Urban Botany

As Spring starts to appear, so too do the flowering plants. I have been starting to notice these around my estate and on the walk to my local shops I plucked a few specimens to take home and identify. I was fairly sure I knew what they were, but wanted to make sure - it's good to keep botanical knowledge up-to-date, especially after winter when it inevitably fades slightly with lack of practice.

The violet is likely to be Common Dog Violet (Viola riviniana). The leaves and flowers do not all come from the same location at the root; heart shaped leaves are sparsely hairy; flowers have mid-purple petals with a cream spur and darker purple branched veins; sepals are pointed and the flower has no obvious scent. The leaves are stem are tinged red/purple though so this may be a garden variety.

Shown in the pot is Variegated Yellow Archangel (Lamiastrum galeobdolon ssp argentatum). This is a non-native varient of Yellow Archangel. It differs as the leaf edges are more regularly toothed, and the colouring is variegated with silver which turns a chocolate brown colour over winter. The native plants is very similar but has just a few flecks of silver and never has the chocolate colouring.

The trefoil plant with the yellow flower is Black Medick (Medicago lupulina). This has the three leaves typical of the trefoil family. The leaves are hairy and have a distinctive point at the tip, as shown opposite. Once the flowers die off, distinctive black seed heads are left.

Also common at this time of the year is a weed common in my garden, Wavy Bittercress (Cardamine flexuosa). This is the straggly plants (second from left in bottom photograph) with narrow leaves and small, white four petalled flowers. It has long seed pods and is one that I will be digging up before it can spread to my mini allotment patch!

The last once shown is, I think, Wall Lettuce (Mycelis muralis) a dandelion type plant that has tiny yellow flowers later in the year, with the leaves heavily clasping the stem. 

Improving Urban Sites

Our assignment for the Habitat Management course is to work as a group and come up with a management plan for an urban site in West Leeds. We visited the site at the weekend and it was all rather depressing - there is a lot of litter, the site is next to a major road and it doesn't look very cared for.

There are signs of invasive plants in the form of Himalayan Balsam and Japanese Knotweed that will need managing. Despite this though, in amongst a valley that provides overflow relief for the reservoir, we found good early pollinators such as butterbur and lesser celandine. There were also signs of fox dens in the dry valley.

There were a range of ducks on the reservoir such as mallard, coot, moorhen and the more exotic tufted duck. There was evidence of over-feeding by the locals though. Walking around the reservoir on the path, you could not seen the lake and some management of the trees to open up the views might help engage the locals more.

Some areas of the beck further down looked as though they could provide some good habitat, although the water itself was rather fast flowing. The woodland alongside the beck was mixed, though the plantation area and some older trees could do with some management to remove dangerously overhanging branches.  Thinning out the woodland to let in more light might also allow some more interesting ground flora to develop.

Another visit is needed as we still need to visit the site on the other side of the beck, but this will be an interesting and challenging project.

Bats and Bridges

Late last month I attended an event with the West Yorkshire Bat Group where I learned how to survey for bats using bridges as roosts.

We met at Kirkstall Bridge in Leeds where we worked as a large group to look at the various features. Metalwork on bridges is not favoured by bats as it conducts the heat away and can be too cold, so we were looking for small cracks in the stone-work of the bridge.  Rubbish from the recent winter floods was in evidence, but we found few crevices suitable for bats on that first bridge.

We then split into two smaller groups, and my group went for a walk along the Leeds-Liverpool canal taking in two further bridges. This took us alongside Hollybush Farm, and the canal towpath was well used by people walking, biking or jogging, but it was still peaceful compared to the busy roads above.

The first bridge showed little promise, though we did see an American Mink on the opposite bank. This is an invasive mammal that predates on our native water voles and is a menace on the water ways, but as I watched I could not help feel sorry for this maligned animal that is just trying to survive in a situation it has found itself in.

The second bridge along showed a bit more promise, with some cracks in the stonework, and mature, ivy-clad trees in woodland along the bank of the canal. It will be interesting to see if dusk surveys are carried out later in the season and whether they capture bat calls using the canal as a foraging corridor.

Woodland Management

This week has seen the start of my next MSc module on habitat management. After an introductory lecture, our first visit was to Anston Stones Wood near Rotherham where we looked at management practices in a mixed deciduous woodland in a limestone/calcareous area.

Coppicing was traditionally carried out in the woods for hundreds of years, with larger trees being taken for timber for buildings and ships. This ensured trees of different ages were present, and the clearings created during felling allowed ground flora to flourish. The difference in conditions in these  different pockets created small micro-climates and is one reason why there is such high biodiversity in woodlands. The area in the photo had a good assemblage of ferns and mosses, as it was largely damp and shaded.

Since the industrial revolution, woods have become largely redundant from an economic perspective and the lack of management has had an impact on woodland.  Offering no income, many woods were cleared to make way for more productive agricultural land. Many trees were also felled during the first and second world wars when timber could not be imported. This has left many woodlands that are uniformly around 100 years old and/or on steep slopes that made clearance difficult.

Today, woodlands do have to be managed to ensure a high level of diversity. Coppicing can take place - it is labour intensive but some groups do the work for free if they can take the products. Firewood, fence posts, charcoal, hurdles and beanpoles can all be harvested and sold for a profit. Remaining brash can be made into habitat piles (though the value of these was questioned) or chipped and used to line muddy paths. 

The site had some areas of grassland on the plateau. Scrub will always try and take over, though we learned that this needs cutting back to the point at which none of the grassland features are visible.  The meadow is cut once a year, and the arising are raked off, otherwise they would decay and smother new seedlings trying to come through. Grazing can work well, but consideration needs to be given to public interaction with livestock, and whether dogs could harm them. The cost of installing fencing can be prohibitive and may look unsightly.

An agricultural field had recently been converted to hay meadow, by ploughing it up and spreading the cut hay over it - this was not successful. Possibly due to high nutrients levels, all that appeared were weeds and thistles. When the area was sown with grass and then seeded, the result was more successful. I hope this doesn't mean that our hard work at Coronation Meadow last year will have been wasted.

Planting new trees does not make a woodland. A woodland is more than trees - it needs soil biota, mycorrhizal fungi, ground flora and invertebrates to establish a successful woodland community. It is better to expand an existing woodland, and these elements should then naturally move in and allow the woodland ecosystem to develop. However, this all takes time. One problem with modern woodland management is that it is too short term - plans need to be made that look decades ahead. One example of this is Toothwort (Lathraea squamaria) - a parasitic plant often growing near hazel that needs the interconnected relationships of the woodland to survive.

Unmanaged, wild woodland can be worse for wildlife as the denser shade leads to less ground flora and less cover for prey, though it is good to leave some areas unmanaged within a wider site. 

When planting trees, it's necessary to be wary of the spread of invasive species and disease, and there are problems for ash and larch in the UK at the moment. Even if seeds are gathered in the UK they can sometimes be sent to nurseries abroad to be grown on, so it's important to understand the provenance of saplings and source seeds locally where possible.

Damper, sheltered areas in valleys and gorges create good habitats for mosses and ferns, and leaving dead wood to rot (both standing and on the ground) is very good for invertebrates.

Finally, consideration needs to be given to other land users. There may be access routes through the site, and railways as much as roads needs a clear route with no overhanging vegetation. Clearance also needs to be maintained along power lines. Such work can be harsh on the environment but are necessary in our modern world. These considerations aside, remember that a woodland is a natural environment and should not be over-managed  so it becomes a landscape garden.

Tree Clearance at Water Haigh

For the past two weeks the Lower Aire Valley volunteers have been busy at Water Haigh plantation. This is a mixed woodland with undergrowth including bramble and cleavers, with a few more interesting mosses, ferns and fungi in between.  It was planted around fifteen years ago and timber is now starting to be removed. Late last year, the council forestry officer worked through the plantation, marking up trees that should be removed with spray paint. The trees that were marked for removal were mostly small, crowded or leaning, and by removing them the remaining trees will have more room to grow strong and straight. We also took out a few additional trees to facilitate access, or where the tree was dead and it was unsafe to leave it standing.

Most of the trees were small enough to be removed with hand saws, so we learnt how to do this safely, controlling the direction of the fall. Trees were mostly larch and scots pine, with many birch, alder and oak also present. When taking out each tree, the task was broken down as follows:

1. Look up. Make sure there are no loose branches that might fall on you, and check to see that the branches aren't caught up in other trees as this may affect how it falls.

2. Look at the tree. Is it leaning? If so, it's best to use this where possible, and make the tree fall in the direction it's already leaning.

3. Look around. Identify a gap that the tree can fall into, where the ground is free of obstructions. Also make sure there is room for you to work and escape to if things don't go to plan!

4. Remove any of the lower branches. This simply makes it easier to work.

5. Working at a comfortable level, create a 'birds-mouth' cut. The first cut is horizontal, on the side that you want the tree to fall towards, and at right angles to the direction of the fall. This should go to a third to half way through the tree. Next, cut down at a 45 degree angle, so that the two cuts meet and a wedge is taken out of the tree.

6. The next cut is the felling cut. On the opposite side of the trunk, about 1cm above the base of the birds-mouth cut, cut horizontally. Before the two cuts meet, the tree should start to lean towards the birds-mouth cut, and will fall when the wood shears through. This gives you time to stand back out of the way. If done right, it should leave a neat cut on the top of the stump, with a slight difference in height between the two sides.

7. Once the tree is on the ground it can be processed. We cut the trunk into approximately three metre lengths, with side branches removed.

8. Tidy the site. A chainsaw was used to cut the remaining stumps low to the ground. The timber was stacked in piles (less than a metre tall to prevent it from becoming unstable) and the brash in separate piles.

The wood/timber will be taken off site, but the brash will slowly decay and in the meantime provides a wildlife refuge.

The site now looks a lot more open. Whilst the task had a commercial focus and was aimed at increasing the quality of the remaining trees, hopefully the increase in sunlight reaching the woodland floor will also benefit ground flora. Overall, an exhausting task but satisfying that we managed to clear all of the marked trees. One of those tasks that has a visual impact and we could certainly see the progress that had been made in the woodland.