Wednesday, 1 February 2012

A tree of damp places

At this time of the year the riverside alders often hold chattering flocks of siskins and redpolls, noisy affairs that pull your gaze to the outermost branches and to the fidgety silhouettes of these small finches. The tree itself has a ‘twiggy’ silhouette and, with its characteristic female cones, can appear somewhat fuzzy around the edges.

Alders are often encountered in riverine surroundings, either along the river banks themselves or on the damp ground that occurs where fen and carr sit nearby. You might think that this suggests an association with waterlogged ground but this is not the case. Alder is more particular in its habits and favours ‘flushed’ soils, i.e. those where there is a movement of water through the soil. Riverside soils provide these conditions, as do spring-lines and similar features elsewhere.

We have a fair bit of alder on the Nunnery Lakes Reserve in Thetford, where it is sometimes cut as part of the wider management of the site. The timber is white when freshly cut but quickly takes on an orange-red colouration through the process of oxidisation. Interestingly, it made ideal charcoal for the production of gunpowder and this may explain the presence of planted alder woods close to sites where gunpowder used to be produced. The timber has also been used in the framework supporting the banks of canals, in the handles of farm and garden tools and as lure for woodworm. Although found across the whole of Norfolk, alder is more common in the east of the county, where it has traditionally been viewed as the first coloniser of early successional habitats.

Alder is a tree whose shade I enjoy in the summer, when sat by the river, or whose rough bark I scour for insects and spiders throughout the warmer months. During the winter it is the crown of the tree that I watch, scanning for finches that have come to feed on the tiny seeds, held within rather delicate and open-looking cones. I can remember cursing these cones as a child as it was all too easy to leave a fishing line entangled within their grasp. Compared to other trees (think of oak, yew and elm) the alder does not attract that much attention and it remains a largely overlooked part of our countryside. This is a real shame because I think that the alder has a strong character, in part defined by its waterside habits but also by its twisting branches, thick mass of smaller twigs and rich-coloured catkins. The tree did catch the news a few years ago, however, when a Phytophthora fungus was found to have killed roughly one in ten trees over parts of Wales and southern England.

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