Rainfall patterns influence vegetation almost like the amount

Dec. 12 () –

A new study led by NASA has found that the way rain falls in a given year is almost as important to the world’s vegetation as the amount.

In a report published in Naturethe researchers showed that even in years with similar rainfall totals, The plants behaved differently when the water came in fewer bursts and in greater quantity.

In years with less frequent but more concentrated rainfall, plants in drier environments like the southwestern United States were more likely to thrive. In humid ecosystems such as the Central American rainforest, vegetation tended to perform worse, possibly because it could not tolerate longer dry periods.

Scientists had previously estimated that almost half of the world’s vegetation is driven primarily by the amount of rain that falls in a year. Less known is the role of daily variability, he said in a statement lead author Andrew Feldman, a hydrologist and ecosystem scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Changing precipitation patterns are producing stronger storms, with longer dry periods between them, compared to a century ago.

“You can think of it this way: If you have a houseplant, what happens if you give it a full jar of water on Sunday instead of a third of a jar on Monday, Wednesday and Friday?” Feldman said. If we apply that measurement to the size of the US Corn Belt or a rainforest, The answer could have implications for crop yields and, ultimately, for the amount of carbon dioxide that plants remove from the atmosphere.

The team, which includes researchers from the United States Department of Agriculture and several universities, analyzed two decades of field and satellite observations covering millions of square kilometers. His study area covered diverse landscapes from Siberia to the southern tip of Patagonia.

They found that plants on 42% of Earth’s vegetated land surface were sensitive to daily variability in rainfall. Of those, just over half performed better (often showing greater growth) in years with fewer but more intense wet days. These include cropland as well as drier landscapes such as grasslands and deserts.

In contrast, hardwood forests (e.g., oak, maple, and beech) and low- and mid-latitude rainforests tended to perform worse under these conditions. The effect was especially pronounced in Indo-Pacific rainforests, including those of the Philippines and Indonesia.

Statistically, daily rainfall variability was almost as important as annual rainfall totals. to drive growth around the world.

The new study was based primarily on a set of NASA missions and data sets, including the Integrated Multi-satellite Retrievals for GPM (IMERG) algorithm, which provides rain and snowfall rates for most of the planet every 30 minutes using a network of international satellites.

ANALYSIS OF ‘GREENNESS’ BY SATELLITE

To measure the plants’ response from day to day, the researchers calculated how green an area appeared in satellite images. ‘Greenness’, also known as the normalized difference vegetation index, is commonly used to estimate the density and health of vegetation. They also tracked a faint reddish light that plants emit during photosynthesis, when a plant absorbs sunlight to convert carbon dioxide and water into food, its chlorophyll “losing” unused photons. This faint light is called sun-induced fluorescence and is a telltale sign of flourishing vegetation.

Not visible to the naked eye, plant fluorescence can be detected by instruments aboard satellites such as NASA’s Orbital Carbon Observatory-2 (OCO-2). Launched in 2014, OCO-2 has observed the US Midwest with strong fluorescence during the growing season.

Feldman said the findings highlight the vital role plants play in moving carbon around the Earth, a process called the carbon cycle. Vegetation, including crops, forests and grasslands, forms a vast carbon “sink”, which absorbs excess carbon dioxide from the atmosphere.

“A more precise understanding of how plants thrive or decline day to day, storm to storm, could help us better understand their role in that critical cycle,” Feldman said.