Costa Rican plants: Studying the present to understand the past

March 15, 2016
Camilla Crifò

I am researching how tiny fossilized plant particles, known as phytoliths, can be used to reconstruct past landscapes at a relatively fine spatial scale for my dissertation. Being able to use phytoliths to reconstruct past habitat structure can help us understand what particular habitats and conditions may have led to animal diversity.

Woman kneeling on forest bed

Camilla Crifò doing research for her dissertation and collecting some great material for the Burke Museum!
Photo: Mireya Córdoba

Costa Rica rainforest – La Selva

I recently visited the Costa Rica rainforest to collect samples for my research. Mireya Córdoba, a professor in sustainable development at the Universidad Distrital Francisco José de Caldas, in Bogota, Colombia, joined me. Mireya is a botanist and environmental consultant and she’s done floral inventories all over Colombia. She knows Los Llanos—the savanna region between Colombia and Venezuela—very well and will also accompany me when I go there.

I collected soil samples (from which I can extract phytoliths) from several quadrants along a transect. In each quadrant, I made an inventory and collected plant species to compare the phytolith composition with the plant species composition. The plant specimens I collected will become part of the Burke Museum Herbarium collection (with copies going to the herbarium of the National Museum of Costa Rica) and the phytoliths will be part of the Burke’s paleobotany collection.

I then took a hemispheric photo at each sampling site. Hemispheric photos are "pictures of the sky" and are used to calculate the openness of the vegetation (a dense forest is very closed, a savanna is very open). The phytolith samples also provide information on vegetation openness. I want to compare this information with the one obtained from the photos to determine how accurate it is. In particular, I will use the "phtolith undulation index," a proxy for canopy openness based on phytolith shape that was developed by Regan Dunn, former paleobotany grad student and collections manager at the Burke.

Two women standing in forest

Camilla and Mireya using a pole pruner to sample the leaves of the tallest trees.
Photo: Camilla Crifò

Woman measuring tree trunk diameter

Mireya is using a diametric tape to measure the tree trunk diameter.
Photo: Camilla Crifò

Woman taking photograph

Camilla taking a hemispheric photograph. We take one photo at each sampling site.
Photo: Mireya Córdoba

Hemispheric photograph looking up into the forest canopy

Hemispheric photograph of the canopy, used to calculate the Leaf Area Index (LAI), an approximation for the amount of light that comes through the forest canopy. Then, we compare the LAI with similar phytolith data.
Photo: Camilla Crifò

At the end of each day, we walked three kilometers through the forest trail back to the research station to enter their data in the computer, dry the soil samples and press the leaf samples.

Soil samples in open oven

Soil samples are dried in this oven at 45°C.
Photo: Camilla Crifò

Leaves stacked in newspaper pages

Each herbarium sample is sprayed with alcohol to prevent molds from attacking the leaves then pressed between newspaper pages.
Photo: Camilla Crifò

Two women in front of glass doors

Last day at the La Selva Lab.
Photo: Camilla Crifò

Costa Rica dry forest – Palo Verde

I then went to Palo Verde, a dry forest in Costa Rica, to continue my study. It was hot and dry!

Palo Verde forest

Palo Verde forest is a seasonal deciduous forest— during the dry season many trees drop their leaves. Certain areas of the park are greener than other depending on which species dominate.
Photo: Camilla Crifò

Rubiaceae

Calycophyllum candidissimum (Rubiaceae)
Photo: Camilla Crifò

Camilla in a hemispherical photo

Camilla in a hemispherical photo.
Photo: Camilla Crifò

Woman collecting soil in forest

Camilla collecting soil.
Photo: Mireya Córdoba

Two people sitting at table with plant specimens

Ulises Chavarría, former director of the herbarium of Palo Verde helps Mireya identifying some specimens. Over 60 species were identified in 11 quadrants.
Photo: Camilla Crifò

Coming up

Next I will soon head to a savanna in Colombia to collect more samples. Then I would like to use phytoliths to relate habitat structure with fauna diversity in the past. For this last piece my advisor, and Burke Museum paleobotany curator, Caroline Stromberg and I have already collected 17-million-year-old rock and fossil soil (paleosol) samples from Patagonia (Argentina).

Vertebrate paleontologists have already found an incredible faunal diversity at this site during a time of climate change called the Middle Miocene Climatic Optimum (MMCO). The MMCO is the last warming event before the current one, and climatic conditions changed in a way that is probably comparable to climate change predictions for the future.

This makes the MMCO a very interesting time period to study because understanding what happened at that time can help us in predicting future changes in ecosystems as well as taking smarter conservation initiatives.

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