Fullscreen
Loading...
 
Print

Wildflower grassland creation at Stansted Airport, Essex

Location
County: Essex
Nearest town or settlement: Stansted
Contact details
Project description

Although not a substitute for the long-established, intimately varied plant communities with their complex of animal associates, new flowery grasslands have a role to play in nature conservation. Penny Anderson explains how these have been created and managed at London's Stansted Airport.


Flower-rich grasslands can support the common and widespread species such as skylark and common blue butterflies, which are in danger of becoming rarer in some localities. They can provide new habitats, stepping stones and links between the often isolated and fragmented "semi-natural" grasslands, (provided they are not also a source of unwanted invaders).


Properly designed in the local ecological context, they can help knit the landscape back together, along with new hedges, woodlands and other habitats. Their considerable visual appeal brings nature closer to people, and can contribute to environmental education resources.


It is probably fair to say that in 1986 not all these concerns were paramount when the opportunity arose to create extensive flowery grasslands within the landscape framework of London's Stansted Airport, (located in north-west Essex). Wild flower seed had not been generally available, tried or tested, at the time of the public inquiry into the airport's redevelopment in 1981,so the creation of flowery grassland was very much a case of grasping the opportunity to try something exciting and new.


With more than 32 ha available for seeding with wild flowers, it was important to have a suite of species suited to the chalky boulder clay soils. The soils available, however, were highly variable. In one small area (about 1 ha), the topsoil had been stripped off an ex-barley field. After 30 cm or more of the whole soil profile had been removed, an intractable gooey clay surface was revealed which took a couple of years to settle.


Inadvertently, the topsoil stripping also broke all the field drains resulting in a natural ooze, resembling a wet ready-mixed concrete slurry in the first two years, which settled into an ephemeral stream down the shallow valley of the field. The flora which developed down this ooze was surprisingly rich in species, none of which had been planted, or previously recorded on the site.


Other soils available for sowing were respread from topsoil heaps, mostly on roadside banks or mounding where only a thin layer (15 cm or less) persisted after settlement. On ex-agricultural land (the greater area available), in-situ topsoils were the third soil type to be sown.


Ideally three different seed mixes were warranted to suit the different nutrient levels and soil depths in these three areas, but this proved too costly. A specified seed mix, consisting of individual species selected from a reputable seed merchant, exceeded the available budget.


The eventual solution was to buy seed (£15/kg in 1986-8) from Dr Miriam Rothschild's Sudborough hay meadow. This is situated on chalky boulder clay near Peterborough and contains a wide range of common and widespread species, most of which also occurred in other grassy fragments in the Stansted area.


This mix was sown on to all the grassland areas which were expected to be retained in the future expansion plans for the airport, but on some areas it was diluted with seed from a cheaper (£5/kg) second generation hay meadow grown from the original one. The sowing rate was about 30 kg/ha, although when the seed looked particularly chaffy a higher application rate was used. The ground was properly cultivated and harrowed as for any crop, and subsequently rolled with a Cambridge roller or equivalent.


Seeding was most effective from an autumn sowing, although this judgement is strongly affected by the severe droughts in the south in 1989 and 1990. A spring 1989 sowing, for example, resulted in one ribwort-rich sward, but with a dearth of other species. Some areas were so poor they had to be re-sown.


Subsequent growth of the mixtures tended to make a mockery of the standard cutting regimes so often recommended. On the subsoil, establishment in 1986 was slow, and no cutting was needed until the end of the second year after the customary display of red clover and oxeye daisies. The latter then declined and from 1988 to 1992 yellow rattle dominated (Table 1). This could have been a product not just of plant succession, but also drought (1989 and 1990) and rabbit grazing (which was intensive at times). This area is now fairly diverse (i.e. rich on a 1m2 basis), with more than a hundred species recorded, of which sixty-nine were definitely or probably in the original seed mix. Except when rabbit grazing reduces flowering, it also is a pleasure to behold.


One of the greatest assets of using a hayfield mix is the abundance of native grasses, including meadow barley, meadow brome, soft brome and others. Some of these are annuals, and the continuing openness of the sward oat the subsoil has ensured both their persistence in good numbers, and the spread of species like cowslips which were slower to establish.


In contrast, on the deeper in situ topsoils, newly-established swards have frequently been dominated by scentless mayweed, annual sow thistles or prickly oxtongue (depending on the seed bank present) in their first year. Usually, these have mostly been allowed to flower, but then only cut where their vigour was threatening the establishing seedlings beneath. Thus for some areas, the establishing sward has been mown and the cuttings cleared (an essential operation) in mid-July and September, while in others, only the later harvesting was necessary. This variability was related to the dryness of the year as well as the nutrient richness, and requirements could be more rigorous in a wet year.


The cheaper seed mix only registered some thirty to forty species after establishment (Table 2), and these have declined in number and many in abundance on some areas since. Grasses have gradually gained in dominance, especially tall fescue, cock's-foot, rye-grass and rough stalked meadow-grass, but bird's-foot trefoil and red clover are still abundant. On such soils, seed mixes which exclude legumes may be more appropriate in developing a greater diversity, but may be less attractive to common blue butterflies.


In other areas, the species range was higher (sixty to seventy by the third year, see Table 2)and more diverse (i.e. with none being dominant), and this has been maintained over five years so far.


The most attractive swards on topsoil are on the shallow cover to the road-side slopes, and the richest (seventy-nine species in 1992 after being sown in 1988) are grazed by rabbits. It would suggest that for wild flower establishment, storing topsoil for one or two years without great care (but avoiding anoxic conditions) is of benefit to establishing wild flower seed. It is a topic which merits further investigations.


Swards which are particularly vigorous, and where grasses are gaining at the expense of broad-leaved herbs, are harvested in spring where possible. The aim is to cut after initial growth has started, but not so late that nesting birds and emerging invertebrates are affected. Wet ground frequently prevents such management but where it is achieved, vigour is reduced, flowering is generally delayed slightly (which is useful in maintaining a display of colour through the summer), and diversity seems to be maintained. All the grasslands are then cut and cleared in September/October (or later depending on the weather).


Swards containing a high proportion of vigorous species will need additional management. Grazing is being considered as an additional management tool, which is a novel concept in the context of British airports. In a period of stringent financial restrictions, the stock will need to provide management savings, so their traditional use after hay cutting is not necessarily appropriate.


All kinds of scenarios need to be assessed, ranging from grazing only, to cutting once and integrating grazing into the schedule. The aim is to maintain or enhance the floristic diversity and attractive appearance of the grasslands, provide a much-needed habitat for as many typical animals as possible (without compromising air safety considerations), and keeping costs to a minimum. In other words, it embraces all the usual site manager's dilemmas!


In this case, though, there is the added onus of maintaining a landscape which, with the 64 ha of native woodland/ copse and hedge planting and other habitat creation, was awarded one of the premier awards in the CBI's Business Commitment to the Environment Scheme in 1991.


Back to top


Table 1.
Hay meadow mix on subsoil
Planted 1986 c. 30 kg/ha.
69 species known to be, or probably in, seed mix.
Date Total nos. of species recorded Main species

----------------------------

1988 104
oxeye daisy, melilot, red clover

----------------------------

1989 91
oxeye daisy, bird's-foot trefoil, yellow rattle,
red and white clovers

----------------------------

1991 94
bird's-foot trefoil, black medick, self-heal,
creeping buttercup, yellow rattle

----------------------------

1992 76*
oxeye daisy, meadow buttercup, yellow rattle,
lesser yellow trefoil

----------------------------

1993 79*
Yorkshire fog, bird's-foot trefoil, yellow rattle,
meadow and creeping buttercups, red clover

----------------------------

1994 111
Yorkshire fog, bird's-foot trefoil, meadow
buttercup, red clover, rough-stalked meadowgrass

----------------------------

  • only part surveyed, no evidence of loss of species.




Table 2.
Wild flowers sown on top soil
Site 1 sown 1987, site 2 sown 1988
In situ ex.arable land
Date Site 1 Site 2

----------------------------

1988 31

----------------------------

1989 37
42

----------------------------

1991 57
58

----------------------------

1992 72
62

----------------------------

1993 48
71

----------------------------

Site 1: Cheaper seed mix, half from second generation Sudborough hayfield.
Site 2: Richer seed mix - only 1/4 to 1/3 from second generation Sudborough hay field.


Penny Anderson runs an ecological consultancy based in the Peak District, Derbyshire.
The views expressed in this article are her own and not necessarily those of Stansted Airport Ltd.

For more information on Penny's current work see Penny Anderson Associates wesbite

For an uptodate view of wildflowers in transport projects see Wildflowers for transport projects :A best practice guide to creative conservation for the Merseyside transport network produced by Landlife in 2010.


Page last modified on Monday 10 of December, 2012 13:25:09 GMT