Walton Hall Nature Trail

by Mike Dodd


Start - Mulberry Lawn

1. Outside the library there is an ancient looking black mulberry (Morus nigra). The tree produces raspberry like fruits in the autumn which are edible raw although not particularly pleasant, they can also be made into jam. Also on the lawn is a young tulip tree (Liriodendron tulipifera)[LEFT]. It is native of eastern North America, produces large green flowers in June and July and also often gives good autumn colour.

Go south between the library and Walton Hall towards the church

2. The pond - contains various species of amphibians including large numbers of great crested newts. The sometimes large year to year fluctuations in population size have been studied by members of the Open University Ecology and Conservation Research Group.
There are also several interesting species of plants growing round the pond including branched bur-reed (Sparganium erectum), water mint(Mentha aquatica)[RIGHT], and greater pond sedge (Carex riparia) . The trees are kept well cut back from the south and west part of the pond to allow in plenty of light for water plant growth.


3. The graveyard is a good place to look for lichens , there are several species present on the gravestones such as the bright orange Xanthoria parietinaor yellow Candelariella aurella and Caloplaca citrina. Lichens have often been used as pollution indicators as they are slow growing and very sensitive to the levels of sulphur dioxide and other toxic chemicals in the air. The limited range of species here suggests a level of approximately 60 µg/m3 of sulphur dioxide and shows that Milton Keynes is quite polluted although not as bad as many other cities. The borough council now monitors pollutants in the atmosphere and has documented a reduction in mean annual sulphur dioxide levels from about 90 µg/m3 in 1969 down to about 20 µg/m3 in 1994. This large fall in sulphur dioxide pollution was due to a reduction in the use of coal for domestic heating and the introduction of a smoke control area covering all of Bletchley.

QuicktimeVR movie from the church tower.

River bridge

4. The river Ouzel rises in the area south of Leighton Buzzard and flows past the Open University before joining the Great Ouse, the river then goes on to Bedford, Huntingdon and Kings Lynn before entering the North Sea at the Wash. Looking down from the bridge fish such as dace, roach and perch are often seen among the water weeds. The river is not always gently flowing between its banks, heavy rains can cause extensive flooding of the surrounding meadows and so this land is unsuitable for building.

Turn right over the bridge and head along the Redway towards the gap in the hedge.

5. On passing through the hedge there is an area of ancient hay meadow with the very uncommon plant great burnet (Sanguisorba officinalis). Hay meadows themselves are becoming very uncommon mainly due to changes in agricultural practice. This area is now managed by MK parks trust who allow many of the species to set seed before hay cutting.
Hedgerows have also suffered badly from the intensification of agricultural systems with 23% lost between 1984 and 1990. Large hedgerows such as this provide an important source of food and shelter for many birds such as the robin [LEFT] and other animals. Chiffchaffs, song-thrushes and wrens are common in this area and are often heard singing. Foxes also breed here and cubs can sometimes be spotted playing early on summer mornings.
While walking through the meadow one evening, writing the nature trail, I heard a beer can making strange noises. It turned out to be a shrew trapped inside which I released but many animals are killed by thoughtlessly discarded litter.

Bear left keeping on the Redway

6. Walton 'Lake' was excavated in 1972/3 and served as a temporary balancing lake to help reduce flooding along the river but is now a nature reserve(check). The southern part of the reserve is a reed bed dominated by common reed (Phragmites australis), bulrush (Typha latifolia), lesser bulrush (Typha angustifolia) and sallow (Salix sp.). In early summer the air is filled with the loud 'tuc-tuc' of sedge warblers. Later in the autumn these small brown birds migrate across Europe, the Mediterranean and the Sahara Desert in one single flight. Other birds such as heron, mallard and reed warbler (Bird species list for the whole walk) are also common in this area. Cuckoos are sometimes seen in the spring probably looking for reed warblers nests in which to lay their eggs. One regular and unexpected visitor to the lake and river is the common tern. Terns look like seagulls but have a forked tail, long wings and a very graceful flight. They are normally thought of as seabirds nesting on shingle beaches and flying thousands of miles each year to winter off the western African coast. However some choose to nest by inland lakes such as Willen and catch fish from lakes and canals.

Continue round Walton Lake leaving the Redway to walk across the steep open grassy bank.

7. During the summer months there are often many butterflies such as skipper [LEFT], meadow brown and gatekeeper on this grassy bank. The larvae of these species feed on grasses and the adults take nectar from plants such as common knapweed (Centaurea nigra) [LEFT]. There is a butterfly monitoring scheme on campus which occasionally needs volunteers to count species round a set 40 minute walk.
Looking across the lake towards the university there is a rich assortment of water plants such as flowering-rush (Butomus umbellatus), water-plantain (Alisma plantago-aquatica), purple-loosestrife (Lythrum salicaria) and lesser water parsnip (Berula erecta) round the margin of open water.

Continue on round the lake towards the Open University and river

8. Running alongside the lake is a culvert carrying a stream and storm water from road drains. This often suffers oil pollution and there may be wicks or barriers to reduce the oil getting into the river and damaging the ecosystem. Despite this pollution there are several species of plant growing in the culvert such as fool's watercress (Apium nodiforum) and great willow herb (Epilobium hirsutum). Higher up species such as the succulent reflexed stonecrop (Sedum rupestre) and bright purple Rosa rugosa[LEFT] struggle through cracks in the concrete. This rose is not a native species but seeds from the very large hips have been carried here from roadside plantings. Further along the culvert by a small wooden bridge you may also find the paler blue-purple flowers of the legume tufted vetch (Vicia cracca).
Screening the road is a large hedge containing mature trees such as ash (Fraxinus excelsior) and, at one time, elm (Ulmus sp). Elms still occur there but only as suckering shrubs, once their bark develops the rough ridged texture of a tree the elm bark beetles which carry Dutch elm disease are attracted and the tree is killed. On the warm south facing side of the hedge there are many large brambles and dog-roses which provides ideal conditions for insects. The hedge also provides nest sites for birds such as blackbird, chaffinch and yellow hammer.

Just before the river turn left along the tarmac path

9. Ahead is a group of very large black poplars (Poplus nigra). These fast growing trees are generally uncommon in Britain except along the lowland river valleys of central and eastern England. Large numbers of a variety of poplar species have been planted in Milton Keynes to give the new city a rapidly growing framework of trees.
On the river bank besides the poplars there may be a thick tangle of hop (Humulus lupulus) vines. Male and female flowers are borne on separate plants and it is the female flowers that develop into the cones which are used in beer making.
Damselflies and dragonflies are very common catching insects along the river during the summer. The metallic blue or green banded agrion [LEFT] is one of the most obvious, the male having a large blue patch on its wings. They tend to flit about in the waterside vegetation along with several smaller species of damselfly. Much stronger flying are the dragonflies such as Aeshna grandis which is distinguished by its amber wing membranes and can be over 7cm long. Both dragonflies and damselflies have an unusual mating system involving sex in the tandem position.

Head downstream towards the footbridge back to the university side

10. Teasels (Dipsacus fullonum) are common along the river bank, the prickly flower heads were used to raise the nap on woollen cloth and a cultivated form of the plant is still occasionally grown for this purpose. In the autumn the seedheads are very popular with seed eating gold finches and green finches.
In recent years surveys have shown a substantial increase in the amount of stinging nettles (Urtica dioica) growing along Britain's river banks. At the same time there has also been an increase (a doubling between 1974 and 1991 in some areas) in phosphate and nitrate pollution of rivers. [River Ouzel water quality] These nutrients tends to favour rapidly growing competitive plants such as nettles. However in places along the river bank there is a rare parasitic plant great dodder (Cuscuta europaea)[LEFT] which 'eats' nettles. The plant has no chlorophyll and produces a dense tangle of red and yellow thread-like shoots which wrap round the nettle and take nutrients directly out of the stem. It may take some searching to locate the plants as they are annuals and tend to be found on different patches of nettles each year.

Follow the path to the university through a grove of Scots Pines

11. Scots pines (Pinus sylvestris) are easily distinguished from other species of pine by the orange bark towards the top of the trunk, they also have rather small cones and paired needles. In the autumn there are often fungi such as plums and custard (Tricholomopsis rutilans) and sulphur tuft (Hyphaloma fasciculare) in this area, their English names very aptly describing their colour although not, unfortunately, their edibility. There is one white species which normally comes up in this area and looks rather like the horse mushroom (Agaricus arvensis) however, perhaps surprisingly, identification in the Agaricus group is difficult and a few of the species are somewhat toxic so they are perhaps best avoided.

Head for the sports pavilion then turn right and go between the buildings in the middle of campus.

12. House martins build their mud nests below the eaves on the Venables building and during the summer months the air can be filled with parents bringing back insects for the ever growing young. The Venables building also provides homes for several colonies of wild bees, on hot days hundreds of workers can often be seen outside the nest clustered together on the brickwork. Another visitor to the brickwork and especially the window frames is the blue-tit, they search diligently and acrobatically round every nook and cranny for insects and spiders.
Providing nectar for the bees in surrounding shrub boarders is the purple butterfly bush (Buddleja davidii). It was introduced from China in about 1890 but has become naturalised in many parts of Britain even threatening to take over from native vegetation in some places. The bush also acts as a strong attractant for butterflies and provides nectar to species such as the Painted Lady [Left].

Go past the bank and shop towards the lecture theatre and Mulberry Lawn.

13. At the centre of campus is a small wild area with a copse of english oak (Quercus robur) trees towering over a spectacular display of spring wildflowers. Oak trees can live for many hundreds of years, as they get older they are increasingly attacked by insects and fungi which damage branches and eventually hollow out the trunk. However far from being a disaster this actually helps the tree to survive as the hollow shell with few branches is more resistant to storm damage and can still produce a substantial crop of acorns.

QuicktimeVR movie in the oak copse.

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