Biosphere 2 studies the impacts of drought on tropical rainforests using flow measurement

As the Earth’s climate changes, scientists expect that a hotter, drier world will have severe impacts on global ecosystems, with many areas subjected to increased water stress and/or drought. However, it is difficult to forecast the specific impact climate change will have on soil, air, and water quality across different regions of the world.

In 2019, an interdisciplinary team of more than 80 scientists from around the world came together to conduct an unprecedented experiment tracking the impacts of drought and drought recovery on tropical rainforests. The experiment was funded in part by a grant from the European Research Council and spurred several partnerships, including one with Alicat.

Challenge: Measure the effects of water stress on a rainforest ecosystem

In this experiment, the team sought to measure the effects of water stress on rainforest ecosystems. They

conducted their studies in Biosphere 2, a man-made, multi-million dollar facility s built in the 1980s to simulate a fully contained Earth ecosystem. The facility is now used for research, education, and tourism. Its tropical rainforest biome boasts more than 90 different species of plants with an enclosed space the size of several tennis courts.

In this environment, the team of scientists conducted a controlled whole-ecosystem drought and stable isotope labeling experiment in the Tropical Rainforest Biome of Biosphere 2. The campaign, named Water, Atmosphere, and Life Dynamics (WALD, meaning forest in German), is a collaborative effort led by Laura Meredith, B2 Tropical Rainforest Director, University of Arizona, Christiane Werner, ERC Consolidator Grant Awardee, University of Freiburg, Germany, and Nemiah Ladd, University of Freiburg, Germany.

Biosphere 2, outside of Tucson, Arizona


The experiment

In October 2019, Biosphere 2’s tropical rainforest biome was closed to the public, and Christiane Werner of the University of Freiberg in Germany released nearly $20,000 worth of carbon dioxide spiked with Carbon-13, an isotopic tracer.

Alicat mass flow controllers closely monitored the release of the isotope into the system, which was chosen at the appropriate tracer because it occurs relatively infrequently in nature. As such, it is a useful tool with which to track and measure changes in soil, water, and air systems.

The experimental setup and data acquisition process included tapping into tree xylem, bagging leaves, probing soil, and using air composition analyzers. According to the Director of Rainforest Research, Dr. Laura Meredith, “The plants look a little bit like they’re hospitalized with all of the sensors.”

Alicat mass flow controllers set up for use in Biosphere 2


It is known that rainforests play an important role in the global carbon cycle; what isn’t understood is how this function may change when a biome is water stressed. According to Dr. Meredith, this experiment sought to better understand if ecosystems will respond to droughts in a way that releases carbon and worsens climate change or “in a way that helps mitigate it, helps slow down the process.”

Dr. Meredith had previously used Alicat mass flow controllers in experiments conducted during her time at the University of Arizona Landscape Evolution Observatory. During those experiments, Dr. Meredith was pleased with the accuracy and repeatability of the Alicat controllers. She reached out in search of a partnership to support her current work at Biosphere 2.

We were excited to be part of this important and unique experiment. Dr. Meredith presented the preliminary findings of this experiment on March 3, 2020, at the PittCon 2020 convention in Chicago.

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