TY  - JOUR
A1  - Kahmen, Ansgar
A1  - Schefuss, Enno
A1  - Sachse, Dirk
T1  - Leaf water deuterium enrichment shapes leaf wax n-alkane delta D values of angiosperm plants I experimental evidence and mechanistic insights
JF  - Geochimica et cosmochimica acta : journal of the Geochemical Society and the Meteoritical Society
N2  - Leaf wax n-alkanes of terrestrial plants are long-chain hydrocarbons that can persist in sedimentary records over geologic timescales. Since meteoric water is the primary source of hydrogen used in leaf wax synthesis, the hydrogen isotope composition (delta D value) of these biomarkers contains information on hydrological processes. Consequently, leaf wax n-alkane delta D values have been advocated as powerful tools for paleohydrological research. The exact kind of hydrological information that is recorded in leaf wax n-alkanes remains, however, unclear because critical processes that determine their delta D values have not yet been resolved. In particular the effects of evaporative deuterium (D)-enrichment of leaf water on the delta D values of leaf wax n-alkanes have not yet been directly assessed and quantified. Here we present the results of a study where we experimentally tested if and by what magnitude evaporative D-enrichment of leaf water affects the delta D of leaf wax n-alkanes in angiosperm C3 and C4 plants. Our study revealed that n-alkane delta D values of all plants that we investigated were affected by evaporative D-enrichment of leaf water. For dicotyledonous plants we found that the full extent of leaf water evaporative D-enrichment is recorded in leaf wax n-alkane delta D values. For monocotyledonous plants we found that between 18% and 68% of the D-enrichment in leaf water was recorded in the delta D values of their n-alkanes. We hypothesize that the different magnitudes by which evaporative D-enrichment of leaf water affects the delta D values of leaf wax n-alkanes in monocotyledonous and dicotyledonous plants is the result of differences in leaf growth and development between these plant groups. Our finding that the evaporative D-enrichment of leaf water affects the delta D values of leaf wax n-alkanes in monocotyledonous and dicotyledonous plants albeit at different magnitudes - has important implications for the interpretation of leaf wax n-alkane delta D values from paleohydrological records. In addition, our finding opens the door to employ delta D values of leaf wax n-alkanes as new ecohydrological proxies for evapotranspiration that can be applied in contemporary plant and ecosystem research.
Y1  - 2013
U6  - https://doi.org/10.1016/j.gca.2012.09.003
SN  - 0016-7037
VL  - 111
SP  - 39
EP  - 49
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Hoffmann, Bernd
A1  - Kahmen, Ansgar
A1  - Cernusak, Lucas A.
A1  - Arndt, Stefan K.
A1  - Sachse, Dirk
T1  - Abundance and distribution of leaf wax n-alkanes in leaves of Acacia and Eucalyptus trees along a strong humidity gradient in northern Australia
JF  - Organic geochemistry : the international journal for rapid publication of current research in organic geochemistry and biochemistry
N2  - Environmental parameters such as rainfall, temperature and relative humidity can affect the composition of higher plant leaf wax. The abundance and distribution of leaf wax biomarkers, such as long chain n-alkanes, in sedimentary archives have therefore been proposed as proxies reflecting climate change. However, a robust palaeoclimatic interpretation requires a thorough understanding of how environmental changes affect leaf wax n-alkane distributions in living plants. We have analysed the concentration and chain length distribution of leaf wax n-alkanes in Acacia and Eucalyptus species along a 1500 km climatic gradient in northern Australia that ranges from subtropical to arid. We show that aridity affected the concentration and distribution of n-alkanes for plants in both genera. For both Acacia and Eucalyptus n-alkane concentration increased by a factor of ten to the dry centre of Australia, reflecting the purpose of the wax in preventing water loss from the leaf. Furthermore, Acacian-alkanes decreased in average chain length (ACL) towards the arid centre of Australia, whereas Eucalyptus ACL increased under arid conditions. Our observations demonstrate that n-alkane concentration and distribution in leaf wax are sensitive to hydroclimatic conditions. These parameters could therefore potentially be employed in palaeorecords to estimate past environmental change. However, our finding of a distinct response of n-alkane ACL values to hydrological changes in different taxa also implies that the often assumed increase in ACL under drier conditions is not a robust feature for all plant species and genera and as such additional information about the prevalent vegetation are required when ACL values are used as a palaeoclimate proxy.
Y1  - 2013
U6  - https://doi.org/10.1016/j.orggeochem.2013.07.003
SN  - 0146-6380
VL  - 62
IS  - 9
SP  - 62
EP  - 67
PB  - Elsevier
CY  - Oxford
ER  -