Now as Spring gathers speed we have been paying close attention to buds bursting and the first leaves being visible. There is a definite green haze over lots of trees now and we’re yet to be joined by some. It all makes for some exciting news!
We are based in the Borders and have instructors scattered over the country, so it’s nice to hear what everyone’s local trees are doing. We have seen birch, willow, hawthorn, elder and larch all leafing up! Beech is slowly starting to show signs and ash is still biding its time.
Recording seasonal changes is not just fun but it’s also very important for understanding how trees are responding to a changing climate and to predict how well they may adapt (or not). The Woodland Trust hosts the UK’s largest phenology database Nature’s Calendar, a citizen science project recording the seasons unfold.
WHAT IS PHENOLOGY?
Phenology is the study of the seasonal changes in plants and animals from year to year, such as flowering of plants, emergence of insects and the migration of birds, especially their timing and relationship with weather and climate.
We have been watching the trees closely and enjoying the daily changes in our local trees. Budburst, first leaf and first flower are all things to look out for at the moment. We can see what these stages look like in the 11 tree species monitored here: Woodland Trust, What We Record.
WHY DOES IT HAPPEN?
We associate budburst with spring, but what is it that actually stimulates the trees to open their buds and unfurl their leaves?
There are two main factors at play, temperature, and light. Water availability is also important. With our warming climate budburst has been getting earlier. Nature’s Calendar 2019 report found last year to be an early year in terms of spring changes, with all 11 tree species having an average budburst date earlier than the 2001 benchmark year. Elder budburst being almost a whole month earlier! And the early budburst pattern was followed by an early first leaf for all 11 species.
Interestingly light pollution has been associated with earlier tree budburst across the UK. It was found that budburst occurs up to 7.5 days earlier in brighter areas! So, if you live in an area with lots of street lighting, you may be seeing leaves out earlier than others!
WHY IS IT IMPORTANT?
As mentioned earlier this information is important to understand how tree species will respond to our changing climate and what that could mean for the composition of our woodlands, the resulting carbon storage, habitat and food source and the effect on wildlife.
Nothing stands alone, for example the young leaves of birch are an important food source for caterpillars which in turn, are an important food source for breeding blue tits (see Highlights of Spring 2019 Report). The changing timing of bud burst and first leaf could alter the time that these food sources are available and could have a negative impact on breeding birds.
Ash leaves also play an important role as food plant for the caterpillars of many species of moth. Unfortunately, in addition to climate change, ash is also threatened by ash dieback caused by the fungus Hymenoscyphus fraxineus. Ash dieback causes the death and wilting of leaves and will kill up to 95% of ash trees across the UK. The knock-on effects for the caterpillars, and other species which depend on ash, could be catastrophic.
“Trees are just beautifully adapted … If you look at them structurally… they are more exquisitely and strongly and efficiently built than any of our buildings”
Scott Aker, Head of Horticulture and Education at the US National Arboretum
OUR LOCAL TREES
We have been enjoying the gift of time and have been using it to observe and be more aware of our local surroundings – it turns out there is just so much too see! Paying close attention to the coming of Spring helps to keep us happy and healthy.
Here are a few snaps of trees local to us and we would love to hear how your trees are! Whether it’s a tree you can see from your window, or one in your garden, what is it doing? How is it looking? And who is visiting it?
David Knott