[Talk-GB] Typical plants and features of grassland, heath, scrub and woodland in Britain

SK53 sk53.osm at gmail.com
Thu Sep 16 12:05:42 UTC 2021


Hi Tom,

It's a fairly complicated issue, so not sure if these notes will help you.

The easiest ones are woodland & scrub:

* *Woodland* will generally consist of trees > 5m at maturity (so you can
use natural=wood for saplings, very pertinent in areas where the National
Forest is planting new woods). The number of tree species which one might
regularly encounter doing this is quite small (10-15 perhaps), and often
characteristic of quite a wide area (Ash in the White Peak, Oak in Wales,
Beech in the Chilterns & so on), or particular habitats (Alder & Willow on
wet floodplains). Some wood types dominated by native species are rare to
very rare (Limes, Elm, Yew, Hornbeam come to mind) and will be rarely
encountered. I think clumps of Holly in woodland ("shaws) still count as
woodland. Many other native species of tree (Cherry, Rowan, Crab Apple,
Goat Willow, Field Maple etc tend to be isolated specimens in woods
dominated by a different species.
* *Scrub* will consist of woody plants predominantly under 5 m. Hawthorn &
Blackthorn thickets, Gorse, Broom, invasive Rhododendron, most Willows (not
Crack or White Willow which are trees) & Bramble all qualify. It's
relatively straightforward to produce a list of woody plants which
typically form scrub, so recognising these can help.

* *Wetlands* are also generally straightforward, with relevant subtags.:
marsh, bog, reedbed etc. There are some minor issues as to whether reedbed
also covers areas of Bulrush/Reedmace (certainly true in Germany where the
standard word is broader in meaning).

The following tags have problems, mainly in that they are so broad in usage
to be ecologically meaningless.

* *Heath* is less easy than it looks. The first thing to say is that the
OSM use of natural=heath does not accord with an ecological one. Most of
the upland areas mapped in Britain as natural=heath are either acid
grassland or blanket bog. As Corine has a code for Moors and Heath (3.2.2,
see https://wiki.openstreetmap.org/wiki/Corine_Land_Cover#Tagging), this
also applies in much of Europe.

Proper heaths will have lots of plants belonging to the Heath family
(Ericaceae): Common Heather, Bell Heather, Bilberry, Cowberry, Bearberry.
Also Crowberry and dwarf Gorse species (< 1 m and less spiny than Common
Gorse) are common dominant species. Bracken is quite common in heathy
places, and there's often a mosaic of proper heath & grassy bits. In
lowland Britain I think there's pretty reasonably accord between
landuse=heath and what ecologists classify as heath (aside from some
misinterpretation of imagery)

There are significant differences between actual heath and the other upland
habitats. For instance anyone who has walked across Kinder Scout knows that
he apparent surface of heather belies a lot of treacherous bog, completely
different from the Eastern Moors near the Longshaw Estate. Upland grassland
which is very common does not seem to have been mapped with any kind of tag
at all. Much of the higher hills in Snowdonia are of this type of grassland.

* *Meadow*. landuse=meadow is used for a very broad range of agricultural
grasslands, and has little or any relationship to what a meadow means
ecologically. Most of the land tagged with this will be agriculturally
improved grassland, but in upland Britain may also include poorly drained
unimproved grassland, often recognisable by the presence of clumps of
rushes in aerial imagery. Unfortunately this means we have no adequate way
of mapping *Proper meadows*. These are floristically rich traditionally
managed meadows, nothing at all like the landuse=meadow tag which seems to
largely mean farmland which is not arable. These are really quite rare now
in Britain, to the extent that many people will never have encountered one.
Again existing tagging makes it hard to find a way actually mapping them is
an easy to use meaningful way. The most important way to assess any
grassland is to look down and see how many different plants you can see
round your feet. In general improved grassland will have very few, whereas
true meadows will have loads.

* *Bracken*. Bracken is technically a herb (it's growing points are not
above ground in winter), and habitats dominated by it belong to a class
called tall herb vegetation. I don't think we have a tag for dominant
stands of bracken. Somewhere I once read that about 1% of the world's land
surface is covered by Bracken so perhaps it deserves it's own tag. (But
also see comment about bracken in heathland).

Long ago Tim Foster suggested using something called Phase 1 Habitat
Mapping as a way of supplementing these top-level OSM tags in such a way to
represent more coherent ecological units, but without forcing every mapper
to use them. In a somewhat desultory way I keep adding bits to the
relevant wiki
page
<https://wiki.openstreetmap.org/wiki/Plant_Community/UK_Phase_1_Habitat_Classification>.
The manual referenced on that page has a good section of how to classify
different habitats, although it does make extensive use of scientific plant
names. Helpfully, the whole of Wales was mapped by CCW/NRW with Phase 1 and
it is available as open data. If you know places in Wales looking at how
they were classified can often help in making choices elsewhere.  There are
also open data from Natural England for particular habitats (e.g., salt
marsh, calcareous grassland) which can be downloaded or visualised on the
MAGIC site. Some councils also provide online listings of the more
ecologically important sites within their boundaries, these days called
Local Wildlife Sites (formerly SINCs), and if you are lucky a reason for
the listing.

These days there are some excellent apps for mobile phones which help
identifying plants, through use of machine learning. Personally I like
iNaturalist, but there are around 10 or so which are widely used. They are
an excellent way to obtain information, to learn more, or just connect a
plant one recognises with a name. The iNaturalist website allows browsing
an area to see what plants are around, or just looking at lots of pictures
of a given type of plant.

Jerry



On Wed, 15 Sept 2021 at 21:34, Tom Crocker <tomcrockermail at gmail.com> wrote:

> Hi fellow mappers
>
> I was wondering if anyone has summarised how to distinguish grassland,
> heath, scrub and wood and the common plants or features in Britain that
> help define these for the non-botanist like me.
>
> While many places are easy to classify (acres of heather or mature beech
> trees) I'm often unsure of where to draw the line. For example, when should
> I see holly and hawthorns as wood instead of scrub (if ever). Do gorse,
> broom and bracken belong with heath or scrub? How about an area of brambles
> or nettles?
>
> I have seen the Heath wiki talk page about distinguishing heath and scrub
> which is useful, but some of the comments are contradictory and I don't
> know the Latin names to make much headway with the linked Wikipedia
> articles. if no-one else has put something together I'd like to help
> compile this, for my benefit if no-one else's. Of course, there would still
> always be judgements to make and areas for which there's no perfect answer,
> but a handy guide might ease that process.
>
> Thanks in advance.
>
> Tom
> _______________________________________________
> Talk-GB mailing list
> Talk-GB at openstreetmap.org
> https://lists.openstreetmap.org/listinfo/talk-gb
>
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