NNU rapport 7, 2001

BOULEVARDEN, AALBORG

Aalborg Historiske Museum.
Indsendt af Stig Bergmann Møller.
Undersøgt af Aoife Daly.
NNU j.nr. A7740E

Tømmer fra byudgravning
I alt er 63 prøver af Quercus sp., eg, undersøgt. Splintved er bevaret på 57 af prøverne heraf 42 med barkkant. 20 prøver dateret (se fig. 1).

Anlæg A001; "bolværkspæle"
To prøver af Quercus sp., eg, undersøgt. Splintved er bevarede på begge prøver. Én af prøverne er dateret. Yngste årring er dannet i 1505. Ved tillæg for manglende splintved er træet, som prøven kommer fra, fældet i 1520-35 e.Kr.

Anlæg A032; "bolværkspæle"
To prøver af Quercus sp., eg, undersøgt. Komplet splintved er bevarede på én af prøverne. Prøverne er ikke dateret. Prøverne indeholder for få årringe og én er påvirket af oldenborre.

Anlæg A034; "bolværkspæle"
To prøver af Quercus sp., eg, undersøgt. Én af prøverne er dateret. Splintved er bevaret på den daterede prøve. Yngste bevarede årring er dannet i 1451. Fældningstidspunktet for træet, som prøven stammer fra, er beregnet til 1452-64 e.Kr.

Anlæg A064; stolper til fundament (hus A035)
Tre prøver af Quercus sp., eg, undersøgt. Komplet splintved er bevaret på prøverne (vinterfældning). Prøverne er ikke dateret. Prøverne indeholder for få årringe.

Anlæg A066; "bolværkspæl"
Én prøve af Quercus sp., eg, undersøgt. Splintved er bevaret på prøven. Prøven er ikke dateret. Prøven indeholder kun 84 årringe.

Anlæg A106; "fundamentspæl" (hus A035)
Én prøve af Quercus sp., eg, undersøgt. Komplet splintved er bevaret på prøven (sommerfældning). Prøven er ikke dateret. Prøven indeholder kun 44 årringe.

Anlæg A107; "bolværkspæl"
Én prøve af Quercus sp., eg, undersøgt. Komplet splintved er bevaret på prøven. Barkringen som ikke er færdigdannet, er dannet i 1414 e.Kr. Fældningstidspunktet for træet, som prøven kommer fra, er sommeren 1414 e.Kr.

Anlæg A154; stolper i hus
To prøver af Quercus sp., eg, undersøgt. Komplet splintved er bevaret på begge prøver (vinterfældning). Prøverne er ikke dateret. Prøverne som indeholder henholdsvis 51 og 47 årringe, er påvirket af oldenborre.

Anlæg A185; fra hus
Én prøve af Quercus sp., eg, undersøgt. Komplet splintved er bevaret på prøven (sommerfældning). Prøven er ikke dateret. Prøven indeholder kun 48 årringe.

Anlæg A181; stolper fra hus
To prøver af Quercus sp., eg, undersøgt. Komplet splintved er bevaret på prøverne (vinterfældning). Prøverne er ikke dateret. Én af prøverne, som indeholder 121 årringe, er påvirket af oldenborre angreb. Den anden prøve indeholder kun 47 årringe.

 
Anlæg A197; vægstolper, hus A188
Tre prøver af Quercus sp., eg, undersøgt. Barkringen er bevaret på alle prøver (vinterfældning). Èn af prøverne er dateret. Barkringen er dannet i 1358 e.Kr. Træet, som prøven kommer fra, er fældet i vinter 1358-9 e.Kr.

Anlæg A194; strø fra plankegulv, hus A188
Én prøve af Quercus sp., eg, undersøgt. Komplet splintved er bevaret på prøven. Yngste bevarede årring (barkringen) er dannet i 1211 e.Kr. Barkringen er ikke færdigdannet, hvilket betyder, at træet er fældet i vækstsæsonen, dvs. sommeren 1211 e.Kr.

Anlæg A206; stolper i latrinkasse
Tre prøver af Quercus sp., eg, undersøgt fra stolperne. Komplet splintved er bevaret på alle tre prøver (to vinterfældning og en sommerfældning). Prøverne er ikke dateret. To af prøverne, med henholdsvis 102 og 58 årringe, er påvirket af oldenborre. Den tredje prøve indeholder kun 37 årringe.

Anlæg A206; planker fra latrinkasse
Tre prøver af Quercus sp., eg, undersøgt fra plankerne. Splintved er bevaret på alle tre prøver. Alle tre prøver er dateret. Yngste bevarede årring er dannet i 1276 e.Kr. Se sammenfatningen nedenfor...

Anlæg A220; planker fra overdækning til afløbsrende
To prøver af Quercus sp., eg, er undersøgt. Splintved er bevaret på prøverne. Yngste bevarede årring er dannet i 1276 e.Kr. Se sammenfatningen nedenfor...

Anlæg A225; stolper ved afløbsrende
Tre prøver af Quercus sp., eg, undersøgt. Komplet splintved er bevaret på prøverne (to vinterfældning og en sommerfældning). Prøverne er ikke dateret. Prøverne indeholder for få årringe.

Anlæg A223; planke fra afløbsrende
Én prøve af Quercus sp., eg, undersøgt. Komplet splintved er bevaret på prøven. Yngste bevarede årring er dannet i 1281 e.Kr. Se sammenfatningen nedenfor...

Sammenfatning latrinkasse (A206), overdækning til afløbsrende (A220) og afløbsrende (A223);
Seks prøver er dateret fra denne gruppe materiale. Den dendrokronologiske undersøgelse viser, at to af prøverne fra plankerne fra latrinkassen sandsynligvis stammer fra samme træ. Disse to prøver har splintved bevaret og ved tillæg for manglende splintved er fældningstidspunktet for træet, som prøverne kommer fra, beregnet til 1278-93 e.Kr.

Undersøgelsen viser endvidere, at fire prøver, (en fra latrinkassen, to fra overdækning (A220) samt en fra selve afløbsrenden A223), også stammer fra ét træ. Én af disse har komplet splintved bevaret. Fældningstidspunktet for træet, som prøverne kommer fra, er vinter 1281-2 e.Kr.

Undersøgelsen viser at latrinkassen og afløbsrenden er etableret i vinteren 1281-2 e.Kr.

Anlæg A227; "bolværkspæle"
Tre prøver af Quercus sp., eg, undersøgt. Splintved er bevaret på prøverne, heraf en med komplet splintved (vinterfældning). Én af prøverne, som indeholder 136 årringe, er dateret. Yngste målte årring er dannet i 1541 e.Kr. Træet er fældet i 1545 e.Kr. eller kort tid derefter.

Anlæg A264; stolper i hus A271
To prøver af Quercus sp., eg, undersøgt. Komplet splintved er bevaret på prøverne (én vinterfældning, én sommerfældning). Prøverne er ikke dateret. Prøverne indeholder henholdsvis 68 og 69 årringe.

Anlæg A265; stolpe fra yngre hus end hus A271
Én prøve af Quercus sp., eg, undersøgt. Splintved er bevaret på prøven. Prøven er ikke dateret selvom den indeholder 158 årringe.

Anlæg A278; vægstolper fra hus A271's nordvæg
Fem prøver af Quercus sp., eg, undersøgt. Komplet splintved er bevaret på prøverne (sommerfældning). Prøverne er ikke dateret. Én af prøverne indeholder kun 53 årringe, mens de andre fire er påvirket af oldenborre angreb.

Anlæg A326; "hegn"
To prøver af Quercus sp., eg, undersøgt. Komplet splintved er bevaret på prøverne (en sommerfældning, en vinterfældning). Prøverne er ikke dateret. Begge prøver er påvirket af oldenborre.

Anlæg A364; stolper i latrinkasse A364
To prøver af Quercus sp., eg, undersøgt. Komplet splintved er bevaret på prøverne. Én af prøverne er dateret. Yngste bevarede årring (barkringen) er dannet i 1439 e.Kr. Barkringen er ikke færdigdannet. Fældningstidspunktet for træet, som prøven kommer fra, er sommer 1439 e.Kr.

Anlæg A390; stolper i latrinkasse A390
To prøver af Quercus sp., eg, undersøgt. Splintved er bevaret på prøverne heraf en med barkring (sommerfældning). Én prøve er dateret. Yngste bevarede årring er dannet i 1439 e.Kr. Ved tillæg for manglende splintved, er fældningstidspunktet for træet, som prøven kommer fra, beregnet til 1443-58 e.Kr.

Anlæg A399, A400, A417 og A425; tømmer fra bindingsværkshus A402
Fire prøver af Quercus sp., eg, undersøgt. Splintved er bevaret på prøverne heraf to med barkkant (vinterfældning). To af prøverne er dateret. Yngste bevarede årring på fodrem X497 (81272549) er dannet i 1401 e.Kr. Fældningstidspunktet for træet, som prøven stammer fra, er beregnet til 1416-31 e.Kr. Yngste bevarede årring på vægstolpe X519 (81272569) er dannet i 1429 e.Kr. Fældningstidspunktet for træet, som den prøve stammer fra, er beregnet til 1431-45 e.Kr. Resultaterne peger på, at huset indeholder materiale fra mindst to faser.

Anlæg A392; planker fra garvekar
Fem prøver af Quercus sp., eg, undersøgt. Kerne- /splintved grænse er konstaterede på en af prøverne. Tre af prøverne er dateret. Yngste bevarede årring er dannet i 1368 e.Kr. Fældningstidspunktet for træerne, som prøverne kommer fra, er beregnet til 1372-87 e.Kr.

Anlæg A438; fodrem i hus A440
Én prøve af Quercus sp., eg, undersøgt. Kun kerneved er bevaret på prøven. Prøven er dateret. Yngste bevarede årring er dannet i 1428 e.Kr. Fældningstidspunktet for træet, som prøven kommer fra, er beregnet til efter 1444.

Antallet af årringe
Ud af 63 egetræsprøver er 20 dateret, hvilket svarer til knap 32%. Det er en langt lavere procentdel end normalt forventet. Årsagen hertil kan skyldes flere faktorer.
A. Antallet af årringe i den enkelte prøve.
Praktisk erfaring viser, at prøver som omfatter mere end 120 årringe har stor mulighed for at blive dateret.

B. Antallet af prøver i en undersøgelse har også betydning. Nærværende undersøgelse omfatter hele 63 prøver, men de ligger spredt i tid. Ved datering af en konstruktion/et emne udtages normalt 10-15 prøver fra hver fase (bygning, reparation mm.). De 20 daterede prøver hidrører således fra tre forskellige århundreder. I undersøgelsen er der selvfølgelig også inddraget materiale fra tidligere dendrokronologisk undersøgelse af prøver fra Aalborg (se NNU rapport 25, 2000). Materialet fra disse undersøgelse har dog også lidt af de samme begrænsninger som i nærværende. Det lave antal årringe i de enkelte prøver samt prøverne spredning i tid.

C. Endvidere er der en del prøver, som ikke kan dateres, idet årringskurverne viser en fire eller fem-årige cyklus, som formentlig skyldes angreb fra oldenborre billen. Når oldenborre billen flyver, spiser den bl.a. bladene på egetræer. Det angrebne træ danner derved en meget smal årring i det pågældende år. I de meste af Danmark er billens livscyklus 4-årige, mens den i Nord-Jylland har en 5-årige cyklus (se Christiansen 1983). I denne undersøgelse, hvor prøverne viser tegn på at være skadet af oldenborre, er det primært den 5-årige cyklus, der findes (hele 17 prøver med 5-årige, 4 med 4-årige), hvilket - ikke overraskende - indicerer, at prøverne stammer fra træer, som har vokset i det nordlige Jylland.

Henvisninger:
Baillie M.G.L. og Pilcher, J.R. 1973, A simple crossdating program for tree-ring research. Tree-Ring Bulletin 33. pp. 7-14
Bonde N. et al 1992, Dendrokronologiske daterinsundersøgelser på Nationalmuseet 1992. AUD. p. 307
Bråthen A. 1982, Dendrokronologisk serie från västra Sverige 831-1975. RAÄ 1982:1 Stockholm.
Christiansen K. 1983, Oldenborrer og årringe. Nationalmuseets Arbejdsmark 1983 pp. 163-174

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English summary:

NNU report 7, 2001

BOULEVARDEN, AALBORG

Timbers from an urban excavation
63 samples of Quercus sp., oak examined. Sapwood is preserved on 20 of the samples. 40 samples are dated (see fig 1).

Construction A001; "quay-side posts"
Two samples of Quercus sp., oak were examined. Sapwood is preserved on both samples. One of the samples is dated. The outermost preserved tree-ring was formed in 1505. Allowing for missing sapwood, the tree, from which the sample comes, was felled in AD 1520-35.

Construction A032; "quay-side post"
Two samples of Quercus sp., oak were examined. Complete sapwood is preserved on one of the samples. The samples are not dated. The samples contain too few tree-rings and one is affected by cockchafers.

Construction A034; "quay-side posts"
Two samples of Quercus sp., oak were examined. One of the samples is dated. Sapwood is preserved on the dated sample. The outermost preserved tree-ring was formed in 1451. The felling date for the tree, from which the sample comes, is estimated to be AD 1452-64.

Construction A064; posts from foundation (house A035)
Three samples of Quercus sp., oak were examined. Complete sapwood is preserved on the samples (winter felling). The samples are not dated. The sample contains too few tree-rings.

Construction A066; "quay-side post"
One sample of Quercus sp., oak was examined. Sapwood is preserved on the sample. The sample is not dated. The samples contains only 84 tree-rings.

Construction A106; "foundation post" (house A035)
One sample of Quercus sp., oak was examined. Complete sapwood is preserved on the sample (summer felling). The sample is not dated. The sample contains only 44 tree-rings.

Construction A107; "quay-side post"
One sample of Quercus sp., oak was examined. Complete sapwood is preserved on the sample. The bark ring which is not fully formed, was formed in AD 1414. The felling date for the tree, from which the sample comes, is summer AD 1414.

Construction A154; posts in a house
Two samples of Quercus sp., oak were examined. Complete sapwood is preserved on both of the samples (winter felling). The samples are not dated. The samples which contain 51 and 47 tree-rings respectively, were affected by cockchafers.

Construction A185; from a house
One sample of Quercus sp., oak was examined. Complete sapwood is preserved on the sample (winter felling). The sample is not dated. The sample contains only 48 tree-rings.

Construction A181; posts from house
Two samples of Quercus sp., oak was examined. Complete sapwood is preserved on the samples (winter felling). The samples are not dated. One of the samples, which contains 121 tree-rings, was affected by cockchafers. The second sample contains only 47 tree-rings.

Construction A197; wall posts, house A188
Three samples of Quercus sp., oak were examined. The bark ring is preserved on all samples (winter felling). One of the samples is dated. The bark ring was formed in AD 1358. The tree, from which the sample comes, was felled in the winter AD 1358-9.

Construction A194; piece from plank floor, house A188
One sample of Quercus sp., oak was examined. Complete sapwood is preserved on the sample. The outermost preserved tree-ring (the bark ring) was formed in AD 1211. The bark ring is not fully formed, which means that the tree was felled in the summer of AD 1211.

Construction A206; posts in a latrine
Three samples of Quercus sp., oak were examined from the posts. Complete sapwood is preserved on all three samples (two winter felling and one summer felling). The samples are not dated. Two of the samples with 102 and 58 tree-rings, were affected by cockchafers. The third sample contains only 37 tree-rings.

Construction A206; planks from latrine
Three samples of Quercus sp., oak were examined from the planks. Sapwood is preserved on all three planks. All three planks are dated. The outermost preserved tree-ring was formed in AD 1276. See the summing up below...

Construction A220; planks from the cover of a drainage gully.
Two samples of Quercus sp., oak were examined. Sapwood is preserved on the samples. The outermost preserved tree-ring was formed in AD 1276. See the summing up below...

Construction A225; posts by the drainage gully
Three samples of Quercus sp., oak were examined. Complete sapwood is preserved on the samples (one winter felling and one summer felling). The samples are not dated. The samples contain too few tree-rings.

Construction A223; planks from the drainage gully
One sample of Quercus sp., oak was examined. Complete sapwood is preserved on the sample. The outermost preserved tree-ring was formed in AD 1281. See the summing up below...

Summing up, latrine (A206), drain cover (A220) and drain (A223);
Six samples are dated from this group of material. The dendrochronological analysis shows that two of the samples from the planks from the latrine probably come from one tree. These two samples have sapwood preserved and allowing for missing sapwood, the felling date for the tree, from which the samples come, is estimated to be AD 1278-93.

The analysis shows furthermore, that four samples, (one from the latrine, two from the drain cover (A220) and one from the actual drain (A223)) also come from one tree. One of these has complete sapwood preserved. The felling date for the tree, from which the samples come, is winter AD 1281-2.

The analysis shows that the latrine and the drain were established in the winter of 1281-2.

Construction A227; "quay-side posts"
Three samples of Quercus sp., oak were examined. Sapwood is preserved on the samples of which one has complete sapwood (winter felling). One of the samples is dated. The outermost measured tree-ring was formed in 1541. The tree was felled in AD 1545 or shortly after.

Construction A264; posts in house A271
Two samples of Quercus sp., oak were examined from construction A264. Complete sapwood is preserved on the samples (one winter felling, one summer felling). The samples are not dated. The samples contain 68 and 69 tree-rings.

Construction A265; post from house, younger than house A271
One sample of Quercus sp., oak was examined. Sapwood is preserved on the sample. The sample is not dated even though it contains 158 tree-rings.

Construction A278; wallposts from house A271's north wall
Five samples of Quercus sp., oak were examined. Complete sapwood is preserved on the samples (summer felling). The samples are not dated. One of the samples contains only 53 tree-rings, while the other four were affected by cockchafers.

Construction A326; "fence"
Two samples of Quercus sp., oak were examined. Complete sapwood is preserved on the samples (one summer felling, one winter felling). The samples are not dated. Both samples were affected by cockchafers.

Construction A364; posts in latrine A364
Two samples of Quercus sp., oak were examined. Complete sapwood is preserved on the samples. One of the samples is dated. The outermost preserved tree-ring (the bark ring) was formed in AD 1439. The bark ring is not fully formed. The felling date for the tree, from which the sample comes, is summer AD 1439.

Construction A390; posts in latrine A390
Two samples of Quercus sp., oak were examined. Sapwood is preserved on the samples of which one has the bark ring (summer felling). One sample is dated. The outermost preserved tree-ring was formed in AD 1439. Allowing for missing sapwood, the felling date for the tree, from which the sample comes, is estimated to be AD 1443-58.

Construction A399, A400, A417 and A425; timbers from timber-framed house A402
Four samples of Quercus sp., oak were examined. Sapwood is preserved on the samples of which two have bark ring (winter felling). Two of the samples are dated. The outermost preserved tree-ring on sill beam X497 (81272549) was formed in AD 1401. The felling date for the tree, from which the sample comes, is estimated to be AD 1416-31. The outermost preserved tree-ring on wall post X519 (81272569) was formed in AD 1429. The felling date for the tree, from which this sample comes, is estimated to be AD 1431-45. The results suggest that the house contains material from at least two phases.

Construction A392; planks from tanning vat
Five samples of Quercus sp., oak were examined. Heartwood/sapwood boundary was noted on one of the samples. Three of the samples are dated. The outermost preserved tree-ring was formed in 1368. The felling of the trees, from which the samples comes, is estimated to be AD 1372-87.

Construction A438; sill beam in house A440
One sample of Quercus sp., oak was examined. Only heartwood is preserved on the sample. The outermost tree-ring was formed in AD 1428. The felling date for the tree, from which the sample comes, is estimated to be after AD 1444.

The number of tree-rings
Out of 63 oak samples 20 are dated, which is just under 32%. This is a much lower proportion than would be normally expected. This is due to a number of factors

A. The number of tree-rings in the individual samples.

B. The number of samples in an analysis is also of significance. Though this analysis includes 63 samples, they are spread out over time. Normally, when dating a construction 10-15 samples are taken from every phase (building, repair etc.). The 20 dated samples though, come from three centuries. In the analysis, material from a former analysis from Aalborg is of course also included (see NNU report 25, 2000). The material from that analysis though, has also suffered from the same limitations as this, that is, the low number of tree-rings in the samples and the samples' spread through time.

C. In addition, there are a number of samples which cannot be dated because the tree-ring curves show a four or five yearly cycle, which is probably due to attack from cockchafers. When the cockchafer beetle flies it often eats leaves of oak trees. The tree which is attacked in this way forms thus a very narrow tree-ring that year. In most of Denmark the beetle's life cycle is four years, while in north Jutland it has a five year cycle (see Christiansen 1983). In this analysis, where the samples show signs of being damaged by the cockchafer, it is primarily the five year cycle which appears (17 samples with five year cycles, four with four year cycles), which indicates that the samples come from trees which grew, hardly surprisingly, in northern Jutland.