Coun­try di­ary: a chain­saw mas­sacre in the alder woods

The Guardian Australia - - Science - Phil Gates

On an over­cast, driz­zly af­ter­noon at Durham Wildlife Trust’s Low Barns na­ture re­serve, alder (Al­nus gluti­nosa) pro­vided the bright­est splash of colour in the land­scape.

A tree had been felled and sawn into logs. Chain­saw wounds on this species can look like a mas­sacre, be­cause soon af­ter the tim­ber is cut, it turns a lurid shade of red, al­most like blood, in stark con­trast to the bat­tle­ship-grey bark. Even­tu­ally those wounds, which briefly re­sem­ble raw meat, fade to or­ange and fi­nally to chest­nut brown.

When this re­serve was es­tab­lished half a cen­tury ago, around old gravel pits, some mois­ture-lov­ing alders were planted to help reveg­e­tate a bare, windswept site. Alder wood is one of the finest sources of char­coal, and the plan­ta­tion trees are old enough now to be cop­piced, to pro­duce bar­be­cue fuel.

There is also an im­por­tant nat­u­ral alder wood here, cre­ated by a cat­a­clysm al­most two and a half cen­turies ago, which led to the des­ig­na­tion of the re­serve as a site of spe­cial sci­en­tific in­ter­est. The Great Flood of 1771 swept through Weardale, wash­ing away bridges all the way to the coast. When the wa­ter sub­sided, the course of the River Wear had shifted half a mile south, and the old riverbed be­came what is now the re­serve’s Long Alder Wood, the finest ex­am­ple of its kind in the re­gion.

In win­ter, when it some­times floods, this tan­gle of gnarled trees has a hint of the Flor­ida Ever­glades about it, with mossy, fallen trunks sink­ing back into the ooze. Year round, there are won­der­ful op­por­tu­ni­ties to watch birds from an em­bank­ment level with the tree canopy. This af­ter­noon an ac­ro­batic flock of about 30 goldfinches bounced and chat­tered through the twigs, feed­ing on tiny seeds that fall from the woody cones.

Sadly, since the mid-1990s, an­other catas­tro­phe has be­fallen this lo­cally unique wood­land: alder dieback dis­ease has killed around half the ma­ture trees. Cop­pic­ing is lead­ing to some re­gen­er­a­tion, though in this pre­cious habi­tat dead tim­ber is al­lowed to lay where it falls, re­served for the needs of a di­verse com­mu­nity of fungi, in­ver­te­brates and wood­peck­ers, rather than back-gar­den burger-flip­pers on sum­mer evenings.

Pho­to­graph: Phil Gates

Freshly cut alder tim­ber turns bright red, be­fore fad­ing to or­ange and then brown.

Pho­to­graph: Phil Gates

Alder logs stacked ready for char­coalpro­duc­tion.

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