Leigh Woods is a 500- acre wilderness of tranquillity on the edge of Bristol overlooking Brunel’s famous suspension bridge. Tor Stanfield, area ranger for the National Trust for the past 14 years, was tasked in 2016- 17 to manage a comprehensive survey of ancient and veteran oak trees.
The majority are in Leigh Woods but she also surveyed those on other National Trust woodland sites in and around Bristol, including the Tyntesfield Estate, where beech, sweet chestnut and hybrids proliferate alongside the oak trees.
The £ 25,000 project required Tor to inspect every tree in a portfolio of 1,000 ancient and veteran trees on the various woodland sites. She worked from early morning to late afternoon five days a week last summer, completing most of the inspections and recording data by early autumn.
She’s now writing a 10- year tree management plan for the National Trust for their ancient and veteran trees in the area. She says: “Previously the different National Trust sites had individual management plans. Now we’ll have one plan covering all ancient and veteran trees.”
Ancient trees are those that are very old for their species: some over 600 years old in the case of oak trees. The veterans at Leigh Woods are around 400– 500 years old and the predominant species are sessile and pedunculate oak.
As part of the project 12 trees were cored: the resulting dendrochronology report will give a more accurate age to the trees and provide information such as when pollarding and grazing stopped in Leigh Woods.
“Ancient trees might have rot holes on the trunk or they may be hollow in the middle. They’re likely to have missing branches and lots of dead wood, which makes them a fantastic habitat for invertebrates or in layman’s terms... bugs, plus birds and even bats. Veteran trees tend to have the same features.
“My job involved laying out a work programme at each location and producing management recommendations to cover the next 10 years at which time each tree will be reviewed and work will be recommended for the following 10 years. The daily routine involved taking a photograph of every tree in the portfolio, measuring it, and looking at the work done before on and around it. Often the most important aspect is what’s happening around a tree.
“I used a software application similar to a GPS Data- Log so when I went to a tree its position was logged. Employing Tree Minder software from Pear Technology, I logged the relevant information about every tree in the database, before beginning to write the management plan. The fundamental rationale behind the management plan — as well as having a schedule of works for each tree — has been to underline the general principles of veteran tree management for the benefit of staff in National Trust properties around Bristol.”
Tor’s plan has laid out a comprehensive picture of best practice in managing veteran trees. “Even though many members of staff are involved in managing trees, they don’t usually specialise in veterans and the management of these is very different from younger specimens. Our aim is to stop the
ancient and veteran trees from failing mechanically. Reduction, however, should be avoided unless it’s absolutely necessary — in which case it should be carried out over a long period rather than quickly... to avoid dysfunction.
“The majority of the trees that fall under my jurisdiction, particularly at Leigh Woods, are lapsed oak pollards. ( Pollarding is a pruning system in which the upper branches of a tree are removed, promoting a dense head of foliage and branches. It has been common in Europe since medieval times and is practised primarily to maintain trees at a predetermined height.)
“These have decaying stems with very big branches coming off that. The threat is that the stem will split apart and collapse — resulting in the loss of the tree. So while I can recommend a programme of end weight reduction to stop trees from splitting, the remedial work has to be assessed on a tree- by- tree basis. “Some rules have to be followed but each case must be assessed individually from the standpoint of the health and vitality of the tree. Looking at the vitality of a tree we have to ask several questions. How much growth is going on? How much epicormic growth is there? Are the leaves in good condition? Are they big, healthy and a good colour? Survival is unlikely unless there’s strong vitality.
“It’s better to leave a tree alone if vitality is low because any form of cutting will cause damage. In some circumstances, of course, if you don’t do anything you’ll definitely
lose the tree — so it often amounts to a fine balancing act.”
Tor says one of the main reasons why ancient and veteran trees are so important is because of the abundance of invertebrate life that dead wood supports, much of which may be very rare and vital for the continuity of habitat. As a result, part of the overall project has involved conducting a dead- wood invertebrate study by Dr. Keith Alexander, the country’s leading expert in deadwood invertebrates.
“We knew we were likely to have a lot of very rare and nationally scarce invertebrates on our sites so we wanted to find out which species of insects etc. are associated with ancient and veteran trees.”
Dr. Alexander set up traps in the trees and returned every month to monitor the results before producing a report from his sample study. His findings included a false darkling beetle last recorded in Leigh Woods in 1865 and a soldier beetle never recorded before in Leigh Woods.
“While the main threat to pollards is structural failure, another is human activity around the trees. Are we parking on their roots for example? Root compaction causes trees to die.
“If we put a car park where there are old trees we’re very likely to lose them. Any activity that’s happening around a tree that is bad for its health should be avoided. We’ve got many very old pollards and we’re planting and creating new young ones that will develop gradually. In the meantime we need to make some middle- aged trees age more
quickly — with the aim of producing ongoing rich dead- wood habitats.
“This is the part of the management plan that deals with the ‘ veteranisation’ of some middle- aged trees to make them age more quickly. One of the ways we do this is to pollard or heavily reduce the crown of the tree and do coronet and rip cutting. Another way is by pulling branches off, perhaps using winches, to create holes and split branches.”
Half of Leigh Woods is owned by the National Trust and the other by the Forestry Commission. The southern part is remnant wood pasture grazed by cattle while the northern half is semi- natural ancient woodland.
Tor says: “Wood pasture is an open land form historically grazed and has scattered veteran trees which are often pollards. Oak and other species were cut in cycles over many centuries to produce firewood and feed for cattle. On most wood pasture sites grazing stopped in the late 19th century. Now in Leigh Woods grazing cattle have been returned.
“As a result of the absence of cattle for many decades the wood pasture has a lot of secondary woodland with younger trees competing with the veterans for light and water.
“Removing the shade by gradual halo releasing is something we’re going to be doing a lot of. Oaks in particular are a light- loving species. Shade can kill them.
“The southern half of Leigh Woods comprises areas of limestone grassland with scattered trees where the cattle graze. It’s also an important habitat for many different species of insects and interesting wild flowers.”
Tor describes Leigh Woods as a fantastic place to visit with its Iron Age fort, a scheduled ancient monument. The semi- natural ancient woodland has had trees continually since the 1600s. It’s open to the public all year and is worth a visit by both amateur and professional tree enthusiasts.
The beautiful and diverse broadleaf woodland stands on a plateau above the Avon Gorge, offering panoramic views across the city and attracts 120,000 visits a year mostly from local people.
Pathways wind through the oak, small- leaf lime and ash forest. Springtime brings an abundance of bluebells and wood anemones, while the summer months provide shady walks.
The red and golden hues of autumn, combined with an interesting array of fungi, are particularly beautiful. The oak pollards are interspersed with areas of flower- rich limestone grassland around old stone quarries. Rockrose, Bristol rock- cress and black knapweed are all native to this area. It is indeed a place of poetic beauty.
Tor — with an inquisitive friend — in the woods.
Work that is needed is assessed on the ground . . .
. . . and undertaken 40 feet up at the top of a tree.
Tor takes a break on an appropriate piece of furniture. ( continued)
Sunlight filters through the beech trees.