Woodland management: Return to Ruislip Woods

However, there is something even more enduring about this part of West London. That is Ruislip Woods, a semi-natural ancient woodland of 294 ha (726 acres) and since 1947 a Site of Special Scientific Interest (SSSI).

Ruislip Woods comprises Bayhurst Wood, Copse Wood, Mad Bess Wood and Park Wood (the single largest area of woodland in London). Ruislip Woods contains substantial areas of native English oak standards over hornbeam, the latter rigorously coppiced for over 500 years until the 1930s.

Fifty years later, in 1982, a 30-year-old arborist called Colin Chambers arrived to take up the position of trees and woodland officer at London Borough of Hillingdon and with it responsibility for the management of this huge and intrinsically valuable woodland. However, first on the agenda was restoration because half a century is a very long time to leave hornbeam coppice to its own devices. Colin was presented with extensive stands of grossly over-stood hornbeam coppice and the job of not only organising its cutting, but finding a home or a use for the mountain of timber thus created.

Grey squirrel damage to hornbeam but kept to a minimum during the 1960s to 1980s by well-organised shoots carried out once a year.

Fortunately, he was given a detailed 20-year management plan, the driving forces of which were Professor David Hawksworth and Dr Colin Bowlt, both eminent in their respective fields and with knowledge of Ruislip Woods second to none. The essence of the plan was respect for the traditional, coppice status in place when Ruislip Woods was working woodland and supplying wood fuel for bakers’ ovens and metal furnaces in London. The council also set up a consultative group known as Ruislip Woods Management Advisory Group, of which Professor Hawksworth and Dr Bowlt were key members.

So, on a brilliant day in early July, I accompanied Colin to Ruislip Woods, which he had last visited 20 years earlier. However, I would soon discover that Colin still knew this vast area like the back of his hand and an indication of the enthusiasm and diligence with which he had clearly carried out his job all those years ago.

Oak and hornbeam are not the only native and naturalised tree species in Ruislip Woods, though they do form an integrated core and are therefore the centrepiece of this article.

First port of call was Bayhurst Wood, to see a uniquely ancient hornbeam tree which set the scene for what turned out to be one of the most enlightening visits I have ever made into ancient woodland.

In the hedge alongside a track leading into Bayhurst Wood was a seriously old hornbeam, once a coppice stool, that had subsequently grown three hefty stems. One was pollarded and the other two laid to become part of the hedge. We would later see many coppice stems that had been laid by Colin and his team to keep horseriders on the bridle paths and out of the woodland. The majority were still largely in place and intact more than three decades later.

When Ruislip Woods was working woodland, 20 standard oaks per acre was the general rule of thumb.

HORNBEAM COPPICE COMPROMISE

But now it was time to see how hornbeam stools coppiced in 1982 had fared over the following 37 years. We were in Mad Bess Wood, claimed to be called so after a lady who had kept pigs there centuries before.

“I soon discovered how the traditional centuries-old way of cutting in Ruislip Woods was not classic coppicing at ground level, but neither was it pollarding,” said Colin. Last cut back in the 1930s, it had taken place not at ground level but 1–2 ft from the ground to leave a short stump from which subsequent sprouting had occurred. Colin surmised this was a convenient height for billhook use.

“We were now faced with three to five massive over-stood stems per stool, representing 50 years of growth. To begin with, we did not revert to the traditional system but instead selected out and saved the strongest and straightest pole and cut the remainder at the previous coppice cut,” said Colin. Nearly four decades later I could see the net effect of this singling approach as conversion to high forest.

Colin agreed this was no bad thing. Hornbeam has invariably been treated as a coppiced understory tree rather than a standard, upper-storey  tree. As such, high hornbeam forest is a rarity in England. I have only come across it once before, in Hadley Wood in North London and the last authentic remnant of Enfield Chase woodland, and inside which coppicing or pollarding of any standard tree had apparently not been practised since the Chase was enclosed in 1777.

I asked Colin why he had opted for the singling approach. “Caution, I suppose, and initially with regard to public reaction,” he said, adding how the general public don’t often appreciate how woodland requires management for long-term sustainability. “They initially regarded traditional all-cut coppicing as destructive in the same way as clear-felling of standard trees. We received a lot of heartfelt criticism when we started coppicing other compartments in the traditional way by cutting all stems on the stool. It wasn’t until several years later that we could then show concerned members of the public how areas were regrowing. In the main, local residents became more accepting.

“But our main concern was for the old stools which may not have recovered if we had cut every pole down to the short stump. And especially since we were then using chainsaws rather than billhooks. In the event, there was some rotting but sometimes the stools recovered by sending up shoots from ground level. Looking back, we could probably have gone right down to ground level in the first place.

“However, in the end, our main aim became maintenance of the historical interest even if that did involve a degree of stool dieback, but perhaps no bad thing given that deadwood promotes and generates biodiversity. Furthermore, these very old, short-stumped (legged) stools had developed bollings (swollen area of a tree following repeated cutting) with all their intrinsic attractiveness. On a positive practical level, cutting relatively high at 1–2 ft meant there was no danger of hitting stones in the soil which might damage the saw chain. All that said, the reason for readopting and resuming the traditional coppicing pattern was to conform to and maintain the historical and nature conservation interest generated when this was worked woodland.”

A testimony to the tenacity of hornbeam. Coppice poles over-stood for half a century since the 1930s were cut back by Colin’s team in the 1980s to the short stump. Colin inspects the growth achieved since then.

HORNBEAM HARVESTING

“Several years into the job and the problem was not so much the cutting, carried out by local contractors, but the sheer size of the harvest, because nobody had thought about what to do with the mountain of wood coming off these hornbeam stools,” said Colin. “Half a century of growth over such a large area produces an unimaginable amount of wood – many tonnes per compartment.

“We considered firewood, but this was a London suburb and in those days there was simply not the market, making the whole concept essentially unviable. We then considered charcoal and engaged an experienced charcoal burner. However, he had never carried a 100 per cent hornbeam burn and it transpired that hornbeam wood takes twice as long to convert to charcoal than wood from other native trees. Indeed he would keep putting his spade over the burner vents to show us how moisture was still coming off the charcoal burn long after other woods would be finished. Apart from this there were practical and marketing difficulties in charcoal.

“As budgets were cash limited through the 1980s we also had to wrestle with the cost of coppicing, while the sheer size of the task meant we were running behind the Ruislip Woods Management Plan with increasing pressure on us to keep up. Burning the brushwood and stacking over-stood coppice wood in piles was also unsatisfactory. The heat sterilised large areas of ground and damaged stools while kids threw the logs around and used them to make dens and fires with all manner of safety implications.

“Finally we took the lead from North Hertfordshire District Council (which had been faced with similar problems) and engaged a pulp mill that supplied its own cutting gangs. These guys came down from the Welsh borders armed with chainsaws, tractors and forwarders to cut, load and extract the wood to roadside where they arranged for lorry transportation to the mill. As I recall, the wood value at mill gate was £26.50/t comprising £22.50/t cost of cutting, extraction and transportation leaving £4/t which they paid to Hillingdon Borough. The pulp wood operation got the programme back on course.

“However, because these guys were paid strictly by the tonne, this wood-quarrying approach of cutting and extraction to roadside was not always a pretty sight and they certainly weren’t there to admire the woodland. Where tree lean permitted, a single swift back cut was often employed for felling.”

Colin told Forestry Journal how on arrival at Ruislip those pulp mill cutters who had attended in previous years would get in touch to try to get hold of the maps so they could claim compartments that would yield top tonnage. They were averse to compartments with poorer regrowth – the more over-stood the coppice and the bigger and heavier the poles the better, said Colin. All logs had to be cut strictly to 2.2 m length and straight because a maximum number had to fit on the forwarder and then the lorry for maximum earnings.

This is the nature, size and weight of over-stood coppice that the pulp mill gangs would have died for, says Colin Chambers. (Image: FJ)

HEARTS OF OAK

So far we had only talked about hornbeam, but there was a lot of good-looking and well-structured standard oak in this woodland, mostly Quercus robur  (pedunculate oak) but transitioning into Quercus petraea (sessile oak) as we moved away from London clay and up the slopes to more sandy soil inside Park Wood.

“When this was working woodland 20 standard oak trees per acre was the rule of thumb,” said Colin. “Under the strict coppicing rotation, oak standards were able to keep their lower limbs, but when coppicing was abandoned in the 1930s, hornbeam grew up and shaded out the lower limbs. So when coppicing was resumed in 1982, we began to expose these dead lower branches on oak trees,” said Colin.

The management group had been concerned about oak regeneration, or rather the lack of it, especially for the predominant Quercus robur. Colin commissioned a survey through the London Wildlife Trust under the direction of Dr Meg Game. In the chosen transects there was a distinct lack of regeneration, but perversely not for sessile oak which would regenerate across the woodland floor as carpets of seedlings. This specific problem for Quercus robur was due to most seedlings regenerating under or very close to the existing oak canopy with subsequent damage from defoliating caterpillars of the green oak tortrix moth coming down from the overhanging foliage, Colin said. The ability of Quercus petraea regen having largely escaped insect predation was considered due to the trees’ spring leaf flush being out of sync with caterpillar emergence and development.

This discovery resulted in a change of management. The oak population had traditionally been managed by felling poor oaks, apparently referred to by some old-timers as maul oaks, and leaving better-formed, evenly spaced trees. This had allowed remaining canopies to spread out, increasing canopy cover, accentuating shade throughout the compartment and aggravating the insect pest situation for seedling oaks. Instead, Colin started to leave clusters of oak irrespective of their form and in consequence increasing light-filled gaps between them, where oak regeneration would hopefully be more successful away from the attentions of the descending caterpillars.

Cutting over-stood hornbeam coppice according to tonnage has always been hard work. (Image: FJ)

QUESTIONS POSED AND ANSWERED

Colin’s memory of what was inside this vast woodland complex and what happened all those years ago is quite remarkable. Inside Mad Bess Wood I was shown some absolutely charming header streams of the River Pinn, displaying the most exquisite natural meanderings.

Alongside was regenerated hornbeam with horrendous levels of bark stripping caused by grey squirrels. Colin recalls how in the 1960s to 1980s, the complex was closed to the public wood by wood, once per year for 14 days to allow a highly organised team of guns to undertake grey squirrel control. The guns carried out control on a voluntary basis and were unpaid. At one point squirrel tails were sold to a fishing fly manufacturer, and provided the team did not exceed 1.5 cartridges per squirrel then ammunition costs were covered. During the 1980s, the council was politically split and after endless debate squirrel control was abandoned and never resumed.

On the train home from days out like this I always like to ask myself questions and try to come up with answers to things I have seen and heard. The first relates to something Colin said about hornbeam being called Hertfordshire Gold. Indeed, hornbeam coppice was prevalent in both Hertfordshire and Essex and also the old county of Middlesex to which Hillingdon and Ruislip woods belonged prior to the formation of Greater London Council on 1 April 1965.

Hornbeam was one of the last broadleaf tree species to cross the land bridge between Britain and Europe and ended up with a natural distribution apparently confined to south-eastern England. So why did hornbeam become such an important source of woodfuel from these three counties north of the River Thames and for the City of London? Was it simply on hand or was it purposely planted due to an obvious need? My guess is a bit of both.

The second question relates to the age of oaks in Ruislip Wood. Like a lot of other ancient woodlands in and around London, there were innumerable trees in the 150- to 200-year age range, but nothing I saw was much above this. The reason could be two-fold. Even though woodland has been on these sites for millennia rather than centuries, a preponderance of clear-felling in the late 18th century means that even for long-lived species like English oak it is difficult to find trees much above 200 years of age. In addition, standard oaks in these old working woodlands of many centuries ago would have been purposely grown to relatively small size due to the limitations of the tools and equipment available for felling, hauling and sawing.

Seriously old hornbeam last coppiced way back in time to yield three over-stood coppice poles – one was subsequently pollarded and the other two laid. The pollard now displays all the pleasing characteristics of a bolling.

Footnote:

In 1992, George Peterken (Nature Conservancy Council) described Ruislip Wood as “becoming one of the best managed woodlands in England”. In 1997, Natural England (now English Nature) made Ruislip Woods a National Nature Reserve.