A SURVEY on Exmoor is celebrating its tenth year – and helping to prove that the first day of spring is May 1.

Since 2006 the Exmoor National Park Authority has been carrying out an annual phenology (the study of seasonal natural phenomena) survey across Exmoor, looking at when trees come into leaf.

The aim of the study is to see if there is any significant long-term change in the timing of bud burst, and if these can be linked to recorded changes in climate, with any short term effects also seen.

A group of dedicated volunteers observe the same 90 trees every spring – 30 each of woodland oaks, beech and hedgerow beech, which are spread over the central third of the National Park across five woodland sites and ten hedgerows.

The trees were selected to give as broad a range of conditions as possible regarding altitude and north or south facing position.

Surveyors visit the trees at least once a week from the start of April, recording when the first bud bursts and when the first leaf is fully opened.

While it is too early to extract any significant scientific results, the survey showed the ten-year average for trees coming into leaf was May 1 – boosting the belief that it really is the first day of spring.

It also showed that, when the Met Office website showed 2011 was the warmest spring on record and 2013 the coldest spring since 1962, bud and leaf burst occurred earliest in 2011 and latest in 2013.