Lead researcher Jaivime Evaristo, a post-doctoral fellow in the School of Environment and Sustainability (SENS), says the study’s finding that groundwater uptake by plants contributes less to plant growth than previously thought could change predictions on how ecosystems will react to climate change.
“Our findings may have implications for how we assess plant vulnerability and growth after a major stress event such as a drought,” he said.
Evaristo, along with co-author and supervisor Jeffrey McDonnell, combined data from 138 scientific papers on water content found in stems of more than 400 species of plants sampled from around the world.
“It is widely recognized that some plants use groundwater to grow and thrive,” said Evaristo. “What we don’t know, however, is the amount of groundwater used by plants and how many plant species use groundwater.”
To determine the role of groundwater in plant growth, researchers tracked specific isotopes within the plant’s xylem, the woody part of the stem that conducts water from the roots to the shoots within the plant.
“We were able to quantify the amount of groundwater plants use through an analysis of stable isotope data which are a powerful tool to study the water cycle,” said Evaristo. “As a water molecule moves from the atmosphere to the ground and is used by vegetation, its molecular composition changes in such a way that we are able to identify if a plant is using groundwater or surface water to grow.”
Evaristo’s results found that in 37 per cent of global vegetation, groundwater contributes to xylem water. However, when groundwater is measured as a majority contributor to plant growth that number falls to just 23 per cent. He says this finding may change assumptions on how to predict transpiration from plant ecosystems within the natural water cycle.
“Our finding that most plants have limited groundwater use may have several implications for how models in climate-vegetation feedbacks are conceptualized,” explains Evaristo.
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