Effects of nutrient fertilization on leaf physiology in the Amazon Rainforest

University of Exeter - College of Life and Environmental Science

Main supervisor: Dr Lina Mercado (College of Life and Environmental Sciences, University of Exeter)

This project is one of a number that are in competition for funding from the NERC Great Western Four+ Doctoral Training Partnership (GW4+ DTP).  The GW4+ DTP consists of the Great Western Four alliance of the University of Bath, University of Bristol, Cardiff University and the University of Exeter plus six Research Organisation partners:  British Antarctic Survey, British Geological Survey, Centre for Ecology and Hydrology, the Met Office, the Natural History Museum and Plymouth Marine Laboratory.  The partnership aims to provide a broad training in earth and environmental sciences, designed to train tomorrow’s leaders in earth and environmental science. For further details about the programme please see http://nercgw4plus.ac.uk/

Tropical rainforests are key players in the earth system. They store large amounts of carbon, are highly productive, host high plant diversity but also regulate climate, through the exchange of large amounts of water, carbon, and energy with the atmosphere. In order to predict their behaviour & resilience to future climate change, it is necessary to understand their functioning & controls. One of the major gaps in our current understanding of tropical forest is related to the controls of their productivity. Contrary to most ecosystems, tropical forests are generally considered to be limited by Phosphorous availability instead of Nitrogen. Nevertheless, we lack understanding of the extent and nature of nutrient limitation and its control on tropical forest net primary productivity (1,2). To address this gap in understanding, we have set up the first large scale nutrient addition experiment (nitrogen, phosphorus and cations) in the Brazilian Amazon. Thus, this studentship represents a unique opportunity for improving understanding how nutrient availability controls on rainforest functioning (3).

The aims of this PhD project are improve our understanding of nutrient control on photosynthesis and other physiological processes such as leaf respiration and stomatal conductance, leaf traits, the nature and extent of nutrient limitation to photosynthesis. The ultimate aim is to improve understanding so that ecosystem and global modellers can best represent rainforest canopy photosynthesis and physiology in vegetation models.

This project will be able to answer fundamental questions on tropical forest nutrient limitation:

  • What is the response of foliar nutrients and traits following nutrient addition?
  • What is the response of key physiological processes such as photosynthesis, stomatal conductance and leaf respiration following nutrient addition)?

The studentship involves a combination measurements of leaf photosynthesis, in the field (near Manaus, Brazil), laboratory analysis of foliar nutrient concentrations and leaf traits, data analysis and potentially, simple modelling at leaf and canopy scale, depending on the student’s interest. The data analysis will combine all the data on photosynthesis, nutrient concentrations and leaf traits to evaluate the effect of fertilization on leaf physiological processes. There are excellent opportunities for generating new understanding and high-impact publications. It is desirable that the candidate is numerically skilled and have an appetite to learn data analysis. Most importantly, the student should be able to work in the field under hot/humid but also challenging conditions.

Please see http://www.exeter.ac.uk/studying/funding/award/?id=2292 for full information regarding applications.

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South West England