Funktionieren von semi-ariden und ariden Beweidungssystemen unter aktuellen und prognostizierten klimatischen Bedingungen untersucht. Auch hier wird die Vegetationsdynamik und – produktivität beider Module mit Hilfe des kleinskaligen Vegetationsmodells abgeleitet. Die Ergebnisse zeigen, dass ein nachhaltiges Management semi-arider und arider Savannen sehr stark vom Verständnis der Farmer für die Funktionsweise des Ökosystems abhängt. Des Weiteren weist das Modell darauf hin, dass ein durch den prognostizierten Klimawandel reduzierter Jahresniederschlag in Kombination mit nicht-angepassten Beweidungsstrategien ein hohes Risiko für diese Ökosysteme darstellt. Meine Arbeit trägt zu einem besseren Verständnis grundlegender Prozesse der Ökosystemdynamik einer ariden Zwergstrauchsavanne im südlichen Namibia bei. Da sich alle drei Simulationsmodelle auf grundlegende Faktoren konzentrieren und spezifische Details ignorieren, können die Schlussfolgerungen auch auf andere semi-aride und aride Beweidungsgebiete übertragen werden.
KW  - Simulationsmodell
KW  - nachhaltige Landnutzung
KW  - Klimawandel
KW  - arid
KW  - simulation model
KW  - sustainable management
KW  - climate change
KW  - arid
Y1  - 2007
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-15103
ER  - 
TY  - JOUR
A1  - Perring, Michael P.
A1  - Bernhardt-Roemermann, Markus
A1  - Baeten, Lander
A1  - Midolo, Gabriele
A1  - Blondeel, Haben
A1  - Depauw, Leen
A1  - Landuyt, Dries
A1  - Maes, Sybryn L.
A1  - De Lombaerde, Emiel
A1  - Caron, Maria Mercedes
A1  - Vellend, Mark
A1  - Brunet, Joerg
A1  - Chudomelova, Marketa
A1  - Decocq, Guillaume
A1  - Diekmann, Martin
A1  - Dirnboeck, Thomas
A1  - Doerfler, Inken
A1  - Durak, Tomasz
A1  - De Frenne, Pieter
A1  - Gilliam, Frank S.
A1  - Hedl, Radim
A1  - Heinken, Thilo
A1  - Hommel, Patrick
A1  - Jaroszewicz, Bogdan
A1  - Kirby, Keith J.
A1  - Kopecky, Martin
A1  - Lenoir, Jonathan
A1  - Li, Daijiang
A1  - Malis, Frantisek
A1  - Mitchell, Fraser J. G.
A1  - Naaf, Tobias
A1  - Newman, Miles
A1  - Petrik, Petr
A1  - Reczynska, Kamila
A1  - Schmidt, Wolfgang
A1  - Standovar, Tibor
A1  - Swierkosz, Krzysztof
A1  - Van Calster, Hans
A1  - Vild, Ondrej
A1  - Wagner, Eva Rosa
A1  - Wulf, Monika
A1  - Verheyen, Kris
T1  - Global environmental change effects on plant community composition trajectories depend upon management legacies
JF  - Global change biology
N2  - 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.
KW  - biodiversity change
KW  - climate change
KW  - disturbance regime
KW  - forestREplot
KW  - herbaceous layer
KW  - management intensity
KW  - nitrogen deposition
KW  - plant functional traits
KW  - time lag
KW  - vegetation resurvey
Y1  - 2017
U6  - https://doi.org/10.1111/gcb.14030
SN  - 1354-1013
SN  - 1365-2486
VL  - 24
IS  - 4
SP  - 1722
EP  - 1740
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Marzetz, Vanessa
A1  - Spijkerman, Elly
A1  - Striebel, Maren
A1  - Wacker, Alexander
T1  - Phytoplankton community responses to interactions between light intensity, light variations, and phosphorus supply
JF  - Frontiers in Environmental Science
N2  - In a changing world, phytoplankton communities face a large variety of challenges including altered light regimes. These alterations are caused by more pronounced stratification due to rising temperatures, enhanced eutrophication, and browning of lakes. Community responses toward these effects can emerge as alterations in physiology, biomass, biochemical composition, or diversity. In this study, we addressed the combined effects of changes in light and nutrient conditions on community responses. In particular, we investigated how light intensity and variability under two nutrient conditions influence (1) fast responses such as adjustments in photosynthesis, (2) intermediate responses such as pigment adaptation and (3) slow responses such as changes in community biomass and species composition. Therefore, we exposed communities consisting of five phytoplankton species belonging to different taxonomic groups to two constant and two variable light intensity treatments combined with two levels of phosphorus supply. The tested phytoplankton communities exhibited increased fast reactions of photosynthetic processes to light variability and light intensity. The adjustment of their light harvesting mechanisms via community pigment composition was not affected by light intensity, variability, or nutrient supply. However, pigment specific effects of light intensity, light variability, and nutrient supply on the proportion of the respective pigments were detected. Biomass was positively affected by higher light intensity and nutrient concentrations while the direction of the effect of variability was modulated by light intensity. Light variability had a negative impact on biomass at low, but a positive impact at high light intensity. The effects on community composition were species specific. Generally, the proportion of green algae was higher under high light intensity, whereas the cyanobacterium performed better under low light conditions. In addition to that, the diatom and the cryptophyte performed better with high nutrient supply while the green algae as well as the cyanobacterium performed better at low nutrient conditions. This shows that light intensity, light variability, and nutrient supply interactively affect communities. Furthermore, the responses are highly species and pigment specific, thus to clarify the effects of climate change a deeper understanding of the effects of light variability and species interactions within communities is important.
KW  - phytoplankton communities
KW  - light variability
KW  - photosynthetic rate
KW  - climate change
KW  - resource competition
KW  - light intensity (irradiance)
KW  - pigment composition
KW  - nutrient supply
Y1  - 2020
U6  - https://doi.org/10.3389/fenvs.2020.539733
SN  - 2296-665X
VL  - 8
PB  - Frontiers Media
CY  - Lausanne
ER  - 
TY  - GEN
A1  - Marzetz, Vanessa
A1  - Spijkerman, Elly
A1  - Striebel, Maren
A1  - Wacker, Alexander
T1  - Phytoplankton Community Responses to Interactions Between Light Intensity, Light Variations, and Phosphorus Supply
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - In a changing world, phytoplankton communities face a large variety of challenges including altered light regimes. These alterations are caused by more pronounced stratification due to rising temperatures, enhanced eutrophication, and browning of lakes. Community responses toward these effects can emerge as alterations in physiology, biomass, biochemical composition, or diversity. In this study, we addressed the combined effects of changes in light and nutrient conditions on community responses. In particular, we investigated how light intensity and variability under two nutrient conditions influence (1) fast responses such as adjustments in photosynthesis, (2) intermediate responses such as pigment adaptation and (3) slow responses such as changes in community biomass and species composition. Therefore, we exposed communities consisting of five phytoplankton species belonging to different taxonomic groups to two constant and two variable light intensity treatments combined with two levels of phosphorus supply. The tested phytoplankton communities exhibited increased fast reactions of photosynthetic processes to light variability and light intensity. The adjustment of their light harvesting mechanisms via community pigment composition was not affected by light intensity, variability, or nutrient supply. However, pigment specific effects of light intensity, light variability, and nutrient supply on the proportion of the respective pigments were detected. Biomass was positively affected by higher light intensity and nutrient concentrations while the direction of the effect of variability was modulated by light intensity. Light variability had a negative impact on biomass at low, but a positive impact at high light intensity. The effects on community composition were species specific. Generally, the proportion of green algae was higher under high light intensity, whereas the cyanobacterium performed better under low light conditions. In addition to that, the diatom and the cryptophyte performed better with high nutrient supply while the green algae as well as the cyanobacterium performed better at low nutrient conditions. This shows that light intensity, light variability, and nutrient supply interactively affect communities. Furthermore, the responses are highly species and pigment specific, thus to clarify the effects of climate change a deeper understanding of the effects of light variability and species interactions within communities is important.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1109 
KW  - phytoplankton communities
KW  - light variability
KW  - photosynthetic rate
KW  - climate change
KW  - resource competition
KW  - light intensity (irradiance)
KW  - pigment composition
KW  - nutrient supply
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-491041
SN  - 1866-8372
IS  - 1109
ER  - 
TY  - JOUR
A1  - Marzetz, Vanessa
A1  - Spijkerman, Elly
A1  - Striebel, Maren
A1  - Wacker, Alexander
T1  - Phytoplankton Community Responses to Interactions Between Light Intensity, Light Variations, and Phosphorus Supply
JF  - Frontiers in Environmental Science
N2  - In a changing world, phytoplankton communities face a large variety of challenges including altered light regimes. These alterations are caused by more pronounced stratification due to rising temperatures, enhanced eutrophication, and browning of lakes. Community responses toward these effects can emerge as alterations in physiology, biomass, biochemical composition, or diversity. In this study, we addressed the combined effects of changes in light and nutrient conditions on community responses. In particular, we investigated how light intensity and variability under two nutrient conditions influence (1) fast responses such as adjustments in photosynthesis, (2) intermediate responses such as pigment adaptation and (3) slow responses such as changes in community biomass and species composition. Therefore, we exposed communities consisting of five phytoplankton species belonging to different taxonomic groups to two constant and two variable light intensity treatments combined with two levels of phosphorus supply. The tested phytoplankton communities exhibited increased fast reactions of photosynthetic processes to light variability and light intensity. The adjustment of their light harvesting mechanisms via community pigment composition was not affected by light intensity, variability, or nutrient supply. However, pigment specific effects of light intensity, light variability, and nutrient supply on the proportion of the respective pigments were detected. Biomass was positively affected by higher light intensity and nutrient concentrations while the direction of the effect of variability was modulated by light intensity. Light variability had a negative impact on biomass at low, but a positive impact at high light intensity. The effects on community composition were species specific. Generally, the proportion of green algae was higher under high light intensity, whereas the cyanobacterium performed better under low light conditions. In addition to that, the diatom and the cryptophyte performed better with high nutrient supply while the green algae as well as the cyanobacterium performed better at low nutrient conditions. This shows that light intensity, light variability, and nutrient supply interactively affect communities. Furthermore, the responses are highly species and pigment specific, thus to clarify the effects of climate change a deeper understanding of the effects of light variability and species interactions within communities is important.
KW  - phytoplankton communities
KW  - light variability
KW  - photosynthetic rate
KW  - climate change
KW  - resource competition
KW  - light intensity (irradiance)
KW  - pigment composition
KW  - nutrient supply
Y1  - 2020
U6  - https://doi.org/10.3389/fenvs.2020.539733
SN  - 2296-665X
VL  - 8
PB  - Frontiers Media
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Maes, Sybryn L.
A1  - Perring, Michael P.
A1  - Vanhellemont, Margot
A1  - Depauw, Leen
A1  - Van den Bulcke, Jan
A1  - Brumelis, Guntis
A1  - Brunet, Jorg
A1  - Decocq, Guillaume
A1  - den Ouden, Jan
A1  - Härdtle, Werner
A1  - Hedl, Radim
A1  - Heinken, Thilo
A1  - Heinrichs, Steffi
A1  - Jaroszewicz, Bogdan
A1  - Kopecký, Martin
A1  - Malis, Frantisek
A1  - Wulf, Monika
A1  - Verheyen, Kris
T1  - Environmental drivers interactively affect individual tree growth across temperate European forests
JF  - Global change biology
N2  - Forecasting the growth of tree species to future environmental changes requires abetter understanding of its determinants. Tree growth is known to respond to global‐change drivers such as climate change or atmospheric deposition, as well as to localland‐use drivers such as forest management. Yet, large geographical scale studiesexamining interactive growth responses to multiple global‐change drivers are relativelyscarce and rarely consider management effects. Here, we assessed the interactiveeffects of three global‐change drivers (temperature, precipitation and nitrogen deposi-tion) on individual tree growth of three study species (Quercus robur/petraea, Fagus syl-vatica and Fraxinus excelsior). We sampled trees along spatial environmental gradientsacross Europe and accounted for the effects of management for Quercus. We collectedincrement cores from 267 trees distributed over 151 plots in 19 forest regions andcharacterized their neighbouring environment to take into account potentially confounding factors such as tree size, competition, soil conditions and elevation. Wedemonstrate that growth responds interactively to global‐change drivers, with species ‐specific sensitivities to the combined factors. Simultaneously high levels of precipita-tion and deposition benefited Fraxinus, but negatively affected Quercus’ growth, high-lighting species‐specific interactive tree growth responses to combined drivers. ForFagus, a stronger growth response to higher temperatures was found when precipita-tion was also higher, illustrating the potential negative effects of drought stress underwarming for this species. Furthermore, we show that past forest management canmodulate the effects of changing temperatures on Quercus’ growth; individuals in plotswith a coppicing history showed stronger growth responses to higher temperatures.Overall, our findings highlight how tree growth can be interactively determined by glo-bal‐change drivers, and how these growth responses might be modulated by past for-est management. By showing future growth changes for scenarios of environmentalchange, we stress the importance of considering multiple drivers, including past man-agement and their interactions, when predicting tree growth.
KW  - basal area increment
KW  - climate change
KW  - Fagus
KW  - Fraxinus
KW  - historical ecology
KW  - nitrogen deposition
KW  - Quercus
KW  - tree-ring analysis
Y1  - 2018
U6  - https://doi.org/10.1111/gcb.14493
SN  - 1354-1013
SN  - 1365-2486
VL  - 25
IS  - 1
SP  - 201
EP  - 217
PB  - Wiley
CY  - Hoboken
ER  -