Back in 2018 the Old Man speculated on what impact Ash Dieback would have on Wytham Woods, the disease having been confirmed as present only in 2017. There was still an unspoken hope that its impact would not be as great as feared. Nonetheless a series of project were put in place to explore what the effects might be. These included ring-barking ash in places to try to mimic the disease, just in case too few trees got infected before the project funding ended. We need not have worried! Four years on, signs of dieback can be found on ash more-or-less throughout the Woods.
Since 2018 I have been looking at how the disease has affected the 164 Dawkins permanent vegetation plots. 22 of these were classed as having ‘high ash’ cover in 2018 and have been looked at annually, along with, each year, a different quarter of the ‘low ash’ cover plots. A simple subjective assessment was made of the overall canopy cover and separately that of each of the major tree species. An estimate was also made of the level of canopy dieback in the plot or around it.
There has been, as expected a decline in the estimated cover of ash in ‘high ash’ plots which is also reflected in the overall canopy cover estimate. There is no decline in overall canopy cover in the low ash plots and the ash decline appears less marked, but this is partly because some of the low ash plots did not contain any ash to start with!
Completely dead trees, so far, are mainly small (less than 15 cm) canopy sub-dominants, which would be expected to be most vulnerable. However it is likely that tree deaths will increase; trees with 20-30 % canopy loss are not uncommon and the trajectories of for canopy dieback look similar in both high and low ash areas. Most of the ash in Wytham is quite young (less than 80 years) but some of the large old trees show substantial dieback as well.
Ash seedlings and small saplings up to about 30 cm remain abundant and generally look healthy. However, most of the promising clumps of taller ash saplings that had grown up after the deer numbers have died off.
The main immediate ground flora response expected was an increase in bramble cover. This does seem to be happening, although bramble had been on the rise anyway over the last decade, so we can’t be sure just how much is a response to the disease, as opposed to recovery from past higher deer browsing. A full re-recording of plots in 2023/24 should help to clarify this
Much of the woodland is minimum intervention. For safety reasons, it has been necessary to fell more ash alongside the major roads and tracks through the Woods than would otherwise be the case; and working in the woods in high winds is more restricted. Even on still days I heard more sounds of branches dropping during this year’s recording than in the past, though fortunately, none close to me. It will be interesting to follow further the response of the woodland system to this major disturbance event.