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Coupling carbon allocation with leaf and root phenology predicts tree-grass partitioning along a savanna rainfall gradient

Haverd, Vanessa; Smith, Benjamin; Raupach, Michael; Briggs, Peter R.; Nieradzik, L.; Beringer, Jason; Hutley, Lindsey; Trudinger, C. M.; Cleverly, J. R.

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The relative complexity of the mechanisms underlying savanna ecosystem dynamics, in comparison to other biomes such as temperate and tropical forests, challenges the representation of such dynamics in ecosystem and Earth system models. A realistic representation of processes governing carbon allocation and phenology for the two defining elements of savanna vegetation (namely trees and grasses) may be a key to understanding variations in tree–grass partitioning in time and space across the...[Show more]

dc.contributor.authorHaverd, Vanessa
dc.contributor.authorSmith, Benjamin
dc.contributor.authorRaupach, Michael
dc.contributor.authorBriggs, Peter R.
dc.contributor.authorNieradzik, L.
dc.contributor.authorBeringer, Jason
dc.contributor.authorHutley, Lindsey
dc.contributor.authorTrudinger, C. M.
dc.contributor.authorCleverly, J. R.
dc.date.accessioned2020-04-01T03:34:15Z
dc.date.available2020-04-01T03:34:15Z
dc.identifier.issn1726-4170
dc.identifier.urihttp://hdl.handle.net/1885/202615
dc.description.abstractThe relative complexity of the mechanisms underlying savanna ecosystem dynamics, in comparison to other biomes such as temperate and tropical forests, challenges the representation of such dynamics in ecosystem and Earth system models. A realistic representation of processes governing carbon allocation and phenology for the two defining elements of savanna vegetation (namely trees and grasses) may be a key to understanding variations in tree–grass partitioning in time and space across the savanna biome worldwide. Here we present a new approach for modelling coupled phenology and carbon allocation, applied to competing tree and grass plant functional types. The approach accounts for a temporal shift between assimilation and growth, mediated by a labile carbohydrate store. This is combined with a method to maximize long-term net primary production (NPP) by optimally partitioning plant growth between fine roots and (leaves + stem). The computational efficiency of the analytic method used here allows it to be uniquely and readily applied at regional scale, as required, for example, within the framework of a global biogeochemical model. We demonstrate the approach by encoding it in a new simple carbon–water cycle model that we call HAVANA (Hydrology and Vegetation-dynamics Algorithm for Northern Australia), coupled to the existing POP (Population Orders Physiology) model for tree demography and disturbance-mediated heterogeneity. HAVANA-POP is calibrated using monthly remotely sensed fraction of absorbed photosynthetically active radiation (fPAR) and eddy-covariance-based estimates of carbon and water fluxes at five tower sites along the North Australian Tropical Transect (NATT), which is characterized by large gradients in rainfall and wildfire disturbance. The calibrated model replicates observed gradients of fPAR, tree leaf area index, basal area, and foliage projective cover along the NATT. The model behaviour emerges from complex feedbacks between the plant physiology and vegetation dynamics, mediated by shifting above- versus below-ground resources, and not from imposed hypotheses about the controls on tree–grass co-existence. Results support the hypothesis that resource limitation is a stronger determinant of tree cover than disturbance in Australian savannas.
dc.description.sponsorshipThe contributions of V. Haverd and P. Briggs were made possible by the support of the Australian Climate Change Science Program. B. Smith acknowledges funding as an OCE Distinguished Visiting Scientist to the CSIRO Oceans & Atmosphere Flagship, Canberra
dc.format.mimetypeapplication/pdf
dc.language.isoen_AU
dc.publisherCopernicus GmbH
dc.rights© 2016 Author(s)
dc.sourceBiogeosciences
dc.titleCoupling carbon allocation with leaf and root phenology predicts tree-grass partitioning along a savanna rainfall gradient
dc.typeJournal article
local.description.notesImported from ARIES
local.identifier.citationvolume13
dcterms.dateAccepted2016-01-06
dc.date.issued2016-02-11
local.identifier.absfor050101 - Ecological Impacts of Climate Change
local.identifier.ariespublicationU3488905xPUB11594
local.publisher.urlhttps://www.biogeosciences.net/
local.type.statusPublished Version
local.contributor.affiliationHaverd, Vanessa, CSIRO Marine and Atmospheric Research
local.contributor.affiliationSmith, Benjamin, Lund University
local.contributor.affiliationRaupach, Michael, College of Science, ANU
local.contributor.affiliationBriggs, Peter R., CSIRO
local.contributor.affiliationNieradzik, L., CSIRO
local.contributor.affiliationBeringer, Jason, University of Western Australia
local.contributor.affiliationHutley, Lindsey, Charles Darwin University
local.contributor.affiliationTrudinger, C. M., CSIRO Marine and Atmospheric Research
local.contributor.affiliationCleverly, J. R. , University of Technology
local.bibliographicCitation.issue3
local.bibliographicCitation.startpage761
local.bibliographicCitation.lastpage779
local.identifier.doi10.5194/bg-13-761-2016
local.identifier.absseo960305 - Ecosystem Adaptation to Climate Change
dc.date.updated2019-11-25T07:47:10Z
local.identifier.scopusID2-s2.0-84958962011
local.identifier.thomsonID000370973900010
dcterms.accessRightsOpen Access
dc.rights.licenseCC Attribution 3.0 License
CollectionsANU Research Publications

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