Understanding the relationships and feedbacks between the global water and carbon cycles is one of the central goals of current climate research as they directly impact continental vegetation, soil quality, weathering, runoff, and ocean processes. Stable isotope geochemistry at the compound-specific level provides a new analytical technique that has potential to link these global cycles.
Finding new approaches and concepts to recover (palaeo-) environmental information sequestered in modern and ancient organic compounds is at the core of climate research. Investigation of carbon (d13C) and hydrogen (dD) isotopic compositions of individual organic compounds derived from higher plant leaf waxes and other organic components is one of the recent major achievements in that research field. This type of isotopic data can be used to explore the isotopic compositions of atmospheric CO2 and precipitation, as well as to investigate changes in the palaeohydrology. This approach, however, is strongly constrained by different types of co-existing higher plants contributing to the sedimentary signal.
Furthermore, because of its highly technical nature, development of new applications for compound specific methodology increasingly requires cross-disciplinary skills. As a result, certain potential research directions remain under explored. For example, one of these new applications is simultaneous d13C and dD measurements of organic compounds in order to investigate physiology of different types of modern higher plants subjected to different climatic conditions.
We propose to explore the links among carbon (C) and hydrogen (H) isotopic compositions of organic compounds in leaf waxes from modern higher trees and organic matter in associated soils, the physiology of these plants, and modern climatic conditions along one north-south and one west-east transect in western Europe. To achieve these goals we will measure compound-specific isotope data from n-alkanes and biomarkers specific to angiosperm and conifer species in both leaves and top soils, and dD composition of tree stem water. Additionally, we will determine plant stomatal conductance and collect air temperature and relative humidity data.
The proposed research will lead to:
1) A significant improvement of our understanding of the factors that control stable C and H isotopic fractionation during biosynthesis, leaf senescence, and soil burial of individual organic compounds derived from modern higher plants.
2) An extensive data set that will improve interpretation of stable C and H isotopic compositions of organic compounds in palaeoclimatic studies.
3) The establishment of a new approach for investigating leaf stomatal behaviour of various conifer and angiosperm plants using simultaneous investigation of compound-specific d13C and dD values.
To our knowledge the research proposed here is the first multi-annual investigation of the factors controlling stable C and H compound-specific isotopic compositions of organic compounds from higher plant leaf waxes in Western Europe. The results of this project will provide fundamental data that can be used to improve modern and past climate research.