PhD Research
1. Sampling phytoliths in modern analogue studies
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To improve paleoenvironmental reconstruction based on fossil phytoliths, it is vital that modern modern calibration studies rely on methods applicable to the deep time fossil record. However, soil phytolith inventories from extant vegetation types, representing modern analogues suffer from several methodological shortcomings limiting inter-study comparisons, and the development of a single, and repeatable protocol for soil sample collection.
In the first chapter of my dissertation I addressed two main methodological questions, regarding the number of phytolith samples required to capture the vegetation signal in a small area, and the soil level to be sampled in a dry forest and a rainforest in Costa Rica. I compared soil phytolith assemblages from several samples collected in a small quadrat (10 x 10 meters) and from at two different soil depths (in the upper and lower soil A-horizon). Results suggest that the use of a single point samples from the lower A-horizon of paleosols, an approach typically used in deep-time paleoecology is valid for the two studied vegetation types. The use of this approach is strongly justified because a) the upper section of the A-horizon is often eroded in paleosols, and b) because point samples can be time-averaged, the combination of multiple point samples might amplify time-averaging rather than providing more accurate reconstructions of the vegetation at a given time. |
Soil sampling
Phytoliths from La Selva Rainforest
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2. Spatial resolution of the phytolith record
Vegetation structure plays a key role for ecosystems (e.g., it contributes to the water cycle through evapotranspiration, and to the carbon carbon cycle as a carbon sink; it influence the albedo; it controls fire regimes and erosion; it is a source of soil nutrients, and controls moisture and temperature in soils; it is a source of food and habitat for animals; it influences plant and animal species composition and diversity...)
In the fossil record, direct (i.e. paleobotanical) evidence for habitat structure is rare.
Phytolith analysis has emerged in the last two decades as one of the most promising tools for vegetation reconstruction because phytoliths are thought to represent a local vegetation signal. My PhD research focused on understanding which aspect of the vegetation (structure or openness, composition, diversity, heterogeneity in this characteristics) can be reconstructed using phytoliths.
I analyzed phytolith assemblages form modern soils collected along vegetation transects through Palo dry forest and La Selva rainforest in Costa Rica. I compared soil phytolith assemblages with the standing vegetation, its Leaf Area Index (LAI) -a measure of canopy openness-, and tree species composition.
In collaboration with my PhD adviser Caroline Strömberg, I have recently submitted an article about this chapter of my dissertation.
In the fossil record, direct (i.e. paleobotanical) evidence for habitat structure is rare.
Phytolith analysis has emerged in the last two decades as one of the most promising tools for vegetation reconstruction because phytoliths are thought to represent a local vegetation signal. My PhD research focused on understanding which aspect of the vegetation (structure or openness, composition, diversity, heterogeneity in this characteristics) can be reconstructed using phytoliths.
I analyzed phytolith assemblages form modern soils collected along vegetation transects through Palo dry forest and La Selva rainforest in Costa Rica. I compared soil phytolith assemblages with the standing vegetation, its Leaf Area Index (LAI) -a measure of canopy openness-, and tree species composition.
In collaboration with my PhD adviser Caroline Strömberg, I have recently submitted an article about this chapter of my dissertation.
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3. Change in vegetation and habitat structure during the Middle Miocene Climatic optimum of Southern Patagonia
Cañodón de las Vacas, Santa Cruz Formation
The Santa Cruz Formation (SCF) of coastal Patagonia (Argentina) is the southernmost (51˚) site spanning the Middle Miocene Climatic Optimum (MMCO) - the last warmest period in the second half of the Cenozoic, characterized by atmospheric CO2 content comparable to the levels predicted for the next century.
SCF fossiliferous horizons can be traced laterally for tens of kilometers and have yielded one of the Earth's most diverse and well-preserved terrestrial vertebrate assemblages. This unique set of geologic sections allow us to, for the first time, combine detailed records of faunal diversity and ecology, vegetation composition and structure, and local climate, and to test hypotheses on the relationship between habitat structure and species diversity.
While we use phytoliths to reconstruct changes in habitat structure (heterogeneity) through time, our collaborators are studying tooth stable isotope data, faunal community structure, and tooth micro- and meso-wear. By integrating these different proxies we will test climate and ecological hypothesis, including the relationship between habitat structure and diversity.
This article is in preparation with my PhD advisor Caroline Strömberg and colleagues.
SCF fossiliferous horizons can be traced laterally for tens of kilometers and have yielded one of the Earth's most diverse and well-preserved terrestrial vertebrate assemblages. This unique set of geologic sections allow us to, for the first time, combine detailed records of faunal diversity and ecology, vegetation composition and structure, and local climate, and to test hypotheses on the relationship between habitat structure and species diversity.
While we use phytoliths to reconstruct changes in habitat structure (heterogeneity) through time, our collaborators are studying tooth stable isotope data, faunal community structure, and tooth micro- and meso-wear. By integrating these different proxies we will test climate and ecological hypothesis, including the relationship between habitat structure and diversity.
This article is in preparation with my PhD advisor Caroline Strömberg and colleagues.
