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F O L I A F O R E S T A L I A P O L O N I C A
c
PAN Series B, Issue 38, 13-26, 2007
PHYSICAL AND CHEMICAL PROPERTIES
OF CONTEMPORARY PINE WOOD
(PINUS SYLVESTRIS L.) IN CONDITIONS
OF A WET ARCHAEOLOGICAL SITE IN BISKUPIN
Magdalena Zborowska∗, Leszek Babiński∗∗,
Julitta Gajewska∗∗∗, Bogusława Waliszewska∗,
Włodzimierz Prądzyński∗
*Institute of Chemical Wood Technology
August Cieszkowski Agricultural University of Poznań
**Conservation Department, Archaeological Museum in Biskupin
***Department of Agricultural Microbiology
Warsaw Agricultural University
SYNOPSIS. Investigations were carried out on the contemporary wood of Scots pine
(Pinus sylvestris L.) recovered following a two-year period of deposition in conditions of
a wet archaeological site in Biskupin. The impact of the natural environment on the ex-
amined wood was assessed on the basis of: its infestation by microorganisms, mass loss,
selected physical properties and chemical composition. The comparison of the investi-
gated parameters revealed small differences of the examined characteristics of pinewood
subjected to the two-year long experiment.
KEY WORDS: wood degradation, microorganisms, chemical composition
INTRODUCTION
Huge quantities of the historic wood from Biskupin have posed a serious con-
servatory challenge from the very beginnings of the archaeological work on that
site. Long-term investigations conducted on the peninsula of the Biskupin Lake
resulted in mechanical damage and biological degradation of historic wood tissue.
Despite undertaking numerous conservatory attempts (Piotrowska 1999), the
achieved results were far from satisfactory. It turned out that the best solution, in
accordance with world trends, was to leave the wooden relics under the layer of
soil.
14 M. Zborowska, L. Babiński, J. Gajewska, B. Waliszewska, W. Prądzyński
The reburial of the excavated wooden remains comprises the re-deposition of
archaeological materials under a layer of sea sediments or in the environment of wet
peat maintaining the deficit of oxygen (in anoxic or anaerobic conditions) which
restricts the growth of bacteria and other harmful organisms (Curci 2006). How-
ever, this kind of wood storage requires comprehensive analysis of the conditions
in which the historic wooden tissue is to be left as well as continuous monitoring
of the site.
Long-term deposition of historical objects is by no means a new idea. First re-
ports describing this method of wood conservation come from 1980s (Jong 1981,
Jespersen 1985). These studies comprised, primarily, monitoring of basic environ-
mental parameters of the sites of the re-burial of historical objects. However, real
evaluation of the impact of long-term storage conditions of the archaeological wood
can be arrived at only by studying changes caused by this type of environment in
this raw material. Therefore, only deposition in this environment of wood, both
contemporary and archaeological, of recognized properties will make it possible
to follow the activities of microorganisms in this particular site (Waddell 1994,
Gregory 1998, Powell et al. 2001, Bj¨
ordal and Nilsson 2003). In the case of
investigations carried out so far, the determination of the effect of the environment
on wooden objects was limited, to a considerable extent, to the visual evaluation
of the degree of their degradation (Gregory 1998) or microscopic observations
(Powell et al. 2001, Bj¨
ordal and Nilsson 2003). The supplementation of the
investigations carried out so far with the analyses of physical and chemical proper-
ties of wood will allow scientists to compare the progress of degradation processes
during the period of its storage. These types of investigations were performed on
contemporary oak wood (Babiński et al. 2006) and cellulose material obtained
from beech wood (Zborowska et al. 2007) buried in the region of the Biskupin
Lake peninsula.
The objective of the performed investigations was to identify microorganisms,
evaluate the extent of wood tissue colonization, determine mass losses, changes
of selected physical properties and chemical composition of the contemporary
pinewood following its two-year storage in conditions of the deposition of Biskupin
archaeological wood. The results of the above-mentioned investigations were sup-
plemented with the data from the basic water and soil parameters monitoring.
MATERIAL AND METHODS
Wood of a 99-year old Scots pine tree (Pinus sylvestris L.) which grew in the
Gołąbki Forest District in the neighbourhood of Biskupin (kujawsko-pomorskie
region) was used in the presented experiment. Basic macroscopic characteristics
of the examined pine wood are given in Table 1.
Physical and chemical properties of contemporary pine wood... 15
Table 1. Macroscopic characteristics of the examined pine wood
Characteristic Mean value Minimum Maximum Standard
value value deviation
Width of annual rings [mm] 1.51 0.42 6.66 0.78
Percentage of latewood [%] 37.63 13.66 57.39 9.18
Preparation and location of samples
Samples measuring 150 ×10 ×10 mm (L ×T×R) with annual increments
running parallel to the tangential direction were divided into two groups. The
samples from the first group (3 batches of 40 pieces) were saturated with water –
10 cycles of 4 hours each at the pressure of 50 hPa and 20 h at the atmospheric
pressure. The final moisture content of the saturated samples ranged from 129 to
134%. Samples from the second group (2 batches of 40 pieces) were not subjected
to water saturation and their final moisture content was about 12%. Wood samples
prepared in this way were left for the period of two years in a layer of wet peat or
at the bottom of a pit filled with water both situated in the area of the Biskupin
archaeological site. The choice of the site and the place of burial of experimental
samples were imposed by the place of deposition of wooden remains of the Łużyce
culture from the 8th century BC. The dry and wet samples were left in the wet
peat at the depth of 50 and 100 cm, whereas at the bottom of the pit filled with
water, only wet samples were deposited (Table 2).
Table 2. Designation of samples, moisture content and places of deposition of pine wood
Wood moisture content
Samples before deposition Place of deposition
[%]
D-50 12 peat, at the depth of 50 cm
W-50 129 peat, at the depth of 50 cm
D-100 12 peat, at the depth of 100 cm
W-100 134 peat, at the depth of 100 cm
W-T 133 bottom of pit filled with water
Monitoring of environment
Throughout the duration of the experiment, the following parameters were
monitored at the place of sample deposition: the level of ground water and the
level of water in the pit, water reaction (pH), soil temperature and redox potential.
The methodology of the performed measurements was presented in another study
(Babiński et al. 2004).
Evaluation of the degree of wood degradation
The degree of degradation of pinewood buried for two years at the Biskupin
site was assessed on the basis of:
16 M. Zborowska, L. Babiński, J. Gajewska, B. Waliszewska, W. Prądzyński
– Microbiological investigations, i.e. identification of microorganisms as well as
determination of the extent of external (to the depth of 1-1.5 mm) and internal
(to the depth of 3.5 to 5 mm) wood colonization,
– Selected physical properties, i.e. moisture content, maximum moisture con-
tent, wood conventional density and longitudinal shrinkage,
– Mass losses,
– Chemical composition, i.e. content of holocellulose, cellulose, lignin, substance
soluble in the mixture of alcohol and benzene as well as in cold and hot water.
The performed microbiological investigations comprised the determination of
the colonization capability of the examined wood by soil proper bacteria (faculta-
tive and obligate anaerobes), actinomycetes as well as yeasts and hyphal fungi. The
following microbiological substrates were employed in order to isolate and identify
the occurring microorganisms: nutritive agar with/without the addition of 10%
de-fibred ram blood, McConkey medium, Bunt&Rovir substrate with the addition
of 1% starch and nystatin, King’s B substrate, Wilson’Blair’s medium, Dubos’s
medium as well as the medium according to Weimer and Zeikus (with the addi-
tion of filter paper as the only carbon source), the substrate for the nitrification
bacteria according to Coppier and de Barjac, de-nitrification bacteria according
to de Barjac and ammonification bacteria (with Winogradski’s salts), N2fixing
bacteria (medium according to D¨obereiner) as well as Martin’s and Sabouraud’s
medium. Cultures of bacteria, actinomycetes and aerobic fungi were carried out in
aerobic conditions at the temperature of 30◦C. Anaerobic bacteria cultures were
conducted using an aerostat (BBL) in the presence of H2and CO2, palladium
catalyser and methylene blue as indicators of anaerobic conditions. Cultures of
mesophilic anaerobic bacteria were carried out at the temperature of 30◦C and
those of thermophilic ones – at the temperature of 55-60◦C. Api tests of the
bioMerieux Company and Bergey’s systematics (Manual of Determinative Bac-
teriology, 2000) were used for the identification of the selected bacterial isolates,
while fungal identification was performed employing the systematics developed by
Barnett (1960-1965) and Fassatiova (1979).
Wood moisture content was determined by the drier-gravimetric method af-
ter drying the samples to the constant mass at the temperature of 105◦C. Wood
maximum moisture content was determined on the basis of the mass of samples
saturated with water many times at the pressure of 50 hPa and the mass of ab-
solutely dry wood. Wood conventional density was determined on the basis of the
mass of absolutely dry wood and the volume of the sample in the state of max-
imum saturation with water determined by the hydrostatic method according to
the formula given below:
d=m0
Vmax
·1000
where: d– conventional density [kg·m−3],
m0– mass of absolutely dry wood [g],
Vmax – wood volume in the state of maximum saturation with water [cm3].
Longitudal shrinkage has been defined by measuring the distance between two
steel pins inserted perpendicularly into tangential and radial sections of the sample.
The pins, 85 mm apart from one another, were hammered into wet wood directly
Physical and chemical properties of contemporary pine wood... 17
before drying the wood to absolutely dry state. The measurement error is 0.01 mm.
Longitudal shrinkage has been calculated according to the following equation:
βL=l1−l0
l1
·100
where: βL– longitudal shrinkage [%],
l1– pin distance in wet wood,
l0– pin distance in dry wood.
The loss of wood mass left in natural environment for the period of two years
was calculated according to the following formula:
UM =m0−m1
m0
·100
where: U M – mass loss [%],
m0– absolutely dry matter of wood prior to burying [g],
m1– absolutely dry matter of wood following a two-year period of depo-
sition in peat [g].
The chemical composition of investigated wood was determined by use all ma-
terial without division on more or less degraded part, in accordance with the Polish
Standard PN 92P/P 50092.
RESULTS
The performed measurements of water levels in the area of the Biskupin Lake
peninsula revealed that the samples buried in peat at the level of 100 cm (D-100
and W-100) as well as those deposited at the bottom of the pit (W-T) were all
submerged in water during the entire experimental period. On the other hand,
wood samples placed 50 cm under the surface (D-50 and W-50) stayed in water
during the period from autumn to spring, whereas from May until the end of
October, they remained above the ground water table, in the layer of moist peat.
The ground water reaction (pH) ranged from 6.27 to 7.32. Higher groundwater
reactions – with maximum values of 8.77 – were recorded in the water from the
pit. The soil temperature changed in the interval ranging from 1.2 to 20.2◦C. The
redox potential which ranged from −250 to −150 mV in the examined soil and from
−250 to −120 mV in the pit filled with water pointed to the reducing conditions
of the experimental environment in which the wood samples were buried.
The wood samples recovered after two years of deposition were characterized
by a slightly darker colour in comparison with the control samples. However, no
deformations or desorption cracks typical for degraded wood were found in them.
The results of bacteriological investigations of the pine wood samples deposited
for the period of two years in anoxic conditions are presented in Table 3 and those
of mycological analyses – in Table 4.
18 M. Zborowska, L. Babiński, J. Gajewska, B. Waliszewska, W. Prądzyński
Table 3. Colonization of pine wood by facultatively anaerobic bacteria, strictly anaerobic
Clostridium spp. bacteria and Streptomyces spp. Actinomycetes
Samples
D-50 W-50 D-100 W-100 W-T
A B A B A B A B A B
Bacillus spp. + + + + + + + + + +
B. mycoides + + + + + + + + + +
B. polymyxa + + + + + + + + + +
Cellulomonas sp. − − − − − − − − + +
Clonothrix fusca − − − − − − − − + +
Clostridium spp.* + + + + + + + + + +
Clostridium perfringens red. sulphates + + + + + + + + + +
E. coli − − ++− − − − + +
Enterobacter sp. − − ++− − − − + +
Enterococcus faecalis − − − − − − − − +−
Nitrosomonas sp. + −+−+−+−+−
Pseudomonas sp. + + + + + + + + + +
P. aeruginosa + + + + + + + + + +
P. fluorescens + + + + + + + + + +
Proteus vulgaris − − +− − − − − +−
Sporocytophaga sp. + + + + + + + + + +
Streptomyces spp. + −+−+−+ + + +
A – external zone (1-1.5 mm), B – internal zone (3.5-5 mm).
*Meso- and thermophilic cellulolytic bacteria from the Clostridium genus.
Table 4. Colonization of pine wood by hyphal fungi and yeasts
Samples
D-50 W-50 D-100 W-100 W-T
A B A B A B A B A B
Aspergil lus spp. + + + −+++++−
A. fumigatus − − +−−−−−−−
A. niger − − +−−−−−−−
Candida sp. − − +++−+−+−
C. jovanica − − +−−−−−−−
Fusarium sp. − − +−−−−−−−
Penicillium spp. + + + + + + + + + −
P. notatum −−−−−−−−+ +
Rhodotorula sp. −−−−−−−−−+
Saccharomyces spp. − − +++−+−+−
Trichoderma spp. + −+−+−+− − −
T. viridae +−+−−−−−+−
A – external zone (1-1.5 mm), B – internal zone (3.5-5 mm).
Physical and chemical properties of contemporary pine wood... 19
Both Gram-positive and Gram-negative bacteria differing with regard to their
morphological, physiological and taxonomic traits were found in the examined
wood samples. The identified bacteria colonized not only the external wood layer
– to the depth of 1.5 mm but also its internal part to the depth of 5 mm, irre-
spective of the fact whether the stored wood was buried dry or wet. The identified
bacteria included, among others: facultative anaerobes from the Pseudomonas,
Bacillus, Escherichia, Enterobacter, Nitrosomonas, Sporocytophaga genera and
actinomycetes from the Streptomyces genus as well as obligate anaerobes from
the Clostridium genus. The isolated microorganisms were characterized by the
ability to carry out many biochemical processes, such as, among others: fermen-
tation of mono- oligo- and polysaccharides, ammonification, proteolysis, nitrifi-
cation, de-nitrification, sulphite reduction and production of hydrogen sulphite.
Cellulolitic Bacillus polymyxa,Sporocytophaga sp. bacteria as well as meso- and
thermophile bacteria from the Clostridium genus capable of cellulose, hemicellu-
loses and lignin degradation could have been responsible for the decomposition
of pine wood. Pinewood samples deposited for 2 years at the bottom of the pit
filled with water were found to be colonized even by a wider range of bacterial set-
tlers. Apart from the bacteria mentioned above, these samples were also infected
with faecal enterococci Enterococcus faecalis, rod-like Proteus vulgaris, thread-like
Clonothrix fusca as well as the cellulolitic bacteria from the Cellulomonas genus.
Nitrification bacteria of the Nitrosomonas sp., which belong to the so called
amonox group, were found to be present in all the examined wood samples but
only on their surface layer, whereas de-nitrification bacteria, e.g. from the Pseu-
domonas and Clostridium genera were determined also inside wood samples. The
observed dark colour of wood samples could have been caused, among others, by
the reduction processes of sulphates into hydrogen sulphide and the production
of dark-coloured sulphides by the bacteria of Clostridium genus. It was further
demonstrated that, apart from saprophytic bacteria, also pathogenic as well as
conditionally pathogenic bacteria were identified, among others bacteria from En-
terobacteriaceae,Pseudomonadaceae and Clostridiaceae genera.
On the basis of mycological investigations it was found that, in anaerobic condi-
tions, the experimental pinewood was colonized by few types of microscopic fungi.
It was observed that pinewood samples were colonized during the two-year pe-
riod of storage more readily when they were introduced into the soil wet. They
were colonised, primarily, on their surface by lignocellulosic hyphal fungi from
Aspergillus,Trichoderma and Fusarium genera. From the external and internal
pinewood surfaces lignocellulosic Penicillium spp. fungi as well as yeasts from the
Saccharomyces and Candida genera were isolated. Inside wood samples buried dry,
the presence of lignocellulosic fungi of the Penicillium and Aspergillus genera were
determined. Fungi of Penicillium spp. and Rhodotorula sp. yeasts were identified
inside the wood stored at the bottom of the pit filled with water. The internal
layer of pinewood samples deposited in the pit with water was completely free
of yeasts but was settled by numerous bacteria and only one species of hyphal
fungi, namely Penicillium notatum. Microscopic fungi colonizing wood belong to
saprophytic fungi but some of them can be pathogenic, for example fungi from the
Aspergillus, Trichoderma, Fusarium and Candida genera.
20 M. Zborowska, L. Babiński, J. Gajewska, B. Waliszewska, W. Prądzyński
Microbiological investigations on the settlement of lignocellulosic pine sub-
strates and their degradation also allow to determine the degree of succession of
microorganisms and their diversity (Kundzewicz et al. 1993, Gajewska 1993,
Gajewska 1994, Gajewska et al. 2005, Gajewska et al. 2006). Pinewood
degradation depends not only on the types of the colonizing microflora, on their
ability for adhesion to the substrate, penetration, infestation but also on, among
others, their ability to proliferate in wood, enzymatic activity of strains, degree of
their sporulation in very specific conditions of the environment described earlier
(refers to: anoxia, low redox potential, temperature and reaction – pH). It appears
that the accumulation of sulphides produced by obligate anaerobes of the Clostrid-
ium genus or by facultative anaerobes of the Proteus genus can impede or limit
the growth of heterotrophic bacteria and fungi as facultative anaerobes and, by
doing so, show pinewood conserving activity.
Table 5 presents physical properties and mass losses of the experimental
pinewood. The mean moisture content of the experimental pinewood wood, both
the one buried in the dry state (wood with the initial moisture content of 12%)
and the wood buried in the wet state (initial moisture content of 132%) after a
two-year period of storage in the archaeological site ranged from 124 to 142%. The
highest moisture content was determined in the samples deposited at the bottom
of the pit filled with water.
The maximum moisture content, which is a sign of the degree of progress of
degradation processes, is one of the most frequently determined physical properties
of degraded wood (Hoffmann 1982, Babiński 1997, Bj¨
ordal 2000, Prądzyński
and Cichocka 2002). The mean maximum moisture content of the experimental
pinewood changed within a very narrow interval of 145 to 151%, with the lowest
value determined for wood samples buried in wet state at the depth of 50 cm
and the highest one – for the wood samples left at the bottom of the pit filled
with water. The comparison of the obtained results with the maximum moisture
content determined in the control samples (141%) indicates slight changes of the
analysed property. The lack of clear degradation of the wood tissue is confirmed
by the values of the conventional density of the examined samples. The lowest
mean conventional density determined for wood samples left in the pit filled with
water was 462 kg·m−3, while the highest one determined for the material buried in
wet state in peat at the depth of 50 cm amounted to 475 kg·m−3. Comparing the
above values with the conventional density of the control samples (483 kg·m−3),
it can be said that the considered property decreased only slightly.
The physical properties discussed so far allow to differentiate the examined
samples from the point of view of the intensity of wood degradation. In compar-
ison with the values determined for the control samples, the greatest differences
regarding wood properties were observed in the case of wood samples left at the
bottom of the pit filled with water (W-T). Values similar to the initial ones were
obtained for wood samples buried wet in peat at the depth of 50 cm.
The next property, namely longitudinal wood shrinkage, failed to reveal signifi-
cant differences between the analysed sample series. The obtained values fluctuated
within the interval ranging from 0.14 to 0.18%. The longitudinal wood shrinkage of
the control samples was 0.12%. Therefore, it can be said that this wood property
Physical and chemical properties of contemporary pine wood... 21
Table 5. Physical properties and mass losses of pine wood
Property Samples
D-50 W-50 D-100 W-100 W-T control
Moisture content [%] min 105 121 113 126 125
max 146 144 141 154 162
mean 124 132 127 141 142
s10 6 8 8 10
Maximum moisture min 131 129 139 139 138 126
content [%] max 170 153 161 162 167 169
mean 150 145 149 151 151 141
s12 6 6 8 9 10
Conventional density min 424 456 438 439 427 426
[kg·m−3] max 508 513 488 488 491 521
mean 465 475 467 463 462 483
s25 15 14 17 18 23
Longitudinal shrinkage min 0.11 0.12 0.14 0.13 0.14 0.11
[%] max 0.20 0.21 0.26 0.22 0.22 0.15
mean 0.14 0.16 0.18 0.17 0.17 0.12
s0.02 0.03 0.03 0.03 0.02 0.01
Mass loss [%] min 1.57 2.14 3.04 2.28 3.61
max 2.96 3.25 4.47 3.99 5.53
mean 2.23 2.83 3.54 3.12 4.41
s0.48 0.35 0.37 0.52 0.50
min – minimum value, max – maximum value, s– standard deviation.
did not change in the course of the two-year period of wood deposition in natural
conditions.
The mass decrement (UM) shows which part of wood underwent decomposition
and/or was extracted from the degraded object (sample). The highest mean UM
value amounting to 4.41% was determined for wood samples left in the pit filled
with water (W-T). This can probably be attributed not only to the high activity
of microorganisms resulting from the higher oxygen content but also to a more
unrestricted extraction of water soluble wood constituents. Values slightly lower
were determined in the samples buried in peat at the depth of 100 cm. Wood
samples buried in the dry state were characterized by the loss of wood substance
amounting to 3.54% and those saturated with water – to 3.12%. The lowest losses
of wood substance were recorded in the case of wood samples buried in peat at
the depth of 50 cm. The mass decrement of wet samples amounted to 2.83%, while
that of dry wood samples – to 2.23%.
Figure 1 presents the percentage proportion of major chemical constituents of
pinewood subjected to the experiment. The percentage proportion of the carbohy-
drate constituents in the examined sample series left in the natural environment
fluctuated within a narrow interval ranging from 69.40% to 71.05%. The compar-
ison of these results with the percentage proportion of holocellulose in the control
22 M. Zborowska, L. Babiński, J. Gajewska, B. Waliszewska, W. Prądzyński
0
10
20
30
40
50
60
70
80
[%]
D-50 W-50 D-100 W-100 W-T control
holocellulose (H) cellulose (C) lignin (L)
71.03 70.5 71.05 70.37 69.4 72.28
47.14 47.88 47.78 47 46.76 48.67
29.54 29.89 28.46 29.56 30.06 27.98
Fig. 1. Percentage content of main chemical constituents of pine wood
material (72.28%) reveals only a sight decrease in the polysaccharide content in
the material subjected to the described two-year experiment. The highest loss of
holocellulose took place in wood samples left in the pit filled with water (W-T)
as 69.40% carbohydrates were determined in this material. The results obtained
for the wet wood samples buried in peat at the depth of 50 and 100 cm were only
slightly higher and reached 70.50 and 70.37%, respectively. The highest propor-
tions of polysaccharides were determined in dry wood samples buried in peat at
the depth of 50 and 100 cm. In comparison with the control material, the content
of holocellulose in these two cases decreased by approximately 1 percentage point.
Also the determined differences in the cellulose contents were small. The propor-
tion of this main wood constituent, following its two-year long exposure to the
effect of the natural environment, ranged from 46.76 to 47.88% and the content
of cellulose in the control sample was only slightly higher amounting to 48.67%.
Again, the lowest cellulose content was determined in the wood samples left in the
water-filled pit (W-T). The consequence of the decrement of polysaccharide com-
ponents was an apparent increase in the lignin percentage content, as this wood
constituent remains resistant to numerous soil microorganisms and hydrolytic pro-
cesses (Wróblewska 1994, Grattan and Mathias 1986, Zborowska et al.
2005). The content of this wood constituent increased in the examined wood sam-
ples from 27.98% to, respectively: 29.54 and 28.46% for the materials D-50 and
D-100 buried in the dry state at the depth of 50 and 100 cm. In the case of wood
samples buried wet in peat at the depth of 100 cm, the content of lignin was almost
identical (29.56%), whereas in the case of wet wood samples buried in peat at the
depth of 50 cm, the content of lignin was 29.89%. As expected, the highest lignin
content (30.06%) was determined in the pinewood samples left at the bottom of
the water-filled pit (W-T).
The determination of the percentage proportion of the main wood constituents
makes it possible to assess the value of the ratio of holocellulose and cellulose
content to the content of lignin (H/L and C/L) (Grattan and Mathias 1986,
Physical and chemical properties of contemporary pine wood... 23
Babiński 2005, Waliszewska et al. 2007). The H/L and C/L values for the
experimental wood are presented in Figure 2. The ratio of the holocellulose pro-
portion to the lignin proportion in the series of control samples was determined
at 2.58. The H/L ratio in the case of the wood used in the two-year experiment
ranged from 2.32 to 2.50. The lowest value indicating the most advanced degrada-
tion of carbohydrate constituents was determined for the material designated as
W-T left in the pit filled with water. Values of the H/L ratio were found slightly
higher (2.36 and 2.38, respectively) in the case of pinewood samples buried wet in
peat at the depth of 50 and 100 cm (W-50 and W-100). In comparison with the
control samples, the smallest changes in the H/L ratio were found in the case of
wood samples buried dry in peat at the depth of 50 and 100 cm. The ratio of the
cellulose content to lignin content (C/L) for the undegraded wood amounted to
1.74. This ratio determined in the samples exposed to the influence of the natural
environment ranged from 1.56 to 1.68. Again, as in the case of the H/L ratio, the
lowest values of the C/L relation were determined for the wood left in the pit
filled with water confirming yet again its most advanced degradation. In the case
of wood samples buried dry at the depth of 100 cm (D-100), the high C/L ratio
reaching 1.68 confirmed their slight degradation changes suggested earlier on the
basis of the content changes in the holocellulose and the value of the H/L ratio.
0.0
0.5
1.0
1.5
2.0
2.5
3.0
D-50 W-50 D-100 W-100 W-T control
H/L C/L
2.4 2.36 2.5 2.38 2.31 2.58
1.6 1.6 1.68 1.59 1.56 1.74
Fig. 2. Ratio of holocellulose to lignin (H/L) and cellulose to lignin (C/L) of pine
wood
The analysis of the secondary wood constituents, whose results are presented in
Table 6, included, among others, the determination of the percentage proportion
of substances soluble in the mixture of alcohol and benzene. In the case of the
control wood samples, this fraction constituted 2.64%. The content of extractable
substances in wood samples following their two-year storage in natural conditions
decreased by more than half and fluctuated within the interval ranging from 1.04
to 1.25%. Also the content of wood constituents soluble in cold water decreased
considerably ranging from 0.62 to 0.77%. On the other hand, the proportion of
24 M. Zborowska, L. Babiński, J. Gajewska, B. Waliszewska, W. Prądzyński
Table 6. Percentage content of extractive substance of pine wood
Substances soluble in:
Samples alcohol benzene cold water hot water
mixture
D-50 1.19 0.77 1.14
W-50 1.15 0.62 1.35
D-100 1.07 0.67 1.08
W-100 1.04 0.64 1.11
W-T 1.25 0.73 1.35
Control 2.64 1.89 1.20
wood constituents soluble in hot water determined in the experimental wood sam-
ples remained on the level found in the control samples fluctuating from 1.11 to
1.35%.
CONCLUSIONS
1. On the basis of the performed investigations similar values were found in the
basic physico-chemical parameters of the environment in which the wood
samples were buried.
2. The performed bacteriological and mycological investigations revealed con-
siderable diversification of the bacterial and fungal microflora occurring in
the examined pinewood. The highest activity of the examined bacteria was
found in the case of wood samples left at the bottom of the water-filled pit.
3. The comparison of physical properties, mass decrements and chemical
composition revealed small differences of the examined characteristics of
pinewood subjected to the two-year long experiment.
4. Further investigations on the degradation of contemporary wood tissue in
conditions of the deposition of the Biskupin archaeological wood will reveal
if the initial results signal long-term trends.
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Received in August 2007
Autors’ addresses:
Dr. Magdalena Zborowska
Dr. Bogusława Waliszewska
Prof. Dr. Włodzimierz Prądzyński
Institute of Chemical Wood Technology
August Cieszkowski Agricultural University of Poznań
ul. Wojska Polskiego 38/42
60-627 Poznań
Poland
Dr. Leszek Babiński
Department of Conservation
Archaeological Museum in Biskupin
Biskupin 17
88-410 Gąsawa
Poland
Dr. Julitta Gajewska
Department of Agricultural Microbiology
Warsaw Agricultural University
ul. Nowoursynowska 159
02-776 Warszawa
Poland
