Fallen giants

On the night of Thursday 5th December, an unusually powerful storm hit the north of Scotland, with winds gusting at over 100 miles per hour. It caused widespread disruption, with all train services cancelled the next morning, numerous roads closed by fallen trees and a loss of power to thousands of homes. At Dundreggan, our staff were left without power and telephones for almost 48 hours, and had no water supply for a while either, but otherwise were not harmed by the storm.

It was a different story for some of the trees on the estate though, and I heard the next day that a number of large ones had been uprooted and blown over. I therefore headed out to see for myself on Saturday 7th December, and was met at the estate by Steve, our Operations Manager there, who showed me some of the fallen trees.

 

 

 

 

 

 

When we reached a group of old Scots pines (Pinus sylvestris) near the top of the exclosure that contains our wild boar (Sus scrofa), Steve headed back down the hill, and I began taking photographs of the fallen trees.

 

 

 

 

 

 

 

The first one I photographed had lost some of its large branches, which had subsequently been covered by a light dusting of snow. Looking at the fallen branches, I saw that some of them were covered in pine cones. When we’re collecting seeds for propagating trees in our nursery, we would not normally be able to reach cones on tall pines like this one, so the tree’s misfortune in losing some of its large branches ironically helped to ensure that some of its progeny will grow in the forest at Dundreggan, which otherwise may not necessarily have been the case.

Near this first tree that I photographed, there was another even more dramatic example of the power of the storm. Two large pines growing beside each other, plus a nearby birch tree, had been blown down together, across the fence of the boar enclosure, completely crushing a section of it. Fortunately, it was the half of the enclosure that the wild boar were not in, so none of the animals were injured, and nor did any of them escape through the breach in the fence.

The 12 hectare (30 acre) boar enclosure has been sub-divided into two halves, and these trees had fallen across the western fence-line of the western half of the enclosure. The boar had been in that half initially for two years after we brought them to Dundreggan in 2009, but they were moved to the eastern half in 2011, and are still there, separated from the western section by an internal electric fence. Checking on the boar was one of the first things Steve had done after the storm abated, and we were all relieved to know they were unharmed and still inside their half of the enclosure.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fortunately, the other large pines that were nearby had survived the storm unscathed. I walked down hill to another stand of Scots pines near the track, and was concerned at what I’d find there.

Some of those pines had been used for the canopy climbs done by staff and students from Plymouth University in 2011 and 2012, as part of their research project into the biodiversity living in the canopy of the Caledonian Forest. They are planning to return for further research in 2014, and it would be a real blow to their work if some of the trees they’ve been monitoring had succumbed to the storm.

However, when I reached the stand, I was relieved to see that all of the trees were still standing, and only minor damage had been done – a couple of relatively small branches had been snapped off from one tree, and on another a branch had broken in the middle but was still attached, hanging down towards the ground. That particular tree is one I’ve photographed many times before during various seasons over the years, and it wasn’t one that had been used for the canopy research.

Near this group of pines, there’s a small clearing in the woodland and one of my favourite Scots pines at Dundreggan grows there. Or rather, I should say that it used to grow there, as I found that it had been uprooted completely and blown flat by the power of the storm. It was growing in an area of very shallow soils, with bedrock just beneath the surface, so I suspect it was particularly vulnerable to the extreme winds that this storm produced.

I was particularly saddened to see the demise of this tree as it had a unique shape, with multiple parallel trunks and a beautiful rounded growth form to its canopy. Growing in a clearing, it had taken full advantage of the available space, and had grown to be almost as wide as it was tall. It was one of the most distinctive Scots pines at Dundreggan. Like the other large pines on the estate, it hasn’t been dated by taking a core sample, but I would guess it was probably over 200 years old.

I’m sure it must have experienced plenty of storms during its life, but this one seemed to have caught it (and the other fallen trees) from a slightly unusual direction, whereby a sustained very strong gust of wind had come across the glen from the south side, hitting this tree full on from the open side, where it was unprotected by any neighbours.

 

 

 

 

 

 

Where the root plate has been lifted up, a large expanse of bedrock has been exposed, and we’ll be instituting an ongoing monitoring project for this area, as it will be very useful to observe and document the colonisation process of the bare rock by vegetation.  This will probably begin with lichens growing on the rock itself, followed by mosses getting established when some organic matter has accumulated, and then later on plants and eventually trees should grow again, once enough soil has developed there. That whole process is likely to take decades or even a century or more to unfold fully, and it will be at least 200 years before another tree, comparable to the one that has been blown down, reaches maturity there.

Windthrow, as it is called, is a natural disturbance phenomenon in the Caledonian Forest, and indeed in most forests of the world. The fallen trees create light gaps, where new life can begin, and also create an abundance of dead wood, which is a habitat for a whole range of species, from fungi to beetles, that make up the detritivore community – the group of organisms that break down dead organic matter in an ecosystem. The loss of this tree, and that of the others blown down by this storm, is part of the natural cycle  of life, and I welcome it, as it’s an essential element of the healthy, self-sustaining ecosystem that we’re aiming to restore through our work at Trees for Life. However, the problem with the loss of these large old pines is that, unlike in a healthy forest, we have no young pines, or even 100 year old pines, that will grow on to replace those that have been lost.

The problem that the death of these pines highlights is the absence of birth – the fact that no young trees , and especially pines, have been able to grow for the last 200 years or so, because of the imbalance in the landscape. In that time, there have been far too many herbivores, both red deer (Cervus elaphus) and sheep, which have prevented, through their grazing, any new trees from becoming established. Thus, we’ve inherited a woodland with a 200 year age gap in it, and although the first pines we planted at Dundreggan in 2009 are now four years old and growing well, it will be at least a century before they can begin to replicate the habitat that large mature pines provide, to replace that which has been lost with these fallen ones.

Moving down the hill through the woodland, I came to the corner of the field by our tree nursery, where Steve had shown me earlier that several of the large aspen trees (Populus tremula) had also been blown down. The trunks of the fallen trees were laid out like giant matchsticks, facing in the same direction, as though swatted down by a giant hand passing over them. These too were covered by a light sprinkling of snow this morning. Because we’d protected these aspens with a fence several years previously, there’s good growth of new suckers, sprouting off the roots of the old trees, up to 25 metres from their parents. These suckers will continue to grow, despite the loss of the parents, and in fact will probably grow more vigorously now, because all the energy from the root systems will go into them, rather than to the parent trees.

This will provide another subject for research and monitoring, particularly as the largest of these aspens – one of those which had been blown down – had flowered last year. Although the tree is now horizontal, the roots at the bottom of the upturned root plate will still allow some sap to flow into the fallen trunk and it’s likely that the tree will produce leaves next spring. Aspen trees also flower more readily when they are stressed, so we’re hopeful that this tree will flower again in 2014, in a near-final effort to reproduce before it succumbs and dies. If it does, this will assist our efforts to collect aspen seed – a very rare commodity from aspen trees in Scotland. We’re involved with the charity Coille Alba in experimental work to promote the flowering and seed production of aspen, so those efforts may just have gained unexpected assistance because of this storm!

Despite the potential gains, both in terms of more rapid growth of the suckers and potential flowering of this aspen, I was nevertheless very sad to see these trees down, and especially the largest one. I’ve spent quite a while with that tree on many occasions, and have photographed various species of fungi growing at its base, and also the rich community of lichens on its trunk. The latter includes one of the largest patches of tree lungwort (Lobaria pulmonaria) on Dundreggan, and that will most likely disappear in the next couple of years, as the trunk deteriorates, and also because of the increased exposure to light and wind that it has, in its position on the now supine trunk of the fallen tree.

I moved on from the aspens to the other side of the lodge at Dundreggan, where another of my favourite trees had also been blown down. This is a large oak tree (Quercus petraea) that was growing on the slope down to the small pond in the front of the lodge itself. The tree was partway down the slope, and its branches on the upslope side were readily reachable from the flat ground beside the road that goes to the lodge.

These branches were festooned with arboreal lichens, making them very attractive and photogenic, and it was also easy to collect acorns there too. Like the lungwort on the fallen aspen, these lichens’ days are now numbered, and they’ll die out as the branches collapse to the ground. However, some lichens, including tree lungwort, fix nitrogen from the air, so when they fall to the ground and decompose, they add that nitrogen as a nutrient to the soil. Thus the loss of these trees and their arboreal lichens enriches the fertility of the soil where they lie – part of the never-ending cycling of nutrients in a natural ecosystem.

Like the fallen pine with the huge root plate higher up the hill, this oak had been caught by the unusual direction of the wind, which had hit it on an exposed, unsheltered side, bringing it down, even though it must have survived countless storms in the past. The tree had two parallel trunks, which separated not far up from the ground, so this may also have been a factor, rendering it weaker than a comparable tree which had only a single trunk.

The storm also took down a couple of trees in the avenue along the road into Dundreggan – a lime and part of a beech tree – but in actuality only about 20 trees came down altogether. This is a tiny proportion of the overall numbers of trees on the estate, but because of their size and age, these fallen giants have a disproportionate significance there. I was sad indeed to see them down, and although there are clear ecological benefits that will arise from their demise, I feel like I’ve lost some special friends, and the character of the forest at Dundreggan has changed as a result. I came away from my day photographing the damage very thoughtful, and also with a palpable sense of awe at the power of the storm, which had allowed it flatten these massive trees. As with other manifestations of the power of Nature, it provided me with a powerful reality check, and it cast my own life, and all our human aspirations and endeavours, in a different perspective.