Overview

Plant waxes from leaf coatings are widely dispersed by wind and can be found everywhere on earth. Due to their chemically resistant nature, leaf waxes tend to get preserved in sedimentary archives for millions of years. They are therefore used as biomarkers for vegetation in paleoclimate research. As such they are of fundamental importance primarily because the isotopic ratios of carbon (δ13C) and hydrogen (δD) are directly related to metabolism and eco-physiological conditions. δD signatures of plant waxes show a strong correlation to hydrological conditions at times of plant growth and their use in palaeoclimate studies has shown that δD of leaf waxes can be used to reconstruct aspects of past rainfall. 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. For example, the hydrological cycle of the Andes linkes to that of the modern-day Amazon basin, the largest tropical fresh watershed in the world. Understanding long term Neotropical climate variability is a key aspect of understanding the Quaternary global climate system. The proposed project involves the collection of exciting sedimentary archives from high Andes and Amazonian wetlands including a systematic sampling of key plant taxa and vegetation units along a range of well-defined environmental gradients. These records will provide highly sensitive records of past precipitation change of the Neotropics. Ground and meteoric water will be collected at specific intervals to obtain better insights into the isotopic behaviour of the source water through time. Leaf lipid distributions from plants will be investigated in relation to environmental gradients and long-term changes from sedimentary records. The results of this study will provide new insights into the hydrological cycle of the Neotropical Andes, and its plant interactions, and ultimately seeks to facilitate significantly improved palaeoclimatological reconstructions of this region.

High Andean wetlands provide ideal conditions for high resolution long term climate archives. This project offers a unique opportunity to investigate climatic gradients from the cold Andean paramo to the Amazon basin.

Methodology

Fieldwork will be conducted in the Ecuadorian Andes in collaboration with Yachay Tech University in Ecuador. Peaty sediments will be sampled using a Russian corer. A large proportion of the project involves laboratory analysis. This will be carried out in the School’s state-of-the-art environmental stable isotope laboratory. This laboratory is fully equipped to carry out organic geochemical analysis of biomarkers. Plant waxes will be extracted from sediments, soils and plants in the laboratory by accelerated solvent extraction.

Four mass spectrometers are available to support this project. A new hyphenated ISQ Quadrupole Delta V plus stable isotope mass spectrometer is available for compound-specific deuterium isotope analysis. For the investigation of leaf-waxes two dedicated quadrupole GC/MS systems and ISQ-GC/MS can be used. Extraction facilities are fully equipped with ultrasonic probes, soxhlet stations and a fully automated ASE350. Other technologies, such pyrolysis and solid phase micro extraction, are also 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: Initial training in sample preparation, GC/MS, mass spectrometry and irm-GC/MS, working with previously-collected sediments and modern plant samples. Planning field sampling campaign for calibration of modern leaf wax dD-climate relations, including arrangements for analysis of contemporary rainfall data.

Year 2: Field sampling in southern America, development and presentation of Andean and Amazonian palaeohydrological records. Construction and refinement of modern calibration datasets.

Year 3: Development of first Ecuadorian palaeohydrological records. Analysis and presentation of contemporary dD climate models, synthesis of late Pleistocene palaeohydrology across regional rainfall zones. Publication of data and presentation at international conferences is anticipated from year 2 onwards.

Partners and collaboration (including CASE)

Boom and Carr have very strong track records in palaeoecology and the development of stable isotope/geochemical proxies. At Leicester, Dr. Berrio, will strengthen the team by providing expertise on Neotropical palaeoecology. Boom has 21 years of experience researching Neotropical palaeoclimate change. Boom directs the state-of-art Leicester isotope facility. The project will be externally co-supervised by Dr. Chase CNRS, Montpellier, a leading international expert on palaeo-hydroclimate and by Dr. Arellano, who is an earth observation scientist and dean of Earth Science at Yachay Tech University. The National Herbarium of Ecuador will provide support with the taxonomic identification of plants.

Further Details

Contact: Dr. Arnoud Boom ab269@le.ac.uk