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Kafuti C, Lehnebach R, Bourland N, Beeckman H, Van Acker J, Luambua N, Van den Bulcke J. Earlier onset and slower heartwood investment in faster-growing trees of African tropical species. Ann Bot 2023:mcad079. [PMID: 37409979 DOI: 10.1093/aob/mcad079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Indexed: 07/07/2023]
Abstract
BACKGROUND AND AIMS Heartwood plays an important role in maintaining the structural integrity of trees. While, its formation has long be thought to be solely driven by internal ageing processes, more recent hypotheses suggest that heartwood formation acts as a regulator of the tree water balance by modulating sapwood quantities. Testing both hypotheses would shed light on the potential ecophysiological nature of heartwood formation, a very common process in trees. METHODS We measured heartwood and sapwood quantities, xylem conduits and growth ring width and number on 406 stems of Pericopsis elata with ages ranging from 2 to 237 years. A subset of 17 trees with similar ages but varying growth rate were sampled in a shaded (slower growth) and sun-exposed (faster growth) site. We used regression analysis and structural equations modelling to investigate the dynamics and drivers of heartwood formation. KEY RESULTS We found a positive effect of growth rate on the probability of heartwood occurrence, suggesting an earlier heartwood onset in faster-growing stems. After this onset age, heartwood area increases with stem diameter and age. Despite the similar heartwood production per unit stem diameter increment, shaded trees produce heartwood faster than sun-exposed trees. Tree age and hydraulics showed similar direct effects on heartwood and sapwood area of sun-exposed trees, suggesting their mutual role in driving the heartwood dynamics of sun-exposed trees. However, for shaded trees, only tree hydraulics showed a direct effect, suggesting its prominent role over age in driving the heartwood dynamics in limited growing conditions. The positive relationship between growth rate and maximum stomatal conductance supports this conclusion. CONCLUSIONS Heartwood area increases as the tree ages but at a slower rate in trees where water demand is balanced by a sufficient water supply. Our findings suggest that heartwood formation is not only a structural but also a functional process.
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Affiliation(s)
- Chadrack Kafuti
- UGent-Woodlab, Laboratory of Wood Technology, Department of Environment, Ghent University, Coupure Links 653, 9000 Gent, Belgium
- Service of Wood Biology, Royal Museum for Central Africa, Leuvensesteenweg 13, 3080 Tervuren, Belgium
- Faculty of Agricultural Sciences, Department of Natural Resources Management, University of Kinshasa, 117 Kinshasa XI, Democratic Republic of the Congo
| | - Romain Lehnebach
- UGent-Woodlab, Laboratory of Wood Technology, Department of Environment, Ghent University, Coupure Links 653, 9000 Gent, Belgium
- CIRAD, UMR Ecologie des Forêts de Guyane (EcoFoG), AgroParisTech, CNRS, INRA, Université Des Antilles, Université de Guyane, 97310 Kourou, France
| | - Nils Bourland
- Service of Wood Biology, Royal Museum for Central Africa, Leuvensesteenweg 13, 3080 Tervuren, Belgium
- Center for International Forestry Research, Situ Gede, Sindang Barang, Bogor (Barat) 16115, Indonesia
| | - Hans Beeckman
- Service of Wood Biology, Royal Museum for Central Africa, Leuvensesteenweg 13, 3080 Tervuren, Belgium
| | - Joris Van Acker
- UGent-Woodlab, Laboratory of Wood Technology, Department of Environment, Ghent University, Coupure Links 653, 9000 Gent, Belgium
| | - Nestor Luambua
- Service of Wood Biology, Royal Museum for Central Africa, Leuvensesteenweg 13, 3080 Tervuren, Belgium
- Faculté des sciences Agronomiques, Université Officielle de Mbujimayi, Mbujimayi, Democratic Republic of Congo
| | - Jan Van den Bulcke
- UGent-Woodlab, Laboratory of Wood Technology, Department of Environment, Ghent University, Coupure Links 653, 9000 Gent, Belgium
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