Coun­trycall

Evergreen - - Contents - Dale le Vack

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 . . .

( con­tin­ued)

. . . and un­der­taken 40 feet up at the top of a tree.

Tor takes a break on an ap­pro­pri­ate piece of fur­ni­ture. ( con­tin­ued)

JAMES AUSTRUM

Sun­light fil­ters through the beech trees.

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