In DepthEcology

Drought test begins in Biosphere 2 rainforest

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Science  18 Oct 2019:
Vol. 366, Issue 6463, pp. 289-290
DOI: 10.1126/science.366.6463.289

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Summary

An unprecedented experimental drought is taking place inside Biosphere 2, a 30-year-old set of greenhouses and artificial ecosystems in the Arizona desert. Earlier this month, the tropical rainforest was sealed shut and exposed to carbon dioxide (CO2) spiked with carbon-13. The isotopic tracer enabled investigators to follow the flows of carbon through the healthy forest. Now, the researchers have shut off the irrigation for 6 weeks to the rainforest, the largest experiment to monitor the effects of droughts with isotopes. Next month, they will inject another pulse of isotopically enriched CO2 into the densely instrumented ecosystem to look for physiological changes, such as how the trees apportion stored carbon to their leaves, trunks, and roots—crucial information for predicting how forests respond to stresses like drought. Another set of tracers will help quantify daytime respiration, a key part of the carbon cycle, and synthesis of volatile organic compounds (VOCs). Plants and microbes releases VOCs for many purposes and they also influence climate. Ultimately, the measurements will improve the way global climate models account for vegetation. Droughts, expected to become more severe as the climate warms, could turn tropical forests from sinks of greenhouse gases into sources that accelerate climate change.

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