Principle Investigator Jon Lloyd Project s53

Environmental Biology Group, Machine VP

Research School of Biological Sciences

Co-Investigators Graham Farquhar, Frank Kelliher and Detlef Schulze

Environmental Biology Group, Research School of Biological Sciences,

Landcare Research, Christchurch, New Zealand and

Lehrstuhl fur Pflanzenokologie, Universitat Bayrurth, Bayreuth, Germany

Interactions Between the Hydrological and Carbon Cycles at a Global Scale

Our longterm objective is to implement state of the art knowledge of plant physiology and soil hydrology into global models of photosynthesis and evaporation. This involves development of improved algorithms decribing stomatal and biochemical responses of plants to

environmental parameters such as light, temperature, humidity and CO2. Where possible, the algorithms developed are being tested against ecosystem carbon dioxide and water flux data which we are also actively involved in acquiring. The final models will not only be useful in improving our current understanding of current and future climatic effects on the global carbon and hydrological cycles, but should also have use as land-atmosphere transfer schemes in General Circulation Models.

What are the basic questions addressed?

How do seasonal patterns of terrestrial photosynthesis and evaporation vary across the planet?

How are they likely to respond to global and climate change?

What are the results to date and what is the future of the work ?

Our early work has concentrated on stomatal behaviour and fluctuations in isotopic discriminations during photosynthesis in response to environmental fluctuations. We have also developed improved parameterisations of rainfall interception and evaporation by plants. We are not satisfied with current global vegetation databases available and are currently working on developing our own. This is an essential next step before further algorithm development.

What computational techniques are used and why is a supercomputer required ?

Calculations are done at 0.5x0.5 degree resolution and the large data sets and computational time involved make the supercomputer the ideal research tool.

Publications

13C discrimination by the terrestrial biosphere, J Lloyd and G D Farquhar, Oecologia 99, 201-215 (1994).

Terrestrial carbon storage at the last glacial maximum, M I Bird, J Lloyd and G D Farquhar, Nature 371, 566 (1994).

Relationships between maximum surface conductance, ecosystem surface conductance, carbon assimilation rate and plant nitrogen nutrition. A global ecology scaling exercise, E-D Schulze, F M Kelliher, C Koerner, J LLoyd and R Leuning, Annual Review of Ecology and Systematics 25, 629-660 (1994).