Tree ring chronology indexes and reconstructions of precipitation in Central Iowa, USA
Over sixty trees were sampled at each of the three Iowa sites; at least two cores were taken from most of the trees. The growth rings of each core were dated by calendar year, following standard procedures. Ring widths were measured to the nearest one-hundredth of a millimeter. Low-frequency variations resulting from tree age, changes in competitive status, and other nonclimatic factors were minimized by fitting a spline curve to the ring-width series and dividing each ring width by the value of the curve for the corresponding span. The average adjusted ring-width index for each year was computed from the indices of all cores at a site to obtain the chronology of ring-width indices (or tree ring chronologies) presented here. Based on the oldest tree samples, the initial years of the three chronologies in the study were 1635 at Pammel, 1654 at Duvick Back Woods, and 1663 at Ledges, Iowa. The sample sizes of the chronologies ranged from 6 to 16 cores by the year 1680 and increased steadily in each chronology after 1800. Indices are included for the three sites through 1981. A reconstruction of annual precipitation for central Iowa for the period 1860-1979 is based on these three chronologies.
- Research Organization:
- Oak Ridge National Lab., TN (USA)
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 6834499
- Report Number(s):
- NDP-002
- Country of Publication:
- United States
- Language:
- English
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