Wessex Silvicultural Group: Field Meeting Notes

2017 Study ‘Regeneration: Renewal and Creation’

Meeting 4: Woodland Creation and Ongoing Challenges (Broomhill Estate, September 28th 2017)

Chris Sorensen

Will Woodlands is a charitable trust set up in the early 1990’s with the express intention of increasing woodland cover by purchasing land and undertaking afforestation. The Trust now owns 4 estates covering approximately 3000 acres. 2000 of those have now been planted, mainly with native species.

First stop.

This area was planted in phase 4 (2005-06). There was a distinct height gradient as you went up the hill with the trees at the top experiencing much slower growth than those nearer the bottom. The site is very exposed but it was felt that not all the failures/slow growth was down to that alone. Salt from the A30 and coastal gales will not help.

There was a lot of discussion on the soil as well – how much free lime is there and what is the pH? If it is above pH7 it will be very problematic. Planting on areas with more clay has shown much better growth. The site is ex-arable and had been ploughed for at least 50 years prior to planting. One of the main problems this has caused is a lack of organic matter. Nutrient leaching is thus likely to be high.

A nurse crop of grey alder (1 row in 7) had been tried but had to be removed due to an outbreak of Phytophthora siskiyouensis on alder elsewhere on the site. And the “jury was out” as to whether it had really worked, with self-seeded goat willow appearing to do a much better job as a nurse.

There was a very quick succession from arable to planted woodland with grass established to keep down weeds. Machine planting had been tried in Phase 1 but the site in general is too flinty for the machine to work so this was abandoned. Pit planting was then tried but the pits tended to waterlog in wet weather and trees suffered from “socketing”. Notch planting is now the preferred method. No fertiliser or mycorrhizae were used (although orchids and new fungi are appearing each successive year). Initial planting was contour based for landscape purposes but is now more East/West because of the wind problems on site.

The whole site is deer and rabbit fenced! However it is not deer proof – car crashes from the A30 breaching the fence are a big problem along with PROW gates being left open, vandalism and a likelihood on such a large-scale that some deer were fenced in during the initial fencing operation.

Planting in terms of species has thus far been random but for the next phase it will be more “grouped” to allow for preferential thinning of timber species. The random mix which included a lot of shrub-type species had served a purpose in terms of establishing woodland cover (the main objective after all) but has done few favours in creating a timber producing high forest. However it was pointed out that on a similar site planted in the 19C at Abbotsbury Estate, initial stocking densities were up to 10,000 sph. Obviously this allowed for a tremendous amount of failures and removal of poor form/growth trees when thinning which has created the current high quality high forest.

However, in general it was felt that at stop 1 creating a “shrubby” shelter belt protecting the site from the A30 and salt-laden coastal gales wasn’t actually a bad outcome anyway. And the objectives of the founder were simply to improve woodland cover which undoubtedly this has done.

Stop Two.

This was a much older site – planted in phase 2 (1997-98). Much of the site had closed canopy. A strip in the valley bottom (mainly alder) had been felled due to disease and restocked with native BL’s in tubes in between existing hazel that was coppiced.

The growth rates (2 years since the felling) were much better than at stop 1. The planted stock was already out of the tops of the tubes in places and the coppice hazel regrowth was 6-8’ high. Discussion centred around reasons for this: was it because the site was already showing characteristics of a “woodland” site for tree growth (mycorrhizae, increased organic matter etc.) as opposed to an ex-arable field? The tubes obviously helped with an improved microclimate and protected individual trees from deer browsing but was there something else as well? It was also further into the site so slightly less exposed.

Elsewhere ash had been felled due to Chalara. This, it was stated, had been of very good quality (there was some very large, old, ex-hedgerow ash on site showing that, pre-Chalara; it was obviously an optimal species to plant). The ash was re-coppicing and areas like the alder site and the ash plantings were now almost turning into a coppice with standards system by accident.

Further discussion centred on what to do with the coppice regrowth. Leave the ash as sacrificial deer browsing material perhaps? When should the hazel be coppiced again before it starts shading out the planted stock and what market is there for it? Wattles, hurdles etc.? Clean hazel sticks are purchased for £2/stick for the walking stick market.

Stop 2 also had some of the original conifer plantings: CP/SP in a 50:50 mix and pure hybrid larch. These crops had already received an early thin/brashing due to concerns over fungal diseases (Dothistroma, P. ramorum etc.). It was hoped these operations would allow more light and air into the crop so limiting fungal growth. However the understorey had responded to the thinning/brashing with increased growth itself and so it was felt it was still very humid within the crop. Also, this part of Dorset is actually very prone to sea fog and has a relatively high rainfall of 1000-1200mm.

The site highlighted some of the problems that an early lack of focus on commercial elements can bring – both species choice (mainly in the broadleaf element - alder) and lack of roading leading to excessive extraction distance, had caused problems meaning that all operations had been at cost so far.

Discussion centred around use of feller-bunchers for broadleaf sites like this and first thinnings in general with all produce being chipped on site. But again, roading is a key issue. It was stated that chip lorries need to be as close as possible to the crop and are very much “road-going” vehicles which will need very good “Cat 1” forest road infrastructure.

Some discussion on maintenance of new crops/restocks. In addition to spot spraying, inter-row mowing is carried out. Does it work? It looks good from a visual perspective. Voles had been a real problem and it was felt that the mowing, along with the provision of raptor posts had helped reduce numbers.

Some discussion on potential Nitrogen overload being as the site is ex-arable. It was suggested that it might increase early growth but that it leads to forking of ash as the growth is too unlimited by a lack of N. However, how much N is left on site with increased soil leaching (due to lack of organic matter) was debated with some observers feeling that a year after abandoning arable there is virtually no excess N left. Squirrels reared their inevitable ugly heads on what is a predominantly hardwood site. They are trapped regularly with around 70 a year being caught. There is no pheasant shoot so there is no winter supply of grain for them but the rule of thumb seems to be that if you are experiencing damage then you have too many. The theory was that you should aim to actually keep the population below a minimum acceptable standard so that in a mild winter you could prevent a population explosion. Some suggestions were that an optimal level of squirrels was 1/acre and to investigate the possibility of “paying to shoot” – particularly as the site has such little public access. Pine marten were mentioned also. The site is very big in woodland terms (for Southern England anyway) which is a plus but is not in a particularly wooded landscape which is a negative. Therefore could an internal population with limited opportunities for inward/outward migration be sustained? Evidence from the Republic of Ireland would suggest a very tentative “yes” but the woodland would probably have to be more mature than it currently is. It probably is not an important enough candidate for a reintroduction programme at the moment (due to woodland size, immaturity and a lack of any remnant marten population in the vicinity) but 20 years from now….who knows. For more information on martens, probably the best place to start is with the Vincent Wildlife Trust (www.vwt.org.uk or for a lot of marten research their Irish partner website www.mammals-in-ireland.ie ). Whilst having no silvicultural remit as such their desire to reintroduce locally extinct UK mammals such as martens and red squirrels requires/leads to the reduction of greys. This has beneficial side effects for quality timber production. However, one note of caution was sounded in that it was pointed out that reds can also strip bark as well….

Stop Three

This was a newly purchased, adjoining arable farm of 185 acres and yet to be planted. This will be phase 8 once complete. Species are likely to include a more commercial mix with DF/WRC etc. included.

Discussions centred around why not plant directly into the stubble? It was felt that without sowing a grass sward first, the weed growth on the site would be too excessive. The grass keeps the weeds down and can be controlled more easily with inter-row mowing and kerb spot sprays.

The site will be deer fenced but not rabbit fenced this time. One interesting suggestion was to fence in any fallow which are using the site and then cull them in situ rather than trying to fence them out to begin with.

In our car on the way back the use of fixed point photography was discussed – wonderful opportunity to create a “film” of a woodland developing because of the starting material (bare arable fields) and the scale.

Also, on a related note, it was asked how much research/survey work was going on. Because of the scale, the nature of the starting material (intensive arable land), the lack of woodland in the vicinity and the “series” nature of the plantings it was felt there was real scope for some very interesting research into biodiversity on a new woodland site. Will Woodlands confirmed that bird, butterfly and flower surveys are undertaken on a regular basis and all show an increase in numbers/species.

It was also mentioned that Forest Research had produced a bulletin 34 in the 60’s on chalk downland afforestation. It might not have direct relevance to today (there was probably a much greater use of herbicide etc.) but there is no point in reinventing the wheel and may be worth a read as follow-up research.

Forest Research has recently undertaken a massive archive operation to save this bulletin and over 400 other older bulletins, booklets etc. as pdf’s. These are free to download (along with 100’s of more modern documents) from www.forestry.gov.uk/publications .

References/Further Information

Wessex Silvicultural Group: Notes from previous meetings can be found here.
Forestry Commission Bulletin 34: Chalk downland afforestion