Carbon isotopes in ombrogenic peat bog plants as climatic indicators: calibration from an altitudinal transect in Switzerland

The accumulation of organic matter in peat bogs potentially constitutes a c ontinuous and high-resolution record of continental climate for the Holocen e period. In order to interpret the carbon isotopic values of bog plant mac rofossils as a record of environmental parameters, we attempted to calibrat e plant-climate relationships by sampling a set of modern plant species (bo th vascular plants and mosses) along an altitudinal transect in Switzerland . Carbon isotope ratios were measured by an on-line combustion/continuous h ow method on both bulk plant material and the alpha -cellulose fraction. Fo r most of the species studied, the delta C-13-values increase with altitude , although the slopes of the trends vary considerably. The primary cause of the delta C-13 increase with altitude is thought to be decreased atmospher ic CO2 partial pressure. In addition, for vascular plants the increase of d elta C-13-values might also partially be due to decreasing temperature. For mosses, the cell water content (and thus precipitation regime) is also an important factor influencing delta C-13-values. (C) 2001 Elsevier Science L td. All rights reserved.