Elm dating

f.maspero
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Real name: Francesco Maspero
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Elm dating

Postby f.maspero » 02 Apr 2009, 11:34

I'm trying to enter in the charming world of dendrochronology, and I'm moving my first steps.
I started using hi-resolution photos to extract the datas. Unfortunately (like anyone else who begins) my only source of master curves is the database from World Data Center for Paleoclimatology.
Now I'm trying to date a sculpture which seems to be made of elm. I read it is possible to use it for dendrochronology, and I'd like to know if there are some sources of master curves including elm, since WDCP doesn't have any.

The origin of the wood should be northern italy.

Thank you
Francesco

ale
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Real name: Alessandro Ravotto
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Re: Elm dating

Postby ale » 02 Apr 2009, 18:09

Ciao Francesco,

After a superficial and really fast search in the web, effectively elm seems to be a poor studied species under dendroarchaeological point of view, or at least free-access data seems to be hard to obtain. I found just one sample of elm from Italy (http://dendro.cornell.edu/reports/report2000.pdf): sadly it’s a protohistoric sample and furthermore it’s not dated because of some problems during growing. Anyway maybe you can find some curves googling in different languages and searching in real libraries.

If you don’t have a reference curve of the species you are interesting in, here goes, just as suggestion, a personal, absolutely inelegant, “protocol”:

1) Search for at least one dated curve of elm from northern Italy, Alps, etc… It have not to be necessarily in digital format: you can convert published diagrams by using the coorecorder facility. Look also for ecological-related papers: often they have short curves, too short for dating purposes but useful by the point of view of this personal method. If you don’t find any, sample yourself a little curve.

2) Search in all databases (two more: http://dendrodb.cerege.fr/ and http://www.wsl.ch/dendro/dendrodb.html) and in published papers all the curves near the zone from which is your little elm dated curve.

3) Play with the data for revealing better correspondence between elm and other species in the same area.

4) Do a “massive attack” comparing all curves you have collected with your undated curve (you can find examples of the process in Lars-Ake’s site, under "Miscellaneous" section), evaluating the results by aid of observations you made after point 3. The dated reference curves, the little dated elm curve and the undated elm sample have to be from the same area.

5) If you are lucky enough, you can obtain some useful deduction and maybe some result too.

6) Since this method is not rigorous and can bring EASILY to incorrect datings, do further and endless verifications. If you are starting now from zero, you can spend years until you can date reasonably the sample.

Anyway, you have to be sure your undated sample is elm, and it aids if you know approximately when the sculpture you are trying to date was made. Probably you already took in account this, but I would pay attention to the context too: may it be an imported sculpture? From where?
Document yourself about dendrochronological characteristics of elm, even from other regions, especially looking for interspecific correlations values (sorry, I never touched elms data). Finally, you probably already know that possibilities of correct dating are proportional (among others parameters) to the number of samples forming your undated curve.

Hope this is sufficient to start. I’m sorry if this reply looks too doctrinaire (and surely I’m not the adequate one...), but you told you was starting with dendrochronology. It’s just a suggestion and the process described could be refined. You can have an overview of Italian dendrochronology status (and, by the way, you can convert to digital data some published long chronology) reading papers by Franco Biondi (search the web for pdf of him), although they are from early '90 and I think elm is not quoted.

Saluti,

Ale

taxelson
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Re: Elm dating

Postby taxelson » 02 Apr 2009, 23:38

Hi Francesco,

According to http://www.wsl.ch/dbdendro/species/Details_EN?id_species=1098 Elm is not a very good specie for cross dating. It says the Crossdating Index (CDI) is "1", which "indicates a species known to crossdate within and between trees (minor importance to dendrochronology)". So unfortunately there seems to be a good reason why there are no elm (ULGL) references available at the ITRDB.

The only elm-sample I have been in touch with myself, is in the prehistoric dataset from Alvastra (Sweden). There is a short floating oak-chronology and one elm-sample from that site and there is a correlation between them, which was interpreted as a match... The data is digitalized and available in an other post on this forum: http://www.cybis.se/forum/viewtopic.php?p=62#p62. Maybe of some interest to see one example of QUSP-ULSP correlation, even if it is from an other and far distant place and time.

Best regards
Torbjörn

f.maspero
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Joined: 30 Mar 2009, 08:40
Real name: Francesco Maspero
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Re: Elm dating

Postby f.maspero » 03 Apr 2009, 08:02

Thank you for your precious help.
I'll try and "play" a little, following your tips.

Thanks also for your warm welcome in the dendrochronological community!

Francesco

ale
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Real name: Alessandro Ravotto
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Re: Elm dating

Postby ale » 03 Apr 2009, 19:35

So maybe a first attempt could pass trough oak correlations. The visual match in the paper quoted by Taxelson seems fine, although I have not yet looked to Taxelson’s interpretation. Anyway it is worth trying, and furthermore there’s plenty of oak chronologies. If you could experiment with oak and just one elm dated curve it would be better.

And, speaking of oak, some members of this forum could be interested in this: viewtopic.php?f=16&t=35

Regards,
Ale

taxelson
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Re: Elm dating

Postby taxelson » 21 Apr 2009, 09:24

I did visit Öland (a Baltic island in south east Sweden, from where I already have a lot of oak samples available) last week, and as I saw two elm stumps, I cored them. The result towards local oak chronology/samples) is not very encouraging. Of course this is just one example, and there may be trees which gives better results than those ones.
The oak-collection is available at: http://www.taxelson.se/dendro/OlandQURO.zip. (Also an almost local Pinus collection is avaliable as ITRDB:swed313).

Code: Select all

2009-04-21  09:56:11 Cybis CDendro, Algorithm: Proportion of last two years growth (2,0,T)
Correlations between available references in OlandQURO.fil and RamsA.d12 (average of two trees)
dated to 2007 with corr >= 0,00 and with overlap >= 60
Results sorted according to decreasing correlation coefficient values.
                   T-  Over
          Corr   Test   lap
all...    0,39   3,26    63   based on 21 members
OlQ73     0,47   4,18    63    2004 
OlQ15     0,45   3,88    61    2002 
OlQ6b     0,40   3,38    61    2002 
OlQ44     0,40   3,38    61    2002 
OlQ71a    0,40   3,38    63    2004 
OlQ14     0,39   3,20    60    2001 
OlQ34a    0,31   2,53    61    2002 
OlQ52     0,31   2,52    61    2002 
OlQ2      0,29   2,33    61    2002 
OlQ33a    0,29   2,29    61    2002 
OlQ33b    0,26   2,05    61    2002 
OlQ31     0,23   1,78    61    2002 
OlQ34b    0,23   1,78    61    2002 
GrdsQ15   0,22   1,75    61    2002 
OlQ51     0,22   1,73    61    2002 
OlQ42     0,21   1,68    61    2002 
OlQ32a    0,20   1,56    61    2002 
OlQ72     0,18   1,39    63    2004 
OlQ32b    0,17   1,33    61    2002 
OlQ43     0,08   0,63    61    2002 
OlQ41     0,00   0,03    61    2002 


The corr between the two cores are 0.52 (prop2yrs).

Code: Select all

RamsA  1 behind Ramsättra röse, Köping sn, Öland             ULSP
RamsA  2 Sweden       Ulmus sp.           25m  6551N1644E          1941 2007
RamsA  3 T. Axelson
RamsA   #### 56º50'33"N, 16º43'33"E
RamsA   #### Cores from two, one yr old, elm stumps (Ulmus glabra or Ulmus minor)
RamsA1  1941   139   142    61    98    92   119   126   139   149
RamsA1  1950   230   249   234   255   152    76   166   167   210   278
RamsA1  1960   316   208   104   309   205   194   133   137   116    96
RamsA1  1970   167   492   545   411   432   393   404   475   368   378
RamsA1  1980   504   620   520   374   710   533   486   440   626   439
RamsA1  1990   262   298   210   363   326   342   307   347   668   747
RamsA1  2000   772   509   434   441   353   352   332   611   999
RamsA1  #### Elm stump
RamsA2  1946   223   268   260   214
RamsA2  1950   196   244   214   260   183   194   289   291   224   216
RamsA2  1960   290   318   240   200   162   142   156   246   268   186
RamsA2  1970   221   338   319   250   206   218   192   257   224   161
RamsA2  1980   192   358   210   168   247   348   365   360   459   288
RamsA2  1990   209   232   167   346   360   373   241   368   907   869
RamsA2  2000   653   557   647   613   606   401   258   307   999
RamsA2  #### Elm stump


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