Saturday 26th July, 2008

Rock whitebeams in Holyrood Park

By Ash

Rock whitebeam leaves; upper surface (left) and silvery lower surface (right).

Rock whitebeam (Sorbus rupicola) is a small tree endemic to north-west Europe. According to ukwildflowers.com, rock whitebeam is

Absent from the south east of England and central and Southern Ireland, the few trees which exist are scarce and slightly more frequent the further north you go.

Not so long ago I stumbled across this .pdf document which provides details of rock whitebeam and its distribution in Edinburgh’s Holyrood Park. The document, marked “Edinburgh Biodiversity Partnership”, is over eight years old now so I will take the liberty of plagiarising big chunks of its content:

Rock whitebeam is found on steep rocky slopes or cliffs of basic rock at low to moderate altitude. It often grows in inaccessible situations... Mature individuals readily produce flowers and fruit, the latter probably being distributed by birds in order to regenerate the species in new locations.

Rock whitebeam is apomictic, which means that it can produce viable seed without the need for sexual exchange as well as preventing the possibility of any crossing with other related species. Populations are often very small and it is quite common for single trees to exist in isolation.

Regarding Holyrood Park’s population, the document has this to say:

[Rock whitebeam] has probably never been common in Edinburgh, with numbers particularly declining since the turn of the century. Rock Whitebeam has been known from Holyrood Park since 1813…

Only one large ‘mother tree’ and one or two very young saplings remain on Dunsapie Crag with a further two or three on the rock face of Raven’s Crag west of Duddingston Loch. However, it is possible that there are still trees hidden away in one of its former sites or elsewhere.

and:

Fire damage, both accidental and as a management tool, has probably had the single largest impact on the Edinburgh population of rock whitebeam. Rabbits are keen to eat the bark of the closely related rowan, and so it is likely that rock whitebeam has also been targeted. This may be the main reason for its occurence [sic] only in inaccessible places.

also:

Although fire is no longer used as a management tool in Holyrood Park there is always the possibility of accidental fires being started. Indeed, the prevelance [sic] of fire may increase as gorse, which is highly flammable, is likely to extend its range as a consequence of the recent removal of grazing cattle and sheep from the Park and the fact that it is no longer collected for winter fodder.

Hearing that there were rare trees within a short distance of our flat, last Monday (July 21) I went on a mission with my flatemate and fellow ecologist to Dunsapie Crag to see a rock whitebeam up close. We were in luck: there were three of them at the Crag. There was a big one high up the rocky Crag face, which I presume to be the aforementioned ‘mother tree’; a smaller one beneath the ‘mother’ but still on the face; and a smaller one still growing in the grass beneath the Crag.

The ‘mother tree’.

The youngest rock whitebeam with Dunsapie Loch in the background. The leaves in the photos at the beginning of this post belong to this tree.

All three Dunsapie Crag rock whitebeams.

We didn’t go and have a look for the rock whitebeams that the “Edinburgh Biodiversity Partnership” said were on the face of Raven’s Crag, but on the way back around the west side of Arthur’s Seat we spied a couple of young specimens just below the path.

Two more Holyrood Park rock whitebeams - new discoveries?

And coming in a future post… more whitebeam wonders at Edinburgh’s Botanic Gardens.

Book announcement: Between Earth and Sky: Our Intimate Connections to Trees, authored by Nalini M. Nadkarni, is a recent release by the University of California Press. Check it out here. UC Press have generously offered to send me a copy to review, so keep your eyes peeled for treeblog’s inaugural book review!

tags: Edinburgh + info + photos + whitebeam

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