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Andrew D. Friend BSc PhD

Professor of Earth Systems Science and Fellow of Clare College


Andrew Friend’s research interests concern controls on terrestrial vegetation type, structure, and productivity over a wide range of time and space scales and the effects of vegetation on atmospheric processes through land surface energy partitioning and carbon fluxes. He develops numerical models in order to test our understanding of processes through the ability of these models to faithfully simulate real-world phenomena, as well as address concerns regarding the effects of global change on terrestrial ecosystems and potential future atmospheric feedbacks. One of the main tools he uses is the individual-based model of vegetation dynamics, HYBRID, which is used to simulate land surface responses to climate change and atmospheric CO2. His current work is particularly concerned with growth processes (i.e. how meristem activity is controlled and how the determine plant form and function), internal plant feedbacks between sources and sinks, physiological differences between plant types and species, the representation of competition, and the global-scale dynamics of biogeochemistry-climate interactions.

PhD supervision

I welcome the opportunity to supervise PhD students who wish to work on modelling and observations in the areas of plant physiology, ecosystem dynamics, global biogeochemical cycles (especially the global carbon cycle), and/or climate systems, especially where one or more of these elements are coupled.

An example of a possible topic is shown at the end of this page, but many other topics are of equal interest – please feel free to suggest what you would like to work on within the general research areas described here.


[Publications will appear automatically from the University’s research database…]


  • Undergraduate: Biogeography (second and third year Geography)
  • Graduate: MPhil in Holocene Climates

External activities

  • European Geosciences Union (member)

Possible topic: The role of ecosystem physiological processes in the historical global carbon cycle on land

Terrestrial ecosystems plays a key role in the global carbon cycle, as well as providing humans and other ecosystem trophic levels with essential services. However, we only have a very poor understanding of the global behaviour of their interaction with the atmosphere, including the surface carbon balance. This is despite numerous observational systems collecting data on ecosystem state and behaviour. These observations include in situ fluxes, tree rings, and structural parameters such as height, as well as remote sensing estimates of surface light absorption, leaf area, and atmospheric CO2 dynamics (which can be used to estimate surface fluxes). It is essential that we improve our understanding of past fluxes and their controls in order to inform future projections of both impacts and feedbacks with the atmosphere. Examples of controls on temporal and spatial variability include seasonal drought, temperatures extremes, and storm damage (e.g. across the Amazon rainforest in 2005).

This PhD project will address this problem using a dynamic global vegetation model (see References below). The model will be further developed, tested, and used to better understand the role of climate and atmospheric CO2 on the historical global terrestrial carbon balance. The model exists in different forms that allow the analysis of controls on ecosystem state as a result of climate variability in space and time. The model will be extended to incorporate land use change over the 1880-2009 period , and simulations will be made of the global distribution of carbon sources and sinks over this period. Comparisons will be made with satellite data (e.g. MODIS), in situ data such as from flux towers, and the dynamics of atmospheric CO2. In addition, collaborations with other research groups will be exploited to compare different model and remote-sensing based estimates of historical carbon fluxes. This will enable the quantification and attribution of uncertainty, and establish methodologies for further improving our understanding of controls on terrestrial ecosystem states and behaviour, particularly their roles in the global carbon cycle.


  • Friend AD et al. 2019. On the need to consider wood formation processes in global vegetation models and a suggested approach. Annals of Forest Science, doi:10.1007/s13595-019-0819-x
  • Friend AD et al. 2014. Carbon residence time dominates uncertainty in terrestrial vegetation responses to future climate and atmospheric CO2. Proceedings of the National Academy of Sciences 111, 3280-3285, doi:10.1073/pnas.1222477110Carbon residence time dominates uncertainty in terrestrial vegetation responses to future climate and atmospheric CO2. Proceedings of the National Academy of Sciences 111, 3280-3285, doi:10.1073/pnas.1222477110
  • Friend AD. 2010. Terrestrial plant production and climate change. Journal of Experimental Botany, doi:10.1093/jxb/erq019
  • Friend, A.D. and Kiang, N.Y. 2005. Land-surface model development for the GISS GCM: Effects of improved canopy physiology on simulated climate. Journal of Climate 18, 2883-2902, doi:10.1175/JCLI3425.1.
  • Friend, A.D. and White, A. 2000. Evaluation and analysis of a dynamic terrestrial ecosystem model under preindustrial conditions at the global scale. Global Biogeochemical Cycles 14(4), 1173-1190.