are especially important if larger oak timbers, which from existing data are
potentially not as degraded as the smaller artefacts, are present on the site.
However, if the water level in Nydam should fall below that of the find lay-
ers, there may be the risk of fungal deterioration. Fungal decay can be
divided into three groups: white, brown and soft rots. White and brown rots
(Basidiomycetes) generally require high levels of oxygen and non-water-
logged conditions in order to decay wood. They predominate in well-drained
and aerated soils and lead to the relatively rapid and total destruction of
wood. Soft rot fungi (ascomycetes and fungi imperfecti) appear to be tol-
erant of lower oxygen concentrations and waterlogged conditions in soils.
Experiments were conducted to simulate the effect of drainage by inoculating
pieces of a sterilized ash spear shaft from Nydam with strains of white and
brown rot fungi. It was found that after 8 weeks, white rot was able to utilise
the already degraded wood tissues, whereas brown rot showed no effect.
Although these results have implications for the long-term preservation
and/or deterioration of archaeological wooden artefacts, the results of the
collapse experiments show that the majority of important archaeological
information (surface details) would be lost as soon as the artefacts begin to
dry (99% relative humidity). Thus, it is important to know whether the arte-
facts are so degraded that they are likely to suffer collapse when considering
their in situpreservation. Similarly, it is important to know whether an arte-
fact has suffered collapse prior to determining bulk density as, if so, artifi-
cially high results will be obtained, giving the impression that artefacts are
better preserved than they really are. It appears that as long as the water level
in Nydam remains stable there will be limited deterioration from micro- and
macro-organisms. Modern wood samples were placed on the site in 2002 and
results after 1-year of exposure show no signs of deterioration. Yet, this may
simply be due to the short exposure time. The major threat still present on the
site appears to be the roots of the Equisetum. Pilot studies to prevent their
growth are ongoing with attempts to physically cut the horsetails periodically
(labour intensive and thus costly). A further method is placing geo-textile
over the parts of the site and monitoring to see if it prevents their growth. The
environment under the geo-textile is also being monitored to see if it is
changing as a result of this.
4.3 Deterioration of Iron Artefacts
Analysis of metal artefacts tells us about their state of preservation, and analy-
sis of any covering corrosion products informs us about the post-depositional
corrosion processes and their thermodynamic stability. This in turn enables
us to forecast the changes in the environment that may be detrimental to their
future preservation.
In-situ Preservation of Waterlogged Archaeological Sites 323