Ontogenetic variation in light interception, self-shading and biomass distribution of seedlings of the conifer Araucaria araucana (Molina) K. Koch

One of the factors thought to contribute to ontogenetic declines in plant growth rates is diminishing light interception efficiency, as a result of the difficulties of avoiding self-shading among a growing number of leaves, and by stems. The effects of plant size on self-shading and light intercepti...

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Autores principales:	LUSK,CHRISTOPHER H, FALSTER,DANIEL S, PÉREZ-MILLAQUEO,MANUEL, SALDAÑA,ALFREDO
Lenguaje:	English
Publicado:	Sociedad de Biología de Chile 2006
Materias:	allocation allometry FLORADIG leaf area ratio virtual plants YPLANT
Acceso en línea:	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-078X2006000300004
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spelling	oai:scielo:S0716-078X20060003000042006-10-03Ontogenetic variation in light interception, self-shading and biomass distribution of seedlings of the conifer Araucaria araucana (Molina) K. KochLUSK,CHRISTOPHER HFALSTER,DANIEL SPÉREZ-MILLAQUEO,MANUELSALDAÑA,ALFREDO allocation allometry FLORADIG leaf area ratio virtual plants YPLANT One of the factors thought to contribute to ontogenetic declines in plant growth rates is diminishing light interception efficiency, as a result of the difficulties of avoiding self-shading among a growing number of leaves, and by stems. The effects of plant size on self-shading and light interception have rarely been quantified, however. We used a three-dimensional digitising system to construct virtual models of the architecture of Araucaria araucana seedlings 71 to 358 mm tall, and modelled their light interception in the forest understorey using the program YPLANT. We also analyzed seedling allometry, to determine the combined effects of biomass distribution and self-shading on total light interception. Average light interception efficiencies calculated for A. araucana (29 %) were the lowest reported for rainforest tree seedlings, reflecting the limitations imposed by short leaves, lack of petioles and an inability to develop planar foliage geometry on branches. Total light interception was related to seedling leaf area by an exponent of 0.735, reflecting increasing self-shading as seedlings grew bigger. However, because leaf area was related to seedling mass by an exponent of 1.24, light interception scaled nearly isometrically (0.91 power) with seedling mass. This resulted from taller plants having proportionally thinner stems, and a smaller fraction of their biomass in roots. Thus, an ontogenetic increase in self-shading in A. araucana is largely offset by allocation changes which increase leaf area ratio as seedlings grow bigger. These mechanisms conserving the relationship of light interception with plant mass seem likely to be restricted to species with long-lived leaves, growing in humid situations protected from wind stress. In open habitats, where wind and drought stress likely make such allocation patterns less feasible, the role of self-shading in ontogenetic declines in relative growth rate may be more evidentinfo:eu-repo/semantics/openAccessSociedad de Biología de ChileRevista chilena de historia natural v.79 n.3 20062006-09-01text/htmlhttp://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-078X2006000300004en10.4067/S0716-078X2006000300004
institution	Scielo Chile
collection	Scielo Chile
language	English
topic	allocation allometry FLORADIG leaf area ratio virtual plants YPLANT
spellingShingle	allocation allometry FLORADIG leaf area ratio virtual plants YPLANT LUSK,CHRISTOPHER H FALSTER,DANIEL S PÉREZ-MILLAQUEO,MANUEL SALDAÑA,ALFREDO Ontogenetic variation in light interception, self-shading and biomass distribution of seedlings of the conifer Araucaria araucana (Molina) K. Koch
description	One of the factors thought to contribute to ontogenetic declines in plant growth rates is diminishing light interception efficiency, as a result of the difficulties of avoiding self-shading among a growing number of leaves, and by stems. The effects of plant size on self-shading and light interception have rarely been quantified, however. We used a three-dimensional digitising system to construct virtual models of the architecture of Araucaria araucana seedlings 71 to 358 mm tall, and modelled their light interception in the forest understorey using the program YPLANT. We also analyzed seedling allometry, to determine the combined effects of biomass distribution and self-shading on total light interception. Average light interception efficiencies calculated for A. araucana (29 %) were the lowest reported for rainforest tree seedlings, reflecting the limitations imposed by short leaves, lack of petioles and an inability to develop planar foliage geometry on branches. Total light interception was related to seedling leaf area by an exponent of 0.735, reflecting increasing self-shading as seedlings grew bigger. However, because leaf area was related to seedling mass by an exponent of 1.24, light interception scaled nearly isometrically (0.91 power) with seedling mass. This resulted from taller plants having proportionally thinner stems, and a smaller fraction of their biomass in roots. Thus, an ontogenetic increase in self-shading in A. araucana is largely offset by allocation changes which increase leaf area ratio as seedlings grow bigger. These mechanisms conserving the relationship of light interception with plant mass seem likely to be restricted to species with long-lived leaves, growing in humid situations protected from wind stress. In open habitats, where wind and drought stress likely make such allocation patterns less feasible, the role of self-shading in ontogenetic declines in relative growth rate may be more evident
author	LUSK,CHRISTOPHER H FALSTER,DANIEL S PÉREZ-MILLAQUEO,MANUEL SALDAÑA,ALFREDO
author_facet	LUSK,CHRISTOPHER H FALSTER,DANIEL S PÉREZ-MILLAQUEO,MANUEL SALDAÑA,ALFREDO
author_sort	LUSK,CHRISTOPHER H
title	Ontogenetic variation in light interception, self-shading and biomass distribution of seedlings of the conifer Araucaria araucana (Molina) K. Koch
title_short	Ontogenetic variation in light interception, self-shading and biomass distribution of seedlings of the conifer Araucaria araucana (Molina) K. Koch
title_full	Ontogenetic variation in light interception, self-shading and biomass distribution of seedlings of the conifer Araucaria araucana (Molina) K. Koch
title_fullStr	Ontogenetic variation in light interception, self-shading and biomass distribution of seedlings of the conifer Araucaria araucana (Molina) K. Koch
title_full_unstemmed	Ontogenetic variation in light interception, self-shading and biomass distribution of seedlings of the conifer Araucaria araucana (Molina) K. Koch
title_sort	ontogenetic variation in light interception, self-shading and biomass distribution of seedlings of the conifer araucaria araucana (molina) k. koch
publisher	Sociedad de Biología de Chile
publishDate	2006
url	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-078X2006000300004
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Ontogenetic variation in light interception, self-shading and biomass distribution of seedlings of the conifer Araucaria araucana (Molina) K. Koch

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