St Nicks

Centre for nature and green living

Spotlight on… Woodland structure: the understory

Woodland layers (image source: http://www.open.edu/openlearn/nature-environment/natural-history/neighbourhood-nature/content-section-1.1)

A woodland can be split into distinct layers of vegetation:

• the canopy: top layer consisting of the tallest trees which receive lots of light
• the understory: the herb or field layer which includes our native spring wildflower bulbs and other plants such as grasses and nettles
• the ground layer: what we find underfoot – mosses, lichens, ivy, rotting leaves filled with creepy-crawlies and soil.

The understory is perhaps the least well known of the woodland layers but arguably one of the most important for wildlife.

If you take a stroll through most areas of St Nicks woodland you will probably see lots of tall thin trees growing close together. Take a look up the canopy (especially in the summer) and you probably won’t be able to see through to the sky because the foliage of these condensed trees blocks out any light. Now look down to the ground. Maybe you’re crunching over twigs and leaf litter or maybe just standing on firm and heavily compacted bare clay soil, with the occasional clump of moss. Now take a look all around you at about head height. Here you may not see much life at all. There might be low branches from the taller trees which are more than likely dead or dying from the lack of light, maybe an odd nettle or bramble stem if you’re lucky.

St Nicks woodland (image by Lewis Outing)

Walking through patches of such woodland can be a very pleasant experience. You might hear nothing but the leaves beneath your feet, or perhaps you can hear the drum of a woodpecker (perfectly happy taking advantage of the decaying standing wood in closed canopy woodland). Very likely you’ll see a grey squirrel or two performing acrobatics amongst the canopy. This lack of natural light can also give a mysterious and eerie feel to a woodland which can then thrillingly burst into life with the beams of a rising or setting sun piecing through. Doesn’t sound unpleasant at all, right?

Now take a walk over to the short path (often muddy!) between Tang Hall Beck culvert and the Foss Islands Cycle Path. As you make your way through, try and take in the difference in structure to the woodland. Rather than uniform standard trees in a closed canopy, you’ll find the odd mature crack willow tree (or remains of one) and various lower growing trees and shrubs. From dense outward growing stands of bright red dogwood to the low formed fruiting archway of wild damson trees, self-seeded ash trees growing into any gaps they can find and old elder trees growing out their crinkly limbs into all sorts of weird and wonderful directions – there is a real diverse range of structure. You’ll also see ivy climbing across many of the older trees, and grasses and sedges plus nettles and brambles providing structure in the field layer. You’re likely to see a greater range of wildlife here too. Flowering trees, shrubs and plants provide a nectar source for woodland pollinators, and from these flowers come the elderberries, hawberries, blackberries which feed a wide range of bird and mammal life. Add to this that many of our bird species require lower and often thicker growing habitat to nest in, ranging from cracks and holes within old exposed elder branches to dense patches of bramble scrub, and the massive value of woodland understory and the field layer is clear.

Ivy growing on elder trees near Tang Hall beck

So why is this small patch of woodland so different to most of the rest? The answer is simply that it wasn’t part of the landfill site. While most of the site was part of Tang Hall Tip before getting drowned in a sea of clay, this small section (along with some other areas along both becks) has been left to develop naturally over a much greater period of time. This means there was always likely to be some level of light between the trees to help the understory and field layer establish. Compare this to the rest of St Nicks woodland, planted with 7000 trees between 1996-2001 in memory of local environmentalist John Lally, and the difference starts to make sense. Creating a woodland from scratch obviously requires a lot of trees to be planted over a short period of time. It’s much more efficient and makes more practical sense to plant a thousand trees in one area at the same time rather than planting a hundred a year over ten years. Plus new woodland is always overplanted. This was especially so at St Nicks as it was assumed not all the saplings would thrive in the thick clay and some were likely to be lost to vandalism. So it is not that surprising that 20 years on St Nicks Community Woodland lacks clear understory and field layers.

Tree planting in the clay

But change is afoot. Four years ago we received a Woodland Improvement Grant from the Forestry Commission which led to a new understanding of our woodland and its management. With the help of local Forestry Commission Field Officer, and long term Friend of St Nicks, Mick Hoban, we surveyed the progress of the developing woodland and began making a long term plan for its future management. We marked trees to fell over the next 5 years as part of a regime of thinning dense areas of closed canopy woodland. We introduced a coppicing programme to parts of the site to encourage the multi-stemmed regrowth of felled trees to create a denser, more horizontal structure. We are planting more traditional, shade tolerant, understory species such as Holly, Hazel, Hawthorn and Field Maple in newly opened woodland areas to ensure a range of age as well as structure, and beginning to plant and sow a greater range of field layer species such as wood anemones, wild garlic, foxgloves, primroses, and various woodland grasses and sedges.

So come this spring and summer you will start to see the fruits (quite literally in places) of this long term project. Walk through the woodland to the north of the Dragon Stones in April and May and enjoy the pungent smell of wild garlic beneath your feet. Take a moment to admire the vigorous growing woodland grasses appearing with the spring warmth to spread across the woodland floor as the sun grows stronger. Marvel at amazing multiplied regrowth of what was once a single stemmed tree struggling to survive in the gloom, now bursting back to life, and keep track of the new growth of brambles weaving their way towards the increased light in the woodland. All this new and varied plant life in all sorts of shapes and sizes will be full of animal life making the most of this new and once rare habitat at St Nicks.

Multi-stemmed regrowth of a coppiced willow tree

The next phase of our woodland improvements has been kindly funded by a grant from the Postcode Local Trust. We will use it to continue to develop St Nicks Community Woodland, introduce more detailed monitoring of woodland wildlife, and raise awareness of the importance of woodlands through putting on a range of both practical and family friendly woodland events and workdays throughout 2018. If you would like to get involved have a look at our event listings for woodland events or contact our Volunteer Co-ordinator, Maria Gill on 01904 411821 or volunteer@stnicks.org.uk for more information.

24 January 2018 | Categories: Spotlight on...