Thaindian News

Washington, March 3 (IANS) It’s been happening a lot in recent times: a warming which suggests an end to winter that even fools spring flowers and birds, followed by a sudden freeze. Some scientists say this unusual weather pattern is a fallout of global warming - and, worryingly, a new study says the ‘thaw and freeze’ syndrome is causing widespread damage to plants.

In a report in the latest issue of the journal Bio-Science, researchers from the Oak Ridge National Laboratory studied plants after a similar ‘thaw and freeze’ in eastern US last winter.

The study found that the freeze killed new leaves, shoots, flowers, and fruit of natural vegetation, caused crown dieback of trees, and led to severe damage to crops in an area encompassing Nebraska, Maryland, South Carolina, and Texas. Subsequent drought limited regrowth.

The study suggests that global warming could lead to more freeze and thaw fluctuations in future winters. This pattern is potentially dangerous for plants because many species must acclimate to cold over a sustained period.

Acclimation enables them to better withstand freezes, but unusual warmth early in the year prevents the process. A cold spring in 1996, in contrast to the 2007 event, caused little enduring damage because it was not preceded by unusual warmth.

The 2007 freeze is likely to have lasting effects on carbon balance in the region. Plants cannot re-absorb nutrients from dead tissue that would normally be remobilized within the plants during autumnal senescence, so many nutrients became less available for plants in 2008.

Wildlife is expected to have suffered harm from lack of food, and changes to plant architecture could have long-term implications.

The study has proposed that the 2007 spring freeze should not be viewed as an isolated event, but as a realistic climate-change scenario.