The flora of Stanmore Common

 

John Dobson

 

Indicators of ancient woodland. 1

Other flora. 3

A few fauna. 4

Management issues. 4

Maps and GIS. 4

 

This presentation covered the botanical survey of Stanmore Common, 2010-2012 and looked at wider issues and some other aspects.

 

Stanmore Common was surveyed using a hand-held GPS unit.

 

Indicators of ancient woodland

 

Stanmore Common has been sheep-grazing land, heathland and a quagmire and marsh in the 19th century.  It has very few ancient trees but the flora indicates that it is an ancient woodland site.  Indicators of ancient woodland spread very slowly from their site of origin.  One example is holly, which is such an indicator, not alone but as part of a suite of species.  The number of indicators which are specific to south-east England have been mapped in an audit of Compartment 11 in the north-east woodland.  The rest of the Common has not really been looked at the right time of year.  Indicators are concentrated in the south-east.

 

 

Among the indicator species are:

·         Ransoms –  2 or 3 colonies just north of Warren Lane;

·         Sanicle – which likes damp conditions, is far commoner than was thought;

·         Remote sedge – which is widespread but is an indicator as part of the suite of species;

·         Broad-leaved helleborine;

·         Wood meadow-grass – again widespread but part of the suite of indicator species;

·         Wood sorrel – very patchy distribution disrupted by previous gravel digging;

·         Ancient common hawthorn – there is only one clear example of an ancient tree on the Common with a 219cm girth (compared to the 12cm minimum for an ancient hawthorn).  It was shielded by acers but has now been opened up on one side;

·         Wild service tree – present as saplings but no mature trees;

·         Creeping soft-grass;

·         Wood millet – near Warren Lane;

·         Sessile oak – there are 3 close together on the northern margin of the Common;

·         Aspen – very strong population and associated invertebrate fauna;

·         Lily of the valley – 3 fine colonies well into woodland so unlikely to be garden escapes;

·         Three-nerved sandwort – in compartment 18; and

·         Wood anemone – very patchy distribution.

 

        

Ransoms                                              Sanicle                                     Remote sedge

 

        

Wood sorrel                             Three-nerved sandwort                       Wood anemone

Other flora

 

Other flora identified during the survey include:

·         Variegated yellow archangel - a garden escape which can be very invasive but is kept under control;

·         Slender St John’s wort – in wet heathland;

·         Square-stemmed St John’s wort;

·         Purple moor-grass – forms discrete tussocks and tunnels of bare earth provide a habitat for ants and bees – it is very invasive;

·         Honeysuckle – in huge amounts;

·         Bristled club-rush – typically in foot or hoof prints, one near car park;

·         Brown bent – rare in Greater London, and is apparently from the seed bank in the soil on the scrape for New Heath;

·         Corn mint – very rare;

·         Cornflower – in Bluebell Heath;

·         Cyprus sedge – just a couple of plants;

·         Devil’s bit scabious – characteristic of acid environments, prefers damp areas, a London rarity;

·         Giant horsetail – this has become common in London in recent years, very extensive colony;

·         Gooseberry;

·         Green-ribbed sedge – a real rarity in London, last recorded at the Common in the 1950s but it reappeared in the scrape at New Heath, apparently from the seed bank in the soil – 4 or 5 plants;

·         Heart fern – reappeared in the scrape at New Heath;

·         Heath grass – one patch found, there is only one other site in London;

·         Hemlock water dropwort – in ditch by cottage north of the Common;

·         Intermediate polypody – on fallen tree trunk, reasonably scarce;

·         Single-bladed fern – recorded historically and still there;

·         Still sedge – on Bluebell Heath.  There were 9 plants in 2000.  Moving the grass cut to the end of the year and using a rotational cut has really benefitted this plant;

·         Ragged robin – not common; and

·         wild privet – one clump next to the horse ride at the northern end of the Common.

 

      

            Purple moor-grass                  Giant horsetails                       Green-ribbed sedge

A few fauna

 

John showed pictures of field vole sign in the form of leaf piles, a hoverfly, which relies on flushed wet acid grassland to breed, a longhorn beetle, one of the deadwood fauna and the white admiral, which was first recorded at the Common in 2003 through the Greater London Assembly borough survey of biodiversity and was fairly common in 2010.

 

Management issues

 

Management issues were illustrated using examples from compartment 13 The Wetwood.  This is seasonally wet woodland which dries out, at least on the surface, every summer, though the summer water table remains very near the surface.  Hydrology is an important consideration.  For example it is not clear whether a pipe under the road provides drainage or a water supply.  Velvet bent is a characteristic species in damp areas with creeping jenny and hawkweed.  There is lots of decaying timber (not deadwood) and mature trees include oak and beeches.  There is a problem with tipping waste (grass cuttings and hedge clippings) over the fence from Stanmore Rugby Club as well as fly tipping   Harrow Council have proposed street lighting for Warren Lane but there will be a thorough bat survey before a decision is taken.  Rabbits graze on the velvet bent but it is possible that it is a small isolated colony and there are probably not enough rabbits to have a huge effect on the ecology.

 

        

         Velvet bent                             Creeping Jenny                         Decaying timber

Maps and GIS

 

John finished by illustrating the use of geographical information systems (GIS) to build up layers of mapped data, geographically align it with the ordnance survey map and add additional data such as target notes.  Obtaining elevation data enabled contouring at 5 and 1m intervals with a coloured elevation map and a watershed analysis to see where water should flow, which pretty well matches where it does apart from two explicable anomalies (artificial constructs).  He also briefly illustrated the use of this system for management planning of maintenance activities.