UK acorn crop 'being hit by climate change'

http://www.theguardian.com/environment/2015/apr/17/uk-acorn-crop-being-hit-by-climate-change

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Climate change could be affecting the quality of acorn crops from the UK’s oak trees, the Woodland Trust has said.

Research using data recorded by members of the public for the trust’s Nature’s Calendar survey of the changing seasons has found that warmer years tend to lead to less synchronised flowering of oak trees, and as a result smaller crops.

Professor Tim Sparks, from Coventry University, analysed more than 160,000 pieces of data and found that the more first flowering dates varied, the poorer the acorn crop was.

There was a 20% drop in average scores for the abundance of the acorn crop recorded in the Nature’s Calendar survey for every four days’ increase in the variation of first flowering.

With eight of the UK’s 10 warmest years on record occurring since 2002 , the trend is likely to continue in coming years, the Woodland Trust said.

Sparks said: “This is a preliminary result which requires further study, but there is a significant correlation for both species of native oak.

“Synchronised years tend to be those with a later mean flowering date, suggesting warmer years are associated with smaller acorn crops.”

Related: Climate change is disrupting flower pollination, research shows

Acorns are a primary food source for a number of species including jays, pigeons, deer and squirrels, with some of the species helping disperse the seeds, but synchronised flowering enables oak trees to spread their genes through wind-dispersed pollen.

Dr Kate Lewthwaite, Woodland Trust citizen science manager, said warmer springs which “stretch things” so flowering was less synchronised, gave oak trees less opportunity to cross-pollinate over wide areas, reducing the acorn crop.

“When you get a cooler year, the flowering dates are more synchronised or similar, which means the cross pollination opportunities are greater,” she said.

“Information added to Nature’s Calendar by the public is hugely important in helping us make sense of changes in the natural environment.

“Identifying trends like these can also help us better plan for the future, building the resilience and diversity of our precious native woodland.”

The public can help record first leafing and flowering of oak trees on Nature’s Calendar, which has information about the changing seasons in nature dating back to 1736, making it the longest biological record of its kind.