Woody thickening: a consequence of changes in fluxes of carbon and water on a warming globe
Date
2007
Authors
Eamus, Derek
Fuentes, Sigfredo
Macinnis-Ng, Catriona M. O.
Palmer, Anthony R.
Taylor, Daniel
Whitley, Rhys
Yunusa, Isa Abdul Muhammad
Zeppel, Melanie J. B.
Editors
Advisors
Journal Title
Journal ISSN
Volume Title
Type:
Working paper
Citation
Statement of Responsibility
Derek Eamus, S Fuentes C Macinnis-Ng, A Palmer, D Taylor, R Whitley, I Yunusa, M Zeppel
Conference Name
Abstract
Understanding patterns, rates and controls of water and CO2 exchange between land surfaces and the
atmosphere is central to the sciences of meteorology, ecology, hydrology, ecophysiology, forestry and
related endeavours. Measurements involving sapflow sensors, eddy covariance and remote sensing have
contributed substantially to our understanding of these issues. In this talk, we apply a combination of
methods in order to apply a soil-plant-atmosphere model to the question: what is causing the globally
observed phenomenon of woody thickening?
The density of woody plants in arid and semi-arid regions is increasing regionally and globally (Fensham et
al., 2005, Hoffman et al., 1999, Bowman et al. 2001, Burrows et al. 2002). This can be deduced from
analyses of tree-ring widths, forest inventory data, aerial photo-interpretation and from long-term monitoring
sites (Spiecker et al., 2003). Potential causes of woody thickening have been extensively discussed in the
past. Mechanisms that have been proposed include the (a) Walther model, which invokes competition for
water and nutrients among the deeper roots of woody plants versus the shallower roots of shrubs and grasses;
(b) a role for changes in the timing, intensity and frequency of fire; and (c) changes in herbivory by large
herbivores. Such thickening may have a large impact on regional CO2 budgets, atmospheric CO2
concentration and ecosystem function and regional water budgets.
We propose an alternative mechanism to explain woody thickening based upon changes in water and carbon
fluxes within the soil-plant-atmosphere continuum resulting from a change in global atmospheric conditions.
Such a mechanism is global in reach, appears consistent with a number of phenomena and has several
testable predictions, which we briefly discuss.
School/Discipline
School of Agriculture, Food and Wine : Wine and Horticulture