Structural scaling of light interception efficiency in Picea engelmannii and Abies lasiocarpa

Abstract

Sunlight interception efficiency was compared at the leaf, shoot, branch and crown levels for Picea engelmannii (Parry) and Abies lasiocarpa ((Hook.) Nutt.), dominant tree species of the central Rocky Mountains, USA. The ratio of silhouette to total leaf area (STAR) was used to quantify the efficiency of direct-beam sunlight interception at each structural scale. Total mean reductions in STAR from the leaf to the crown level were 0.39 to 0.06 in P. engelmannii and 0.46 to 0.02 in A. lasiocarpa. These reductions in STAR occurred for both species as structural scale increased due to a more upright leaf inclination, increased leaf twisting and curvature, or greater mutual shading among plant structures. A steeper leaf inclination between the leaf and shoot level accounted for 26 +/- 19% (95% C.I.) of the total leaf-to-crown STAR reduction; mutual shading among leaves on shoots caused a 14 +/- 7% reduction, whereas leaf curvature and twisting accounted for 22 +/- 3% for a total reduction of 62 +/- 8%. The STAR varied slightly from the shoot to the branch level (+/- 7%) except for a 26% reduction in shade shoots of A. lasiocarpa as a result of increased mutual shading among leaves at lateral nodes. Another substantial reduction in STAR occurred from the branch to the crown level (35 +/- 3% of total) as a result of shading of one branch layer by another within the crown. Thus, light interception efficiency decreased as structural scale increased in both species, especially from the leaf to the shoot level and from the branch to the crown level.

Functional ecology of advance regeneration in relation to light in boreal forests

“…For example, tree architecture has been described by many investigators (Hallé et al 1978;Pickett and Kempf 1980;Shukla and Ramakrishan 1986;Canham 1988;Bonser and Aarssen 1994;King 1994;O'Connell and Kelty 1994;Sipe and Bazzaz 1994) but generally without considering the significance of architectural parameters for light interception. Other studies have described how architecture and morphology change within species in various light environments (e.g., Cornelissen 1993;Hemmerlein and Smith 1994;Parent and Messier 1995;Chen et al 1996), again without relating these changes to light interception. Morphological models, such as those used by Prusinkiwicz and Hanan (1989) or others (Fisher 1992), similarly ignore the functional significance of tree architecture.…”

Light interception and partitioning between shoots in apple cultivars influenced by training

“…Light interception at both the tree and shoot scales was computed from the 3D plant mock-ups. Projected leaf area (PLA, m 2 )-also called silhouette area-and silhouette to total area ratio (STAR, Carter and Smith 1985, Oker-Blom and Smolander 1988, Hemmerlein and Smith 1994 were computed with VegeSTAR Version 3.0 software (2002; B. Adam, N. Donès and H. Sinoquet, UMR PIAF INRA-UBP, Clermont-Ferrand). Projected leaf area characterizes light intercepting leaf area, whereas STAR corresponds to mean leaf irradiance relative to incident radiation.…”

“…Second, virtual experiments allowed us to compute light interception properties and their determinants at several scales: STAR and PLA of the whole tree (Table 1), per shoot type (FS and VS) ( Table 2) and at the individual shoot scale ( Figure 5). Several methods have been proposed to measure total light interception at the tree scale, e.g., arrays of sensors (Oker-Blom et al 1991, Giuliani et al 2000, fisheye photographs below the canopy (Wünsche et al 1995) and photographs of the shadow cast by the crown (Hemmerlein and Smith 1994). At the shoot scale, video projection and photography methods have been proposed for detached shoots (Oker-Blom et al 1991, Niinemets et al 2004.…”