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 continuous and high-resolution record of continental climate for the Holocene period. In order to interpret the carbon isotopic values of bog plant macrofossils as a record of environmental parameters, we attempted to calibrate plant-climate relationships by sampling a set of modern plant species (both vascular plants and mosses) along an altitudinal transect in Switzerland. Carbon isotope ratios were measured by an on-line combustion/continuous how method on both bulk plant material and the alpha -cellulose fraction. For 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 atmospheric CO2 partial pressure. In addition, for vascular plants the increase of delta 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 Ltd. All rights reserved.