treeblog | tagged: Edinburgh

Inflorescence on a common lime a.k.a. European linden (Tilia x europaea). The common lime is a hybrid of the small-leaved lime (Tilia cordata) and the large-leaved lime (Tilia platyphyllos).

Two eucalypts in front of one of the glasshouses: another cider gum on the right, and in the background a ribbon gum a.k.a. manna gum (Eucalyptus viminalis).

Cider gum foliage and seed pods. These are the ‘mature form’ leaves, as opposed to the ‘juvenile form’ leaves currently seen on treeblog’s own cider gums.

A grove of six giant sequoias a.k.a. Sierra redwood (Sequoiadendron giganteum). The largest tree in the world, General Sherman, is a giant sequoia.

This sweet chestnut (Castanea sativa) tree has a massive trunk, which splits into three huge boughs.

Looking up one of the huge boughs. I saw three different sweet chestnuts in the Garden and all were of massive girth. I bet they are easily some of the biggest trees in the collection.

Male sweet chestnut catkins in full bloom. The bright green spiny female parts will develop into the distinctive spiky cupules which each usually contain three chestnuts.

Royal Botanic Garden Edinburgh (27th July 2008) Part 1: Sorbus arranensis and Sorbus pseudofennica

Well, I was down at Edinburgh's Royal Botanic Gardens on Sunday (third time that week) and it was a glorious day. I had myself a good time walking around in the sun admiring trees and taking several hundred photographs. My favourite bit of the Gardens is the Highlands area just on the left when you come in at the East Gate. Not because it is particularly well laid out, or that there are any especially interesting specimens in there, but because it is planted with the things that I am most familiar with and fond of: Scots pines, silver and downy birches, gorse, heather, bilberries (blaeberries), rowans, brooms, alders, foxgloves… These kinds of flora are familiar to me from trips to the Highlands, but mainly from living on the edge of the Peak District, where all of the above are abundant.

Anyway, three small trees in the Botanics' Highland bit specially caught hold of my attention after writing this recent post on Arran whitebeams. Two of the trees were Sorbus arranensis (a.k.a. Arran whitebeam); the third was a Sorbus pseudofennica (a.k.a. Arran cut-leaved whitebeam a.k.a. Arran service tree a.k.a. bastard mountain ash). Neither of the two species are found anywhere in the world except the Isle of Arran. Says the Forestry Commission:

Only a few hundred trees of each species exist, clinging perilously to the steep rocky slopes of two remote glens at the north of the island.

The Arran whitebeam was first recorded in 1897...

The other rare hybrid, the Arran cut-leaved whitebeam, was first noted in 1952. [...] Both species were more abundant in the past, but have been forced to retreat to their restricted enclaves as the island was progressively improved for agriculture.

This is the smaller of the two S. arranensis trees. As you can see, it is only a young 'un.

This is the larger S. arranensis. A poor photo, but it gives an idea of the form.

I found a paper by Robertson, Newton and Ennos (my dissertation supervisor and one of my old lecturers) - Multiple hybrid origins, genetic diversity and population genetic structure of two endemic Sorbus taxa on the Isle of Arran, Scotland (Molecular Ecology (2004) 13, 123–134) – that clears up the origins of both of these Arran whitebeams. From the abstract:

In this study, we use an array of genetic markers in a population analysis to elucidate the hybrid origins of the Arran whitebeams Sorbus arranensis and S. pseudofennica, two woody plant taxa endemic to the Isle of Arran, Scotland. It has been proposed that S. arranensis was derived by hybridization between S. aucuparia [rowan] and S. rupicola [rock or cliff whitebeam], and that subsequent hybridization between S. arranensis and S. aucuparia gave rise to S. pseudofennica. Analyses of species-specific isozyme, nuclear intron and chloroplast DNA markers confirm the proposed origin of S. arranensis, and indicate that S. aucuparia was the female parent in the hybridization. Analysis of microsatellite markers suggests that there have been at least three origins of S. arranensis on Arran. Microsatellite markers also support the proposed hypothesis for the origin of S. pseudofennica, and indicate at least five hybrid origins of this taxon.

And from the Introduction, an explanation of the origins of S. rupicola, the subject of the last treeblog post:

...S. rupicola... (rock whitebeam), itself an autotetraploid derivative of S. aria [common whitebeam]. It is most likely that S. aucuparia was the female parent involved in this cross because S. rupicola produces seed apomictically, but has significant pollen fertility of 20%.

Being the kind and generous human being that I am, I have attempted to sum up all of that information in the following simplified graphic:

Now, I think I'll end the post here. I have more material for a future post about whitebeams in Holyrood Park (again), but I think regular readers must be sick of Sorbi by now so I'll lay off 'em for awhile!

Bonus picture!

When I was photographing the S. pseudofennica this fly accosted my hand. So I took a photograph and was pleased to see what a big fly looks like from so close.

Rock whitebeams in Holyrood Park

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.

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.

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

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.

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!

1 am (25th June 2008)

Squirrels in Britain: the red v. the grey

As you most likely already know, the red squirrel (Sciurus vulgaris) is Britain's native squirrel. But over the last century or so it has been largely superceded by the grey squirrel (Sciurus carolinensis), a native of North America. The greys outcompete the reds, which are then displaced from their territories. According to the Forestry Commission:

Greys can feed more efficiently [than reds] in broadleaved woodlands and can survive at densities of up to 8 per hectare. The density of reds is up to 1 per hectare in broadleaved woodland but can be as low as 0.1 per hectare in coniferous woodland.

The grey squirrel also hosts the ‘squirrel pox’ virus, by which it is rarely affected. But the disease can be passed on to reds to whom it is fatal. The range of red squirrels in Britain is therefore much smaller today than in the good old days before the greys were introduced.

From the point of view of British ecologists and conservationists the reds are the goodies and the greys are the baddies. Of course, individual grey squirrels don't know that they are invasive aliens causing the extinction of a fellow species. They are just doing what comes naturally. But the undesirability of the grey squirrel isn’t limited to its interactions with the reds; greys are predators of bird nests and strip the bark from trees, leading to poorer trees and poorer woodland owners.

So what is to be done? Land managers with a vested interest in reducing grey squirrel numbers (whether for the benefit of red squirrels, trees, or other wildlife) have a few options. Greys can be trapped, poisoned or shot. The Forestry Commission uses poisoned bait, but doesn’t advocate large-scale culls:

Eradication is not a feasible or desirable option given current methods. Worldwide, the record on eradicating small successful introduced mammals is very poor with research showing that low-level widespread culling has no impact on either grey squirrel numbers or upon damage to trees and priority species. As such it is ineffective and a waste of resources.

Even with new methods and unlimited resources, a successful eradication policy would require the total support of the public. Evidence suggests that a substantial proportion of the public would not support a grey squirrel eradication policy. This policy aims to create a balanced approach to wildlife conservation: controlling grey squirrel populations at a level which does not threaten our native woodlands and priority species.

So, member of the public… would you support a grey squirrel eradication policy? I would. The benefits are greater than one might first suspect: see these stories from the Guardian (quoted) and the BBC!

At Ridley's Fish and Game shop in Corbridge, Northumberland, the owner David Ridley says he has sold 1,000 [grey squirrels] - at £3.50 a squirrel - since he tested the market at the beginning of the year.

...

Simpson likens the taste to wild boar. Ridley thinks it is more a cross between duck and lamb. 'It's moist and sweet because, basically, its diet has been berries and nuts,' he said.

Both believe its new-found popularity is partly due to its green credentials. 'People like the fact it is wild meat, low in fat and local - so no food miles,' says Simpson. Ridley reckons that patriotism also plays a part: 'Eat a grey and save a red. That's the message.'

...

'A large squirrel would be enough for one-and-a-half people. The public really are being drawn to it. I think that it's because it is being perceived as a healthy meat. Southern fried squirrel is good. And tandoori style works. It is especially tasty fricasséed with Cornish cream and walnuts. But the one everyone seems to like is the Cornish squirrel pasty.'

Ash at night, Edinburgh (10th April 2008)

The view from my bedroom window at about half an hour past midnight on the morning of April the 10th. Well, actually all I could see was blackness and a crescent moon, but this was a fifteen-second exposure. The tree in the centre is an ash (Fraxinus excelsior).

Marcescent oak leaves in Holyrood Park revisited

Back on the 14th of December I had a wee wander in Holyrood Park and bumped into a couple of young oaks. One was standing naked, but the other was covered in marcescent leaves. I wrote in this post "These dead leaves will probably spend the whole winter attached to the tree. I'll see if I can remember to go back and check in a month or two." Well, I did remember. And the leaves are still there.

Its buddy is still starkers, obviously. The orangey blur in the centre of the photo is the marcescent oak in the background.

There is a little bit of a pine wood growing right in the middle of Holyrood Park. I'm guessing it's all Scots pine.

There were a few juvenile alder trees knocking about near the pines. At least one was old enough to reproduce - notice the seed cones and pollen catkins dangling from this branch silhouetted above Arthur's Seat.

Form: beech, horse chestnut, lime and willow

Look here. I've dug out some photos taken last year on February the 3rd. It was a lovely day with a beautiful clear sky. And some of the leafless trees in the Grange area of Edinburgh looked stunning against the wide blue yonder.

European beech (Fagus sylvatica). Smooth silver bark and fine, delicate branches.

Horse chestnut (Aesculus hippocastaneum). Thicker twigs than beech. Notice how the branches droop downwards but have recurved tips.

Lime (Tilia) - whether common, small- or large-leaved I do not know. Notice the dichotomy in size between the main branches and the finer twigs.

Marcescent oak leaves in Holyrood Park

I had a wee wander in Holyrood Park, Edinburgh, yesterday. And guess what I saw? Some marcescent leaves, of course.

These dead leaves will probably spend the whole winter attached to the tree. I'll see if I can remember to go back and check in a month or two.

But wait! Just a stone's throw away, this oak stands completely devoid of any leaves. Why?

See how close the two oaks are? Only about ten metres. The marcescent oak is ringed to help distinguish it from all that gorse. Hunter's Bog can be seen in the centre of the picture.

Autumn photos from the Innocent Railway

I went for a little stroll down by the Innocent Railway in Edinburgh this afternoon. Next to Holyrood Park, nowadays the railway is just a footpath / cycle path. But it’s still a nice wee place for a wander.

Yellow beech (Fagus sylvatica) leaves. Most of the rest of the leaves on this tree were still green.

A silver birch (Betula pendula). This one had lost about half of its leaves, with the remainder mostly yellow. Other silver birches in the area were almost completely bare.

The ivy was abuzz with honey bees, flies and wasps. They must have been loving all the flowers.

I don’t know what kind of tree these red leaves belong to, but they were very nice from a distance.

Fraxinus excelsior) is staying nice and green. Perhaps this is a consequence of the weird weather we had this year: a red hot spring and a soaking wet summer.

Blackford Hill gallivanting (3rd May 2007)

The young leaves of a small sycamore which was decapitated when a patch of gorse was cleared. The sycamore is a lot quicker off the mark in terms of recovery, by the look of things.

The gorse shieldbug (Piezodorus lituratus). Tenuous tree link: feeds on gorse, which is almost a tree. A wannabe tree.

Wild cherry and gorse (30th April 2007)

A walk on Blackford Hill (27th April 2007)

The bark of a close-by elm of the same species growing on a rocky substrate. Quite a big one; must have avoided Dutch elm disease.

A walk in the Hermitage of Braid (Part 2)

More photos from my Wednesday wander in the Hermitage of Braid. Monochrome!

First up: a stand of trees on a small mound. Some beech and a huge sycamore in there, so I remember. A lot of storm damage though, with plenty of deadwood on the ground and a couple of dead trunks.

This next photo is a closeup of a nicely decomposing dead standing trunk. Check out the little holes made by woodworm or perhaps some kind of bark beetles.

This tall and skinny tree looked like a sycamore. I'm not totally certain it was though - I can't ever remember seeing one so gaunt. But with this being in the bottom of a narrow valley, it would have had to grow tall out of necessity.

Finally, I have a photograph of a fallen branch in the Braid Burn (a burn is the Scots word for a stream or small river).

A walk in the Hermitage of Braid (Part 1)

Yesterday I took a walk in the Hermitage of Braid, a small valley woodland area in Edinburgh. The trees are mainly broadleaved species, and there are quite a few big old specimens. Take the following, for example:

Unfortunately, I didn't pay too much attention to what flavour tree it was. From the photograph the branches look beechey but judging by the bark I'd say this is probably some kind of lime (Tilia) or maybe an oak.

The next photograph shows another tree of the same species with an impressive wound. There was a fair bit of wind damage like this in the Hermitage.

Even with all the deciduous trees still devoid of leaves, this little sycamore seedling growing on a burn-side rock appeared like a symbol of the impending spring.

The beech buds in the next picture might remain closed for another month or so yet. Bring on the summer!