| Popis: |
The "many fragments curse," a special case of the segment length curse, occurs in den- drochronology when time series are broken into fragments, either because of missing part of a sample (e.g., a rot pocket) or when a section of ring growth cannot be crossdated (e.g., a section with extremely suppressed growth and/or many rings absent). We exorcise this curse by inserting values to connect fragments of measurements. This technique permits fitting a single detrending curve to the connected series and thus preserves the low-frequency variance contained in the entire series. Inserted values are discarded after detrending and do not otherwise affect calculations of final corn- posite chronologies. As an example from junipers sampled at a site in Qinghai Province, China, 66 of 117 increment cores have nondatable sections of wood and one core has a gap of rotten wood between dated fragments. After connecting fragments by inserting values and then detrending, the chronology constructed from connected fragments has stronger century to multicentury scale variation than the chronology constructed from separate fragments. This approach is adapted to the library of computer programs developed for dendrochronological research under the auspices of the International Tree-Ring Data Bank. |
