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Overview

Project Highlights:

  • Application of cutting-edge mass spectrometry methods to provide new insights into palaeo-hydrology in the Neotropics.
  • Multidisciplinary research project
  • International research team

Plant waxes from leaf coatings are widely dispersed by wind and can be found everywhere on earth. Due to their chemically resistant nature, they tend to be preserved in sedimentary archives for millions of years. They are used as biomarkers in paleoclimate research as they represent the molecular remains of past vegetation. As such they are of fundamental importance because the isotopic ratios of carbon (δ13C) and hydrogen (δD) are directly related to metabolism of specific plant functional types and ecophysiological conditions (Sachse et al. (2012). δD signatures of plant waxes in particular show a strong correlation to hydrological conditions at times of plant growth (Kahmen et al. 2013) and their use palaeoclimate studies has shown that δD of leaf waxes can be used to reconstruct aspects of past rainfall (Tierney et al. 2008), in particular the amount of precipitation (Schefuss et al. 2005). To fully utilize this palaeoclimate proxy it is important to understand the modern day plant-deuterium relationships. Understanding δD in leaf waxes from modern plants, in the context of the hydrological cycle, is key to interpretations of biomarker δD records of the past. The Neotropical Andes is a key location for palaeoclimate research due to its wealth of Holocene/Quaternary sedimentary archives and its critical role in the global climate system (Boom et al. 2001). For example the hydrological cycle of the Andes affects that of the modern day Amazon basin, the largest tropical watershed in the world. The proposed project involves the retrieval of sedimentary archives including a systematic sampling of Andean plant taxa and vegetation units along a range of well-defined environmental gradients. Ground and meteoric water will be collected at specific intervals to obtain better insights into the isotopic behaviour of the source water through time. Leaflipid distribtutions from plants will be investigated in relation to envrionmental gradients and long term changes from sedimentary records. The results of this study will provide new insights into the hydrological cycle of the Northern Andes, and its plant interactions, and ultimately seeks to facilitate significantly improved palaeoclimatological reconstructions.

High altitude wetlands are sensitive recorders of hydrological change.

Methodology

Fieldwork will be conducted in the vincity of Bogota in the Colombian Andes in collaboration with collaegues from the Universidad de los Andes.

Plant waxes will be extracted from soils and plants in the laboratory using soxhlet extractions. The project will be carried out in the Department of Geography’s state-of-the-art stable isotope laboratory. A new Thermo Delta V plus (installed 2016) and a Sercon 20-20 isotope ratio monitoring mass spectrometer are available for compound-specific and water deuterium isotope analysis. For the investigation of leafwaxes two dedicated quadrupole GC/MS systems (Perkin Elmer and Thermo Scientific) with extraction facilities are be available.

Training and Skills

CENTA students are required to complete 45 days training throughout their PhD including a 10 day placement. In the first year, students will be trained as a single cohort on environmental science, research methods and core skills. Throughout the PhD, training will progress from core skills sets to master classes specific to CENTA research themes.

The student will obtain training in mass spectrometry and the interpretation and analysis of mass spectra (including stable isotope and various multivariate statistical analyses). In addition he or she will receive training in the field.

Timeline

Year 1: Literature review, stable isotope course, specific training for: A) lipid extraction, lipid identification using GC/MS and isotope analysis on lipids. Planning and conducting field work.

Year 2: Extraction of lipids. GC/MS analysis of lipids. Deuterium analysis of meteoric and ground water samples.

Year 3: Deuterium analysis of leaf waxes. Statistical analysis. Testing of results with models for isotopic enrichment in (leaf) water.

Partners and collaboration (including CASE)

Boom is an organic geochemists / isotope geochemist and Berrio is a palaeoecologist. The project will build on existing collaboration with the palaeoecology research group from the University of the Andes and the National University in Bogota, Colombia (Associate professor Dr. Catalina Gonzalez Arango), together with IDEAM (Colombian institute for hydrology, meteorology and environmental studies). In addition the project will collaborate with Dr. Brian Chase (CNRS, Montpellier) a palaeoclimatologist with a strong interest in leaf wax proxies.

Further Details

ab269@le.ac.uk