Tuesday 5th September 2017- By Gavin McEwan

The timing of trees’ budburst is significantly related to average temperature in March, a new citizen science-based study has found.

The collaborative study between the Met Office and Woodland Trust recorded budburst times for 11 familiar UK tree species, and forms a supplement to the Met Office’s State of the UK Climate report.

It found that a 1°C deviation from the average temperature during March was associated with later or earlier leaf budburst of between three days for alder in the south-east and six days for European Larch in the north-east.

A considerable variation in the magnitude of the temperature responses between species and regions was found, however. 

The results also confirm earlier studies revealing an overall long-term trend of earlier budburst in the UK as average spring temperatures have warmed. 

The March to April temperatures for the 2000-2016 period have been on average 1.1 °C warmer than the 1961-1990 climatological average. Last year’s cool spring bucked the trend however, with March temperatures 0.3 °C below, and April 1.5 °C below the average.

Met Office GIS analyst and lead author on the study Rachel Abernethy said:

“Although there is a tendency for budburst to occur earlier, there was a later than average budburst of most species in 2016 associated with cooler March and April temperatures in the UK.”

Woodland Trust citizen science officer Judith Garforth said:

“Citizen science is invaluable when recording data which identifies UK-wide trends over a long period of time.

“Our Nature’s Calendar volunteers have recorded literally millions of pieces of information since the year 2000 and without their support we would understand far less about the impacts of weather and climate change on wildlife in the UK.”

Dr Debbie Hemming, who leads a group studying the interactions between vegetation and climate at the Met Office Hadley Centre, said:

“Collaboration between phenology and climate experts has enabled better understanding of the sensitivity of prominent UK tree species to climate variability and climate change.

“This knowledge can be used to inform appropriate management strategies that support healthy UK trees and woodlands into the future.”

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