Nederland
Oostende Raversijde Oudenburg Jabbeke Oostkamp Damme Lissewege BRUGGE Diksmuide Lo-Reninge Kortemark Ieper Aalter Kluizen Knesselare Kortrijk Menen Zele GENT Merelbeke Ename Oudenaarde Dendermonde Steendorp Hove Brecht Ekeren ANTWERPEN Elewijt Donk Erps-Kwerps BRUSSELFig. 24 Locaties in Vlaanderen waar dendrochronologische analyses zijn uitgevoerd op archeologisch hout. Er wordt hierbij geen onder-scheid gemaakt tussen geslaagde en niet-geslaagde dateringen. De kleuren geven de verschillende Vlaamse ecoregio's weer (Seve-nant et al. 2002).
Locations in Flanders where dendrochronological surveys were executed on archaeological wood. No distinction was made between suc-cessful and unsucsuc-cessful dating analyses.
Summary
The wooden century of a Flemish town. Archaeological and dendrochronological research in Ypres (prov. of West-Flanders)
European oak is the most suited species for dendrochronological research in Flanders. However, a local reference chronology, in-dispensable for the optimal implementation of dendrochronol-ogy as a dating tool, is not yet available. This is partly due to the assumption that in Flanders ‘lowland’ oaks grow very fast and do not record a climatological signal in their growth-ring pattern. Furthermore, the strong pressure of humans on local forests is believed to have often disrupted the ‘natural’ growth pattern of trees. As a consequence, little dendrochronological research has been carried out, making it impossible to develop a local refer-ence chronology. This has resulted in poor dating success in the few cases in which analyses were attempted. This situation has led to the assumption that dendrochronology is not the most recommended dating technique for archaeological timbers and artefacts of local origin.
In 1993, during an archaeological inspection of the Verdronk-en Weide outside the town walls of Ypres, numerous woodVerdronk-en tim-bers from a deserted medieval village were found (fig. 1). This find revived the demand for an intensive dendrochronological survey. This survey was first undertaken as part of a masters’ degree thesis (Dept. of Biology, Ghent University, in collabora-tion with the Laboratory of Wood Biology & Xylarium, Africa-museum, Tervuren) and was later continued by the Laboratory of Wood Technology (Ghent University). Over the years, wood from more archaeological sites in Ypres has been added to the database (fig. 2). This paper presents the results and historical in-terpretation of the dendrochronological research of wood from the Verdronken Weide and six other archaeological sites in Ypres
(fig. 3): an underground car park in the Gevangenisstraat, an un-derground car park at the hotel Novotel in the Sint-Jacobsstraat, the real estate project Twaalf Apostelen in the Rijselseweg, an un-derground office for the courthouse in the Korte Torhoutstraat, an underground car park for a bank office in the Rijselsestraat and an underground car park near the Karmelietenklooster in the Patersstraat.
Verdronken Weide
Through this area south of Ypres (fig. 4), flows both a natural (Ieperlee) and an artificial waterway (the ‘Nieuwe Leye’, con-structed as a bypass for the Ieperlee). Wood samples were taken from a variety of constructions. The revetments of the Ieperlee (fig. 6) (including a small harbour; fig. 5), the Nieuwe Leye, and several buildings along these waterways yielded numerous tim-bers for dendrochronological research.
In total, 62 posts could be dated, providing a detailed chronol-ogy consisting of several construction dates. Some of the wood-en posts from the revetmwood-ents of the Nieuwe Leye still had bark attached. This enabled the dating of the construction phase to around 1290, contemporaneous to the construction of the small harbour along the Ieperlee. For the Ieperlee, it was only possi-ble to identify an intensive construction phase around 1285, but many wooden posts have felling dates both earlier and later, in-dicating the presence of reused wood (or the presence of an ear-lier revetment) and later restorations.
Furthermore, foundation posts of four different buildings, situ-ated between the Ieperlee and Nieuwe Leye could be dsitu-ated. This yielded nearly simultaneous felling dates for two of these build-ings in 1257-1258. The other two were certainly constructed after 1280.
Fig. 25 Overzicht van sitechronologieën uit Vlaanderen die zijn opgebouwd met lokaal, archeologisch hout. De meetgegevens zijn opgeno-men in de dendrochronologische databank van het VIOE.
Overview of site chronologies from Flandersconstructed using local, archaeological wood samples. The data are incorporated in the den-drochronological database of the VIOE.
9 6 78 1 1 2 2 2 4 28 2 200 BC/AD 200 400 600 800 1000 1200 1400 1600 1800 Knesselare (waterput) - 142BC Donk - 136BC Aalter - 19BC 4 BC 42 AD 52 AD 69 AD 92 AD 100 AD 4 3 3 5 7 Menen (waterput) - 180BC Menen (waterput) - 171BC Damme (waterput) - 68BC Elewijt - 90BC Kluizen - 49BC Merelbeke Axxes - 107BC Ekeren (waterput) - 185BC Knesselare (boomstamwaterput) - 79 A 116 AD 123 AD 135 AD 137 AD 239 AD 369 AD 1051 AD 1057 AD 1057 AD 1084 AD 83 13 4 8 1 19 Oudenburg (dubbele waterput)-248AD
1782 AD 1115 AD 1240 AD 1244 AD 1300 AD 1362 AD 1530 AD Damme - Veldhoek - 891 AD Damme - Lieve - 1244 AD Dendermonde (grafkisten) - 808 AD Aalter - 908 AD Reninge - 908 AD Steendorp - Blauwe hof- 908 AD
Steendorp - Blauwe hof - 1087 AD Oostkamp - Blauw kasteel - 1258 AD
Ieper - 1132 AD
Hove (waterputten) - 1356AD
Gevangenisstraat
In the backyard of a nobleman’s house (fig. 7, 8), the remains were found of a three-aisled wooden building and of a building erected upon an iron-sandstone construction. Two out of five posts from these two buildings could be dated. These provided two termini post quem (= earliest possible felling dates for the wooden posts): 1250 and 1256, respectively.
Novotel
On the Novotel site (fig. 10) traces of several buildings were found, constructed with iron-sandstone, bricks or wood (fig. 9). Thirteen out of 21 sampled posts could be dated. Again, the wood samples provide a precise date for the construction of some of the excavated buildings. The presence of bark enabled the calcula-tion of a felling date for the trees used in the construccalcula-tion of one particular building to the winter of 1272-1273. A beam, used for the stabilisation of another building, was felled between 1250 and 1280. Although this building is probably older, the dating makes sense since a number of years probably elapsed between the erec-tion of the building and the need for addierec-tional support. Twaalf Apostelen
From this site (fig. 11) only 4 wood samples could be dated. They probably indicate the presence of a mill, certainly constructed after 1229.
Gerechtsgebouw
From this site, which is difficult to interpret archaeologically (fig. 12, 13), 13 pieces of wood were selected for dendrochronological research. So far, however, only one piece could be dated, giving an earliest possible felling date of 1082. This makes it possibly one of the oldest wooden constructional timbers in Ypres. It should be clear that this post was probably reused for the construction of a more recent building.
Rijsselstraat
This is the only archaeological site (fig. 14) where dendrochrono-logical dating failed. So far none of the posts from an originally wooden building, later rebuilt using bricks, could be dated. Karmelietenklooster
Both stone and wood was used as construction material for house extensions along the Patersstraat. On this site two in-complete courtyards could be identified (fig. 15, 16). From 15 col-lected cross-sections of wooden posts, only two could be dated. Remarkably, the felling dates of both pieces of wood lay approxi-mately 200 years apart, where the oldest post has a felling date after 1049. Thus, based solely on dendrochronological data, it is not possible to distinguish between the reuse of old wood and the restoration of an old building. However, pottery finds and the archaeological context as a whole support the reuse of wood from an old building in a newer one, halfway the 13th century. General dendrochronological output
In total, 261 wooden posts, originating from archaeological sites in and near the medieval town of Ypres, were sampled for den-drochronological research. Comparison of the measured growth-ring patterns with reference chronologies from The Netherlands, Germany, southern Belgium and northern France allowed the dating of 81 (=31,0%) of all the series. All dated series are present-ed in a bar graph (fig. 19). This is a promising result, since most of the recorded series have a relatively low number of growth
rings (fig. 17, a). However, it should be clear that the chances for a successful dating increase proportionally with the length of the recorded tree-ring series (fig. 17, b).
In order to estimate the exact felling date for samples where the sapwood is only partly preserved, it is necessary to have reliable local sapwood estimates. Through fieldwork, it was established that, in Flanders, oak trees of less than 100 years old have, on average, 7 sapwood rings (fig. 18).
The dated tree-ring series allowed the construction of an abso-lutely dated local reference chronology. This chronology covers the period 1132 to 1362. However, based on the quality criterion of Wigley et al., only the period of 1176–1272 can be considered as a well-replicated chronology (fig. 20). This led to the conclu-sion that at least 14 contemporary dated series are necessary to build a reliable reference chronology in the Ypres region. Historical significance
Historical documents mention the city of Ypres for the first time in 1066. During the 12th–13th century, the city evolved into a true metropolis, mainly due to its favourable geographical posi-tion (fig. 21). The dendrochronological data proved to be crucial in the interpretation of the medieval building chronology. The 13th century in particular seems to be a ‘wooden’ century. A gi-gantic amount of wood was used in the revetments of the new waterways, the harbour and in other constructions. The 13th century represents the commercially most prosperous period for Ypres, a period when it was also possible to buy huge amounts of timber. Bricks may well still have been too expensive and, most probably, not yet available in large quantities.
Ecological information
It should not be forgotten that wood is a biological material, growing in forests and woodlands. The growth patterns ob-served on the wooden posts are a potential source of informa-tion on the growth condiinforma-tions experienced by the trees that were felled for timber supply. In the case of Ypres, it is striking that a lot of young trees were cut down. Even more remarkable is the fact that the youngest trees have experienced a more vigorous growth compared to the trees that were felled at an older age (fig. 22). This can also be observed when plotting the increase in stem diameter for the old and young trees separately (fig. 23). Hence, the trees that were cut at less than 50 years old are not simply the younger versions of the trees that were felled at an older age. General conclusions
The results of this dendrochronological survey can be put into perspective taking into account other analyses that have been executed at different locations in Flanders, over the last few years (fig. 24). When all dated local chronologies are plotted, it becomes clear that a Flemish dendrochronological reference database is starting to develop (fig. 25). The Ypres chronology, together with all other local chronologies, will allow us to use dendrochronology for future archaeological and chronological studies on a larger scale. However, to increase the power of den-drochronology as a dating tool, and thus in order to enrich the reference database, it will remain necessary to take a maximum number of samples on archaeological sites.
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