Nitrogen is key to faster regrowth in deforested areas, say researchers

Tropical forests can recover twice as quickly after deforestation if they have adequate soil nitrogen, according to new research published today.

A team of scientists led by the University of Leeds established the world’s largest and longest experiment to see how nutrients affect forest regrowth in areas cleared for activities such as logging and agriculture.

They identified 76 forest plots across Central America – each about one third of the size of a football pitch and of varying ages – and studied the growth and death of trees for up to two decades.

Our experimental findings have implications for how we understand and manage tropical forests for natural climate solutions.

Dr Sarah Batterman, School of Geography

The plots were given experimental treatments of either nitrogen fertiliser, phosphorus fertiliser, nitrogen and phosphorus fertiliser together, or no fertiliser at all.

The team found that the levels of nutrients in the soil strongly influenced tropical forest regrowth, with trees recovering twice as fast in the first 10 years when they had access to sufficient nitrogen, compared with when they did not.

The results of the research, which also involved scientists from the University of Glasgow, the Smithsonian Tropical Research Institute, Yale University, Princeton University, Cornell University, the National University of Singapore, and the Cary Institute of Ecosystem Studies, are published today in the journal Nature Communications.

Lead author Dr Wenguang Tang, who carried out the research while studying for his PHD at the University of Leeds, said: “Our study is exciting because it suggests there are ways we can boost the capture and storage of greenhouse gases through reforestation by managing the nutrients available to trees.”

Managing nutrients

The research team used nitrogen fertiliser for the purposes of the experiment but do not advocate for fertilising forests as that would have negative consequences, including emissions of the powerful greenhouse gas nitrous oxide.

Instead, they advocate that forest managers should plant trees from the legume (bean) family which naturally fertilise the forest with nitrogen, or plant trees in areas that already have sufficient nitrogen because of the effects of air pollution.

Tropical forests are seen as vital global carbon sinks which can mitigate against climate change by removing carbon from the atmosphere and storing it in trees, a process known as carbon sequestration.

The researchers believe that if their findings were extended to include young tropical forests globally, a lack of nitrogen could be preventing the annual sequestration of 0.69 billion tonnes of carbon dioxide, roughly equivalent to two years of carbon dioxide and other greenhouse gas emissions in the U.K.

The research is published just weeks after the close of COP 30 in Brazil where the Tropical Forest Forever Facility (TFFF) fund was announced to support tropical forest countries in protecting and restoring their forests.

Principal investigator Dr Sarah Batterman, an Associate Professor in Leeds’ School of Geography, said: “Our experimental findings have implications for how we understand and manage tropical forests for natural climate solutions.

“Avoiding deforestation of mature tropical forests should always be prioritised, but our findings about how nutrient impacts on carbon sequestration is important as policymakers evaluate where and how to restore forests to maximise carbon sequestration.”