de Weger, L.A., Verbeek, C., Markey, E., O’Connor, D.J. & Gosling, W.D. (2024) Greater difference between airborne and flower pollen chemistry, than between pollen collected across a pollution gradient in the Netherlands. Science of The Total Environment 172963. DOI: 10.1016/j.scitotenv.2024.172963
Amazonian rainforests are incredibly biodiverse and provide global ecosystem services, but are threatened by fires, which completely alter ecosystem function and structure. Fires, especially in western Amazonia, almost always have an anthropogenic origin. However, much is unknown about the long-term recovery and multi-generational successional processes following fire events. Due to the long lifespan of tropical trees, past fires may have left ecological legacies in modern forest composition in Amazonia. The goal of this thesis is to investigate how past fire events impact successional trajectories of past vegetation change and whether these fire events and related human impacts have left ecological legacies in modern Amazonian forests. I specifically focus on western Amazon and changes in palm abundances and composition through time, as palms were an economically important plant family to past peoples. I compared lake charcoal records across the Amazon Basin and found fire was least prevalent in western Amazonia. On a local scale, very limited evidence of past disturbances was present in forest plots in northwestern Amazonia. Palm abundances have been increasing since the mid-Holocene, but this increase is not related to past fire events. Past fire likely have left low to none ecological legacies in these forest plots. Modern trait composition across western Amazonia is associated with past fire events, but more research is necessary to disentangle relationships between past fire, soils, and modern vegetation. Overall, western Amazonia likely contains the least intense ecological legacies in comparison with the rest of Amazonia.
Poaceae (the grass family) is one of the most diverse angiosperm families on Earth, comprising close to 12,000 species. The history of grass-dominated biomes extends back over 20 million years, yet the spatial and temporal development of these biomes and the underlying drivers remains unresolved. This thesis addresses these questions in South America, focusing on modern grass pollen and ancient samples dating from the early Miocene to the present. The thesis reveals several key points: (i) Grass pollen size varies significantly both among genera and species and within species. Pollen size shows no correlation with (a)biotic factors, indicating its limited utility as a generally applicable proxy for reconstructing past vegetation and climate; (ii) Grass pollen exhibits high diverse on surface ornamentation. The morphotypes identified by descriptive terminology are well-supported by a combination of SEM images of pollen surface patterns and computational image analysis. The findings reveal that pollen sculpture is unrelated to (a)biotic variables but is diverse across the phylogeny; (iii) Tropical grass pollen morphology suggests a gradual rather than punctuated evolution, based on the trend toward a less dense ornamentation of the exine since c. 23 Ma. The changes in the exine of grass pollen since the early Miocene might be driven by evolutionary processes (evolutionary drift and/or directional selection), and potentially immigration at the continental scale. In summary, the thesis reveals the trajectory of grass pollen morphological changes over time and examining the drivers that have contributed to their evolution and geographical expansion at the continental scale.
Developing new applications for plant wax n-alkane biomarkers can deepen our understanding of ecosystem history. In this thesis I study modern and sedimentary n-alkane signals, sourced along the tropical Andes, to better understand how they can be used as a proxy for past environmental change. The overarching question addressed in this thesis is: what do n-alkane patterns extracted from sedimentary records reflect? Specifically, I address:• Do environmental or taxonomic factors dominate the n-alkane signal?• Does the n-alkane signal alter as the plant material degrades?• How much of the n-alkane variability can be explained by our analytical protocols?I find that the taxonomic and environmental signals of n-alkane patterns are entangled, especially in leaf n-alkanes. Soil n-alkane patterns reflect environmental conditions at the site, but the results cannot rule out a taxonomic signal in soil n-alkane patterns. I also find that, as the source material degrades (leaves), the n-alkane patterns are altered. Although the n-alkane signal is recognizable as having plant origin, there is a reduction in n-alkane pattern variability and the metric for degradation becomes an increasingly important descriptor of the n-alkane pattern shifts observed in soils and sediments. I find evidence that the metric for degradation can be used as proxy for past environmental change, but the application of this n-alkane signal proxy is not straightforward. Finally, I find there is little understanding of how much extraction and measurement protocols contribute to the n-alkane pattern variability and what implications this has on interpretations of the n-alkane signal.
The high tropical Andes harbours vital ecosystems that sustain biodiversity, carbon storage, and environmental service provision for millions of people. They are identified as one of the most vulnerable terrestrial ecosystems to global environmental changes, particularly to climate change and land use conversion. Despite their vulnerability and the importance of global biodiversity conservation and Andean societies, they are among the least studied ecosystems in the world. In this thesis, I studied the patterns of summit plant community’s across the tropical section of the Andes. Further, I studied what environmental factors influence plant community composition, species diversity, and thermal niche traits in high tropical alpine ecosystems. Based on the thermal niche traits, I assessed the potential vulnerability of species and communities to climate warming, considering the effect of the climate variability hypothesis on the species niche breadths. Further, I synthesised the current state of knowledge and assessed the current and projected landscape changes in the high Andes due to the combined effect of glacier retreat and climate warming. I reviewed documented glacier changes and landscape evolution over past decades to millennia and assessed projected future glacier shrinkage until 2100 for two case studies in the Andes of Ecuador and Peru. I also evaluated the capacity of high Andean ecosystems to recover from land use changes using the aptitude to store and take up carbon together with plant diversity. Lastly, I carried out an applied research analysis aimed at informing conservation policy formulation in continental Ecuador through defining critical areas for biodiversity conservation.
Using phytolith analysis to detect palm enrichment in AmazoniaNina Witteveen (University of Amsterdam)
Starch grains as indicators of plant food consumption in Neanderthals and Early Modern HumansAmanda Henry (University of Leiden)
Paleoenvironmental history of an archaeological lagoon in Central Italy: Insights from diatom analysisMajoi Nacimiento, Teye Aukes & Jan Sevink (University of Amsterdam)
15:45-17:30 – Laboratory activities
Advances in topical phytolith identificationNina Witteveen (University of Amsterdam)
Finding Suitable Grounds – combining the on/off site approach through phytolith investigation in FlevolandAna Smuk (Rijksuniversiteit Groningen)
On November 17, 2023, Caixia Wei (魏彩霞) accomplished a pivotal milestone by successfully defending her thesis titled “Morphometrics of Modern and Fossil Poaceae Pollen from South America” at the distinguished Agnietenkapel (University of Amsterdam). During the defense ceremony, Caixia showcased her professional knowledge and expertise in the field of paleoecology in a relaxed and cheerful manner. The committee members, promoters (Carina Hoorn, William Gosling, Phillip Jardine), and attendees (~50 people) responded with frequent smiles, laughter, and numerous rounds of applause! After the defense, a delightful reception and dinner were held, where Caixia was showered with an abundance of hugs, kisses, heartfelt wishes, and thoughtful gifts. These wonderful memories will support Caixia on her journey ahead…
For a glimpse into the event, you can watch Caixia’s insightful 10-minute project presentation here:
Additionally, most of Caixia’s thesis is available for download at this link:
A new funding stream is about to open up (1 December 2023) to support African scientists to carry out PhD research at Dutch universities. The GROW research programme (Graduate Research on Worldwide Challenges) will fund 51 PhD positions to be based at one of five Dutch universities, including with the Institute for Biodiversity & Ecosystem Dynamics, at the University of Amsterdam.
Ecology of the past 