Climate Information from Stable Hydrogen and Carbon Isotopes of C₃ Plants — Growth Chamber Experiments and Field Observations

Summary

This chapter deals with the processes that affect the carbon and hydrogen isotope ratios of plant cellulose. Under natural conditions the influence of a single climate parameter on the isotope composition of tree-rings cannot be evaluated exactly, because of the strong interdependences of the climatic parameters. Results from growth chamber experiments with bean plants (Vicia faba) are presented, in which temperature, relative humidity and irrigation were varied independently from each other. All these parameters were found to be negatively correlated with the δ¹³C values of stem cellulose. The δD values of stem cellulose were influenced mainly by the humidity of the ambient air and by the isotope signal of the source water. The experimental results may help to explain δD and δ¹³C values in plant material for the purpose of climate reconstructions. As an example, stable isotope chronologies from tree-rings of spruces (Picea abies) from two different sites in Southern Germany are interpreted in the light of the experimental results.