Amazon’s Growth Constraints Due to Phosphorus Deficiency – Can That Be Improved?

[This study is part of a genre that is becoming more common. We could call it the Wet Blanket, the Eyore, the Marvin the Robot, or the Every-Silver-Lining-has-a-Cloud genre.~cr]

A peer-reviewed publication


New research suggests that the growth of the Amazon rainforest in our increasingly carbon-rich atmosphere may be limited by a lack of phosphorus in the soil.

Higher concentrations of carbon dioxide (CO2) cause plants to grow faster, which means they store more carbon.

This storage – especially in huge forests like the Amazon – helps limit CO2 levels from rising, slowing climate change.

However, plants also need nutrients to grow, and new research suggests that the availability of a specific nutrient, phosphorus, can limit a plant’s ability to increase yield (growth rate) Amazon as CO2 rises.

This could also make rainforests less resilient to climate change, the researchers warn.

The study was published in the journal Naturewas carried out by an international team led by Brazil’s National Research Institute of the Amazon (INPA) and the University of Exeter.

Lead author Hellen Fernanda Viana Cunha from INPA said: “Our results call into question the potential to sustain the current high rates of carbon sequestration in Amazonia.

“About 60% of the Amazon Basin is on old low-phosphorus soil, but the role of phosphorus in yield control is unclear because most fertilization experiments are in other regions. around the world are in more phosphorus-rich systems.

“Our test, Amazon Fertilization Test (AFEX), examined the effects of the addition of phosphorus, nitrogen, and base cations (other potentially important nutrients) in an aging, low-phosphorus growing area of ​​the rainforest.

“Only phosphorus increased yields in the first two years of the trial.

“Having such rapid and strong responses to phosphorus, both above and below ground, is an indication that the entire system is operating under severe phosphorus limitation.”

Soils in tropical regions like the Amazon are often formed millions of years ago, and some nutrients can be lost over time.

While nutrients such as nitrogen can be absorbed from the air by microorganisms associated with certain plants and soils, phosphorus is not available as a gas in the atmosphere – so a when it is depleted there will be little chance to level up.

In the new experiment, two years of additional phosphorus application significantly increased good root growth (29%) and canopy yield (19%).

The growth of the trunk does not increase. This may be because roots and leaves require more phosphorus than the stem, Cunha said, and stem growth is a slower process.

Long-term follow-up of the experiment is needed to determine whether the woody yield response becomes apparent.

The findings have major implications not only for carbon storage but also for the resilience of forests to climate change.

“To cope with and recover from increased threats like drought, we need forests to grow better than before,” said Professor Iain Hartleyin the Department of Geography of the University of Exeter.

“Composting with CO2 could increase forest resilience, but our findings suggest that phosphorus availability will limit that impact – and therefore the risks posed by climate change.” is becoming increasingly important.

“In short, portions of rainforest that grow on low-fertile soils may be more vulnerable than currently recognized.”

Testing this suggestion is an urgent research priority. The AmazonFACE The trial – whose international team includes researchers from INPA and Exeter – is working to address this important priority.

The new study was funded by the Natural Environment Research Council.

The paper was titled: “Direct Evidence of Phosphorus Restrictions on Amazon Forest Productivity.”




10.1038 / s41586-022-05085-2


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Direct evidence for phosphorus restriction on Amazon forest productivity


August 10, 2022

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