DATASET TITLE: TREE-RING CHRONOLOGY INDEXES AND RECONSTRUCTIONS OF PRECIPITATION IN CENTRAL IOWA, USA CONTRIBUTORS: T. J. BLASING AND D. N. DUVICK, ENVIRONMENTAL SCIENCES DIVISION, OAK RIDGE NATIONAL LABORATORY, OAK RIDGE, TENNESSEE 37831. SCOPE OF THE DATA: CORE SAMPLES 4 MM IN DIAMETER WERE EXTRACTED FROM THE TRUNKS OF WHITE OAK (QUERCUS ALBA) TREES AT LEDGES, PAMMEL AND DUVICK BACK WOODS IN CENTRAL IOWA. GROWTH RINGS OF EACH CORE WERE DATED BY CALENDAR YEAR FOLLOWING THE STANDARD PROCEDURE DESCRIBED IN STOKES AND SMILEY (1968). RING WIDTHS WERE MEASURED TO THE NEAREST HUNDREDTH OF A MM. LOW-FREQUENCY VARIATIONS DUE TO TREE AGE, CHANGE 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 YEAR (FRITTS 1971; FRITTS 1976). THE ADJUSTED RING WIDTHS ARE KNOWN AS RING-WIDTH INDICES. THE AVERAGE RING-WIDTH INDEX FOR EACH YEAR WAS COMPUTED FROM THE INDICES OF ALL CORES AT A SITE. INITIAL YEARS OF THE CHRONOLOGIES WERE 1635 AT PAMMEL, 1654 AT DUVICK BACK WOODS, AND 1663 AT LEDGES, IOWA. SAMPLE SIZES RANGED FROM 6 TO 16 CORES BY THE YEAR 1680 AND INCREASED STEADILY IN EACH CHRONOLOGY AFTER 1800. THE INDICES EXTEND THROUGH 1981. THE INDICES ARE USED TO ESTIMATE OR RECONSTRUCT PAST VALUES OF NUMEROUS CLIMATIC AND HYDROLOGIC VARIABLES, INCLUDING LARGE-SCALE SEASONAL PATTERNS OF TEMPERATURE, PRECIPITATION, AND ATMOSPHERIC CIRCULATION (DUVICK AND BLASING 1981; BLASING AND DUVICK 1984). DATA FORMAT: FOUR ASCII TEXT FILES ARE PROVIDED WITHIN THIS SUBDIRECTORY (NDP002) INCLUDING THIS DESCRIPTIVE FILE (NDP002.TXT), ONE DATA FILE CONTAINING TREE-RING INDICES FROM THE THREE SITES (NDP002.TRE), ONE DATA FILE CONTAINING RECONSTRUCTED PRECIPITATION ESTIMATES FOR CENTRAL IOWA (NDP002.PRE), AND A FORTRAN RETRIEVAL CODE TO READ AND PRINT ALL THESE FILES (NDP002.FOR). THE TREE-RING INDICES FILE IS FORMATTED SUCH THAT COLUMNS 1-6 CONTAIN THE SITE IDENTIFICATION DENOTED AS FOLLOWS: IDENTIFIER SITE 645814 DUVICK BACK WOODS 648813 LEDGES STATE PARK 464813 PAMMEL STATE PARK COLUNMS 7-10 CONTAIN THE YEAR OF THE FIRST DATUM ON THE CARD. COLUMNS 11-80 CONTAIN 10 SETS OF SEVEN COLUMNS EACH. FIRST FOUR COLUMNS CONTAIN THE RING-WIDTH INDEX VALUE IN DIMENSIONLESS UNITS, TO THREE DECIMAL PLACES (E.G., AN INDEX OF 1234 IS ACTUALLY 1.234), AND THE NEXT THREE COLUMNS CONTAIN THE NUMBER OF CORE SAMPLES (SAMPLE SIZE) USED TO OBTAIN THE INDEX VALUE. A 9990, FOLLOWED BY EITHER THREE BLANKS OR A ZERO, INDICATES NO DATA FOR THAT YEAR. THESE VALUES OCCUR EITHER AT THE BEGINNING OR END OF A SERIES. AND THUS, HAVE VALUE IN INDICATING THE START/END OF A SERIES. THE FIRST DATUM, OR 9990, ON A CARD CORRESPONDS TO THE BEGINNING OF A DECADE (E.G., 1650, 1660, ETC.). THE ANNUAL PRECIPITATION RECONSTRUCTION DATA ARE FORMATTED AS DECADAL YEAR FOLLOWED BY 10 VALUES (ONE FOR EACH YEAR IN THE DECADE). THE UNITS ARE CM. AND THE DATA ARE FORMATTED ON FILE 4 AS: FORMAT(I4,10(1X,F6.2)) ****************************************************************** REFERENCES ****************************************************************** BLASING, T. J. AND D. N. DUVICK. 1984. "RECONSTRUCTION OF PRECIPITATION HISTORY IN NORTH AMERICAN CORN BELT USING TREE RINGS," NATURE 307(12):143-145. DUVICK, D. N. AND T. J. BLASING. 1981. "A DENDROCLIMATIC RECONSTRUCTION OF ANNUAL PRECIPITATION AMOUNTS IN IOWA SINCE 1680," WATER RESOURCES RESEARCH 17:1183-1189. FRITTS, H. C. 1971. "DENDROCLIMATOLOGY AND DENDROECOLOGY," QUATERNARY RESEARCH 1:419-449. FRITTS, H. C. 1976. TREE RINGS AND CLIMATE. ACADEMIC PRESS, NEW YORK. STOKES, M. A. AND SMILEY, T. L. 1968. AN INTRODUCTION TO TREE- RING DATING. UNIVERSITY OF CHICAGO PRESS, ILLINOIS.