We saw that oak trees came into leaf about a month earlier than usual this year because of unseasonably high temperatures. The ash, on the other hand, came into leaf much later as. I believe, it is photoperiod-driven rather than temperature. This gives an explanation for the old weather lore based on long observation 'oak before ash, in for a splash, ash before oak, in for a soak.' Tell that to the people of Gloucester and Worcester!!

Presumably, it is the oak's leafing out that varies around the more regular ash, due to its temperature response.
At the time, this led me to ask the question whether carbon capture by early leafing deciduous trees might help mitigate against CO2-induced climate warming . Any such effect would require an extended period of active photosynthesis i.e. a normal time of senescence and leaf fall.

My current question is- ' is this going to happen or will autumn come early for the oaks. Do deciduous trees have a fairly fixed period of active growth or is is flexible? I have just returned south from a trip to Northumberland where senescence is notably more advanced. Chestnuts are most advanced but sycamore and oak are well on the turn. The ash stands out as being still green.

I'll carry on my observations in Wales through the autumn. Any thoughts or observations. please?


Deciduous trees tend to drop their leaves at around the same time each year - I believe that this is a photoperiodic response and not likely to be affected by climate change. I was out in a forest reserve in Nottinghamshire yesterday and the leaves are just beginning to turn here too.

As for absorbing more carbon, you have to ask where the carbon actually goes. The only way for trees to lock up carbon is for it to go into woody tissues - trunks and branches - and stay there. In fact, only a fraction of the annual photosynthetic production does this. Any carbon that goes into leaves, flowers or fruits will only decay and return to the atmosphere at the end of the year. This causes an annual carbon cycle, with the global atmospheric concentrations rising and falling, driven by the larger vegetated land masses in the northern hemisphere.

There is some circumstantial evidence that carbon may be 'fertilising' extra woody growth in forests, but more recent evidence has shown that tree growth rates in tropical forests are in fact declining. Other studies suggest that the rate of turnover in forests, that is, the cycle of tree death and regrowth, is increasing. This would mean that even carbon stored in wood will fall and be released more quickly. There is a lot of controversy - as a generalisation, atmospheric scientists tend to believe that trees are taking up more carbon, while most foresters disagree. The likely reason for the confusion is that any forest will reach a maximum carbon storage potential when it can hold no more. Even if some forests have taken up more carbon, they will not do so indefinitely.

On balance, I think that any extra carbon uptake by early leafing trees is likely to be of negligible importance, and will not mitigate against climate change.