On 14/05/2011 18:28, TimSC wrote:
On 14/05/11 17:39, Andy Mabbett wrote:
The Woodland Trust do something similar (no URL, sorry, as I'm mobile).
Do you mean http://www.woodlandtrust.org.uk/en/visit-woods/ ? I
already asked for their data set but they were not very
communicative... It would be cool to have though. (A fairly
comprehensive list of public and permissive access woods for the UK
and their operator.)
TimSC
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I'm sure Andy means this
http://www.ancient-tree-hunt.org.uk/discoveries/interactivemap/ which I
think is backed by the Woodland Trust.
My own experience & discussions with local tree experts suggest that the
data collected by this survey is fairly unreliable. There are too many
'citizen science' programmes of this kind which don't produce really
useful data because they lack any quality thresholds. It's best to see
them as designed to get people involved: essentially they are marketing
exercises. I've got a blog entry on the stocks about a similar issue:
I'll probably end up doing several.
To put a bit of context on the 10,000 trees in the Kent programme: the
Girona tree import was 28,000 trees and I think Tom Chance's Lambeth set
is of a similar size. The figure I have at the back of my mind for
Nottingham street trees is 8000, but I suspect that this is too low. I
know that Nottingham University Campus & the adjacent Wollaton Park have
over 3000 significant trees (probably excluding ones in woodland): these
are in our local tree expert's patch. With his guidance the council have
produced some excellent leaflets on trees in local parks, such as The
Arboretum <http://www.nottinghamcity.gov.uk/index.aspx?articleid=3383>.
I presume the BCTV Kent project is therefore restricted to large trees:
one of the problems with the Ancient Trees survey is that it has tended
to be affected by wild overestimates of trees size and age. Another is
that prominent and fast growing trees (think Poplars, which are
short-lived) tend to be over-represented
I've got a limited experience of a systematic tree survey: I attempted
to locate all the Oaks in Attenborough Nature Reserve, mapped them
<http://www.flickr.com/photos/sk53_osm/5492103506> with GPS & measured
BHG (Breast Height Girth). In an area of around 250 ha this took me 5
1.5 hour visits for around 100 trees from small saplings to ones upto 3
m BHG. I did this for the following reasons: a) because the ability to
say I found insect x on tree y was useful; b) to see how much work was
required; c) oaks are relatively rare at Attenborough so it was an
achievable set of data to collect. The data set is now very out-of-date:
I have not resurveyed to see which trees have survived the new flood
defense work (most by the railway line will have gone for good), and I'm
continually noticing trees I missed.
Tree identification is often non-trivial: a professional botantist I
know was hired to re-survey the Brithdir Arboretum within Coed-y-Brenin
because the orginal planting plan had either not survived, or which
trees had survived was not known. He told me that identifying some
individual trees took him hours. Certain heritage trees have been
surveyed on a national level for decades: notably ancient Yews, and the
native Black Poplar
<http://sppaccounts.bsbi.org.uk/content/populus-nigra-1> (/Populus nigra
betulifolia/). In the latter case a book
<http://www.amazon.co.uk/Black-Poplar-Ecology-History-Conservation/dp/1905119054>
was published by the Botanical Society's Black Poplar referee Fiona
Cooper. However, the map was selective as landlords have been known to
fell trees to prevent visits by Poplar geeks. Many counties include
native Black Poplar in their BAP (Biodiversity Action Plans). Richard
Mabey has good accounts of both these trees in /Flora Britannica/.
So to summarise: its important to have a clear objective before mapping
trees. So far on OSM most mapping of trees has been casual, and
therefore implicitly is for the renderer. I can think of several areas
where clear objectives can be formulated:
* In many urban contexts - parkland, amenity grassland, churchyards
- mapping isolated trees or groups of trees seems both achievable
and potentially useful.
* Tom Chance (and others) are interested in locating fruit trees:
again achievable.
* I'm probably more interested in rare or unusual trees which are
usually specimen trees in parks and larger gardens, and I'm keen
that they be accurately identified. Having a known location of a
given tree means that one can visit that tree and familiarise
oneself with its appearance. It's then a lot easier to spot other
specimens.This, though, is really a complete activity in itself.
A reasonably accurate identification is what really adds value, and
that's the hard bit.
Jerry
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