Ring-width-index of five west african tree species, Aguima Catchment, Benin

Core samples were taken from a total of 191 trees with an increment borer (Suunto, Finland) with an inner diameter of 5 mm at the measured diameter at breast height (DBH = 130 cm height) from two perpendicular directions. In addition from each species at least one stem disc was taken. The samples were dried and transported to the dendrochronological laboratory of the University of Göttingen, Germany. Core samples were polished together with the stem discs consecutively with sandpaper up to a grain of 600 µm. Ring widths were measured with a digital measuring device (LINTAB, Rinntech, Heidelberg, Germany) to the nearest 0.01 mm. Individual tree-ring series were cross-dated visually and statistically and combined to a mean curve (chronology). Measures for the statistical cross-dating were the Student's T-value (Baillie and Pilcher, 1973) and the percentage of parallel run (p.p.r.) indicating the year-to-year agreement in the oscillation of two curves within the overlapping interval (Schweingruber, 1988, Fichtler et al., 2004). Tree-ring statistics were performed with the computer program TSAP (Time Series Analysis and Presentation, Rinntech, Heidelberg, Germany). This program also transforms raw ring curves into index curves by removing long-term growth trends using a 5-year moving average. The residuals of this procedure are normally distributed, which is a basic condition for the correlation with climate data (Cook and Briffa, 1990).Datasets created by IMPETUS subproject A3. IMPETUS data set ID: 435