10.6092/issn.1973-9494/7116
In questo lavoro si riportano i risultati della caratterizzazione di un tronco subfossile rinvenuto in profondità nel fango del canale Piavon, a Chiarano (TV), in occasione dei lavori di scavo del canale nel 2008. Il tronco, di imponenti dimensioni, privo di rami e corteccia, presenta la superficie esterna profondamente fessurata, nera, fortemente degradata, dall’apparenza carbonizzata, mentre internamente ha la tipica colorazione nerastra della cosiddetta quercia annegata. Gli studi hanno dimostrato che si tratta di un albero appartenente al genere Quercus, farnia o rovere. La datazione al radiocarbonio e le analisi dendrocronologiche hanno collocato il periodo di crescita della pianta in epoca medievale, intorno al XIII secolo. La determinazione della MCW e della densità basale residua indicano che il degrado decresce dall’esterno all’interno; il contenuto delle ceneri è elevato esternamente, e diminuisce andando verso l’interno. Il Piavon è attualmente un canale di irrigazione, ma in epoca veneziana era navigabile e veniva utilizzato per il trasporto di merci e legname. Tutta l’area lungo il Piavon presentava boschi di farnia e rovere di notevole estensione, la cui dimensione e composizione è documentata dai catasti veneziani, che riportano anche le distanze tra i boschi e i corsi d’acqua più vicini, a testimonianza dell’importanza del trasporto fluviale del legname. In particolare, nella villa di Chiarano, nel catasto Surian (1569-70) si trova censito un bosco di roveri di 18 ettari. I roveri erano utilizzati dalla Serenissima soprattutto per la costruzione e manutenzione della flotta navale. Il tronco di Chiarano, considerata la collocazione temporale e la zona di ritrovamento, può essere quindi un tronco abbattuto in epoca veneziana, forse destinato all’impresa navale, andato perduto durante il trasporto per fluitazione.
application/pdf
1973-9494
7116
2
en
Tobia Scortegagna
Conservation Science in Cultural Heritage
floating
The Subfossil Trunk of Chiarano (TV)
Text.Serial.Journal
https://conservation-science.unibo.it/
15
Articles
2017-06-01
2017-07-04
2017-06-01
2017-09-04
41-52
CSCH
Tobia Scortegagna
2015
10.6092/issn.1973-9494/7116
41
Dendrodata s.a.s., Verona
1973-9494
2
floating
en
52
The Subfossil Trunk of Chiarano (TV)
https://conservation-science.unibo.it/article/download/7116/6827
15
T     HE SUBFOSSIL TRUNK OF CHIARANO (TV)

    Tiziana Urso*3
    TESAF Dept., Università di Padova, Italy
    Nicoletta Martinelli, Olivia Pignatelli
    Dendrodata s.a.s., Verona, Italy
    Tobia Scortegagna
    Graduate in Evolutionary Biology, Italy

    Keywords: archaeological wood, dendrochronology, oak, radiocarbon, floating


    1. Introduction

    On the occasion of maintenance work by the Consorzio di Bonifica Basso Piave on
the banks of the Piavon canal in 2008, a large tree trunk was dug up in the municipality
of Chiarano (TV) It was found lying in the mud 3 metres below ground level, on a bend
of the watercourse near Villa Zeno (Figure 1).
    The trunk is around 15 metres in length, with an approximate diameter of 50 cm,
lacking branches and roots, with a carbonized exterior appearance. Its surface is dark
and deeply cracked, while the interior is still practically intact despite some cracks that
penetrate deeply into the interior of the wood.
    The trunk appears to bear signs of felling and debranching, so it cannot be the remains
of a fallen tree. The obviously lengthy time it had been buried and its discovery in an area
full of Roman (Oderzo is nearby) and Venetian relics, aroused interest in studying the find
that, due to the location, may be of archaeological or archaeobotanical interest.




                                                                                                    CONSERVATION SCIENCE IN CULTURAL HERITAGE
    It was recovered by the owner of the surrounding land, Mr.Giovanni Moro, and left in
the open prior to being used. Before being cut into planks, he kindly agreed to a cross-
section slice being removed for the purposes of this study (Figure 2).




                      Figure 1. The trunk after its recovery from the canal.


*   Corresponding author: tiziana.urso@unipd.it

                                                                                               41
T. Urso, N. Martinelli, O. Pignatelli, T. Scortegagna - THE SUBFOSSIL TRUNK OF CHIARANO (TV)




                                                                                                                                    Figure 2. Slice used for the study.

                                                                                                      According to the standard UNI 11205:2007 [1], the study involved identification of the
                                                                                                    woody species, its physical characterization, dating and evaluation of the deterioration.

                                                                                                       2. Materials and methods

                                                                                                       The slice appears well preserved, with only the outer area being carbonized, friable
                                                                                                    and deeply cracked. The colour tones vary from black on the outside to natural light
                                                                                                    brown in the central area.
                                                                                                       Samples were removed according to the different tests to be performed (Figure
                                                                                                    3). Samples for the anatomical characterization and determination of the woody spe-
                                                                                                    cies, of approximately 1x1x1 cm were taken from the outer area immediately beneath
                                                                                                    the deteriorated part; for the physical characterization, 2 irregular-shaped pieces were
                                                                                                    used from the same area in which the samples for microscopic analyses were taken.
                                                                                                    The ash content was determined on samples taken from the outer deteriorated area
                                                                                                    and the underlying parts. Determination of ash content was also performed on a con-
                                                                                                    trol sample taken from a plank of recent common oak.




                                                                                                    Figure 3. Testing: samples for the anatomical analyses are in red, for the physical characterization
                                                                                                    in yellow, for the ash analysis in blue. Material was also taken for ash analysis from the outer area
                                                                                                    (not shown).


                                                                                               42
   The anatomical characterization was performed under the microscope on samples
prepared according to standard methods, cutting three sections with a microtome and
mounting them on slides without staining.
   The physical characterization involved complete saturation of the samples through
prolonged immersion in water until they sank, after which the volume was determined
according to the Archimedes’ principle. They were then dried in an oven at 103°C until
reaching constant weight.
   The following formulas were then used:
   Basic density BD=P0/Vfr
   Residual basic density RBD=100*Db/Dbrif, with Dbrif= 0.57gr/cm3
   Maximum water content MWC=100(Pu-P0)/P0

    The ash content was assessed on finely ground wood coming from different areas
of the slice in a muffle kiln at 500°C.
    Dating was done using both dendrochronology and radiocarbon dating. The den-
drochronological investigation was conducted by measuring the ring widths along 5
different directions with a LEICA S8AP0 Dendrochronograph available at the TESAF
Dept. of the University of Padua. The subsequent elaborations were performed at the
Dendrodata s.a.s. laboratory in Verona, following classical dendrochronology proce-
dures [2-4], according to the standard UNI 11141 [5], and using TSAP and CATRAS
programs [6].
    The radiocarbon dating was done at the Centro di Datazione e Diagnostica (CE-
DAD) of the University of Salento using high resolution mass spectrometry on a sam-
ple taken from the outer part of the slice, selected and prepared at the Dendrodata
s.a.s. laboratory.


  3. Results




                                                                                                 CONSERVATION SCIENCE IN CULTURAL HERITAGE
  3.1 Identification of the woody species and evaluation of the biological dete-
  rioration

   The anatomical characteristics point clearly to an example of deciduous oak. It is
most probably common oak (Quercus robur L.), given the diffusion of this species in
the area where the trunk was found and on the Veneto plain in general, even if it is not
possible on the basis of the wood anatomy to exclude that it is sessile oak (Q. petraea
L.) (Figure 4) [7]. The colour of the wood is typically blackish and from the outside
inwards gradually becomes natural. If it lies in water for a long period of time, oak
may develop a black coloration (drowned oak) due to the reaction of the tannins with
the iron ions present in the water and sediment. This type of oak, typical of wood that
remains for a long time in an acid and poorly oxygenated environment, was used in the
past as an economic substitute for ebony in marquetry [8], while it is still sought-after
for making items of furniture.
   Under the microscope the cells appear to be well preserved, even if some areas
are visible in which the cells present walls with slight bacterial attacks, surrounded by
healthy wood. No soft rot from fungal attacks has been observed (Figure 5).




                                                                                            43
T. Urso, N. Martinelli, O. Pignatelli, T. Scortegagna - THE SUBFOSSIL TRUNK OF CHIARANO (TV)




                                                                                                                                 Figure 4. Transverse section, x40.




                                                                                                                                Figure 5. Transverse section, x400.


                                                                                                       3.2 Physical characterization

                                                                                                       Physical characterization is useful for quantifying the deterioration of archaeological
                                                                                                    wood that, having remained in a damp and poorly oxygenated environment for a long
                                                                                                    time, is especially subject to bacterial attacks that slowly consume the cell walls. The
                                                                                                    weight reduction and increase in the maximum water content, provide useful indica-
                                                                                                    tions on the magnitude of biological attack [9]. The basic density is determined for
                                                                                                    saturated archaeological wood which, by measuring the dry weight of the specimen
                                                                                                    in relation to the saturated volume, eliminates any errors in determining the volume


                                                                                               44
due to disintegration produced by the desiccation of the deteriorated wood [10]. The
percentage ratio between the basic density and that reported in the literature for recent
wood is an index of diminution of wall matter. Furthermore, if the walls are deteriorated
they become thinner, while the porosity increases and consequently the amount of
water that can be contained in the wood. So, as wall deterioration increases so does
the maximum water content.
   The basic density, residual basic density, maximum water content were therefore
determined and compared with the data in the literature for the wood of recent com-
mon oak.
   The basic density is just under that of reference, while the residual basic density is
91%, so the weight of the cell walls is only slightly reduced. The maximum water con-
tent is therefore lower than that determined on healthy wood (Table 1).

Table 1. Average values of the physical characterization tests. The MWC of healthy common oak
was determined using the Tsoumis formula [11], assuming an anhydride density of 0.66 g/cm [12].
    Ring middling 10-2 mm                 Test sample                  Current healthy wood

          Db (gr/cm3)                        0.5217                             0.57

            Dbr (%)                           91.5                              100

           MCW (%)                            79.89                           114.51

    This contradictory situation can be explained by hypothesizing that the lengthy stay
in the river sediment would have favoured the entry of inorganic matter in the wood,
artificially increasing the weight and limiting the space available for water. The ash
content, rather high in the outer part and lower in the more internal layers, confirms this
hypothesis. Moreover, also in the innermost part values were always higher than in the
literature data for recent wood (Table 2).




                                                                                                       CONSERVATION SCIENCE IN CULTURAL HERITAGE
          Table 2. Average values of the ash content in the different parts of the disc.




   3.3 Dendrochronological dating

   The slice is completely lacking sapwood (i.e. the most external part of the trunk),
probably decayed. It provided a definitive sequence, 97 rings long (Table 3), obtained
averaging the five directions measured (Figure 6).




                                                                                                  45
                                                                                                                Table 3. Dendrochronological parameters of the elaborated sequence.
                                                                                                     Ring middling 10-2 mm     Standard Deviation      Autocorrelation     Sensitivity average

                                                                                                              254.2                    98.9                 0.674                 0.159
T. Urso, N. Martinelli, O. Pignatelli, T. Scortegagna - THE SUBFOSSIL TRUNK OF CHIARANO (TV)




                                                                                                    Figure 6. Average dendrochronological curve of the measured ring sequences. Chiarano – oak.

                                                                                                       Deciduous oaks are in general particularly suitable for dendrochronological analy-
                                                                                                    ses, due to being ring-porous species that do not form false rings. Deciduous oaks
                                                                                                    also have steady features that facilitate dendrochronological elaboration and synchro-
                                                                                                    nization procedures, even between specimens with different origins [13]. Nonetheless,
                                                                                                    there are no available standard centuries-old curves of the oak valid for Italian regions.
                                                                                                    The synchronizations performed with chronologies and local curves present in the
                                                                                                    Dendrodata s.a.s. databank and the attempts to link up with the chronologies beyond
                                                                                                    the Alps have not allowed the find to be dated. However, good synchronization has
                                                                                                    been obtained with some curves, still not dated, elaborated for the city of Venice and
                                                                                                    ascribable to the 12th-14th century. The curve elaborated for the trunk from Piavon will
                                                                                                    be added to the Dendrodata s.a.s. databank (Veneto, recent centuries) for the future
                                                                                                    creation of an oak reference chronology [14].

                                                                                                       3.4 Radiocarbon dating

                                                                                                       In order to obtain a precise dating, radiocarbon dating of the outer rings of the disc
                                                                                                    was performed using high resolution mass spectrometry. The test provided a radiocar-
                                                                                                    bon age of 795 ± 35 years B.P., corresponding to a calibrated chronology in the period
                                                                                                    between the second half of the 12th century and second half of the 13th century A.D.
                                                                                                    (2 s) (Figure 7).

                                                                                                       4. Discussion and conclusions

                                                                                                       The wood remains in the bed of the Piavon are those of a common-oak trunk of
                                                                                                    more than a century old, even if it cannot be precisely aged due to the absence of the
                                                                                                    outer sapwood rings. The last rings present on the find date to the period between the
                                                                                                    second half of the 12th and second half of the 13th century A.D. (2 s); the tree could
                                                                                                    therefore have been felled between the end of the 12th and early 14th century A.D.. It

                                                                                               46
               Figure 7. Calibration of chronology by radiocarbon data [15, 16].


clearly demonstrates signs of a very long stay in the mud, due to the carbonized ap-
pearance of the outer layer and the typical change in colour towards black.
   The presence of signs of felling and debranching exclude that it fell by chance into
the river. The straight shape and the dimensions are those of a trunk destined to be
used in carpentry, whole or divided in planks.
   The territory where the trunk was found is agricultural-rural land crossed by numer-




                                                                                                  CONSERVATION SCIENCE IN CULTURAL HERITAGE
ous irrigation canals. Nowadays, the Piavon is one of these, but it was formerly an
important branch of the Piave, made up in succession by the Piavesella, Lia, Navisego
and then the Piavon. In Roman times it was navigable, as proved by the discovery of
structures of consolidation, consisting of wooden caissons and other riverbank sys-
tems, as well as a wharf in the south-western part of the town of Oderzo and was the
means of communication of Oderzo with the lagoon [17]. After a disastrous flood in
589 A.D. which disrupted the hydrography of the entire low-lying plain, the Piavon was
reduced to a small affluent of the Piave and was no longer utilizable. Around the 13th
century, the Caminesi family, the local feudal lords and later the Republic of Venice re-
opened a channel, starting from a diversion of the river Lia, with the aim of reactivating
the Piavon which by that time was almost atrophied, and reconnecting it with the old
bed of the Piave. The Republic of Venice ordered the dredging and maintenance of the
Piavon more than once: in the Venice State Archive there is a Decree dated 23 June
1447 that orders the cleaning and dredging of the Piavon canal to make it once again
navigable and useful for the transport of timber to the area of Lido di S. Nicolò [18].
   In medieval times much of the Veneto plain was covered by mixed woodlands, in which
the main tree species were common oak (Quercus robur), together with hornbeam, ash,
sycamore, poplar and elm. The Piave and Piavon flowed through these woodland areas.
The Republic of Venice took an active interest in the plains woodlands after 1400, as
they supplied the important oak assortments (both common and sessile oak, Q. petraea)
required for shipbuilding. The management of these woodlands was regulated by laws


                                                                                             47
                                                                                                    that specified the methods for the various types of timber required: straight planks, or
                                                                                                    “stortame” (twisted) for the uses that required curved pieces (Figure 8).
T. Urso, N. Martinelli, O. Pignatelli, T. Scortegagna - THE SUBFOSSIL TRUNK OF CHIARANO (TV)




                                                                                                    Figure 8. Shape and proportion to give the oaks to produce the shipbuilding assortments. From
                                                                                                    the Atlante della Terminazione del 1777 (Tip. Pinelli, Venezia 1778) [18].

                                                                                                       The oaks were carefully listed in the cadastres, used to census the woodlands of the
                                                                                                    Republic of Venice, from the 15th century. The oaks were sorted into branded, i.e. des-
                                                                                                    tined for the naval industry, and non-branded, for other uses. In the Oderzo area, 8684
                                                                                                    branded oaks and 11499 non-branded were registered by the Surian cadastre (1569-
                                                                                                    70). In particular, the villa at Chiarano had an oak woodland of 18 hectares (Figure 9).




                                                                                                                                    Figure 9. Surian cadastre [18].

                                                                                                       The cadastres also cited the distances between the woodlands and the nearest
                                                                                                    watercourses, fundamental for transporting the trunks to the lagoon by floating. The
                                                                                                    Venetian maps also report these woodlands and their position with respect to the rivers
                                                                                                    (Figure 10) [19].
                                                                                               48
Figure 10. Part of a map of 1561 showing the woodland areas between Oderzo, Piavon and
Ceggia [19].

   Floating was a mode of transport via river widely utilized for timber in the past since
Roman times and even until recently. In the case of the Piave, the first testimony of
floating with rafts dates back to 1308. Venice required vast quantities of timber for
building both houses and ships and for heating. The transport of timber from the moun-
tain areas to the coast was entrusted to specialists, the zattieri (rafters), who exploited
the small rivers and canals with a regular flow, including the Piavon, to transport the
wood needed by the city. The trunks were assembled in rafts that were then loaded
with other timber, animals and also passengers. At destination the raft was dismantled,
the trunks were cleaned and sold with the cargo and the zattieri returned home on foot
or in carts [20].




                                                                                                      CONSERVATION SCIENCE IN CULTURAL HERITAGE
   The trunk at Chiarano may have been part of a load of timber destined for Venice
that was lost during the journey.

      Acknowledgements

   The authors thank Rosalinda and Ruggero Zamuner for their collaboration at Chi-
arano and Giovanni Moro for having kindly allowed the study of the trunk by providing
the material.


      References

[1]     UNI 11205:2007 - Beni culturali. Legno di interesse archeologico e archeobot-
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                                                                                                    [14]   Martinelli, N., Kromer, B., (2002) A new oak chronology for early medieval times
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                                                                                                           legname dal Trentino a Venezia. In: Priuli e Verlucca (eds.) Quaderni di cultura
                                                                                                           alpina, 94. Aosta




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   Biographical notes


   Tiziana Urso graduated in Biological Sciences at the University of Padua, she is
a researcher and lecturer in xylology and wood technology at the same University.
Her research interests are in the sectors of wood anatomy and technology, the char-
acterization of woods and artifacts of historical, artistic and architectural interest, the
anatomy and ecophysiology of forest plants. She has been the scientific head of vari-
ous research programmes at local and national level. She is author and co-author of
numerous publications in scientific journals, monographs and Italian and international
conference proceedings.
   Nicoletta Martinelli has a PhD in Archaeological Sciences from the University of
Padua, with a Specialist Diploma in Prehistoric and Protohistoric Archaeology from the
University of Pisa. She is a founding member of the company Dendrodata in Verona,
where she conducts archaeological research. Lecturer in Dendrochronology for Cul-
tural Heritage Course at the University of Verona, her research interests include the
chronology of European Prehistory and the wooden structures of Alpine palafittes. She
has been a member of working groups of the Archaeological Superintendence. Author
of more than 150 publications in scientific journals, Italian and international mono-
graphs, catalogues and Italian and international conference proceedings.
   Olivia Pignatelli graduated in Natural Sciences at the University of Padua, and
has a PhD in “Technologies for building restoration and technological innovation”. She
is a founding member of the company Dendrodata, where she conducts research in
the sector of dendrochronology and xylology, on subjects regarding wood anatomy
and the dating of woods and articles of historical-artistic and architectural interest.
Lecturer on Botany for Cultural Heritage Course at the University of Verona, she has
participated in Italian and international research programmes. Author and co-author




                                                                                                   CONSERVATION SCIENCE IN CULTURAL HERITAGE
of numerous publications in scientific journals and Italian and international conference
proceedings.
   Tobia Scortegagna graduated in Biology (ordinary degree) in 2008 and Evolution-
ary Biology (master’s degree) in 2015 at the University of Padua. An expert artisan and
passionate connoisseur of wood, he currently devotes himself to artistic woodwork in
his small workshop on the hills above Vicenza.




                                                                                              51
                                                                                                        Summary
                                                                                                        This paper reports the results of the characterization of a subfossil trunk found bur-
                                                                                                    ied in the mud of the Piavon canal, at Chiarano (TV), when dredging took place in
                                                                                                    2008.
                                                                                                        The trunk, of imposing dimensions, lacking branches and bark, has a black, deeply
                                                                                                    cracked and strongly deteriorated outer surface with a carbonized appearance, while
                                                                                                    internally it has the typical blackish colour of the so-called drowned oak. The studies
                                                                                                    have demonstrated that it is a tree belonging to the genus Quercus, common oak
                                                                                                    or sessile oak, that may have been felled between the end of the 12th and early 14th
                                                                                                    century A.D.. Determination of the MWC and residual basic density indicate that the
                                                                                                    deterioration decreases from the outside inwards; the ash content is high externally
                                                                                                    and diminishes moving toward the centre.
                                                                                                        Nowadays, the Piavon is an irrigation canal, but in Venetian times it was navigable
T. Urso, N. Martinelli, O. Pignatelli, T. Scortegagna - THE SUBFOSSIL TRUNK OF CHIARANO (TV)




                                                                                                    and was used for the transport of goods and timber. There were extensive woodlands
                                                                                                    of common oak and sessile oak all along the Piavon, the size and composition of which
                                                                                                    is documented in the Venetian cadastres, which also report the distances between the
                                                                                                    woodlands and the nearest water courses, proof of the importance of river transport for
                                                                                                    the timber. In particular, an 18 hectare oak woodland is recorded in the Surian cadas-
                                                                                                    tre (1569-70) for the villa at Chiarano. The oaks were used by the Republic of Venice
                                                                                                    mainly for the construction and maintenance of the shipping fleet.
                                                                                                        The Chiarano trunk, given its age and the area where it was found, may therefore be
                                                                                                    a trunk felled in Venetian times, perhaps destined for naval use, which was lost during
                                                                                                    its transport by floating.


                                                                                                        Riassunto
                                                                                                        In questo lavoro si riportano i risultati della caratterizzazione di un tronco subfossile
                                                                                                    rinvenuto in profondità nel fango del canale Piavon, a Chiarano (TV), in occasione dei
                                                                                                    lavori di scavo del canale nel 2008.
                                                                                                        Il tronco, di imponenti dimensioni, privo di rami e corteccia, presenta la superficie
                                                                                                    esterna profondamente fessurata, nera, fortemente degradata, dall’apparenza carbo-
                                                                                                    nizzata, mentre internamente ha la tipica colorazione nerastra della cosiddetta quercia
                                                                                                    annegata. Gli studi hanno dimostrato che si tratta di un albero appartenente al genere
                                                                                                    Quercus, farnia o rovere. La datazione al radiocarbonio e le analisi dendrocronologi-
                                                                                                    che hanno collocato il periodo di crescita della pianta in epoca medievale, intorno al
                                                                                                    XIII secolo. La determinazione della MCW e della densità basale residua indicano che
                                                                                                    il degrado decresce dall’esterno all’interno; il contenuto delle ceneri è elevato esterna-
                                                                                                    mente, e diminuisce andando verso l’interno.
                                                                                                        Il Piavon è attualmente un canale di irrigazione, ma in epoca veneziana era na-
                                                                                                    vigabile e veniva utilizzato per il trasporto di merci e legname. Tutta l’area lungo il
                                                                                                    Piavon presentava boschi di farnia e rovere di notevole estensione, la cui dimensione
                                                                                                    e composizione è documentata dai catasti veneziani, che riportano anche le distanze
                                                                                                    tra i boschi e i corsi d’acqua più vicini, a testimonianza dell’importanza del trasporto
                                                                                                    fluviale del legname. In particolare, nella villa di Chiarano, nel catasto Surian (1569-70)
                                                                                                    si trova censito un bosco di roveri di 18 ettari. I roveri erano utilizzati dalla Serenissima
                                                                                                    soprattutto per la costruzione e manutenzione della flotta navale.
                                                                                                        Il tronco di Chiarano, considerata la collocazione temporale e la zona di ritrova-
                                                                                                    mento, può essere quindi un tronco abbattuto in epoca veneziana, forse destinato
                                                                                                    all’impresa navale, andato perduto durante il trasporto per fluitazione.

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