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Explaining biomass growth of tropical canopy trees: the importance of sapwood.

van der Sande MT, Zuidema PA, Sterck F - Oecologia (2015)

Bottom Line: We found that variation in biomass growth was chiefly explained by a positive effect of SA, and not by tree size or other traits examined.SA itself was positively associated with sapwood growth, sapwood lifespan and basal area.Accurate predictions of C dynamics in tropical forests require similar studies on biomass growth of individual trees as well as studies evaluating the dual effect of sapwood (water provision vs. respiratory costs) on tropical tree growth.

View Article: PubMed Central - PubMed

Affiliation: Forest Ecology and Forest Management Group, Wageningen University, PO Box 47, 6700 AA, Wageningen, The Netherlands, masha.vandersande@wur.nl.

ABSTRACT
Tropical forests are important in worldwide carbon (C) storage and sequestration. C sequestration of these forests may especially be determined by the growth of canopy trees. However, the factors driving variation in growth among such large individuals remain largely unclear. We evaluate how crown traits [total leaf area, specific leaf area and leaf nitrogen (N) concentration] and stem traits [sapwood area (SA) and sapwood N concentration] measured for individual trees affect absolute biomass growth for 43 tropical canopy trees belonging to four species, in a moist forest in Bolivia. Biomass growth varied strongly among trees, between 17.3 and 367.3 kg year(-1), with an average of 105.4 kg year(-1). We found that variation in biomass growth was chiefly explained by a positive effect of SA, and not by tree size or other traits examined. SA itself was positively associated with sapwood growth, sapwood lifespan and basal area. We speculate that SA positively affects the growth of individual trees mainly by increasing water storage, thus securing water supply to the crown. These positive roles of sapwood on growth apparently offset the increased respiration costs incurred by more sapwood. This is one of the first individual-based studies to show that variation in sapwood traits-and not crown traits-explains variation in growth among tropical canopy trees. Accurate predictions of C dynamics in tropical forests require similar studies on biomass growth of individual trees as well as studies evaluating the dual effect of sapwood (water provision vs. respiratory costs) on tropical tree growth.

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Related in: MedlinePlus

The relation of sapwood area (SA) with total leaf area (TLA), based on a regression analysis. Symbols represent four species: Sweetia (squares), Hura (triangles), Schizolobium (circles), and Cariniana (diamonds). Note that the axis for SA has a log scale and the axis for TLA a square root scale
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Fig4: The relation of sapwood area (SA) with total leaf area (TLA), based on a regression analysis. Symbols represent four species: Sweetia (squares), Hura (triangles), Schizolobium (circles), and Cariniana (diamonds). Note that the axis for SA has a log scale and the axis for TLA a square root scale

Mentions: The functional role of sapwood is to supply water with nutrients to the crown, and this is likely how SA increases biomass growth in our study trees. Sapwood assures water supply in two ways: by water transport from the roots to the leaves (Goldstein et al. 1998; Meinzer et al. 2001), and by water storage to buffer the use of soil water and allow more persistent water supply to the crown during the course of the day (e.g., during hot afternoons) or the dry season (Wullschleger et al. 1998). Our canopy trees were all emergent and thus most likely not primarily limited by light, but their high stature (on average 26.2 m) may have caused hydraulic limitation for the supply of water to the crown. We found a positive effect of SA on TLA (Fig. 4), without differences in slope and intercept between species. This suggests that a large SA indeed supports a large TLA, and that, independent of species, a certain SA is associated with a certain TLA. A positive relation between SA and TLA was also found for two mountain ash species in south-east Australia (Vertessy et al. 1995), and a strong relation between SA and water flow rate was found for five tropical canopy trees in Panama (Goldstein et al. 1998). These studies and our results thus suggest that the water supply to the crown may limit the TLA and growth of these tropical forest trees.Fig. 4


Explaining biomass growth of tropical canopy trees: the importance of sapwood.

van der Sande MT, Zuidema PA, Sterck F - Oecologia (2015)

The relation of sapwood area (SA) with total leaf area (TLA), based on a regression analysis. Symbols represent four species: Sweetia (squares), Hura (triangles), Schizolobium (circles), and Cariniana (diamonds). Note that the axis for SA has a log scale and the axis for TLA a square root scale
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4363484&req=5

Fig4: The relation of sapwood area (SA) with total leaf area (TLA), based on a regression analysis. Symbols represent four species: Sweetia (squares), Hura (triangles), Schizolobium (circles), and Cariniana (diamonds). Note that the axis for SA has a log scale and the axis for TLA a square root scale
Mentions: The functional role of sapwood is to supply water with nutrients to the crown, and this is likely how SA increases biomass growth in our study trees. Sapwood assures water supply in two ways: by water transport from the roots to the leaves (Goldstein et al. 1998; Meinzer et al. 2001), and by water storage to buffer the use of soil water and allow more persistent water supply to the crown during the course of the day (e.g., during hot afternoons) or the dry season (Wullschleger et al. 1998). Our canopy trees were all emergent and thus most likely not primarily limited by light, but their high stature (on average 26.2 m) may have caused hydraulic limitation for the supply of water to the crown. We found a positive effect of SA on TLA (Fig. 4), without differences in slope and intercept between species. This suggests that a large SA indeed supports a large TLA, and that, independent of species, a certain SA is associated with a certain TLA. A positive relation between SA and TLA was also found for two mountain ash species in south-east Australia (Vertessy et al. 1995), and a strong relation between SA and water flow rate was found for five tropical canopy trees in Panama (Goldstein et al. 1998). These studies and our results thus suggest that the water supply to the crown may limit the TLA and growth of these tropical forest trees.Fig. 4

Bottom Line: We found that variation in biomass growth was chiefly explained by a positive effect of SA, and not by tree size or other traits examined.SA itself was positively associated with sapwood growth, sapwood lifespan and basal area.Accurate predictions of C dynamics in tropical forests require similar studies on biomass growth of individual trees as well as studies evaluating the dual effect of sapwood (water provision vs. respiratory costs) on tropical tree growth.

View Article: PubMed Central - PubMed

Affiliation: Forest Ecology and Forest Management Group, Wageningen University, PO Box 47, 6700 AA, Wageningen, The Netherlands, masha.vandersande@wur.nl.

ABSTRACT
Tropical forests are important in worldwide carbon (C) storage and sequestration. C sequestration of these forests may especially be determined by the growth of canopy trees. However, the factors driving variation in growth among such large individuals remain largely unclear. We evaluate how crown traits [total leaf area, specific leaf area and leaf nitrogen (N) concentration] and stem traits [sapwood area (SA) and sapwood N concentration] measured for individual trees affect absolute biomass growth for 43 tropical canopy trees belonging to four species, in a moist forest in Bolivia. Biomass growth varied strongly among trees, between 17.3 and 367.3 kg year(-1), with an average of 105.4 kg year(-1). We found that variation in biomass growth was chiefly explained by a positive effect of SA, and not by tree size or other traits examined. SA itself was positively associated with sapwood growth, sapwood lifespan and basal area. We speculate that SA positively affects the growth of individual trees mainly by increasing water storage, thus securing water supply to the crown. These positive roles of sapwood on growth apparently offset the increased respiration costs incurred by more sapwood. This is one of the first individual-based studies to show that variation in sapwood traits-and not crown traits-explains variation in growth among tropical canopy trees. Accurate predictions of C dynamics in tropical forests require similar studies on biomass growth of individual trees as well as studies evaluating the dual effect of sapwood (water provision vs. respiratory costs) on tropical tree growth.

Show MeSH
Related in: MedlinePlus