title: Controls on declining carbon balance with leaf age among 10 woody species in Australian woodland: do leaves have zero daily net carbon balances when they die?
abstract: * Here, we evaluated how increased shading and declining net photosynthetic capacity regulate the decline in net carbon balance with increasing leaf age for 10 Australian woodland species. We also asked whether leaves at the age of their mean life-span have carbon balances that are positive, zero or negative. * The net carbon balances of 2307 leaves on 53 branches of the 10 species were estimated. We assessed three-dimensional architecture, canopy openness, photosynthetic light response functions and dark respiration rate across leaf age sequences on all branches. We used YPLANT to estimate light interception and to model carbon balance along the leaf age sequences. * As leaf age increased to the mean life-span, increasing shading and declining photosynthetic capacity each separately reduced daytime carbon gain by approximately 39% on average across species. Together, they reduced daytime carbon gain by 64% on average across species. * At the age of their mean life-span, almost all leaves had positive daytime carbon balances. These per leaf carbon surpluses were of a similar magnitude to the estimated whole-plant respiratory costs per leaf. Thus, the results suggest that a whole-plant economic framework, including respiratory costs, may be useful in assessing controls on leaf longevity.
authors.affiliation: University of Minnesota, 1530 Cleveland Avenue North, St Paul, MN 55108, USA.
authors.forename: Peter B
authors.initials: PB
authors.lastname: Reich
authors.affiliation: Macquarie University, Department of Biological Science, N Ryde, NSW 2109, Australia.
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Falster
authors.affiliation: University of Western Sydney, Locked Bag 1797, Penrith, South DC, NSW 1797, Australia.
authors.forename: David S
authors.initials: DS
authors.lastname: Ellsworth
authors.affiliation: Macquarie University, Department of Biological Science, N Ryde, NSW 2109, Australia.
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Wright
authors.affiliation: Macquarie University, Department of Biological Science, N Ryde, NSW 2109, Australia.
authors.forename: Mark
authors.initials: M
authors.lastname: Westoby
authors.affiliation: University of Minnesota, 1530 Cleveland Avenue North, St Paul, MN 55108, USA.|Institute of Dendrology, Polish Academy of Sciences, Parkowa 5, PL-62-035 Kórnik, Poland.
authors.forename: Jacek
authors.initials: J
authors.lastname: Oleksyn
authors.affiliation: University of Wisconsin - Eau Claire, Department of Biology, Eau Claire, WI 54701, USA.
authors.forename: Tali D
authors.initials: TD
authors.lastname: Lee
mesh_terms: D001315:Australia; D002244:Carbon / Q000378:metabolism*; D019069:Cell Respiration; D003624:Darkness; D017753:Ecosystem; D008027:Light; D010788:Photosynthesis / Q000502:physiology*; D063245:Plant Development; D018515:Plant Leaves / Q000254:growth & development / Q000378:metabolism*; D010944:Plants / Q000378:metabolism*; D014197:Trees / Q000254:growth & development / Q000378:metabolism
chemical_list: D002244:Carbon