Carbon dioxide boosts pine tree reproduction

Scientists have found that a species of pine tree thrives in the carbon dioxide-enriched air expected in the future, becoming reproductively mature earlier and producing more cones and seeds than identical trees living in today’s CO2 concentrations.

The researchers at Duke University, USA, have been investigating the effects of increasing CO2 on young loblolly pines, the most economically important forest product in the US Southeast. When dosed with extra CO2, immature pines, previously not reproductively active, became twice as likely to produce cones as untreated pines, and also produced three times as many cones per tree and more than twice as many seeds, researchers said.

The study is intended to evaluate how forests will respond to the higher CO2 atmosphere expected by the mid-21st Century, involving six 90 foot diameter circular plots of entire forest ecosystems, including the 19 year old loblollies. Three of the plots are bathed in one and a half times today’s levels of atmospheric carbon dioxide, and results from them are compared with three matching plots receiving no extra CO2.

The scientists’ data also showed that CO2-enriched trees allocate a larger proportion of carbon into cone production, and there are also preliminary suggestions that pollen production will increase in a similar manner to the cones.

Whether this effect gives the loblolly pines a competitive advantage over other tree species in a future higher CO2 world remains to be seen, say the scientists. Under current natural conditions loblolly pines are replaced by hardwoods after 50 to 100 years.

“If the seed production of everything was boosted, it’s a tough question how that would play out,” said James Clark, Duke Botany Professor, who studies seed production and species competition in forests. “If just a few species really scored big because of high CO2, the answer seems more straightforward. Those are going to win more often and the others are going to lose more often.”

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