BSBINews - BSBI Archive - Botanical Society of the British Isles

60 Conference Report - 2009 - BSBI Spring Conference on alien trees and shrubs, Berwick
regular rows, and this is not always easy.
Re-planting of a clear-felled plantation poses
particular problems, and care needs to be taken
that the mix and density of species is done
sensitively and enhances the landscape.
Biomass plantations are a flourishing industry.
Three to four different hybrids involving
Salix alba (White Willow) are most frequently
used, which put on over six feet in a season
and are normally cleared after three years.
Different cultures are used to try and avoid a
build up of pests and diseases.
Woods are also often used for farming
livestock, especially pigs, and new native
broadleaved plantations attract higher grants
than conifers. The Forestry Commission have
a 'Field Survey' pack to help farmers decide
which taxa are best to plant in a particular
habitat, and it is vitally important to take into
account elevation, wind factor, drainage and
surrounding trees. The minimum planting rate
is 1,100 stems per hectare, and it is important
to try to avoid planting in species rich habitats.
Britain is divided into four main seed zones,
which are themselves divided into 24 smaller
zones, for providing seeds for planting in
specific areas, and it is important that the
provenance of all seeds and saplings is
recorded for all plantations. It is preferable to
use seed from local souces where practicable.
Magee then went on to discuss what taxa we
should be planting now, to take into account
climate change, where we might, in the future,
have vineyards rather than barley fields. Some
research is presently being carried out, and it
is suggested that seed from different provenances,
especially from zones further south,
might be used in addition to local strains, in
order to widen the genetic base. It was also
suggested that regeneration of local stock be
used as this was obviously well suited to the
present environment. She concluded by
mentioning that a large estate in the Scottish
borders was conducting trials on growing
stands of Eucalyptus.
The next speaker was Clare O'Reilly who
gave a stimulating account on 'Identifying
some look-alike native and alien trees &
shrubs', which she said was inspired by Peter
Sell's 2006 article in Nature in Cambridge-
shire, 48, as reprinted in BSBI News 105
(April,2007).
She first concentrated on three very similar
species of cherry with racemose inflorescences
of white flowers - Prunus padus (Birdcherry)
(native),P. serotina (Rum Cherry) and
P. virginiana (Choke Cherry). The fruits of
the latter were different from the other two,
but as it is not mentioned in the 2 nd edn of
Stace's New flora of the British Isles, it is
likely to key out to P. padus. A sheet of colour
photocopies of four Rosaceae leaves was
handed out, and conference members were
invited to pick the odd one out, which
provoked much discussion and disagreement
before Clare revealed that three of the leaves
belonged to the species mentioned above and
the fourth to Amelanchier lamarckii. There
were in fact two odd ones out - taxonomic ally
Amelanchier (not a Prunus) , and biogeographically
Prunus padus (native). Clare went on to
mention the brilliant new Vegetative key to the
British flora by John Poland and Eric
Clement, from which the vegetative characters
she used to separate the taxa were taken, and
remarked that it had taken her up to 'warp
speed' in identifying plants to subspecies level
in some areas, based purely on vegetative
characters, although the book was very much
a 'work in progress', and it was vital that the
authors receive feedback so that any errors can
be corrected in the next edition!
The next group to be dealt with was Corylus
avellana variants, with two alien variants
often planted alongside the native one. Clare
asked: 'Does it matter?', and went on to
explain that infraspecific taxa are expressly
included as part of biodiversity under the Rio
Convention on Biological Diversity 1992, so
arguably we should 'count' them as part of the
diversity in a hedge, even if they are nonnative.
But this affects judgements about the
age (and therefore often conservation value) of
hedges - clearly the method used to determine
an 'ancient' hedgerow of counting the number
of species per 30m section is flawed where
there are multiple non-native taxa. The
method is also unclear on whether hybrids and
infraspecific taxa 'count' or not. Oliver
Rackham has raised this point in his recent