CO2 ‘delays autumnal leaf fall’

Increasing levels of carbon dioxide in the atmosphere is extending trees’ growing season, say scientists.

However, as reported in the blog Science Centric, the news had been welcomed by the forestry sector.

Writing in the journal Global Change Biology, Professor David Karnosky from Michigan Technological University, US, led an international team of researchers that suggested that the lengthening of the growing season would make forests more productive because they would absorb more carbon before shedding their leaves.

The researchers from the US and Europe collected and analysed two years’ data of what they called “autumnal senescence“, or the changing of colours and falling of leaves, which was triggered by declining photosynthesis.

They found that the forests on both continents stayed greener longer as CO2 levels rose, independent of temperature changes.

However, they added that the experiments were too brief to indicate how mature forests may be impacted over time. Professor Karnosky also said that other factors, such as increasing levels of low-level ozone, could limit the beneficial effects of elevated carbon dioxide levels.

The blog said the research was another example of an expanding body of scientific evidence that global climate change was affecting the world’s forests.

Science Centric added that the effects of increased atmospheric CO2 on tree growth had been documented before, however, this report had challenged the prevailing view among scientists that other factors, such as temperature and length of day, were the primary elements influencing autumnal senescence.

Source: Science Centric blog

Date: 16/08/2008

Source: Michigan Technological University

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