This year, there’s a twittering about a glut of acorns. Last year, I seemed to be constantly treading beechnuts underfoot; this year, acorns are similarly abundant. Squirrels and other rodents have more acorns than they can possibly nibble or store for winter. Wily trees rely on the animals’ forgetfulness to get their seeds dispersed. Nature’s design is at work. A bumper crop stands better odds of growing into mighty oaks one day. This glut is called a mast year.
Research suggests that mast years happen every 5 to 10 years. What triggers a mast year is still not fully understood. A reaction to the weather? Certainly, 2020 was an extraordinary year with heavy rain early on, followed by high temperatures and drought. Do trees communicate surreptitiously to synchronise their seed production? Does the response predict a harsh winter?
Climate Change Research
A Swedish study on Beech, Fagus sylvatica, discovered that the interval between mast years is decreasing and related it to climate change. The average interval was 4-6 years from the end of the 17th century until the 1960s, while it has reduced to 2.5 years over the past 30 years. Mast years often follow years in which summer temperatures are higher than the recorded average. The researchers also observed that an increase in atmospheric nitrogen deposition might play a role.
Energy-draining Seed Production
A mast year requires a tree to use an enormous amount of energy in seed production. It is not an every year occurrence as a result. Increased mast frequency places a greater strain on Oak and Beech trees.
Nature at Work
The past winter’s extreme storms toppled some of our local, mighty Oaks. It was heartbreaking to see them uprooted at first. Then, I noticed that the springtime woodland flora was taking advantage of the breach in the canopy. The ancient woodland indicator, Adoxa moschatellina (Townhall Clock), enjoyed a chance to spread out further than the previous year. Storm Ellen recently took out a huge branch from a local Beech. Beech is notorious for closing the canopy on woodland floor vegetation. Fallen trees and branches end up providing homes for all sorts of woodland invertebrates and fungi.
One of my favourite English proverbs has always been:
Mighty oaks from tiny acorns grow.
This year, Oaks are trying to plant a lot of seeds. They are promoting natural regeneration. Nature has a better recovery plan for climate change than any Man can put together.
Gallery of Images
References and Further Reading
- Armitage, Charlotte (2017): What is a ‘mast year’ and why is it making autumn bigger than ever?Woodland Trust Blog 31 October 2017.
- Brown, Paul (2017): Mystery of the mast years. Weatherwatch. Trees and forests. The Guardian. 4 July 2017.
- Moran, Emily (2019): Tons of acorns? It must be a mast year. The Conversation. 15 November 2019.
- Övergaard, R. & Gemmel, P. & Karlsson, M. (2007): Effects of weather conditions on mast year frequency in beech (Fagus sylvatica L.) in Sweden. Forestry: An International Journal of Forest Research Volume 5, December 2007, pp. 555-565.