Humidity levels affect plants’ ability to counteract climate change

Updated Sep 16, 2016
The Ameriflux Tower at Morgan-Monroe State Forest in Indiana monitors micro-meterological data. Photo: Indiana UniversityThe Ameriflux Tower at Morgan-Monroe State Forest in Indiana monitors micro-meterological data.
Photo: Indiana University

A recent Indiana University study has found that low relative humidity in the atmosphere can stress a plant more than dry soil.

Scientists looked into the topic to gauge the effect that steadily declining relative humidity has on ecosystems and found that plants are less effective at removing carbon from the atmosphere in low humidity environments.

“There is much uncertainty when it comes to our ability to predict future patterns of carbon uptake by plants,” said Kimberly Novick, assistant professor in the IU Bloomington School of Public and Environmental Affairs and the lead author of the study. “A lot of that uncertainty is related to an incomplete understanding of how ecosystems respond to drought. Our work suggests that properly specifying how plants respond to variations in atmospheric humidity is one way to reduce this uncertainty.”

Low relative humidity creates a demand that pulls water from plants. During dry weather, plants close their stomates, which are small pores on their leaves, to prevent the loss of excessive moisture. However, closing of the stomates also causes the plant to fail to capture as much carbon because the stomates are used for carbon dioxide uptake.

In previous studies it was hard to tell how much of the plants’ response was from dry soil and how much from the dry air. Novick and her colleagues separated the effects by analyzing the data collected in hourly increments from the “flux towers” in the AmeriFlux Network, which monitors different ecosystems and collects micro-meteorological data.

While the soil moisture changed very little throughout the day, humidity could vary significantly, enabling the researchers to differentiate the humidity levels’ effects on the plants.

It was found that as the weather grows hotter and drier, humidity tends to influence the plants more than soil moisture.

Naturally, as plants take in less carbon, they do less to counteract climate change.

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