Nitrogen is necessary for young tropical rain forests to combat climate change.

By absorbing carbon dioxide from the atmosphere and storing it in wood, tropical rainforests contribute to the slowing of climate change. Forests that develop quickly are even more important because they absorb carbon more quickly.

Nowadays, young woods that recover from farming, logging, or fires can be found in many tropical locations.

Researchers are trying to figure out what regulates growth rate in the early stages of recuperation. According to recent studies, nitrogen is a key factor in how quickly young tropical forests retain carbon.

Forest recovery is shaped by nutrients.

Sunlight, water, and soil nutrients are essential for tree growth. Photosynthesis and leaf growth are supported by nitrogen. Soil frequently loses nitrogen due to rain runoff and gas release after land is cleared for crops or cattle.

Even in the presence of water and sunlight, poor soil nitrogen hinders plant development. Carbon capture consequently slows down as well.

Forest age may alter fertiliser requirements, according to ecologists' predictions. While mature forests may be limited by other nutrients like phosphorus, early regeneration stages may have nitrogen shortages.

Long-term experiments in woods of various ages were necessary to test the theory.

Assessing development across age groups

An extensive experiment was planned in Panama by a research team headed by Wenguang Tang from the Universities of Leeds and Glasgow. 76 sizable forest plots spread throughout Panama's geography served as study locations. Initially, several areas were open pastures for cattle.

Other plots showed mature forests that had seen little human disturbance for centuries, or woods that had been recovering for ten or thirty years. Nitrogen, phosphorus, both nutrients, or none at all were added by scientists. Tens of thousands of trees were monitored for growth and death over a long period of time.

Nitrogen is necessary for rapid growth.

The findings revealed a distinct pattern. In relatively young woods, growth was severely restricted by nitrogen. When nitrogen was added, aboveground biomass growth increased by 95% in recently abandoned pastures and by 48% in woods that had recovered for roughly ten years.

As tree trunks and branches expanded more swiftly, carbon storage increased as well. According to Sarah Batterman, senior author at the Cary Institute of Ecosystem Studies, "nitrogen is limiting how quickly young forests can regrow."

Forests recovered nearly twice as quickly in the first ten years after nitrogen was introduced to the soil. We may be able to cut our carbon emissions for a few more years if we have quicker growth rates, which also result in faster carbon dioxide absorption.

Instead than decreasing tree death, added nitrogen primarily increased growth. Although there was some natural thinning as a result of faster-growing trees' increased competition for light and space, overall carbon storage increased.

Older woods react in different ways.

Additional nitrogen had little effect on forests older than 30 years. As nitrogen-fixing trees grow, soil nitrogen naturally accumulates over time.

These trees work in tandem with microbes to transform atmospheric nitrogen gas into soil nitrogen that can be used. Nitrogen shortages lessen as recovery proceeds.

Additionally, there was no discernible phosphorus restriction at any forest age. Long-held beliefs about tropical soils were called into question by that outcome. Tropical trees seem to have ingenious methods to obtain phosphorus that is trapped in organic matter or soil minerals.

Even when soil phosphorus levels seem low, roots can still grow because they secrete enzymes that release phosphorus. According to Tang, "this result challenges the long-standing theory that phosphorus availability fundamentally constrains tropical forest carbon sinks."

Forests' carbon-nitrogen feedback

A carbon and nitrogen feedback loop is produced by forest recovery. The requirement for nitrogen rises during the early stages of recovery due to rapid carbon uptake.

In response, nitrogen-fixing organisms enrich the soil with nitrogen. Growth quickens, nitrogen availability increases, and nitrogen fixation slows down once more over time. The reason nitrogen restricts early growth but not later phases can be explained by this cycle.

A common assumption in models is that phosphorus restricts the growth of tropical forests. Nitrogen needs more care in the early stages of recovery, according to data from Panama. As species composition and forest structure vary, so do nutrient constraints.

Benefits of rapid regrowth for the climate

Young tropical trees may not be able to store 470–840 million metric tonnes of carbon dioxide annually due to nitrogen scarcity.

That sum is about the same as the emissions from over 140 million gasoline-powered vehicles. Since global emissions are still high, faster regrowth in the early years is crucial.

The use of fertilizer in woods is opposed by scientists. Greenhouse gases are released and energy is used in the manufacturing of fertiliser. Rivers and oceans are also harmed by runoff. Rather, scientists recommend more intelligent forest management.

According to Batterman, "ideally, forest stewards could ensure that some of the trees in a regrowing forest are nitrogen-fixers."

Restoring woods in the vicinity of pollution

Restoring forests close to cities or farms that already have nitrogen pollution is another strategy. Before pollution enters waterways or produces toxic gases, growing trees absorb excess nitrogen.

According to Batter man, "these practices could increase how quickly these recovering forests take in carbon dioxide."

"The forests won't be able to sequester more carbon in the long run, but they can do so more quickly in the first ten years, which is what we really need right now."

Clean energy and emission reductions cannot be replaced by young tropical trees. However, as countries move away from fossil fuels, quicker forest recovery can buy valuable time.