1. Mid-Late Miocene and Early Pliocene grass communities of the Central Andean Plateau (CAP)
The Central Andean Plateau was about ~1700 m.a.s.l. in the Middle Miocene and had reached near-modern elevations (~4000 m.a.s.l.) by the Early Pliocene. The paleobotanical record of the Descanso formation, in the Peruvian Altiplano (Cuzco region) was recently investigated by Martinez et al. (2020) who documented a shift from of a montane ecosystem in the Miocene to Puna-like vegetation in the Early Pliocene, this latter representing the earliest evidence of a Puna-like ecosystem. Climate inferences from fossil evidence suggest wetter conditions in the Miocene and modern precipitation levels in the Pliocene.
The processes that lead to the evolution of modern high-elevation Andean ecosystems (Paramo, Puna, austral alpine vegetation) are debated, and wide range of climatic (e.g., hydric gradients), geographic and ecological factors have been hypothesized to have led to floristic differences between these ecosystems.
I used phytolith assemblages to better characterize the Neogene plant communities of the Descanso formation, and shed further light on the origin of the modern day Puna in the CAP.
I also extracted phytoliths from modern soil surface samples and plant specimens collected in different high elevation Andean ecosystem (e.g. Puna, Paramo) in order to compare them with the Descanso formation phytolith assemblages and increase the accuracy of vegetation reconstructions.
Preliminary results comfirm the establishment of modern-like grassland ecosystems since the Pliocene. Furthermore, grass phytoliths form the Descanso formation (from both Miocene and Pliocene members) are unique in their morphology, suggesting the occurrence of either early-diverging (propably extinct or currently rare) grass species, or the occurrence of taxa for which the phytolith morphology of modern representatives is currently unknown or differs from that of their ancestors.
2. Using C3/C4 grass phytoliths to build a palethermometer for the Northern Andes
I worked on this project at the ISEM (in Monptellier) in collaboration with Laurent Bremond, Juan Carlos Berrio, Arnoud Boom (University of Leicester), and Diego Cañas (Universidad Nacional de Colombia).
I used the data collected by my collaborators to build a transfer function in that predicts temperature from grass phytolith assemblage composition. Grass phytoliths were extracted from soil samples collected along an altitudinal and temperature gradient in
the Northern Andes (Colombia).
The proportion of grass C3/C4 phytoliths shows a strong negative correlation with temperaure. I used logistic regression to model this relationship. The results of this work have been submitted for publication and are currently under review.