Woodland Survey from English Nature supported by the
Woodland Trust. Long-term ecological change in British woodland
(1971-2001)
The countryside and its woods have changed greatly over the last 50
years. This project explores and measures changes in woodland soils,
tree and shrub layers and the ground flora through a re-survey of
woods first studied 30 years ago. The work was carried out largely
by the Centre for Ecology and Hydrology and was funded by
Countryside Council for Wales, Department of Environment, Food and
Rural Affairs, English Nature, the Forestry Commission, Joint Nature
Conservation Committee, Scottish Natural Heritage and the Woodland
Trust.
In 1971 103 woods across Britain were selected as representative of
a wider sample of 2,453 woods (> 4 ha) surveyed in the late 1960s.
Within each of the 103 woods sixteen 200m2 plots were located at
random and records made of soils, tree and shrub composition, and
ground flora with each plot. Between 2000 and 2003 (the '2001'
survey) the sites were revisited and the plots re-recorded on as
close to the same point as possible. The original recording methods
were used. The results from the 2001 survey were compared with the
original data and changes identified at plot and site levels. The
key findings were:
• a marked decline in ground flora richness, particularly amongst
woodland specialists;
• a reduction in small woody stems and regeneration, but an increase
in basal area of woody species
• a decrease in the open habitats;
• a marked increase in soil pH.
The broad composition and structure of the whole suite of woods was
not dramatically different in 2001 from that in 1971. Some of the
results indicate some recovery from past damage – for example the
increase in soil pH. Other changes, most particularly the decline in
woodland specialist richness, represent deterioration in the quality
of the woods.
For the full report or other publications on this subject, please
contact the Enquiry Service at English Nature on 01733
455100/101/102 or email enquiries@english-nature.org.uk
For further information about the work of English Nature, please
visit our website at:
www.english-nature.org.uk
We also found effects on species distributions and abundance
correlated with climate change over the last 30 years. Given the
changes that are already being observed in the phenology of species,
it seems likely that effects on woodland species abundance will
become even more common in the next 50 years. Under climate change
conditions, in general, larger populations (or meta-populations) are
more likely to survive and spread than small ones. This supports the
case for an increase in woodland area and for improving connectivity
within the landscape, but also for addressing other causes of
species decline that do have a clear management solution. Signs of
eutrophication in the ground flora were detected that were
correlated with models of diffuse pollution and the management of
adjacent land. Increased nitrogen inputs at the edges of woods from
adjacent agriculture can be addressed in part through developing
buffer strips next to woodland and by developing dense vegetation at
the wood edge. The significance of diffuse pollution impacts for
woodland species is becoming more widely appreciated. Impacts may be
reduced by maintaining high shade levels – in effect ensuring that
light levels rather than nutrients act as the limiting factor. Given
the generally young nature of most of the stands, then without
deliberate management intervention broadleaved woods are, on
average, likely to become older and darker in the next twenty years.
Opening out the wood temporarily may increase the abundance of some
species, which is desirable if existing woods are to act as sources
for the colonisation of new woodland. In undertaking such management
we must be aware of the increasing potential of interactions with
and between other drivers (climate change, nitrogen deposition, deer
grazing) to influence the outcome.
All long-term woodland studies gain in value with time: equally we
(English Nature) are conscious that some of our analyses would be
more useful if there were not such a long gap between the survey
times. The data will be made available for further analyses.
Consideration will be given to linking at least some of the sites
surveyed into other woodland surveillance programmes. |
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