Vegetation Function Network supported by Australian Research Council and Landcare Research NZ
26. Phosphorus in landscapes in the context of global vegetation models
First meeting held 24 - 27 April 2007 at Network Headquarters, Sydney

PARTICIPANTS INCLUDE
 Mark Westoby - Macquarie, leaf economics
Ying Ping Wang - CSIRO Marine and Atmospheric Research
Hans Lambers - U Western Australia, plant physiology
Peter Reich - Minnesota, USA, plant physiological ecology
Garry Willgoose - U Newcastle
Patricia Saco - U Newcastle
Jon Lloyd - U Leeds, UK
Damian Gore - Macquarie
Geoffrey Humphreys - Macquarie
Anna Richards - Macquarie

Unable to attend first meeting and will participate in future meetings:
Keith Syers - Mae Fah Luang University, Thailand
Oliver Chadwick - University of California at Santa Barbara

Apr 07 >

At the first meeting discussion ranged widely. Six potential projects were identified. Some of these should move forward quickly, others are for the longer term.

1. Incorporating modeling of soil depth, fine-particle sorting and P concentration into existing landform evolution models. The next step will be to code and run this for a simple hillslope (1-D) formulation. After that, a wide range of elaborations and field quantifications are possible.

2. Fusing expertise in soils, hydrology/landform and plant ecology to improve understanding of some common Australian toposequences. This will be achieved by joint visits to fieldsites, with discussions leading on to proposals and/or papers. Likely sites include Lake Mere in October 2007 and Corrigin at some later date.

3. Soil age, P fractions and the Walker-Syers diagrammatic model. The idea would be to recouch Walker-Syers in any of several ways. The fractions of P might be rewritten to correspond more closely to "available to cluster roots", "available to ecto and ericoid mycorrhizas", "available to arbuscular mycorrhizas " and so forth. There might be a more quantitative treatment of the rates. There might be a better index of what so far has been called "soil age". Jon Lloyd will be leading email discussion to determine whether there is any consensus about these possibilities, and will also propose dates and participation for a second meeting.

4. A practical protocol for working from geological maps plus topography to a reasonable best guess at soil P, or other rock-derived nutrients. One potential use for such data is in worldwide vegetation models. The other is in accounting for variation in leaf N and P within climate zones. An outline protocol has been drafted. Initially Geoff Humphreys will investigate summaries of nutrient contents in rock types. Then a meeting will be called to work through the protocol for some examples.

5. A large dataset has been analysed on the response of potential photosynthetic rate Amax to leaf P content in conjunction with leaf N content. Peter Reich and others will write a manuscript shortly.

6. How soil P information (if it were available worldwide) would best be used in global vegetation models). Options include (a) P might influence what PFTs can be successful at a site. (b) P might influence the N-cycle or C-N relations and especially the incidence of N-fixing. (c) P might nfluence costs, for example low P greatly increases allocation to roots and mycorrhizas away from foliage growth (d) Low P might restrict the LAI that can be supported at a site (compared to what would be supported just on a climate basis), and that lesser degree of shading would then lead on to shorter stature and to a range of other traits.

Last updated May 2007.