The amount of rainfall in an area is one of the key factors in plant growth. But a recent study, based on satellite data, has found that importance is not only how much rainfall a particular area receives over the course of a year, but also how evenly it is distributed over time.
Satellite plant survey
NASA researchers have recently published the results of a study on how the amount of rain in a certain area affects the plants there. For this purpose, they used a large amount of satellite data, which allowed them to learn something new in a field where, it would seem, everything had been known for a long time.
After all, it is already clear that plant growth is related to moisture in one way or another. More than half of all plants on Earth show direct correlations between rainfall and biomass. However, when one talks about how much rain falls in a particular area, they are referring to the average annual rainfall.
But in reality, this number can fluctuate not only from year to year, but even within a single year. Rainfall may occur evenly over time or three months of drought may be followed by heavy rains. It is only in the case of flowers on the windowsill there is no difference between watering them once a week, or three times using the same amount of water.
Results of the research
The team, which included researchers from the U.S. Department of Agriculture and several universities, analyzed two decades of field and satellite observations covering millions of square miles. Their study area included diverse landscapes from Siberia to the southern edge of Patagonia.
They have found that in all ecosystems, rainfall uniformity affects plant conditions in one way or another. Satellite images taken in the visible and near-infrared bands helped to establish this. In the first case, the amount of greenness in a certain area was monitored, because it indicated the presence of new leaves and shoots.
It’s more complicated with infrared light. During the process of photosynthesis, some of the photons are not fully utilized by plants in the form of very weak emission in this range. However, there is enough of it to be seen and measured by satellites.
The overall conclusions are as follows. 42% of plants on the Earth’s surface are sensitive to changes in rainfall. This is primarily arable land, but also drier landscapes such as grasslands and deserts. And the correlation is direct: more moisture — more green.
Forests, on the other hand, are mostly negatively affected by increased rainfall. This effect is particularly strong in tropical forests in the Philippines. Statistically, daily rainfall variability was almost as important as annual total rainfall in stimulating growth worldwide.
Provided by phys.org
